Ecology and Management of Blacktailed and Mule Deer of North America 2022054030, 2022054031, 9781032407609, 9781032407623, 9781003354628

Table of contents :
Cover
Half Title
Title Page
Copyright Page
Dedication
Table of Contents
List of Figures
List of Tables
Foreword
Preface
Acknowledgments
Editors
List of Contributors
Section I Biology and Ecology
Chapter 1 Origin, Classification, and Distribution
Chapter 2 Historical Trends in Black-tailed Deer, Mule Deer, and Their Habitats
Chapter 3 Physical Characteristics
Chapter 4 Digestive Physiology and Nutrition
Chapter 5 Modeling Population Dynamics of Black-tailed and Mule Deer
Chapter 6 Diseases and Parasites
Chapter 7 Carnivore-Prey Relationships
Chapter 8 Competition with Other Ungulates
Section II Ecoregion Habitats and Population Dynamics
Chapter 9 Northern Forest Ecoregion
Chapter 10 Coastal Rainforest Ecoregion
Chapter 11 Intermountain West Ecoregion
Chapter 12 Great Plains Ecoregion
Chapter 13 California Chaparral and Oak Woodlands Ecoregion
Chapter 14 Southwest Deserts Ecoregion
Chapter 15 Colorado Plateau Ecoregion
Section III Population Management
Chapter 16 Population Monitoring
Chapter 17 Harvest Management
Chapter 18 Human Dimensions
Section IV Habitat Management
Chapter 19 Conflict Management
Chapter 20 Threats to Habitat Function
Chapter 21 Habitat Improvement and Water Supplementation
Chapter 22 Migration
Section V The Future
Chapter 23 Challenges and Opportunities for the Future Conservation of Black-tailed and Mule Deer
Bibliography
Index

Citation preview

Ecology and Management of Black-tailed and Mule Deer of North America Black-tailed and mule deer represent one of the largest distributions of mammals in North America and are symbols of the wide-open American West. Each chapter in this book was authored by the world’s leading experts on that topic. Both editors, James R. Heffelfinger and Paul R. Krausman, are widely published in the popular and scientific press and recipients of the O. C. Wallmo Award, given every two years to a leading black-tailed and mule deer expert who has made significant contributions to the conservation of this species. In addition, Heffelfinger has chaired the Mule Deer Working Group sponsored by the Western Association of Fish and Wildlife Agencies for more than 15 years. This working group consists of the leading black-tailed and mule deer experts from each of 24 states, provinces, and territories in western North America, putting them at the forefront of all conservation and much of the research on this species. The book represents all current knowledge available on these deer, including how changing conditions such as fires, habitat alteration and loss, disease, climate change, socio-economic forces, energy development, and other aspects are influencing their distribution and abundance now and into the future. It takes a completely fresh look at all chapter topics. The revisions of distribution, taxonomy, evolution, behavior, and new and exciting work being done in deer nutrition, migration and movements, diseases, predation, and human dimensions are all assembled in this volume. This book will instantly become the foundation for the latest information and management strategies to be implemented on the ground by practitioners and to inform the public. Although this book is about deer, the topics discussed influence most terrestrial wildlife worldwide, and the basic concepts in many of the chapters are applicable to other species.

Ecology and Management of Black-tailed and Mule Deer of North America

Edited by

James R. Heffelfinger and Paul R. Krausman Illustrated by Randall Babb and Copyedited by Allison Cox

First edition published 2023 by CRC Press 6000 Broken Sound Parkway NW, Suite 300, Boca Raton, FL 33487-2742 and by CRC Press 4 Park Square, Milton Park, Abingdon, Oxon, OX14 4RN CRC Press is an imprint of Taylor & Francis Group, LLC © 2023 selection and editorial matter, James R. Heffelfinger and Paul R. Krausman; individual chapters, the contributors Reasonable efforts have been made to publish reliable data and information, but the author and publisher cannot assume responsibility for the validity of all materials or the consequences of their use. The authors and publishers have attempted to trace the copyright holders of all material reproduced in this publication and apologize to copyright holders if permission to publish in this form has not been obtained. If any copyright material has not been acknowledged please write and let us know so we may rectify in any future reprint. Except as permitted under U.S. Copyright Law, no part of this book may be reprinted, reproduced, transmitted, or utilized in any form by any electronic, mechanical, or other means, now known or hereafter invented, including photocopying, microfilming, and recording, or in any information storage or retrieval system, without written permission from the publishers. For permission to photocopy or use material electronically from this work, access www​.copyright​.com or contact the Copyright Clearance Center, Inc. (CCC), 222 Rosewood Drive, Danvers, MA 01923, 978-750-8400. For works that are not available on CCC please contact mpkbookspermissions​@tandf​.co​​.uk Trademark notice: Product or corporate names may be trademarks or registered trademarks and are used only for identification and explanation without intent to infringe.

Library of Congress Cataloging‑in‑Publication Data Names: Heffelfinger, Jim, 1964- editor. | Krausman, Paul R., 1946- editor. Title: Ecology and management of black-tailed and mule deer of North America / edited by James R. Heffelfinger, Paul R. Krausman. Description: First edition. | Boca Raton, FL : CRC Press, 2023. | Includes bibliographical references and index. | Summary: “This book represents all current knowledge available on black-tailed and mule deer, including how changing conditions such as fires, habitat alteration and loss, disease, climate change, socio-economic forces, and energy development are influencing their distribution and abundance now and into the future. The revisions of distribution, taxonomy, evolution, behavior, and new work being done in deer nutrition, migration and movements, diseases, predation, and human dimensions are all assembled in this volume, which will become the foundation for the latest information and management strategies to be implemented on the ground by practitioners and to inform the public”-- Provided by publisher. Identifiers: LCCN 2022054030 (print) | LCCN 2022054031 (ebook) | ISBN 9781032407609 (hbk) | ISBN 9781032407623 (pbk) | ISBN 9781003354628 (ebk) Subjects: LCSH: Mule deer--North America. | Mule deer--Ecology--North America. | Mule deer--Conservation--North America. | Wildlife management--North America. Classification: LCC QL737.U55 E335 2023 (print) | LCC QL737.U55 (ebook) | DDC 599.65/3--dc23/eng/20230113 LC record available at https://lccn.loc.gov/2022054030 LC ebook record available at https://lccn.loc.gov/2022054031

ISBN: 978-1-032-40760-9 (hbk) ISBN: 978-1-032-40762-3 (pbk) ISBN: 978-1-003-35462-8 (ebk) DOI: 10.1201/9781003354628 Typeset in Times by Deanta Global Publishing Services, Chennai, India

Dedication We dedicate this volume those who came before us and those who will someday step up into our places. Stalwarts in the world of research and conservation of black-tailed and mule deer, such as Allen E. Anderson, Richard M. Bartmann, Len H. Carpenter, Guy E. Connolly, Valerius Geist, William Longhurst, Richard Mackie, Dale R. McCullough, Ian McTaggartCowan, Leslie Robinette, Henry L. Short, Richard D. Taber, O. C. Wallmo and others have laid a solid foundation upon which we all stand. This foundation has also grown wider and stronger through the efforts of thousands of local, regional, and state or provincial biologists whose names we may not know, but whom have toiled none-the-less day after day, year after year, to assure proper management and conservation of this species through difficult challenges. Through all these efforts in the past and the future, black-tailed and mule deer will continue to thrive in a complex and changing environment.

Contents List of Figures.................................................................................................................................................................................. ix List of Tables.................................................................................................................................................................................xvii Foreword........................................................................................................................................................................................xix Preface...........................................................................................................................................................................................xxi Acknowledgments........................................................................................................................................................................xxiii Editors........................................................................................................................................................................................... xxv List of Contributors.....................................................................................................................................................................xxvii

Section I  Biology and Ecology 1 Origin, Classification, and Distribution................................................................................................................................ 3 James R. Heffelfinger and Emily K. Latch 2 Historical Trends in Black-tailed Deer, Mule Deer, and Their Habitats........................................................................ 25 William F. Jensen, Vernon C. Bleich, and Donald G. Whittaker 3 Physical Characteristics....................................................................................................................................................... 43 Levi J. Heffelfinger and James R. Heffelfinger 4 Digestive Physiology and Nutrition..................................................................................................................................... 71 Kevin L. Monteith, Tayler N. LaSharr, Chad J. Bishop, Thomas R. Stephenson, Kelley M. Stewart, and Lisa A. Shipley 5 Modeling Population Dynamics of Black-tailed and Mule Deer...................................................................................... 95 Paul M. Lukacs and J. Joshua Nowak 6 Diseases and Parasites........................................................................................................................................................ 103 Margo J. Pybus, Mary E. Wood, Karen A. Fox, and Brandon A. Munk 7 Carnivore-Prey Relationships............................................................................................................................................ 125 Mark A. Hurley, Charles R. Anderson Jr, Tavis D. Forrester, and Justin A. Gude 8 Competition with Other Ungulates................................................................................................................................... 141 R. Terry Bowyer, Kelley M. Stewart, James W. Cain III, and Brock R. McMillan

Section II  Ecoregion Habitats and Population Dynamics 9 Northern Forest Ecoregion................................................................................................................................................. 161 Justin D. Gilligan, Darren A. Clark, Ethan S. Lula, Thomas A. Perry, Andrew B. D. Walker, and Laura B. Wolf 10 Coastal Rainforest Ecoregion............................................................................................................................................ 179 DeWaine H. Jackson, Karin R. McCoy, Scott M. McCorquodale, Sara J. K. Hansen, Sean R. Pendergast, and David S. Casady 11 Intermountain West Ecoregion.......................................................................................................................................... 203 Kelley M. Stewart, Brian F. Wakeling, Justin M. Shannon, Cody Schroeder, Donald G. Whittaker, and Gary Bezzant 12 Great Plains Ecoregion....................................................................................................................................................... 217 Andrew J. Lindbloom, Peter J. Bauman, Melissa A. Foster, Lloyd B. Fox, Shawn S. Gray, Levi J. Heffelfinger, Luke R. Meduna, and Scott D. Stevens

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13 California Chaparral and Oak Woodlands Ecoregion................................................................................................... 241 David S. Casady, Julie K. Garcia, and Kenneth E. Mayer 14 Southwest Deserts Ecoregion............................................................................................................................................. 257 Orrin V. Duvuvuei, James R. Heffelfinger, Paul R. Krausman, Shawn S. Gray, and Carlos H. Alcalá-Galván 15 Colorado Plateau Ecoregion............................................................................................................................................... 275 Eric J. Bergman and Chad J. Bishop

Section III  Population Management 16 Population Monitoring........................................................................................................................................................ 291 J. Joshua Nowak, Mark A. Hurley, Paul M. Lukacs, Daniel Walsh, and C. Leann White 17 Harvest Management.......................................................................................................................................................... 307 Donald G. Whittaker, A. Andrew Holland, Andrew J. Lindbloom, and Thomas W. Keegan 18 Human Dimensions............................................................................................................................................................. 321 Terry A. Messmer, Edward B. Arnett, Steven R. Belinda, Kenneth E. Mayer, and Rob Southwick

Section IV  Habitat Management 19 Conflict Management.......................................................................................................................................................... 333 Brian F. Wakeling, Orrin V. Duvuvuei, Justin M. Shannon, Annette Roug, Chad Wilson, and Sara J. K. Hansen 20 Threats to Habitat Function.............................................................................................................................................. 349 Edward B. Arnett, Steven R. Belinda, Shawn Gray, Mike Ielmini, Brian Logan, Matt Pieron, and Ian Tator 21 Habitat Improvement and Water Supplementation........................................................................................................ 363 Randy T. Larsen, Paul R. Krausman, Nicole Nielson, Jill Randall, Daniel D. Summers, and Covy D. Jones 22 Migration............................................................................................................................................................................. 383 Matthew Kauffman, Rhiannon Jakopak, Lucas Olson, Anna Ortega, Jill Randall, Gabe Rozman, Jodi Berg, Scott Bergen, Julie Garcia, Evan Greenspan, Mark Hurley, and Cody Schroeder

Section V  The Future 23 Challenges and Opportunities for the Future Conservation of Black-tailed and Mule Deer..................................... 397 Paul R. Krausman and James R. Heffelfinger Bibliography................................................................................................................................................................................ 405 Index............................................................................................................................................................................................. 497

List of Figures Figure 1.1  Primitive deer species that form the foundation of the deer family, Cervidae, include A) Stephanocemas, B) Dicrocerus, and C) Procervulus. Illustrations by Randy Babb........................................................................................................ 4 Figure 1.2  Five million years ago, 3 types of mid-sized deer appear in the fossil record of North America: A) Eocoileus, B) Odocoileus, and C) Bretzia. Illustrations by Randall Babb....................................................................................... 5 Figure 1.3  Physical differences among black-tailed and mule deer subspecies and ecotypes: A) Sitka black-tailed deer, B) Columbian black-tailed deer, C) mule deer - California ecotype, D) mule deer - desert ecotype, E) mule deer - Rocky Mountain ecotype. Illustration by Randall Babb, based on Geist (1990)...................................................................................... 16 Figure 1.4  Mature Tiburón Island mule deer harvested on Tiburón Island. Photo by Derick Lopez........................................ 17 Figure 1.5  Young male mule deer on Cedros Island with lack of brow tines, buff color instead of white undersides, and dark dorsal stripe. Photo by José Antonio Soriano.................................................................................................................. 17 Figure 1.6  Geographic range and subspecies of black-tailed and mule deer in North America. Cartography by Sue Boe...... 21 Figure 2.1  The first mule deer described for science was based on a deer shot 17 September 1804 by a member of the Lewis and Clark expedition and subsequently described by Gass (1807). Illustration by Randall Babb...................................... 26 Figure 2.2  Building of railroad lines in the United States between 1850 and 1890 opened the West to farming, ranching, logging, and mining. Between 1860 and 1890, the total railroad mileage in the region west of the Mississippi River increased from 2,175 miles (3,500 km) to 72,389 miles (116,500 km), thus ushering in the exploitation of, and forever changing, western North America. This illustration depicts the 1879 construction of a temporary winter bridge crossing the ice of the Missouri River, Dakota Territory. F. Jay Haynes, artist; image courtesy of State Historical Society of North Dakota 0714-00001.......................................................................................................................................................... 28 Figure 2.3  Unregulated hunting decimated big game populations across the West in the late 1800s. This 1886 hunting party, in what is now the North Dakota badlands, harvested 11 mule deer (3 fawns, 4 adult females, and 4 adult males), and 4 bighorn sheep; (1 lamb, 1 adult female, and 2 adult males). By 1905, mule deer were becoming a rare sight and bighorns had been extirpated from the state. Osborn Photo Studio, Image courtesy of State Historical Society of North Dakota 0119-00001......................................................................................................................................................................... 29 Figure 2.4  Writings of Theodore Roosevelt, John Muir, and others helped change public attitudes regarding wildlife and conservation, leading to the development of the North American Model of Wildlife Conservation. Image courtesy of United States Biological Survey Collection, United States Fish and Wildlife Service Museum and Archives............................ 30 Figure 2.5  Aldo Leopold (A) gave wildlife managers the textbook for managing mule deer and other wildlife. Carl Shoemaker (B) drafted the Federal Aid in Wildlife Restoration Act, and Senator Key Pittman (NV; C) and Representative A. Willis Robertson (VA; D) sponsored the Act that provided states with a funding source to put wildlife management on the ground. Images courtesy of the Aldo Leopold Foundation and University of Wisconsin-Madison Archives, National Wildlife Federation Collection, United States Fish and Wildlife Service Museum Archives, and United States Senate Historical Office........................................................................................................................................... 31 Figure 2.6  Trapping, poisoning, and hunting with dogs have long been used as a means of predator control to protect livestock and game animals. This photograph is of wolfer Alfred Benson and his dogs and was taken in southwestern North Dakota around 1902. Image courtesy of State Historical Society of North Dakota 0227-00002....................................... 38 Figure 2.7  Fire suppression throughout the West has led to significant vegetative changes. In the North Dakota Badlands, fire suppression has resulted in the dramatic expansion of Rocky Mountain juniper. These photographs were taken at the same photo-point in McKenzie County, North Dakota in 1962 (A) and in 2012 (B). Images courtesy of North Dakota Game and Fish Department............................................................................................................................................... 38 Figure 3.1  A) Mule deer, B) Columbian black-tailed deer, C) Sitka black-tailed deer, and D) white-tailed deer. Photos by George Andrejko (A, D), Scott McCorquodale (B), and Kris Larson (C)................................................................................. 45 Figure 3.2  Comparison of metatarsal glands from A) mule deer, B) Columbian black-tailed deer, C) Sitka black-tailed deer, and D) white-tailed deer. Illustration by Randall Babb......................................................................................................... 55

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Figure 3.3  Preorbital glands of A) mule deer B) Sitka black-tailed deer, and C) white-tailed deer. Photos by James Heffelfinger..................................................................................................................................................................................... 55 Figure 3.4  Interdigital glands between the phalanges of deer generate scent and may reduce foot infections. Photo by James Heffelfinger.......................................................................................................................................................................... 56 Figure 3.5  Antlers are complex structures of velvet, nerves, protein, blood vessels, skin, bone. Illustration by Randall Babb, based on the work of Wyatt Heffelfinger.............................................................................................................................. 57 Figure 3.6  Antler size in black-tailed and mule deer increases with age but reaches an asymptote at 6 years. Unpublished data from L. J. Heffelfinger, K. L. Monteith, and L. A. Harveson........................................................................... 59 Figure 3.7  Stotting is an escape gait that is efficient in rugged terrain with many obstacles but also may serve as a visual signal to predators that pursuit is pointless. Photo by Levi Heffelfinger............................................................................. 65 Figure 3.8  Black-tailed and mule deer do not normally have upper maxillary canine teeth but are documented on rare occasions in all members of the Genus Odocoileus. Photo by James Heffelfinger........................................................................ 66 Figure 4.1  Female mule deer in sagebrush in early spring in western Wyoming; sagebrush is a major diet component for many mule deer populations. Photo by Tayler LaSharr............................................................................................................ 74 Figure 4.2  A) Digestible energy intake of pellets (measured in megajoule/fawn/day) and B) dry matter intake of pellets (measured in grams/fawn/day) by newborn mule deer to 18 weeks of age in 3 levels of treatment groups designed to simulate early to late declines in forage quality from summer to autumn of 2005 in Pullman, Washington. Adapted from Tollefson et al. (2010)...................................................................................................................................................................... 77 Figure 4.3  Concentrations of A) fat, B) protein, and C) lactose in milk produced by 24 mule deer from birth to 24 weeks while being fed diets across a range of digestible energy used to simulate an early decline in nutritional quality from summer to autumn of 2005 in Pullman, Washington. Adapted from Tollefson et al. (2011)................................................ 77 Figure 4.4  Male mule deer on winter range shortly after the rut in western Wyoming. Photo by Tayler LaSharr................... 78 Figure 4.5  Length of annual new growth of leaders of bitterbrush (key winter forage for mule deer) relative to water content of snow pack in April (A) and average kidney fat index of female deer collected in March (B) each year as a function of percent bitterbrush in diet during March during a phase of decline (1985–1990) and increase (1991–1998) in abundance in Round Valley, California. Adapted from Pierce et al. (2012a)................................................................................ 85 Figure 4.6  Body mass and ingesta-free body fat (IFBFat) of 2 mule deer that reside in the Wyoming Range in western Wyoming. Both deer were part of the Wyoming Range Mule Deer study from December 2013 to March 2019 and were captured each autumn and spring during that time period (with the exception of 073, which was not able to be captured in Dec 2018). These animals have disparate body sizes, with deer 001 consistently weighing more than deer 073. Nutritional condition of these animals does not correlate with their size, and in many seasons the smaller deer, deer 073, has a higher percentage of body fat compared with the larger deer. This highlights the potential issue of using body mass as an indicator of nutritional condition........................................................................................................................................... 86 Figure 4.7  Conceptual illustration of the relationship between recruitment number and populations size for a large ungulate. In most instances, female deer produce more young than they can feasibly recruit given degree of resource limitation; thus, a portion of those attempted recruits must perish each year. The difference in the number of attempted recruits and those that can be recruited given the capacity to support recruitment is the degree of mortality that is compensatory, and mortality that exceeds that amount become additive. That is, only once mortality exceeds the proportion that would be lost anyway does it become additive. Rate of mortality means nothing relative to interpreting its additive versus compensatory role in a deer population, but instead, consequences of mortality for the population is contingent upon the proximity of the population to nutritional carrying capacity (NCC). Adapted from Monteith et al. (2014b), which was originally based off data contained in McCullough (1979)............................................................................ 88 Figure 4.8  A female mule deer on winter range with her 3 offspring in western Wyoming. Black-tailed and mule deer are highly fecund; most commonly give birth to twins, and occasionally will produce and successfully rear 3 young to weaning. Photo by Tayler LaSharr.................................................................................................................................................. 89 Figure 4.9  A male mule deer at 2.5 years old (A) resembling the characteristic size of a 1.5-year-old deer from the region, and at 3.5 years old (B) resembling the characteristic size of a 2.5-year-old deer from the region; this deer was born to an adult female deer following the severe winter of 2016–2017 in the Wyoming Range in western Wyoming. Severe winter conditions led to high levels of starvation throughout the population, and in this instance, almost certainly resulted in the transmission of a negative maternal effect that is hampering growth of this male................................................ 90

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Figure 4.10  Mean nutritional condition (ingesta-free body fat; IFBFat) in spring as a function of lambda (annual population growth) of mule deer in the Sierra Nevadas in California from 1991–2008. The point wherein mean nutritional condition results in a stable population reflects the position of animal-indicated nutritional carrying capacity (NCC), wherein nutritional levels above that point reflect nutritional potential for growth and nutritional levels below that position reflect a population exceeding the capacity of the habitat to sustain the population. Adapted from Monteith et al. (2014b).................................................................................................................................................................................... 91 Figure 4.11  Population size (solid circles with standard error bars) relative and percent ingesta-free body fat (IFBFat; white diamonds with standard error bars) of adult female mule deer in March from 1985 to 2009 in the Sierra Nevadas in California. Notably, 1992 and 1998 (emphasized in red) represent 2 years of nearly identical IFBFat with corresponding similarities in relatively stable population growth, which was expected at the near 6.7% IFBFat for animal-indicated nutritional carrying capacity (NCC) in this population. In 1992, population abundance was low as was April snowpack (6.2 inches [15.7 cm]), whereas in 1998, population abundance was high as was April snowpack (18 inches [45.7 cm]). The interactive roles of density dependence along with forage growth as dictated by winter snowpack resulted in the population during both years being at NCC, as was appropriately reflected in March IFBFat. Interpreting expectations for population growth based solely on abundance or on moisture conditions would have led to erroneous conclusions; however, the approach to animal-indicated NCC inherently integrates degree of density dependence as determined by per capita availability of food. Adapted from Monteith et al. (2014b)................................................................... 92 Figure 4.12  Female mule deer standing in a recent burn in previously coniferous forest of the Intermountain West in western Wyoming. Photo by Tayler LaSharr.................................................................................................................................. 92 Figure 4.13  The classic example of the irruption of mule deer between 1905 and 1940 on the Kaibab Plateau in Arizona serves as a lesson in history and likely context to understanding deer populations today. The coinciding cessation in regular surface fires in the 1890s and dramatic reduction in sheep grazing, likely led to a rapid rise in the carrying capacity (K) of the plateau. The rise in K combined with intensive removal of predators (displayed by the horizontal lines) probably led to the irruption in deer abundance, likely an overshoot of K, followed by a population crash. The severe irruption resulted in intense herbivory and probably reduction in carrying capacity as continued predator removal failed to support recovery in the deer population. Redrawn from Leopold (1943)........................................... 93 Figure 5.1  A life cycle diagram of mule deer representing 3 age classes: fawn (fawn or f; 0–6 months old), juvenile (j; 7–18 months old), and adult (a; >18 months old). This harvest-pulse model assumes a 1 December anniversary date and a 1 June birth pulse. Each circle represents the number of animals (N) in each age and sex class (female [f] and male [m]). Fecundity (B) occurs midyear; therefore, survival (S) is prorated for half a year in the recruitment term. Sex ratio (r, proportion of female fawns) is typically close to even, but it is included here for completeness.............................................. 96 Figure 5.2  A simplified life cycle diagram including only female (f) mule deer in 2 age classes: juvenile (j; 7–18 months old) and adult (a; >18 months old). This harvest-pulse model assumes a 1 December anniversary date and a 1 June birth pulse. Each circle represents the number of animals (N) in each age class and is influenced by fecundity (B) and survival (S)............................................................................................................................................................................... 97 Figure 5.3  Population growth rate (λ) of mule deer as a function of recruitment (fawns/female) and adult female survival. The contour line where λ = 1.0 delineates population stability....................................................................................... 98 Figure 5.4  Population growth rate (λ) of mule deer as a function of over-winter fawn survival and adult female survival with 0.65 fawns per adult female on 1 December. The contour line where λ = 1.0 delineates population stability........ 98 Figure 6.1  Three deer with chronic wasting disease (CWD). A) An apparently healthy deer as seen throughout most of the disease course: this deer tested positive for CWD on tonsil biopsy. B) A deer in the early terminal phase of the disease: flanks tucked up, enlarged fluid-filled rumen, abnormal ear position, prominent points of the shoulders and hips, and hair standing up. C) An emaciated deer consistent with end-stage disease. Photos by M.W. Miller, Colorado Parks and Wildlife (A and B); Justin Binfet, Wyoming Game and Fish Department (C)...................................................................... 104 Figure 6.2  Systemic deer adenovirus infection causing characteristic hemorrhagic disease lesions in the lungs of a black-tailed deer. Note the widened interlobular septae (walls) and the thickened, semi-opaque material over portions of the lung indicative of severe pleural edema. Multiple dark hemorrhages fill entire lung lobules and free fluid surrounds the dorsal and ventral margins of the lungs. Photo courtesy of California Department of Fish and Wildlife............................ 105 Figure 6.3  Dictyocaulus lungworms in mule deer lungs. Photo c­ ourtesy of Alberta Fish and Wildlife.................................112 Figure 6.4  Bot fly larvae in a mule deer. Photo courtesy of Alberta Fish and Wildlife...........................................................116 Figure 6.5  Deer keds, also known as louse flies or hippoboscid flies, on a mule deer. Photo courtesy of Alberta Fish and Wildlife...................................................................................................................................................................................116

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Figure 6.6  Chewing lice on a mule deer. Photo by W. M. Samuel, University of Alberta.......................................................116 Figure 6.7  A black-tailed deer with hairloss syndrome (HLS). Photo by Gregory A. Green...................................................117 Figure 6.8  Winter ticks on the chest of a mule deer. Photo courtesy of Alberta Fish and Wildlife.........................................118 Figure 6.9  Two black-tailed deer males with abnormally shaped antlers, thickened at their base by numerous growths, and with retained velvet. Photo by Connie Cushing, California...................................................................................................119 Figure 6.10  A mule deer with rumen acidosis. The rumen is filled with corn (A) and the abomasum is severely ulcerated because of the acidic contents of the stomach (B). Photo courtesy of Colorado Parks and Wildlife.......................... 120 Figure 7.1  Management recommendations for antlerless harvest in Montana in mountain-foothill mule deer populations, for the management objective of maintaining a stable population size at the long-term average. This figure is from Mackie et al. (1998) and based on long-term monitoring and research data in Montana during the 1960s through the 1990s. These management recommendations have formed the basis for antlerless harvest management in the Mountain-Foothill Population Management Unit in Montana since 2001 (Montana Fish, Wildlife and Parks 2001)................ 136 Figure 7.2  Management recommendations for antlerless harvest in Montana in prairie-breaks mule deer populations, for the management objective of maintaining a stable population size at the long-term average. This figure is from Mackie et al. (1998) and based on long-term monitoring and research data in Montana during the 1960s through the 1990s. These management recommendations have formed the basis for antlerless harvest management in the PrairieBreaks Population Management Unit in Montana since 2001 (Montana Fish, Wildlife and Parks 2001).................................. 137 Figure 8.1  Bivariate plots of niche partitioning based on elevation and slope (left) and on logged forest and xeric grasslands (right). Ellipses are 95% confidence intervals for domestic cattle, North American elk, and mule deer, across spring, summer, and autumn, on the Starkey Experimental Forest and Range, Oregon, 1993–1995 (from Stewart et al. 2002)............................................................................................................................................................................................. 144 Figure 8.2  Niche dynamics of selected North American native, feral, and domestic ungulates based on elevation and topography. Illustration by Randall Babb......................................................................................................................................145 Figure 8.3  Overlap in distributions of black-tailed and mule deer with livestock and feral ungulates in western North America. The distribution of mule deer is from Chapter 1; other distributions are adapted from Bureau of Land Management (2020); distributions are based on data from 1993 to 1995.................................................................................... 152 Figure 9.1  Northern Forest Ecoregion in relation to other ecoregions throughout the range of black-tailed and mule deer. Map courtesy Mule Deer Working Group, adapted by Laura Wolf.................................................................................... 162 Figure 9.2  The diverse Northern Forest Ecoregion is best characterized by large public forests. Photo courtesy of Laura Wolf, Idaho Department of Fish and Game....................................................................................................................... 163 Figure 9.3  Changes in deer forage availability during succession in coniferous forests. Age spans shown are rough averages for Douglas-fir-Englemann spruce forests of the Northern Forest Ecoregion. Illustration by Randall Babb, based on Wallmo and Schoen (1981:figure 46).............................................................................................................................174 Figure 9.4  Dense forest canopies across the Northern Forest Ecoregion present considerable detection challenges for mule deer surveys, particularly from aircraft platforms. Conducting surveys with ground snow cover improves observability. Surveying before deer cast their antlers improves accuracy of cohort structure estimates. Photo courtesy of British Columbia Forestry, Lands, and Natural Resource Operations......................................................................................175 Figure 10.1  Coastal Rainforest Ecoregion in relation to other ecoregions throughout the range of black-tailed and mule deer. Map courtesy Mule Deer Working Group, adapted by Laura Wolf........................................................................... 180 Figure 10.2  This watershed on northeastern Chichagof Island, Alaska, 2010, exemplifies the varied habitat available to Sitka black-tailed deer. Forested valleys with interspersed extensive muskeg meadows transition through steep forested slopes to high alpine meadow ridges. Harvested stands (center left) typically occur in valleys and lower slopes at elevations below 1,500 feet (457 m). Photo by Phil Mooney.................................................................................................... 182 Figure 10.3  Sitka black-tailed deer contend with significant snow in coastal areas of Alaska and British Columbia, while deep snow conditions are more limited to areas interior from the coast in the central and southern portions of the ecoregion. Sitka black-tailed deer, Prince of Wales Island, Alaska, December 2018. Photo by Jim Baichtal............................ 183 Figure 10.4  During the most severe winters, deep snow can accumulate in the forest and up to the high tide line, forcing Sitka black-tailed deer out onto the beach where they remain until rising temperatures and precipitation consolidate the snow enough to allow deer to walk on top. Sitka black-tailed deer, Chichagof Island, Alaska, March 2007. Photo by Steve Lewis, Alaska Department of Fish and Game........................................................................................... 184

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Figure 10.5  Black-tailed deer are less fecund than mule deer and often produce singleton litters, but twins are also common. Depending on population health and age structure, as much as 66% of litters may consist of twins. Columbian black-tailed deer, western Washington. Photo by Gregory A. Green.......................................................................................... 185 Figure 10.6  Within the same litter, newborn male black-tailed deer fawns (bottom; 20 inches [51 cm] long, 4.85 pounds [2.2 kg]) are often slightly larger and heavier than a female twin (top; 19 inches [48.5 cm] long, 3.75 pounds [1.7 kg]). Sitka black-tailed deer, Prince of Wales Island, Alaska, June 2012. Photo by Karin McCoy, Alaska Department of Fish and Game.............................................................................................................................................................................. 186 Figure 10.7  In the northern part of the ecoregion, deer often die of starvation and freeze from exposure on beaches during severe winters when heavy snow accumulates in the forest and along the high tide line. Bug Island, Alaska, March 2007. Photo by Steve Lewis, Alaska Department of Fish and Game............................................................................... 190 Figure 10.8  Population surveys using direct observations are difficult to conduct in the Coastal Rainforest Ecoregion because of the secretive nature of black-tailed deer and the densely forested environments where they occur. Columbian black-tailed deer, Coastal Range, Oregon, 2020. Photo by Keith Kohl........................................................................................191 Figure 10.9  Black-tailed deer in the Coastal Rainforest Ecoregion are very adept at swimming between islands. Sitka black-tailed deer, Auke Bay, Alaska, May 2019. Photo by Karin McCoy.................................................................................... 194 Figure 10.10  When humans and deer live in close proximity, nuisance complaints may arise if commercial or ornamental trees and plants become attractive forage to deer. Columbian black-tailed deer, northwest Washington. Photo by Gregory A. Green.................................................................................................................................................................... 197 Figure 11.1  Intermountain West Ecoregion in relation to other ecoregions throughout the range of black-tailed and mule deer. Map courtesy of the Mule Deer Working Group, adapted by Laura Wolf................................................................. 204 Figure 11.2  Basin and range topography typical of the Intermountain West Ecoregion Photo by Kelley M. Stewart........... 205 Figure 11.3  Relative sources of mortality for mule deer predominantly occupying the Intermountain West Ecoregion in Utah, 2010–2018 (Utah Division of Wildlife Resources 2019)................................................................................................ 208 Figure 11.4  Adult females and their young are dependent on free water within the largely arid portions of the Intermountain West Ecoregion, such as the Great Basin of Nevada. Photo by James Nelson.....................................................210 Figure 11.5  Disturbance associated with mining in the Intermountain West, Nevada: A) land disturbance as a result of mining operation and B) a closeup of vehicles from photo A to illustrate the scale of the disturbance. Note the size of the haul trucks, indicated by black arrows, next to the utility truck (similar in size to a standard pickup truck) illustrated by the white arrow. Photo by Marcus Blum...................................................................................................................................... 212 Figure 11.6  Pinyon-juniper woodland with dense canopy has little to no understory vegetation. Note the absence of any herbaceous plants, such as forbs and grasses, and most of the shrubs have little to no growth. This dense woodland provides little to no forage for mule deer, although it does provide thermal cover for mule deer during hot summers. Photo by Jason Gundlach...............................................................................................................................................................214 Figure 12.1  Great Plains Ecoregion in relation to other ecoregions throughout the range of black-tailed and mule deer. Map courtesy of Mule Deer Working Group and adapted by Laura Wolf....................................................................................218 Figure 12.2  Native prairie, steadily diminishing throughout the Great Plains, provides excellent forage and structural habitat for mule deer throughout the year. Photo by Tom Perry...................................................................................................219 Figure 12.3  General variability of temperature and precipitation in the Great Plains Ecoregion, 1970–2020. Map by Samantha Nichols, data from AdaptWest (2020)......................................................................................................................... 220 Figure 12.4  A mule deer herd in a landscape of rangeland, irrigated farmland, power lines, energy development, and road development in the Texas Panhandle, a common occurrence in the Great Plains Ecoregion. Photo by Levi Heffelfinger................................................................................................................................................................................... 227 Figure 12.5  Where available, mule deer make use of less-altered landscapes in the Great Plains Ecoregion. Photo by Levi Heffelfinger........................................................................................................................................................................... 232 Figure 12.6  Geographical distribution of private prescribed burn association focal areas in the central Great Plains of the United States. Map by Samantha Nichols, data from the Great Plains Fire Science Exchange (www​.gpfirescience​.org, accessed 26 Oct 2020).................................................................................................................................................................. 234 Figure 12.7  A small mule deer herd takes advantage of readily available forage in a stored hay yard in central South Dakota, which often causes financial hardships to private landowners and lowers social tolerance during severe winters. Photo by Andrew Lindbloom....................................................................................................................................................... 236

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List of Figures

Figure 12.8  Strong recruitment and herd growth of mule deer in the Great Plains, even in northern latitudes with snow and cold temperatures, can be experienced following periods of low deer densities, adequate precipitation, and mild winters. Photo by Andrew Lindbloom.......................................................................................................................................... 237 Figure 13.1  California Chaparral and Oak Woodlands Ecoregion in relation to other ecoregions throughout the range of black-tailed and mule deer. Map courtesy Mule Deer Working Group and adapted by Laura Wolf...................................... 242 Figure 13.2  Location of major mountain ranges, Great Central Valley, San Francisco Bay, and Sacramento and San Joaquin rivers within the California portion of the California Chaparral and Oak Woodlands Ecoregion................................ 243 Figure 13.3  Chaparral-oak woodlands plant community in black-tailed deer range in Northern California. Photograph by David Casady........................................................................................................................................................................... 245 Figure 13.4  Oak woodlands in central California. Photograph by David Casady................................................................... 247 Figure 13.5  Mule deer female and fawn in the San Joaquin Valley, California. Note the wide tail stripe pattern on this ecotype. Photograph by David Casady......................................................................................................................................... 248 Figure 13.6  A mixed group of mule deer on oak woodlands winter range in the southern Sierra, California. Photograph by Evan King............................................................................................................................................................. 251 Figure 13.7  Mule deer foraging in chaparral-oak woodland in central California. Photograph by Evan King...................... 253 Figure 14.1  Southwest Deserts Ecoregion in relation to other ecoregions throughout the range of black-tailed and mule deer. Map courtesy Mule Deer Working Group, adapted by Laura Wolf.................................................................................... 258 Figure 14.2  The Mojave Desert and its iconic Joshua-tree is the smallest of the 4 North American deserts. Photo by Levi Heffelfinger........................................................................................................................................................................... 259 Figure 14.3  The Chihuahuan Desert differs from other deserts in that it receives more summer rain in the form of monsoons and colder winters. Photo by Erin Duvuvuei.............................................................................................................. 260 Figure 14.4  The Sonoran Desert is rich in tree species and gigantic columnar cacti, which give it the appearance of a predominantly tree-like landscape. Photo by George Andrejko.................................................................................................. 261 Figure 14.5  Artificial water sources of all designs are increasingly important on a human-altered landscape in the Southwest Deserts Ecoregion. Photo by Tim Carlson.................................................................................................................. 271 Figure 15.1  Colorado Plateau Ecoregion in relation to other ecoregions throughout the range of black-tailed and mule deer. Map courtesy Mule Deer Working Group, adapted by Laura Wolf.................................................................................... 276 Figure 15.2  An oakbrush-aspen interface on mule deer summer range on the Uncompahgre Plateau, Colorado. Photo by Chad J. Bishop, Colorado Parks and Wildlife......................................................................................................................... 278 Figure 15.3  Mule deer on heavily used sagebrush winter range. Understanding density dependence is a key aspect of deer population and habitat management. Photo by David J. Freddy, Colorado Parks and Wildlife.......................................... 282 Figure 16.1  Population model for black-tailed and mule deer. Here we assume that the important biology can be captured by 2 age classes, juveniles and adults. Juveniles are recruited into the population as a proportion (R) of the adult female population. The recruitment term R can be informed by data in the form of age ratio estimates. At the next time step, juvenile animals are either harvested or transition to the adult class at some rate (Sj) representing survival from natural causes of mortality. The adult population is a function of the incoming juvenile animals and those adults that survive natural causes (Sa) and harvest to remain in the population. The model is meant to frame a discussion of population monitoring and highlight the relatively few parameters that can be measured in the field. Inputs to the population model, data, are represented by boxes........................................................................................................................ 292 Figure 16.2  Comparisons of hypothetical sample and target population definitions. The sample population is often much smaller than the target population (A). Making the sample population match the target population can have advantages for monitoring and simplify inference (B)................................................................................................................. 293 Figure 16.3  Comparisons of sampling designs for wildlife monitoring. The sampling frame defines the set of potential spatial units. Simple random sampling selects units while assuming equal probability of being selected. Stratified random sampling divides the population up into more homogenous sub-populations before selecting units. Cluster sampling groups spatial units and then randomly selects from the set of groups........................................................................ 296 Figure 16.4  Resulting binomial confidence limits when survival and the number of collared deer are assumed known. The width of the confidence interval is contingent on the value of survival. The graphic depicts confidence interval width when survival is 0.85 and 0.5, values that approximate an average estimate for adult females and fawns....................... 300

List of Figures

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Figure 17.1  Hunting and harvest of black-tailed and mule deer is a critical component and product of deer management. Photo courtesy Jim Baichtal................................................................................................................................... 308 Figure 17.2  Check stations or field sampling provide an important opportunity for deer managers to engage directly with hunters and collect harvest information. Photo by Oregon Department of Fish and Wildlife.............................................318 Figure 17.3  Multiple factors and sources of information interact to affect how deer seasons and hunting opportunities are developed. Graphic by Don Whittaker....................................................................................................................................319 Figure 18.1  Contemporary management requires science and the art of human dimensions to create landscapes that provide habitat for wildlife and the humans that enjoy them (Artwork by Wyatt Heffelfinger).................................................. 322 Figure 18.2  Changes in hunter numbers and revenues for Wyoming resident deer license holders, 2012. Total revenues include expected Wildlife Restoration funds appropriated to the state. Additional reference materials used: Watson et al. (2007). .......................................................................................................................................................................................... 328 Figure 19.1  Oil and gas development potential in the United States Intermountain West (Copeland et al. 2009) illustrating the potential for oil and gas development (areas in red have the highest potential and tan have the lowest). Black dots show producing (active or inactive) well locations..................................................................................................... 335 Figure 20.1  Oil and gas pad infrastructure and associated roads remove habitat and can result in behavioral avoidance of otherwise suitable habitat. Photo by Ed Arnett........................................................................................................................ 353 Figure 20.2  Wind turbines remove habitat for deer and other wildlife and also may generate behavioral avoidance of otherwise suitable habitat. More research is needed to understand the effects of renewable energy development on blacktailed and mule deer. Photo by Ed Arnett.................................................................................................................................... 354 Figure 20.3  Roads are pervasive across all ecoregions for black-tailed and mule deer. Paved and unpaved roads remove habitat, may create behavioral avoidance of surrounding habitat, and present barriers to migratory movements. Photo by Ed Arnett....................................................................................................................................................................... 356 Figure 20.4  Mitigating vehicle collisions with deer is important for human and animal safety. Overpasses like this one can reduce these collisions and allow for safe passage by deer and other animals and connect their habitats. Photo by Leon Schatz and Gregory Nickerson, Wyoming Migration Initiative......................................................................................... 356 Figure 20.5  A) Sagebrush plants (green) are being overrun by non-native cheatgrass. Photo by Jennifer Strickland, U.S. Fish and Wildlife Service. B) In August and September 2007, a lightning strike sparked the 48,000-acre (19,425-ha) Castle Rock wildfire near Ketchum, Idaho. Cheatgrass helped fuel the fire. Photo by Kari Greer, U.S. Fish and Wildlife Service.......................................................................................................................................................................................... 357 Figure 21.1  Robust response of desired vegetation (aspen) to prescribed fire in western Wyoming: pre-burn (A) including lop and scatter of conifer trees, immediate post-burn (B), 1 year after fire (C), and 2 years post-burn (D). Treatment included mechanical slash prior to a prescribed burn during July. Photo by Jill Randall.......................................... 366 Figure 21.2  Image of an Ely chain on a second pass as it is pulled by two bulldozers to improve habitat for mule deer in Utah, USA. Photo by Nicole Nielsen........................................................................................................................................ 367 Figure 21.3  Mulching of pinyon-juniper trees with a bullhog on an excavator to promote growth of forbs, grasses, and shrubs important to mule deer. Photo by Nicole Nielsen............................................................................................................. 369 Figure 21.4  Mowing of a shrub community in Wyoming, USA to promote forbs and grasses along with creation of diversity (heights; species composition) to improve habitat for mule deer. Photo by Jill Randall.............................................. 370 Figure 21.5  A pipe harrow pulled behind a tractor in a sagebrush plant community to improve habitat for mule deer. This method creates more soil disturbance than mowing which can be beneficial in some situations. Photo by Jill Randall... 371 Figure 21.6  A Lawson aerator pulled behind a tractor in a sagebrush plant community. The paddles on the drums of this aerator create microsites favorable to seedling growth and establishment and can be used to improve habitat by promoting growth of forbs and grasses. Photo by Jill Randall.................................................................................................... 372 Figure 21.7  Response (modeled through a resource selection function at the 3rd order, Johnson 1980) of a female mule deer during winter to a lop and scatter project in Utah, USA designed to remove encroaching conifers from sagebrush. The project (hashed area) was completed in late fall of 2014 and mule deer locations are shown as dots. Selection coefficients for this treatment showed increasing strength (preference for treated areas) in the subsequent 4 years following treatment after accounting for anthropogenic, topographic, and other vegetative covariates. Relative probabilities of use are depicted as high (red), medium high (orange), medium (yellow), medium low (light green), and low (dark green). Image by Randy Larsen and Ryan Howell....................................................................................................... 373

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Figure 21.8  Aerial application of herbicide in a sagebrush plant community to control invasive grasses and improve habitat for mule deer. Photo by Jill Randall................................................................................................................................. 374 Figure 21.9  Hand planting of shrub seedlings to restore habitat. Although expensive and time-intensive, this technique can help improve success of restoration efforts. Photo by Nicole Nielsen................................................................................... 377 Figure 21.10  Mule deer at water sources, including lactating female at a guzzler (A), male visiting a guzzler with fencing removed for easier access (B), small group at a spring during November when many wildlife water developments can be frozen (C), and mature male licking ice from a guzzler that is frozen in November (D). Photos by Randy Larsen....... 378 Figure 22.1  Mule deer in the American West typically migrate from low-elevation winter ranges to high-elevation summer ranges. The San Francisco Peaks herd in Arizona is one of many mule deer herds in the West that have recently been mapped from global positioning system data, allowing delineation of low-, medium-, and high-use corridors and stopover areas. Redrawn with permission from Kauffman et al. (2021b).................................................................................... 384 Figure 22.2  Some Sitka black-tailed deer migrate above tree line to lush alpine areas in the summer and then back down to subalpine areas when those meadows cease to be productive. Photo by Jim Baichtal................................................. 385 Figure 22.3  Mule deer encounter many fences along their migrations. Wildlife and land managers, who have long used local knowledge to target and convert problem fences to wildlife friendly design, are increasingly using detailed maps of migration corridors to guide such conservation efforts and allow free passage of animals during their seasonal migrations. Photo by Mark Gocke, Wyoming Game and Fish Department................................................................................ 389 Figure 22.4  Mule deer on the Red Desert to Hoback migration must navigate numerous natural and man-made obstacles on their 150-mile journey. These deer are crossing the outlet of Fremont Lake during their fall migration, squeezing through a 0.25-mile bottleneck bordered by the lake and expanding subdivisions from the town of Pinedale, Wyoming. Photo by Tanner Warder, Wyoming Migration Initiative, University of Wyoming................................................... 392 Figure 22.5  Mule deer migration routes for selected portions of their range across the western United States. Mule deer migration can be found throughout their range, but not all herds have been mapped. Vacant areas on the map thus represent areas where mule deer movement data have not yet become available. Image courtesy Wyoming Migration Initiative, University of Wyoming................................................................................................................................................ 393

List of Tables Table 1.1  Classification of black-tailed and mule deer............................................................................................................... 11 Table 1.2  Subspecies of black-tailed and mule deer currently supported by the weight of ecological, morphological, and genetic evidence....................................................................................................................................................................... 20 Table 2.1  Estimated numbers of mule deer in the United States, expressed in thousands of animals from 1950 to 1975 (Connolly 1981a:230). Trend data = increasing (I), decreasing (D), and stable (S). Small numbers of mule deer were reported to occur in Iowa, Minnesota, and Oklahoma. Because of the difficulty in obtaining population estimates and variation in methodologies, these estimates should be considered general trends........................................................................ 33 Table 2.2  Estimated number of mule deer in the United States and Canada, 1976–2020, expressed as thousands of animals. Population trends are expressed as increasing (I), decreasing (D), or stable (S). Small populations of mule deer occur in Oklahoma (~2,000) and the Yukon (~1,000), and vagrants are reported rarely in the Northwest Territories. Because of the difficulty in obtaining population estimates and variation in methodologies used, these figures should be viewed with caution........................................................................................................................................................................ 34 Table 2.3  Estimated number of black-tailed deer from 1950 to 2020 in the United States and Canada expressed as thousands of animals. Information from 1950 to 1976 is from Connolly (1981a:230) unless otherwise noted. Information from 1977 to 2020 was provided by wildlife agency representatives or obtained from published sources, as indicated by footnotes. Trend data = increasing (I), decreasing (D), and stable (S). Because of the difficulty in obtaining population estimates and variation in methodologies used, these estimates should be viewed with caution.................................................. 36 Table 3.1  Mule deer physical characteristics from western North America, USA, 1949–2021................................................. 46 Table 3.2  Black-tailed deer physical characteristics from the west coast of North America, 1956–2021................................. 52 Table 4.1  Trace elements with descriptions of their primary functions, reported concentrations in black-tailed and mule deer, signs of deficiencies, and associated references............................................................................................................ 82 Table 6.1  Overview of selected parasites of black-tailed deer and mule deer...........................................................................111 Table 6.2  Diseases recognized in black-tailed deer and mule deer but rarely causing significant population effects............ 122 Table 7.1  Mortality rates of neonatal mule deer and black-tailed deer by cause as determined from cause-specific mortality research projects. Rates presented represent the mean rate for the entire duration of the studies that reported for a specific cause of mortality.................................................................................................................................................... 126 Table 7.2  Mortality rates of 6–12-month-old mule deer by cause as determined from cause-specific mortality research projects. Rates presented represent the mean rate for the entire duration of the studies that reported for a specific cause of mortality................................................................................................................................................................................... 127 Table 7.3  Mortality rates of adult female mule deer and black-tailed deer by cause as determined from cause-specific mortality research projects. Rates presented represent the mean annual rate for the entire duration of the studies that reported for a specific cause of mortality..................................................................................................................................... 128 Table 8.1  Seasonal percent diet composition by forage class (grass, forb, browse, and succulent) of mule deer, black tailed deer, and sympatric ungulates. Values presented represent the range in percent seasonal diet contribution.................... 146 Table 10.1  Survival estimates of female (♀) and male (♂) Sitka and Columbian black-tailed deer along the west coast of North America (Alaska, British Columbia, Washington, Oregon, and California)................................................................. 187 Table 10.2  Density estimates of Sitka and Columbian black-tailed deer along the west coast of North America (Alaska, British Columbia, Washington, Oregon, and California).............................................................................................. 192 Table 10.3  Home range estimates of female and male Sitka and Columbian black-tailed deer along the west coast of North America (Alaska, British Columbia, Washington, Oregon, and California)..................................................................... 195 Table 11.1  Important forage plants used by mule deer in the Intermountain West Ecoregion, modified after Cox et al. (2009:83)....................................................................................................................................................................................... 206

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Table 12.1  Summary of seasonal mule deer movements based on research of radio-collared deer in states and provinces of the Great Plains........................................................................................................................................................ 224 Table 12.2  Summary of average adult mule deer home range sizes in states and provinces of the Great Plains. Variance expressed as standard error (SE) or range (min.–max.)................................................................................................ 226 Table 12.3  Primary population surveys conducted by state and provincial agencies to monitor mule deer populations in the Great Plains Ecoregion....................................................................................................................................................... 235 Table 14.1  Peak breeding and parturition dates for mule deer in the Southwest Deserts. Adapted from Heffelfinger (2006)............................................................................................................................................................................................ 262 Table 14.2  Southwest Deserts mule deer densities reported by various methods. Adapted from Heffelfinger (2006)............ 266 Table 14.3  Home range estimates for Southwest Deserts mule deer (minimum convex polygon method). Adapted from Heffelfinger (2006)....................................................................................................................................................................... 267 Table 15.1  Reported parturition dates (mean and range) of mule deer across the Colorado Plateau Ecoregion..................... 279 Table 16.1  Description of wildlife disease surveillance methods............................................................................................ 302 Table 16.2  Common sample types used to detect the presence or exposure of disease-causing agents in wildlife................ 302 Table 17.1  Some components, and expected effects, of hunting regulations for black-tailed deer and mule deer (modified from Strickland et al. 1994 and Connelly et al. 2020)..................................................................................................317 Table 18.1  Financial contributions for wildlife conservation, research, and management from 7 sportsmen’s-based non-governmental organizations in the United States and Canada (from Arnett and Southwick 2015)..................................... 324 Table 18.2  Hunting license revenues for states within black-tailed and mule deer range; all types of hunting statelevel data were not available from the later surveys, and these results are for all deer species in 2018 (from Southwick Associates 2012a)......................................................................................................................................................................... 327 Table 21.1  Questions associated with response of mule deer throughout their range in North America to sources of free water and publications addressing them (adapted from Larsen et al. 2012)......................................................................... 379

Foreword Welcome to the most complete collection of information on black-tailed and mule deer in North America. Early works by O. C. Wallmo, W. P. Taylor, V. Geist, and others are considered the classic foundational work on western deer. In the last few years, technology has greatly advanced the collective knowledge of all aspects of black-tailed and mule deer ecology and management. Extended drought in the West and historical wildfires are changing the landscape for deer. Invasive plant species are replacing native vegetation at an alarming rate resulting in decreased habitat. Development of the western landscape has resulted in loss of winter ranges, fragmented habitat, and reduced quality of seasonal ranges. Summer range is influenced by fires, reduced active forest management, and drought, which is reducing the overall productivity of many deer herds. The loss of habitat and the increase in the number and diversity of predators on the landscape have created stresses on populations that were not present a few decades ago. In some cases, these issues have created more deer-human conflicts in urban areas. The identification of seasonal habitat use and migration pathways used by mule deer have allowed biologists to address barriers preventing these movements and to implement policies to conserve important habitat. Mule deer populations reached historical highs in various places from the 1950s to the 1970s, but for many reasons outlined in this book, it is not reasonable to expect we can return to those conditions. As wildlife agencies work to manage blacktailed and mule deer herds to population objectives, the public desires increasingly diversified management. Demands for special hunts segregated into smaller areas, specific methods of take, more desirable season dates, and restricted definitions of legal animal make deer management all the more challenging. As hunter numbers are decreasing, some hunters want deer managers to provide more access to mature males and less competition for them. Balancing mature male management and ample opportunity for everyone has become one of the modern challenges of deer management for western agencies. The editors of this book, James R. Heffelfinger and Paul R. Krausman, have distinguished themselves as the leading authorities on mule deer. Both editors have won the prestigious O. C. Wallmo Award given to the leading black-tailed and mule deer researcher or manager in North America. Both have received multiple publication awards from The Wildlife Society and numerous other awards. The authors in this book have hundreds of years of experience in black-tailed and mule deer management, research, and public involvement. From a retrospective of the history of management to cutting edge research and data analysis, the readers will find that managing deer, restoration of deer habitat, and socio-political issues are not one-size-fits-all. Managing deer populations in Alaska and British Columbia differs greatly from managing deer in the deserts of the Southwest. There is the added complexity of

managing deer herds on public lands versus in areas that are predominantly private land. The saying that deer management is as much an art as it is a science has never been truer. A huge unknown on the horizon is the continued expansion of chronic wasting disease (CWD) across the entire United States. Managers have to follow the best science and manage public perception of harvesting a CWD-positive animal. Misinformation about CWD has also complicated deer management when difficult harvest decisions are made to attempt to control CWD prevalence and spread. The progression of CWD in mule deer has altered how some agencies manage deer. Many other diseases affect deer and the authors do an excellent job of guiding the reader through the many complexities of each one. The Western Association of Fish and Wildlife Agencies (WAFWA) created the Mule Deer Working Group (MDWG) in 1997 to work specifically on black-tailed and mule deer issues that were contributing to a long-term decline in the number of mule deer rangewide during the 1990s. The MDWG created supporting materials for mangers and biologists to aid in habitat management, setting hunting seasons and regulations, guiding future research needs, addressing disease and predation, and generally helping to communicate to the public and other agencies. Many of the authors of chapters in this book have been, or are, current members of the MDWG. O. C. “Charlie” Wallmo’s 1981 book Mule and Black-tailed Deer of North America has been the bible for mule deer information for 4 decades, but much has changed in that time. The MDWG saw the need for a new book anchored in the solid foundation of mule deer science that addressed the current issues facing managers and biologists today and in the future. This required more than a simple update to Wallmo’s book, and this collection of black-tailed and mule deer experts have risen to the occasion and provided just that. Many long-tenured biologists and researches have retired leaving a younger generation of deer biologists. This book connects the great foundation of information from those past generations to serve future generations of deer biologists as they wrestle with the complex issues influencing the management of deer herds and the increased social pressure from hunters, guides, outfitters, land owners, and the public. This book will be the catalyst for new ideas in management and research and create renewed interest in a new generation of biologists emerging from college to focus their careers on deer management and research. Black-tailed and mule deer face many issues throughout their life history. Many of those issues that affect deer herds are beyond the control of a deer biologist. This book will help to identify those issues that are in the control of managers and the wildlife agency. The authors have provided a roadmap for biologists tasked with managing deer herds that may be declining, stable, or increasing.

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xx The MDWG and their collaborators are to be commended for their vision to bring forward a new, fresh compendium of what we know about the ecology and management of this species throughout its range. It is not an easy task to pull together such a diverse group of experts and keep them focused on the task of creating this important work. Finally, to quote Walter P. Taylor from the preface of his 1956 book The Deer of North America: “No bulletin and no book dealing with living creatures is in any sense final. The subject matter is so fascinatingly complicated that no

Foreword contribution can be much more than a progress report.” Editors Heffelfinger and Krausman have compiled the latest progress report including current research, management techniques, effects of climate change, and soci-economic importance of black-tailed and mule deer, which will be of interest for wildlife, students, and the public interested in these 2 icons of the West. Miles Moretti Past President and CEO of the Mule Deer Foundation

Preface Aldo Leopold (1966:227) wrote, “Babes do not tremble when they are shown a golf ball, but I should not like to own the boy whose hair does not lift his hat when he sees his first deer.” Black-tailed and mule deer (Odocoileus hemionus) are keystone species relative to their influence on hunting opportunity, watchable wildlife, cultural heritage, wildlife management, and rural economies. This icon of the West is the most visible and important species of wildlife in western North America with a following of more than 1.4 million hunters (Mule Deer Working Group 2021). A 2016 national survey of hunting, fishing, and outdoor recreation (U.S. Department of the Interior et al. 2016) reported that big game hunters each spend an average of $1,619 each year on equipment and trip-related expenses, which means western black-tailed and mule deer hunters collectively spend about $2.3 billion annually. Deer are not managed for hunters but are held in public trust with all other native wildlife and managed by the responsible agencies for the benefit of all citizens. What camping trip is not enhanced at the sight of wild deer? About 11.8 million people travel away from their home for the primary purpose of watching large land mammals and they spend an average of $769/year, for a total expenditure of more than $9 billion annually (U.S. Department of the Interior et al. 2016). The Mule Deer Working Group, sponsored by the Western Association of Fish and Wildlife Agencies, consists of the leading black-tailed and mule deer authorities in each of 24 states, provinces, and territories in western North America. This working group has been collaborating, producing, and summarizing valuable information about the conservation and management of this species since 1997. With the infrastructure and professional network of the Mule Deer Working Group, it seemed obvious that we had direct access to much of the latest and most-significant mule deer research and management occurring in North America. It is their collaborative network that made this book possible. The mule deer working group was foundational to developing the scope and coverage of the book and specific chapter topics and proposing lead authors. The intended audience of this book is professional wildlife managers, researchers, students, habitat managers, and administrators, but is written in a way to be useful to all deer enthusiasts. Reliable and science-based information is not reserved for those who work in professional conservation careers. All information assembled by the authors of this book is built on the foundation of hundreds of other researchers, managers, and technicians who have devoted years to the accumulation of reliable knowledge of deer ecology and management. This book builds on 2 previous classics about deer in North America: Taylor (1956) and Wallmo (1981a). The authors of the book edited by Taylor (1956) cited >600 manuscripts and when Wallmo (1981a) published his work on black-tailed and mule deer 25 years later, the authors included >1,500 citations with a higher proportion from scientific journals. The

information in this book is supported by 3,000 citations, most of which come from peer-reviewed journals rather than agency reports, conferences, proceedings, and symposiums. The increasing reliance on peer-reviewed work in these volumes is commensurate with the trend in management agencies basing their activities on a higher standard of science. This reflects a more general shift in the ways research is reported and used in the management of deer; managers and biologists use more peer-reviewed information and rely less on popular and gray literature (Barrett and Rodriguez 2021). In a recent survey of state agencies, most were reported to use ≥3 different types of data when making management recommendations: existing management plans, peer-reviewed scientific literature, and expert opinion. Approximately 90% of the agencies reported that an increased use of peer-reviewed literature could improve management recommendations (Barrett and Rodriguez 2021). This book will provide an important portal for managers and researchers to access that information. But what have we learned about black-tailed and mule deer over the past 40–65 years since Taylor (1956) and Wallmo (1981a) were published? Life-history data are often considered passé for deer because they have been the subject of decades of research, but there is still much to learn. As evidenced in this book, nearly 100 authors and deer experts examined most aspects of deer ecology and management over the decades and questions still remain. Although knowledge has advanced, biologists continue to raise questions about basic physiology of deer including information on functions of skin glands, aspects of antler growth, vomeronasal organs, vocalizations, energetic expenditures, stotting, nutritional relationships, the influence of feral ungulates, and how renewable and nonrenewable energy extraction will affect deer populations and their habitats. The authors of each chapter are recognized leaders in the wildlife profession and experts in the topics they write about. Both editors and 3 additional chapter authors are past recipients of the prestigious O. C. Wallmo Award presented every 2 years for outstanding contributions to knowledge and improved management of black-tailed and mule deer in North America. The first section of the book covers Biology and Ecology. Taxonomy of black-tailed and mule deer has been confusing and poorly supported from the beginning, but advances in genetic analyses have provided us with techniques to reduce the number of subspecies from 11 to 5 (Chapter 1). The historical trends in deer populations and their habitat go hand in hand and are covered well in Chapter 2 to provide a foundational understanding of the past to better understand the future. Books like Wallmo (1981a) and this volume are the best place for fundamental information on physical characteristics (Chapter 3) and physiology and nutrition (Chapter 4). This book will not disappoint on those topics and will serve as the most important compendium of that basic information

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xxii for decades. This first section includes a detailed discussion of deer population dynamics (Chapter 5) and the significance of diseases and parasites to individual deer and to deer management (Chapter 6). Finishing out this section are chapters on the ecological relationships with predators (Chapter 7) and an overview of the complexities of competition between this deer species and other native and non-native ungulates that share their landscape (Chapter 8). The second section of the book is devoted to an in-depth look at Ecoregion Habitat and Population Dynamics in geographically distinct ecoregions. Because of the diversity of climate, weather events, geology, vegetation structure, and population dynamics, the Mule Deer Working Group categorized the overall geographic range of black-tailed and mule deer into 7 ecoregions (Chapter 9–15). Within these ecoregions, ecological relationships between deer and their habitat have relevant commonalities; thinking in terms of ecoregions helps managers and researchers in different jurisdictions communicate and collaborate on black-tailed and mule deer conservation (Heffelfinger et al. 2003). The third section of the book, Population Management, contains detailed discussions of the relevant issues faced by those who are responsible for managing deer herds and their habitat. Proper monitoring of deer abundance and important demographic parameters (Chapter 16) are the fundamental first steps to effective deer management. The sustainable harvest of deer only happens because of the science and management experience accumulated from decades of refinement. Chapter 17 explains how harvest is regulated by agencies and how harvest information helps monitor the population and provides feedback that influences adaptive harvest management. Because wildlife resources are held in public trust and managed by agencies, human dimensions (Chapter 18) research has become vital to understanding the desires and expectations of the public. Human dimensions research is also important when finding solutions to human-deer conflict management (Chapter 19). As deer and human populations grow, an increasing trend in conflicts can be expected. The threats to proper habitat function (Chapter 20) and techniques to improve habitat and water availability (Chapter 21) are covered in this book by a team of coauthors that collectively have decades of experience

Preface working on the ground managing and enhancing deer habitat. The great strides made in identifying, mapping, and conserving movement and migration corridors has revolutionized how we view the interconnectedness of our western landscapes. Chapter 22 pulls together this information in one place to give biologists, agency administrators, and decision makers an informative overview of this important topic. Looking into the future is always difficult, but the final chapter (23) discusses the emerging issues in the management of deer and their habitat. What influence will recovered large carnivores and widespread diseases have on deer abundance in the future? The most significant habitat challenges are likely to be human population growth, mineral and energy development, and the complex interrelated factors of climate change, extreme weather events, fire, and invasive species. Interagency collaboration within and among ecoregions will be increasingly important for future conservation of black-tailed and mule deer populations and the habitat upon which they rely. A small amount of redundancy one might find in parts of this volume is desirable as these types of books are rarely read cover to cover by those interested in a particular region or topic. Avoiding all overlap volume-wide would leave unfortunate gaps in certain specific topics. Any gaps in overall coverage should be seen by others as opportunities to complete the knowledge base of this important species. It is our job to be vigilant and effective stewards of blacktailed and mule deer populations and their habitats for those who will come after us. Deer populations will continue to fluctuate in the future as they have in the past and through it all, we must keep our collective eyes on the habitat. If we are successful in conserving and protecting the most important areas and habitat components, we will succeed in maintaining robust and sustainable deer herds. Information in this book provides the foundation for solid sustainable conservation and management of black-tailed and mule deer throughout their range and through that, it is hoped, a greater understanding and appreciation for these wild creatures and the wild places they live. James R. Heffelfinger and Paul R. Krausman 30 August 2022

Acknowledgments Edited books involve a team effort and we had the help of the world’s best black-tailed and mule deer biologists, managers, and researchers to assist us throughout the production of this volume. The Mule Deer Working Group, sponsored by the Western Association of Fish and Wildlife Agencies, provided the organizational infrastructure and network to organize and coordinate this book. Their assistance, review, counsel, and active participation at all stages truly made this book a compendium of the latest, most accurate, and comprehensive black-tailed and mule deer information. We thank the many wildlife professionals working in the field for their attention to detail, willingness to collect data, sharing photos and observations, questions, and their overall contribution to the knowledge and understanding of black-tailed and mule deer. We also thank the hunters, habitat managers, landowners, wildlife enthusiasts, land management agencies, and the public who make ongoing contributions to the conservation and management of our wildlife resources. A. P. Aksyonov, J. R. Allen, C. R. Anderson, S. Anderson, M. Atamian, D. B. Barber, J. F. Baichtal, D. L. Belisle, R. A. Belisle, J. F. Benson, S. Bergen, E. J. Bergman, L. P. Bilyk, S. Blair, R. A. Botta, B. A. Boukall, R. T. Bowyer, A. C. R. Braid, R. D. Brown, D. S. Casady, G. A. Chapman, T. D. Cochran, J. A. Coltrane, R. D. Connors, L. Cornicelli, M. Cox, M. A. Cronin, S. M. Czetwertynski, R. R. Davis, N. J. DeCesare, M. DeVivo, J. Diamond, J. J. Dinsmore, K. G. Downing, O. V. Duvuvuei, B. Ehler, D. M. Elliot, W. H. Ellsworth, J. T. Ensign, D. E. Evans, S. Fitkin, S. P. Floray, P. F. Frame, M. T. Freese, J. T. French, J. Garcia, K. Garcia, S. C. Gardner, S. L. Gilbert, J. D. Gilligan, W. M. Glasgow, N. Graveline, S. P. Gray, J. D. Gilligan, S. L. Griffin, M. G. Grue, E. P. Gustafson, M. A. Hackett, S. J. Hansen, C. N. W. C. Hardie, T. M. Harms, L. A. Harveson, D. A. Haukos, W. L. Heffelfinger, J. Heinlen, K. R. Hersey, P. Hnilicka, A. A. Holland, S. Holm, A. H. Hubbs, K. Huebner, K. S. Huggler, T. Hutchison, S. E. Hygnstrom, W. M. Inselman, D. H. Jackson, N. J. Jackson, L. A. Jaster, M. Jeffress, S. A. Johnson, C. D. Jones, J. T. Jorgensen, B. L. Joynt, M. J. Kauffman, T. Kroeker, J. L. Kolar, T. J. Kreeger, G. W. Kuzyk, C. Lackey, E. Lamontagne, R. T. Larsen, T. N. LaSharr, M. Latofski-Robles, A. Lawson, B. D. Leopold, W. D. Lewis, A. J. Lindbloom, M. Lonner, T. Lonner, D. D. Lopez, K. A. Luttschwager, D. W. Lutz, J. M. Mahoney, L. R. Meduna, K. R. McCaffery, K. R. McCoy, H. W. McKenzie, B. R. McMillan, E. H. Merrill, K. L. Monteith, D. L. J. Moyles, A. Munig, R. R. Nack, R. D. Newberg, S. E. Nielsen, R. L. Nelson, S. L. Nichols, A. S. Norton, A. Ortiz, L. A. Parsons, S. R. Pendergast, C. E. Penner, T. Perry, A. L. Peterson, A. M. Powers, M. J. Pybus, R. V. Rea, E. A. Roche, M. S. Russell, A. P. Schmidt, H. S. Sawyer, C. A. Schroeder, W. Schultz, J. M. Shannon, R. Shinn, L. A. Shipley, K. G. Smith, A. Stephens, S. D. Stevens, M. J. Suitor, K. M. Stewart, B. A. Stillings, J. C. Thalmann, G. W. Telford, S. A. Telford, D. J. Thiele, T. J.

Thier, M. Tonkovich, B. F. Wakeling, K. B. Wallenfang, A. B. D. Walker, S. M. Walker, D. J. Waltee, J. Ward, R. L. Ward, R. W. White, D. G. Whittaker, L. M. Wiechmann, E. Williams, R. M. Wilson, C. A. Wright, and C. J. Yahnke, provided advice, data, consultation, information, models, deer distribution information, opportunities to examine deer closely, and an array of important assistance that enhanced, and made possible, this volume. Chapters were reviewed by J. Allen, R. Babb, J. F. Baichtal, R. Barrett, J. A. Bissonette, R. D. Brown, T. J. Brinkman, T. Buck, James W. Cain III, L. Carpenter, A. S. Cox, M. Cox, D. J. Decker, S. Demarais, J. Diamond, E. Duvuvuei, E. EbadiRad, J. T. Flinders, V. Geist, S. L. Gilbert, E. Goldstein, J. P. Jacobson, J. Jenks, W. Kessler, J. Kie, G. Kuzyk, E. Leonhardt, B. D. Leopold, D. M. Leslie, Jr., D. W. Lutz, J. C. MacDermott, B. McMillian, E. Merrill, M. Miller, D. Naugle, K. Nicholson, C. Ogata, E. Olstead, L. Parsons, D. J. Rinella, P. Rocha, K. A. Schoenecker, H. Schwantje, J. M. Shannon, K. Smith, N. Tatman, I. Tator, K. Tyler, B. F. Wakeling, G. C. White, R. White, and R. M. Williamson. We thank the Alaska Department of Fish and Game, Alberta Fish and Wildlife Division, Arizona Game and Fish Department, British Columbia Ministry of Forest Land and Natural Resources, California Department of Fish and Wildlife, Colorado Parks and Wildlife, Idaho Department of Fish and Game, Kansas Department of Wildlife Parks and Tourism, Montana Fish Wildlife and Parks, Nebraska Game and Parks Commission, Nevada Department of Wildlife, New Mexico Department of Game and Fish, North Dakota Game and Fish Department, Department of Environment and Natural Resources—Northwest Territories, Oklahoma Department of Wildlife Conservation, Oregon Department of Fish and Wildlife, Saskatchewan Ministry of Environment, South Dakota Game Fish and Parks, Texas Parks and Wildlife Department, Utah Division of Wildlife Resources, Washington Department of Fish and Wildlife, Wyoming Game and Fish Department, and Yukon Department of Environment for sharing their black-tailed and mule deer population data and for allowing their employees to work on this important project. F. A. Abarca, G. A. Andrejko, J. F. Baichtal, V. Barr, B. A. Britten, D. S. Casady, J. K. Garcia, J. A. Góngora-Salinas, E. King, A. Tapia-Landeros, M. Latofski-Robles, A. Manriquez, F. A. Méndez-Sánchez, A. Ortiz, J. E. Ponce, A. J. Schornak, C. M. Soria, J. A. Soriano, J. Visser, and B. T. Wilder provided important photos and phenotypic information about subspecies to inform and enhance the volume. Other photographs were provided by the Aldo Leopold Foundation and University of Wisconsin-Madison Archives, Colorado Parks and Wildlife, Mercer International, National Wildlife Federation Collection, Nevada Department of Wildlife, North Dakota Game and Fish Department, North Dakota State Archives, Saskatchewan Ministry of Environment, State

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xxiv Historical Society of North Dakota, United States Biological Survey Collection, United States Fish and Wildlife Service Museum and Archives, United States Senate Historical Office, and Wyoming Game and Fish Department. R. D. Babb provided fantastic illustrations that helped liven the text. S. Boe, J. D. Gilligan, K. R. McCoy, and L. B. Wolf produced ecoregion and range maps for several chapters. Thanks to M. E. Bucci for producing the index. Chapter 2 is based on Professional Paper 133 from the Eastern Sierra Center for Applied Population Ecology. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the United States Government or the employers of any authors or editors. Support for the preparation of the book was provided by the Alaska Department of Fish and Game; Alberta Environment and Parks, Fish and Wildlife Stewardship; Alta Science and Engineering; Arizona Game and Fish Department; Brigham Young University; British Columbia Ministry of Forests, Lands, Natural Resource Operations and Rural Development; Caesar Kleberg Wildlife Research Institute; California Fish and Wildlife Department; Colorado Parks and Wildlife; Idaho Department of Fish and Game; Kansas Department of Wildlife and Parks; Montana Fish, Wildlife and Parks; Mule Deer Foundation; Nebraska Game and Parks Commission; Nevada Department of Wildlife; New Mexico Department of Game and Fish; New Mexico State University; North Dakota Game and Fish Department; Oregon Department of Fish and Wildlife; Saskatchewan Ministry of the Environment; South Dakota Game, Fish and Parks; South Dakota State University; Southwick Associates; Texas A&M University, Kingsville; Texas Parks and Wildlife Department; United

Acknowledgments States Geological Survey; United States Forest Service; University of Wisconsin, Milwaukee; University of Montana; University of Nevada, Reno; University of Pretoria; University of Washington; University of Wyoming; Universidad de Sonora; Utah Division of Wildlife Resources; Utah Division of Wildlife Resources; and Washington Department of Fish and Wildlife. Special thanks to Brigham Young University, R. T. Larson, and B. R. McMillan, for providing funding for publication costs. We also thank CRC Press, especially Alice Oven for her excellent and expeditious work on all aspects of this book. B. Moloney assisted with the proofs. T. Gasbarrini was instrumental in the selection of our publisher and D. G. Hewitt put us in touch with CRC Press at a critical moment to assure a highquality product. Everyone involved with the production of the book have our heartfelt appreciation for their management and conservation of black-tailed and mule deer for today and future generations. This volume is a testimony to the dedication of wildlife biologists for sound stewardship of everyone’s natural resources. Special thanks to J. Pedersen, S. R. Belinda, and M. Moretti of the Mule Deer Foundation for their untiring support of the Mule Deer Working Group and for support and funding for illustrations and distribution of this book.

Editors James R. Heffelfinger is Wildlife Science Coordinator for Arizona Game and Fish Department and Full Research Scientist in the School of Natural Resources and the Environment at University of Arizona, Tucson. He received a B.S. degree from the University of Wisconsin – Stevens Point (1986) with majors in Wildlife and Biology and an M.S. from Texas A&M University – Kingsville (1989). Since 2005, he has served as Chairman of the Mule Deer Working Group sponsored by the Western Association of Fish and Wildlife Agencies. This working group consists of the leading black-tailed or mule deer expert from each of 24 states, provinces, and territories in western North America. James has worked as Manager of Wildlife Operations for Horlock Land and Cattle in South Texas (1989-1990), Research Assistant at Mississippi State University (1990-91), Wildlife Biologist for U.S. Department of the Interior – Bureau of Land Management (1991-92), and for the Arizona Game and Fish Department as Regional Game Specialist (1992-2015) and Wildlife Science Coordinator (2015-present). His interests center on game bird and large mammal conservation, conservation genetics, taxonomy, evolutionary history, wolf recovery, and hunting as the cornerstone of wildlife conservation. James is a Certified Wildlife Biologist, Professional Member of the Boone and Crockett Club, and recipient of the O. C. “Charlie” Wallmo Award for contributions to black-tailed and mule deer knowledge and conservation in North America, Mule Deer Foundation’s Professional of the Year Award, Pope and Young Club’s Lee Gladfelter Memorial Award, Dallas Safari Club’s Conservation Trailblazer Award, and Distinguished Alumnus University of Wisconsin – Stevens Point. He has authored and coauthored >65 scientific papers, 30 book chapters, >300 magazine articles, several TV scripts, and the book Deer of the Southwest published by Texas A&M University Press. James lives in Tucson, Arizona.

Paul R. Krausman is Professor Emeritus from the School of Natural Resources and the Environment, University of Arizona, Tucson. He was raised in North Africa, Europe, and Asia, and returned to the United States for college where he graduated from The Ohio State University with a B.S. in Agriculture (1968). He then served in the United States Air Force in New Mexico and Texas as a research assistant with the space program. During his service, he also attended New Mexico State University and obtained his M.S. degree in wildlife management. Upon his discharge from the Air Force, he attended the University of Idaho where he received his Ph.D. in wildlife science (1976). After graduation he was appointed Assistant Professor at Auburn University (1976-1978) and Professor, and Associate Director of the Arizona Agricultural Experiment Station at the University of Arizona (1978-2007) before accepting the Boone and Crockett Professor of Wildlife Conservation at the University of Montana (2007-2015). He was also Visiting Professor at the Wildlife Institute of India intermittently (1989-2000) and at the Universidade de Trásos-Montes e Alto Douro, Vila Real, Portugal (2005-2006). His research interests primarily revolved around large mammals and their response to anthropogenic influences in arid areas of the world. Paul is a Certified Wildlife Biologist, Wildlife Fellow, Honorary Member of The Wildlife Society, and served as faculty advisor for the student chapters of The Wildlife Society at Auburn, Arizona, and Montana. He has served as editor, associate editor, and guest editor for numerous scientific outlets including the Journal of Wildlife Management, Wildlife Monographs, and the Wildlife Society Bulletin. He is currently the Editor-in-Chief of the Journal of Wildlife Management. Paul has published 41 book chapters, 14 books, >100 conference proceedings, and >270 peer-reviewed monographs and manuscripts. He has received numerous awards for his teaching and research including the O. C. “Charlie” Wallmo Award (1999), the Desert Ram Award (2000), and the Aldo Leopold Memorial Award (2006). Paul currently lives in Santa Fe, New Mexico with his wife, cat, dogs, and horses.

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List of Contributors Carlos H. Alcalá-Galván Profesor-Investigador Universidad de Sonora

David S. Casady Senior Environmental Scientist California Department of Fish and Wildlife

Charles R. Anderson, Jr. Mammals Research Leader Colorado Parks and Wildlife

Darren A. Clark Wildlife Research Program Director Oregon Department of Fish and Wildlife

Edward B. Arnett Adjunct Professor Colorado State University

Orrin V. Duvuvuei Deer Program Manager New Mexico Department of Game and Fish

Peter J. Bauman Natural Resources Field Specialist South Dakota State University Extension

Tavis D. Forrester Wildlife Research Biologist Oregon Department of Fish and Wildlife

Steven R. Belinda Director of Conservation Mule Deer Foundation

Melissa A. Foster Wildlife Biologist Montana Fish, Wildlife, and Parks

Jodi Berg Natural Resource Scientist – Spatial Analyst Alta Science and Engineering

Karen A. Fox Wildlife Pathologist Colorado Parks and Wildlife

Scott Bergen Senior Wildlife Research Biologist Idaho Department of Fish and Game

Lloyd B. Fox Kansas Department of Wildlife and Parks, Retired

Eric J. Bergman Wildlife Research Scientist Colorado Parks and Wildlife

Julie K. Garcia Environmental Scientist California Department of Fish and Wildlife

Gary Bezzant Regional Habitat Program Manager Utah Division of Wildlife Resources

Justin D. Gilligan Wildlife Biologist Alberta Fish and Wildlife

Chad J. Bishop Director, Wildlife Biology Program University of Montana

Shawn S. Gray Mule Deer and Pronghorn Program Leader Texas Parks and Wildlife Department

Vernon C. Bleich Research Professor University of Nevada, Reno

Evan Greenspan Senior GIS Analyst California Department of Fish and Wildlife

R. Terry Bowyer Senior Research Scientist and Professor Emeritus University of Alaska Fairbanks

Justin A. Gude Wildlife Research and Technical Services Bureau Chief Montana Fish, Wildlife, and Parks

James W. Cain III Unit Leader, U.S. Geological Survey, New Mexico Cooperative Fish and Wildlife Research Unit New Mexico State University

Sara J. K. Hansen Statewide Deer Specialist Washington Department of Fish and Wildlife

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List of Contributors

James R. Heffelfinger Wildlife Science Coordinator Arizona Game and Fish Department

Emily K. Latch Professor University of Wisconsin – Milwaukee

Levi J. Heffelfinger Assistant Professor of Research Caesar Kleberg Wildlife Research Institute Texas A&M University - Kingsville

Andrew J. Lindbloom Senior Wildlife Biologist South Dakota Game, Fish, and Parks

A. Andrew Holland Big Game Manager Colorado Parks and Wildlife

Paul M. Lukacs Senior Associate Dean of Research and Graduate Studies University of Montana

Mark A. Hurley Research Supervisor Idaho Department of Fish and Game

Brian Logan National Wildlife Program Lead U.S. Forest Service

Mike Ielmini National Invasive Species Program Coordinator U.S. Forest Service

Ethan S. Lula Wildlife Biologist Montana, Fish, Wildlife and Parks

DeWaine H. Jackson Wildlife Research Supervisor – West Region Oregon Department of Fish and Wildlife Rhiannon Jakopak Research Scientist University of Wyoming William F. Jensen Big Game Biologist North Dakota Game and Fish Department Covy D. Jones Wildlife Section Chief Utah Division of Wildlife Resources Paul R. Krausman Professor Emeritus University of Arizona Matthew Kauffman Unit Leader, U.S. Geological Survey, Wyoming Cooperative Fish and Wildlife Research Unit University of Wyoming Thomas W. Keegan President Sprig Technical Editing and Wildlife Consulting

Kenneth E. Mayer Fire and Invasive Initiative Coordinator Western Association of Fish and Wildlife Agencies Scott M. McCorquodale Regional Wildlife Program Manager Washington Department of Fish and Wildlife Karin R. McCoy Wildlife Biologist Alaska Department of Fish and Game Brock R. McMillan Professor Brigham Young University Luke R. Meduna Big Game Program Manager Nebraska Game and Parks Commission Terry A. Messmer Professor Utah State University Kevin L. Monteith Professor University of Wyoming Miles Moretti Retired President/CEO Mule Deer Foundation

Randy T. Larsen Professor Brigham Young University

Brandon A. Munk Senior Wildlife Veterinarian California Department of Fish and Wildlife

Tayler N. LaSharr Research Scientist University of Wyoming

Nicole Nielson Wildlife Impact Analysis Coordinator Utah Division of Wildlife Resources

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List of Contributors J. Joshua Nowak President, Speedgoat Wildlife Solutions, LLC University of Montana

Thomas R. Stephenson Senior Environmental Scientist California Department of Fish and Wildlife

Lucas Olson Cooperative Mule Deer Biologist Mule Deer Foundation/Arizona Game and Fish Department

Scott D. Stevens Senior Wildlife Biologist Alberta Fish and Wildlife

Anna Ortega Research Scientist University of Wyoming

Kelley M. Stewart Professor University of Nevada, Reno

Sean R. Pendergast Fish and Wildlife Section Head British Columbia Ministry of Forests, Lands, Natural Resource Operations and Rural Development

Daniel D. Summers Habitat Restoration Coordinator Utah Division of Wildlife Resources

Thomas A. Perry Wildlife Biologist Fish, Wildlife and Lands Branch, Saskatchewan Ministry of the Environment Matt Pieron Natural Resource Program Coordinator Idaho Department of Fish and Game Margo J. Pybus Provincial Wildlife Disease Specialist Alberta Fish and Wildlife Jill Randall Big Game Migration Coordinator Wyoming Game and Fish Department Annette Roug Wildlife Veterinarian University of Pretoria, South Africa Gabe Rozman Research Scientist University of Wyoming Cody Schroeder Wildlife Staff Specialist Nevada Department of Wildlife Justin M. Shannon Deputy Director Utah Division of Wildlife Resources Lisa A. Shipley Professor Washington State University Rob Southwick President Southwick Associates

Ian Tator Statewide Terrestrial Habitat Manager Wyoming Game and Fish Department Brian F. Wakeling Game Management Bureau Chief Montana Fish, Wildlife and Parks Andrew B. D. Walker Senior Wildlife Biologist British Columbia Ministry of Forests, Lands, Natural Resource Operations and Rural Development Daniel Walsh Quantitative Ecologist U.S. Geological Survey National Wildlife Health Center C. Leann White Deputy Center Director U.S. Geological Survey National Wildlife Health Center Donald G. Whittaker Ungulate Coordinator Oregon Department of Fish and Wildlife Chad Wilson Public Wildlife Private Lands Coordinator Utah Division of Wildlife Resources Laura B. Wolf Wildlife Biologist Idaho Department of Fish and Game Mary E. Wood State Wildlife Veterinarian Colorado Parks and Wildlife

Section I

Biology and Ecology

1 Origin, Classification, and Distribution James R. Heffelfinger and Emily K. Latch CONTENTS Introduction....................................................................................................................................................................................... 3 Origin of Black-tailed and Mule Deer.............................................................................................................................................. 3 Genesis of the Deer Family (Cervidae)....................................................................................................................................... 4 Appearance of Mid-sized Deer in North America....................................................................................................................... 5 The Eastern and Western Divide.................................................................................................................................................. 6 Proposed Theories Describing the Origin of Black-tailed and Mule Deer.................................................................................. 7 Taxonomy and Classification.......................................................................................................................................................... 10 Cervidae..................................................................................................................................................................................... 11 Odocoileus................................................................................................................................................................................. 12 Odocoileus hemionus................................................................................................................................................................. 12 Subspecies and Ecotypes........................................................................................................................................................... 12 Summary of Geographic Variation in Odocoileus hemionus..................................................................................................... 19 Distribution..................................................................................................................................................................................... 20 Peripheral Observations, Natural Expansions, and Contractions.............................................................................................. 21 Extralimital Translocations........................................................................................................................................................ 22 Ecoregions.................................................................................................................................................................................. 23 Summary......................................................................................................................................................................................... 23

Introduction

Origin of Black-tailed and Mule Deer

Black-tailed and mule deer (Odocoileus hemionus) are an integral part of western North America. Few animals better represent the wild and natural places we value. To properly conserve this species, we must have a foundational understanding of where it came from and its historical and current relationships with other wildlife. Understanding fosters appreciation for wildlife, which creates the fundamental basis for conservation. Distribution of many animals is changing and this chapter updates the rangewide distribution of black-tailed and mule deer as a basis for science-based management. This chapter also traces the evolutionary history of the species through its emergence from the Miocene forms in Eurasia through the tumultuous North American Pleistocene and discusses the potential scenarios that may explain the genetic, phenotypic, and geographic relationships that exist today. This species has been described as comprising as many as 11 subspecies, but most of those are not sufficiently differentiated by genetic or phenotypic information. Advances in genetic analysis tools and a better understanding of physical variability and phylogenetic relationships in the natural world allows for a taxonomic revision of subspecies to bring mule deer taxonomy more in line with the current state of our understanding of the relationships between species, subspecies, and local ecotypes.

The earliest hoofed animals with an even number of toes (Artiodactyla) appeared during the early Eocene Epoch, 56−34 million years before present (YBP; Theodor et  al. 2007). Rabbit-sized ungulate ancestors, such as Diacodexis and other similar forms, were distributed throughout North America and Eurasia (Prothero and Foss 2007, Theodor et al. 2007). Diacodexis possessed a unique artiodactylid ankle bone, the astragalus, which acts as a double pulley providing great flexibility in the hind foot. This bone marks this animal unmistakably as the first known artiodactyl; all even-toed ungulates have this bone. Similar to the artiodactyls that followed, Diacodexis possessed long limbs that facilitated running. Although all 4 (rear) or 5 (front) hoofed toes touched the ground when they walked, most of their mass was supported by the 2 central toes (digits 3 and 4) of each foot. Thus, even at this early stage, the development towards the 2-toed ungulates of today with their vestigial lateral dew claws was apparent. Primitive artiodactyls diversified and increased in abundance throughout the Eocene as the climate became drier and possibly cooler, allowing them to flourish (Metais and Vislobokova 2007). By the close of the Eocene there were several groups of primitive ruminants that were precursors to the cattle, pronghorn, camel, and deer families. A small rabbit-like ruminant like the Archaeomeryx in Asia gave rise to a subsequent

DOI: 10.1201/9781003354628-2

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4 diversification and radiation into forms like Eumeryx in Eurasia. Although antlerless, Eumeryx already possessed many characteristics seen in today’s cervids and bovids, such as no upper incisors, incisor-like lower canines, low-crowned molars, and much reduced first lower premolars (Vislobokova 1997). Evolutionary development of ruminants continued through the Oligocene Epoch (34−24 million YBP) with the appearance of increasingly complex forms such as the family Moschidae. Moschids, similar to the North American Blastomeryx and the Eurasian Dremotherium, are primitive deer-like mammals with no antlers but with exaggerated tusk-like canines (Prothero 2007). A Eurasian form of these sabre-toothed deer, such as Dremotherium, is the most probable ancestor to all cervids. Moschids disappeared by the end of the Miocene, with the exception of 1 genus, the extant musk deer (Moschus spp.). Musk deer of eastern Asia are not actually within the family Cervidae but represent direct descendants of these primitive forms in the family Moschidae. Long, sharp canine tusks are not normally associated with Cervidae today, but the Chinese water deer (Hydropotes inermis) provides an example of a true deer (Cervidae) that lacks antlers and possesses large canines remarkably similar to fossil deer.

Genesis of the Deer Family (Cervidae) Despite the abundance and diversity of native ruminants in North America (Frick 1937), none of these forms gave rise to

James R. Heffelfinger and Emily K. Latch today’s North American deer (white-tailed deer [Odocoileus virginianus], mule deer, moose [Alces alces], caribou [Rangifer tarandus], or elk [Cervus canadensis]). Eurasian deer-like animals, such as the tusked and antlerless Dremotherium, are recognized as the types of primitive ruminants that eventually gave rise to all cervids. Later Miocene forms in the family Lagomerycidae offer important clues, and a probable missing link, to the early development of deer (Gentry 1994). Many of the lagomerycids, such as Procervulus, possessed large canine tusks and forked antlers that were shed, although probably not every year (Fig. 1.1). Thus, with the occasional casting of antlers, Procervulus and related forms were positioned precisely at the genesis of the deer family 18–15 million YBP (Heckeberg 2020). The earliest true deer (Cervidae) appeared in Eurasia in the middle of the Miocene (11.5–10.7 million YBP; Scott and Janis 1987, Hassanin et al. 2012). One of these ancestral deer had small antlers that normally formed a single fork (Fig. 1.1; Dicrocerus). Another Miocene deer, Stephanocemas, had tusk-like canines and antlers that formed a bowl-shaped palm (Gentry 1994, Wang et  al. 2009). The antlers of these early deer were shed annually from long antler bases much like the present-day muntjac (Muntiacus spp.) of Asia (Fig. 1.1). With the evolutionary development of increasingly elaborate antlers, tusk-like canines became much smaller in the deer family (Fig. 1.1; Eisenberg 1987). The antlerless Chinese water deer have prominent canines (Pitra et al. 2004, Groves 2007),

FIGURE 1.1  Primitive deer species that form the foundation of the deer family, Cervidae, include A) Stephanocemas, B) Dicrocerus, and C) Procervulus. Illustrations by Randy Babb.

Origin, Classification, and Distribution although antlered deer have lost their canines entirely or they are very much reduced (e.g., elk). The muntjac and tufted deer (Elaphodus cephalophus) of Asia occupy an intermediate position with small antlers and small canines. Chinese water deer also have a black labial spot on the chin that accentuates the size and whiteness of their large canines. Guthrie (1971) used this observation to infer that the same black spot on many antlered deer (e.g., Odocoileus) was a relic of the past use of canines in social display. It has been hypothesized that the reduction of large canines occurred because the development of elaborate antlers supplanted the need for these teeth as weapons or sexual display organs (Emlen 2008). There is a close relationship between Eurasian roe deer (Capreolus capreolus) and Chinese water deer, with both of those species more closely related to all North and South American deer than any other European or Asian deer species based on genetic analysis (Hassanin and Douzery 2003, Pitra et al. 2004, Groves 2007).

Appearance of Mid-sized Deer in North America There is no record of true (antlered) deer in North America until the close of the Miocene (Webb 2000), when an ancestral deer of some form immigrated from Eurasia by way of Beringia 7–5 million YBP. The earliest deer in North America are represented by 3 forms (Eocoileus spp., Bretzia spp., Odocoileus spp.) that appear nearly simultaneously in the fossil record about 5 million YBP (Webb 2000, Gustafson 2015, Emery-Wetherell and Schilter 2020). Eocoileus gentryorum is found in 5 million-year-old deposits (5.0–4.7 million YBP) in Florida (Fig. 1.2; Webb 2000, Webb et al. 2008). The antlers of Eocoileus projected slightly rearward from the frontal bones and were very similar to present-day pampas deer (Ozotoceros

5 bezoarticus) in South America (Webb 2000) and Eurasian roe deer. Eocoileus was one of the first North American deer, but it was not the ancestor of mule deer because there are fossil Odocoileus in the same Florida deposits (Gustafson 2015). Another very early North American cervid (Bretzia spp.) is found in deposits of similar age (4.98–4.89 million YBP). Bretzia was very similar to a large mule deer in almost all respects except that the antlers were strongly palmate (Fig. 1.2). This deer primarily was found in Washington and California, but more recent fossils (15,000–10,000 YBP) also have been discovered in South Dakota and Nebraska (Fry and Gustafson 1974, Gunnell and Floral 1994, Morejohn et al. 2005, Gustafson 2015). The antler bases were set wider than most deer and broad antler palms were oriented above the head somewhat more like fallow deer (Dama spp.) than moose. Bretzia was probably uncommon but present for most of the last 5 million years in North America and shared that landscape with the ancestor of today’s white-tailed, black-tailed, and mule deer (Gustafson 2015, Gunnell and Floral 1994). The oldest fossils identified as Odocoileus are found in Florida (5.0 million YBP), Kansas (4.9–1.8 million YBP), and Idaho (3.79–3.40 million YBP; Oelrich 1953, Morejohn and Dailey 2004, Gustafson 2015). These fossils consist mostly of molars that were indistinguishable from modern-day whitetailed, black-tailed, and mule deer; however, based on molars alone, it is not possible to distinguish Odocoileus from Bretzia (Wheatley and Ruiz 2006). Emery-Wetherell and Davis (2018) reported that teeth are too variable to use diagnostically to separate closely related ungulates. Morejohn and Dailey (2004) described a nearly complete deer specimen found in northern California they diagnosed as an Odocoileus that was the size of a small elk. This specimen was large (400–579 pounds [182–263 kg]) and possessed upper maxillary canine teeth,

FIGURE 1.2  Five million years ago, 3 types of mid-sized deer appear in the fossil record of North America: A) Eocoileus, B) Odocoileus, and C) Bretzia. Illustrations by Randall Babb.

6 but it had skeletal characteristics that were Odocoileus-like. Despite the large size, presence of upper canines, and lack of any preserved antlers attributed to this specimen, Morejohn and Dailey (2004) considered this to be an early Odocoileus and ancestral to today’s white-tailed and mule deer. A quantitative analysis of this specimen and other Odocoileus material in collections is badly needed to determine the Pliocene source of white-tailed, black-tailed, and mule deer. Kurtén (1975) described another North American deer he called the American mountain deer (Navahoceros spp.) because it reportedly had short, stout leg bones indicative of a life climbing in the mountains. His original type specimen was only an upper and lower jaw not obviously connected with other specimens. There is an assemblage of miscellaneous specimens from various localities that have since been associated with Navahoceros, including thick lower leg bones, but it is not clear how they are related to the type specimen, or what the type specimen actually is (Webb 1992). Morejohn and Dailey (2004) evaluated Navahoceros specimens and concluded they all belonged to Odocoileus but provided no measurements or other evidence to support their conclusion. Some leg bones associated with Navahoceros appear to be outside the normal range of variation for Odocoileus (Blackford 1995), so further work will be required to determine if the American mountain deer was a legitimate taxon. Churcher (1984) offered convincing evidence that the stilt-legged deer (Sangamona spp.) never existed. He studied the specimens attributed to this deer and concluded they were a disparate mixture of skeletal elements from other species mislabeled and reconstructed together in museum displays. The larger members of today’s North American deer family (elk, moose, and caribou) entered the continent much later than these mid-sized deer through Beringia during the Pleistocene (1.8 million to 11,000 YBP). These larger cervids arrived in phenotypic form very similar to what we see currently. Caribou are the only cervid in mid-Wisconsinan (65,000–23,000 YBP) deposits in Alberta but are also known as far south as Alabama 11,820 YBP (Churcher et  al. 1989, Burns 2010). Elk are not confidently known to be south of Beringia until after 10,000 YBP (Burns 2010). Moose were likely the last cervid to enter North America from Eurasia, as moose fossils south of Beringia are very scarce in the early Holocene (11,700 YBP to the present; Burns 2010).

The Eastern and Western Divide Deer were not very abundant or widespread during the early Pleistocene (1–2 million YBP). The diversity and sheer abundance of other large hoofed animals at that time (Frick 1937) probably resulted in an intense competition for food and other resources and supported a robust predator guild (Geist 1998). With the melting of the glaciers at the close of the Pleistocene (11,000 YBP), mass extinctions occurred throughout the world. North America was no exception as it lost most of its large native mammals in a remarkably short time period (e.g., camels [Camelops spp.], giant sloths [Glyptotherium spp.], mastodons [Mammut spp.], mammoths [Mammuthus spp.], saber-toothed cats [Smilodon spp.], long-horned bison [Bison latifrons], and native horses [Equus spp.]). Of all the primitive forms of North

James R. Heffelfinger and Emily K. Latch American deer, only Odocoileus survived the Pleistocene. In this turmoil and change, they increased in abundance and distribution and came to dominate the landscape. Divergence between the eastern form (white-tailed deer) and the western form (black-tailed and mule deer) occurred sometime in the Pliocene or Pleistocene, 1–4 million YBP. Gustafson (1985: fig. 8) noted that a fossil antler from Idaho (3.8–3.5 million YBP) has brow tines and a mainbeam curve that are suggestive of mule deer but could not diagnose to species. The earliest fossil evidence reported for black-tailed or mule deer comes from southern California in the Pleistocene (1.9–0.7 million YBP; Frick 1937, Savage 1951, Kurtén and Anderson 1980). The partial skull from the Pleistocene depicted in Frick (1937: fig. 20B) has the unmistakably deep lacrymal fossa of black-tailed or mule deer. Using fossils to unravel the complete story of deer evolution throughout the Pliocene and Pleistocene has been hampered by the relative rarity of deer at that time and repeated glaciations that scoured the northern part of the continent for thousands of years, destroying evidence of early North American deer evolution (Geist 1994, 1998). Even with fossils in hand, white-tailed and mule deer are difficult to distinguish without lachrymal fossa, certain leg elements, or antlers from mature males (Jacobson 2003, 2004). There are no known characteristics that allow the differentiation between mule deer and black-tailed deer from skeletal or fossil material even after they diverged phenotypically. Most archaeological material is identified to species based solely on where it was found or size, both of which are problematic. Because Pliocene and Pleistocene geographic ranges are not clearly known and body size is spatially and temporally variable, most of these species assignments are suspect. A re-evaluation of New World deer fossils is badly needed, particularly Odocoileus, using all the information currently available (Blackford 1995; Jacobson 2003, 2004; Morejohn and Dailey 2004; Wheatley and Ruiz 2006). The glaciers that covered the northern part of North America extended approximately as far south as the Canada-United States border and farther south down the Rocky Mountain and Cascade Mountains in the West, and covered the Great Lakes and northeastern states farther east. All North American deer persisted in refugia south of the glaciers, except perhaps the black-tailed deer, which may have been trapped in refugia along the coast by alpine glaciers extending down the Cascade Range through the middle of northern California, Oregon, Washington, and southern British Columbia (precisely where black-tailed deer are separated from mule deer today). Fossil evidence in unglaciated areas indicates white-tailed deer did not change much physically in at least the last 2 million years (Frick 1937, Webb 2000). Florida is well-known for its Pleistocene white-tailed deer fossils that are indistinguishable from today’s white-tailed deer antlers, skulls, and skeletons. White-tailed deer most likely spent the last ice age in the unglaciated areas of southeastern United States, Mexico, and down through Central and South America where they provided ancestral stock for South American deer species. With the lack of a strong fossil record in the north, scientists have turned to genetic analysis to investigate the relationships of white-tailed, black-tailed, and mule deer. By making

Origin, Classification, and Distribution assumptions about the rate that a genome accumulates random mutations, geneticists can estimate the time since 2 organisms diverged from a common ancestor (Avise 1994). These molecular clocks are notoriously sensitive to the assumptions that are used and should be viewed with healthy skepticism (Pulquério and Nichols 2007). Molecular clocks, however, provide another way to estimate the evolutionary divergence between 2 types of animals. Various attempts to use mitochondrial DNA (mtDNA) to estimate the time of divergence between whitetailed deer and a western deer form have resulted in a range too wide to be very useful (750,000−3.7 million years; Baccus et al. 1983, Carr and Hughes 1993, Douzery and Randi 1997).

Proposed Theories Describing the Origin of Black-tailed and Mule Deer Three main theories have been proposed to describe the origin of black-tailed and mule deer and their evolutionary relationship to white-tailed deer. All theories are related to different groups of deer being separated for long periods of time and then subsequently coming into contact secondarily. The scenarios are not mutually exclusive and all are based on different information in an attempt to explain the observed physical or genetic differences. No theory is without contradictions and contrary evidence, which reflects the reality of our fragmented understanding of these genetic, behavioral, geographical, and phenotypic relationships. Dispersal theory.—Considering the physical differences between white-tailed, black-tailed, and mule deer, this traditional theory holds that the ancestral Odocoileus split into a western species (black-tailed deer) and an eastern species (white-tailed deer) more than 2 million YBP (Geist 1994). The original split and maintenance of the east-west separation must have been caused and maintained by some ecological barriers during the periods of glaciation or during the interglacial periods. The dispersal theory proposes that as the last ice age glaciers receded, deer that would become mule deer split off from black-tailed deer and rapidly expanded out into the fertile landscape that was either uncovered by the melting glaciers or altered to now be very productive (Geist 1971, 1986, 1994). This rapid expansion into fertile, unoccupied habitat is said to have fueled the rapid phenotypic changes that we now recognize as mule deer. Mule deer prospered in this new habitat and became much larger than black-tailed deer, with larger and more elaborate antlers, and more contrasting body markings. Prior to the advent of genetic analysis, this theory alone seemed to explain the origin of mule deer given what we know about ecological principles of a species expanding into very productive and unoccupied habitat (Geist 1971, 1986). The more contrasting facial and rump coloration and the larger antlers of mule deer are concordant with an animal living in open areas and using visual communication more than forest forms (Geist 1971, 1986, 1994). With more powerful genetic analyses, scientists can ask and answer more complex questions. Deer carry 2 kinds of DNA that are both informative in their own way. The first, nuclear DNA (nDNA), resides in the nucleus of each cell and contains DNA that offspring inherit from their mother (~50%) and father

7 (~50%). This is the DNA related to how an animal looks and what traits are passed down from its parents. A second type, mitochondrial DNA (mtDNA), is found in the mitochondria floating around in the cytoplasm of the cell outside the nucleus. Mitochondria help supply energy to the cell and they also carry a small package of DNA. The uniqueness of mtDNA is that it is inherited only from the mother and is passed down through the maternal line (Cronin 1991a). Analyzing the nDNA tells us about maternal and paternal lineages, but mtDNA only gives insight into the maternal lineage. Mitochondrial DNA, however, evolves more quickly, is much more abundant in the cell, and is easier to isolate from degraded specimens, making it well-suited to answer many questions. Maternally inherited mtDNA is very similar in mule deer and white-tailed deer but they are very different from blacktailed deer (Carr et al. 1986, Cronin et al. 1988, Cronin 1991b, Carr and Hughes 1993). This unusual and surprising genetic relationship was not expected because black-tailed and mule deer are the same species (different subspecies) and they both differ from white-tailed deer in many ways. If mule deer simply branched off from black-tailed deer and dispersed into lush habitat when the glaciers receded, it is difficult to rectify why they have mtDNA very similar to whitetailed deer but completely different than their black-tailed deer ancestors. It is assumed that a very long period of isolation would be required for the 2 western deer forms to develop the level of observed divergence in mtDNA (7%; Latch et al. 2009) and this contradicts a Pleistocene origin of mule deer as a species. An additional problem with this theory is that the glaciers during the last glacial maximum did not extend south of the Canada-United States boundary throughout the West so there were no large areas of recently glaciated fertile habitat in the western United States to set the stage for this dispersal event and speciation scenario. Hybrid origin theory.—Early genetic evidence spawned an alternative theory proposed by Geist (1990, 1994, 1998) that black-tailed deer and white-tailed deer split more than 2 million YBP, but that mule deer are a relatively new species, resulting from later hybridization between white-tailed and black-tailed deer. Geist (1998) proposed that after the retreat of the last glaciers starting about 14,000 years ago at the close of the Pleistocene, white-tailed deer and black-tailed deer came into contact with one another and interbred, creating the mule deer. The basis of this theory is that if mule deer have very similar mtDNA as white-tailed deer, then perhaps they are the product of male black-tailed deer mating with female white-tailed deer thus creating offspring with mtDNA from their white-tailed deer mothers. The value of this theory is that it explains the very confusing situation of why mule deer and white-tailed deer have similar maternally inherited mtDNA. Although this theory is consistent with the genetic relationships, it is also burdened by other conflicting information. Successful hybridization between mule deer and whitetailed deer is rare throughout most of their range overlap (Geist 1998, Heffelfinger 2000a, Russell et al. 2021). The current geographic distribution of mule deer and white-tailed deer overlaps in ≥21 states and provinces in Mexico, the United States, and Canada. Although hybridization occurs in most of these jurisdictions to some degree, it is uncommon in most

8 areas (Cronin et al. 1988, Derr 1990, Hughes and Carr 1993, Heffelfinger 2000a, Russell et al. 2021). There may be local clusters where hybridization rates are higher. For example, Stubblefield et al. (1986) analyzed 319 deer in 5 Texas counties and the proportion of deer in each county with some level of hybridization was 0–13.8%, with an average of 5.6% hybrids in the study. This geographic overlap represents a secondary contact between these 2 species that evolved separately as evidenced by large differences in nDNA, and physical and behavioral characteristics. Male first filial generation (F1) hybrids from these matings have low fertility and many are completely infertile (Whitehead 1972, Wishart et  al. 1988, Derr et  al. 1991) as predicted by Haldane’s Rule where hybrids of the heterogametic sex (XY males in mammals) are usually infertile or subfertile (Haldane 1922). There are many reproductive isolating mechanisms that create obstacles to widespread hybridization between whitetailed and mule deer, including occupation of different habitat and different elevations, divergent timing of breeding season, large differences in breeding behavior, and physical and physiological differences (Geist 1981, 1998; Heffelfinger 2000a, 2006; Airst and Lingle 2019). Post-partum survival of white-tailed × mule deer and whitetailed × black-tailed deer hybrid offspring is low (Whitehead 1972, Day 1980). Even in captivity when given unlimited food, water, and protection from predators, hybrid fawns have a very low survival. Whitehead (1972) reported that none of the black-tailed × white-tailed deer hybrids in captivity reproduced their first year and only 50% produced fawns their second year, of which 66% were stillborn. Likewise, Nichol (1938) reported the survival of only 4 of 9 captive hybrid fawns and Day (1980) only had 4 of 10 survive their first 9 months. The hybrid offspring that survive the myriad of reproductive barriers show behavioral maladaptation to predator avoidance and would suffer from a high rate of selection by predators in the wild (Lingle 1992). Lingle (1992, 1993) studied locomotion, escape behavior, and mechanics of gait in captive white-tailed, mule deer, and their hybrids when exposed to the approach of a simulated predator. Predator avoidance behavior is very different between white-tailed deer (running escape) and mule deer (stotting) and Lingle (1992, 1993) documented that the hybrids of the 2 species displayed a confused and ineffective mixture of the 2 strategies. Geist (1998) discusses this weakness of the hybrid origin theory but notes that the Pleistocene extinction of large predators may have allowed these hybrids to survive after being released from intense predation pressure. The difficulty of this explanation is that deer at that time were sympatric with the same assemblage of predators they currently face. The universally low production and survival of hybrid fawns from this interspecies pairing make it difficult and unlikely that this would result in a new hybrid species with a strong enough competitive advantage to dominate western North America. Hybridization in the wild has been documented in both directions (i.e., hybrids sired by either mule deer or whitetailed deer males). Behaviorally, one might expect most hybridization between these 2 species to result from the moreaggressive male white-tailed deer breeding female blacktailed or mule deer (Geist 1998), and that has been reported in

James R. Heffelfinger and Emily K. Latch many instances (Cathey et al. 1998, Cronin 1991b, Ballinger et  al. 1992, Kay and Boe 1992, Carr and Hughes 1993). In these cases, hybrids would be expected to have mule deer or black-tailed deer mothers (and their mtDNA) more often. Hybrid offspring in larger female mule deer groups would also be expected to experience higher survival than if they were in smaller white-tailed deer groups. Mule deer females are also more aggressive in protecting their fawns and the fawns of other females, which would favor hybrid fawn survival (Lingle et al. 2007a,b). The hybrid origin theory for mule deer, however, is dependent on hybridization occurring in the opposite direction where black-tailed deer males breed white-tailed deer females. Although hybridization in this direction occurs (Cowan 1962, Carr et al. 1986, Wishart et al. 1988, Ballinger et  al. 1992, Hughes and Carr 1993), it contradicts what one might expect for the successful creation of a hybrid species. Because more recent hybridization is well-documented to occur in both directions, it is reasonable to assume this was the case from the beginning of secondary contact. If black-tailed × white-tailed deer hybridization in the past was so widespread to create a new species, one would expect it to have been bidirectional enough to find white-tailed deer mtDNA in phenotypically black-tailed deer and also black-tailed deer mtDNA to be found in white-tailed deer. These cases are extremely rare, however. The mule deer hybrid theory requires Pleistocene hybridization between only black-tailed deer males and white-tailed deer females, followed by reproductive isolation of the hybrids so they only bred with themselves, then expansion throughout western North America with negligible further breeding with either parental species. After such a significant white-tailed × black-tailed deer hybridization event that was substantial enough to create the dominant western deer, one would expect to also find evidence of contemporary mule deer carrying black-tailed deer mtDNA from reciprocal matings. If mule deer are hybrids of white-tailed deer and black-tailed deer, then nDNA inherited from both parents should be well represented in mule deer, but this is not the case (Cronin 2003). Analyses of bi-parentally inherited nDNA (Latch et al. 2014) and paternally inherited Y chromosome markers (Cathey et al. 1998) show that mule deer and black-tailed deer are very similar subspecies and clearly different from white-tailed deer. In contrast to hybrids with white-tailed deer, which are rare and have low fitness, mule deer and black-tailed deer hybridize readily where they come into contact (Latch et al. 2011, 2014; Haines et al. 2019), indicating they are more closely related. This conflicts with the theory that mule deer are a new species formed from hybrids of white-tailed and black-tailed deer. For the hybrid offspring with black-tailed deer sires to retain their maternal white-tailed deer mtDNA, they would have to breed among themselves or backcross only with white-tailed deer females. If hybrids backcrossed consistently to whitetailed deer, however, they become phenotypically indiscernible from white-tailed deer in only a few generations. Russell et  al. (2021) reported that of the hybrid deer they detected, 4 times as many were characterized as phenotypically more white-tailed deer-like. This means fertile female hybrids were disproportionately selecting white-tailed deer males in subsequent matings, which is contrary to the hybrid mule deer

Origin, Classification, and Distribution hypothesis. For male black-tailed and female white-tailed deer hybridization to eventually result in a new hybrid deer species that has no detectable evidence of white-tailed deer nDNA, the matings subsequent to the original hybridization event must be unidirectional with all female hybrids backcrossing to male black-tailed deer. If that happened, those backcrossed individuals would become rapidly and progressively more blacktailed deer-like, but would simultaneously have to evolve into a very different-looking mule deer. Such a scenario is difficult to envision because none of the current phenotypic changes from a black-tailed deer phenotype (produced by these backcrosses) gradually evolving into mule deer can be explained by the addition of white-tailed deer characteristics. In fact, Whitehead (1972) reported that hybrids between black-tailed deer and white-tailed deer resulted in hybrid offspring that were indistinguishable from black-tailed deer parents. Any backcrossing to white-tailed deer males along that progressive evolution into mule deer characteristics would only serve to retain and increase the amount of white-tailed deer nDNA to the point it would be identified in nDNA analysis and also to push the overall phenotype towards a white-tailed deer-like form. Alternatively, if a new Pleistocene hybrid population bred only with other hybrids, a large portion of their nDNA would still be identifiable as having white-tailed deer ancestry (but it is not). Nuclear DNA is mostly what determines physical appearance, but mule deer do not look like a cross between a black-tailed and a white-tailed deer (Geist 1998). In fact, black-tailed deer have tails, metatarsal glands, and other phenotypic characteristics that appear very similar to true whitetailed deer × mule deer hybrids (Heffelfinger 2000a), but they are not, as both mtDNA and nDNA evidence reveals (Cathey et al. 1998, Latch et al. 2014). One species can acquire, or capture, the mtDNA of another. One of the best examples of this in mammals is the documentation of polar bear (Ursus maritimus) gene flow into brown bears (U. arctos) on a few islands of southeast Alaska (Cahill et al. 2015). In that case, a small remnant population of polar bears hybridized with immigrating male brown bears and the hybrid offspring backcrossed with brown bears. Through time, the population moved phenotypically to be indistinguishable from pure brown bears, but to this day, they carry maternally inherited polar bear mtDNA from that initial hybridization. This scenario shows unidirectional capture of mtDNA is possible but differs in 3 important ways from that of black-tailed and white-tailed deer. First, island biogeography creates barriers to gene flow, allowing more rapid changes in population genetic composition than would be expected in a widespread mainland population. Second, if 1 species is far less common than the other, it is much easier for it to be genetically swamped by an abundant species than if abundances are similar. Lastly, the island bear example describes mtDNA capture of one species by another, whereas in the case of mule deer, 1 species would not only have to capture the mtDNA of the other but also evolve into a third species phenotypically, behaviorally, and ecologically. In consideration of the challenges discussed above, it is difficult to imagine how the ancient hybridization of male black-tailed and female white-tailed deer throughout western North America could have resulted in a new species that retained the mtDNA of white-tailed deer, nDNA very

9 similar to black-tailed deer, and a divergent phenotype that came to dominate the western half of the continent. Glacial refugia theory.—Many species and subspecies differences we see today are because populations of animals were separated by glaciers or isolated from each other by dramatic habitat changes (Avise et al. 1998). The large-scale changes in the distribution of forests, shrublands, and grasslands occurred through the many glacial and interglacial periods in the last few million years. Physical isolation for long periods of time is the most likely cause for the differences between a western deer (mule deer and black-tailed deer) and white-tailed deer (Avise et al. 1998). We can infer the distribution of vegetation associations during the most recent ice age, but there were many others before it and it is not possible to reconstruct what North America looked like >100,000 years ago. Any one of several glacial cycles over the last few million years, each lasting 10,000−100,000 years (Ehlers et al. 2018), could be enough to isolate and differentiate an eastern (white-tailed deer) and western (mule deer and black-tailed deer) type. The last Pleistocene glaciation peaked in North America 26,000– 19,000 YBP and this most recent glaciation probably resulted in the less-obvious divergence of mule deer subspecies and ecotypes (Avise et al. 1998, Latch et al. 2009). Looking at the patterns of genetic diversity across blacktailed and mule deer populations throughout North America can indicate the geographic areas they occupied during the last ice age before expanding behind retreating glaciers. Latch et al. (2009) provided data that indicated mule deer waited out the last glacial maximum in several refugia in southwestern United States and Mexico. Latch et  al. (2009) reported high mtDNA haplotype diversity in the Southwest, with a more uniform pattern among mule deer populations throughout the West, indicating they expanded rapidly out of these southwestern refugia after the glaciers melted. This is similar to the studies by Buchalski et al. (2016) indicating desert bighorn sheep (Ovis canadensis) also persisted in multiple southern refugia during the last glacial maximum. The genetic patterns revealed that black-tailed deer occupied ice-free coastal areas west of the Cascade Mountains in Washington and Oregon and expanded out from there after the glaciers melted. Although most of the post-glacial expansion was northward along the coast, eastward and southward expansion brought black-tailed and mule deer into contact once again along the crest of the Cascade Range and other points of contact in the Pacific Northwest (Latch et al. 2014). We know that scattered Pacific coastal areas from Alaska to California were the first areas that became free of ice starting 17,000–15,000 YBP (Ehlers et  al. 2018; Lesnek et  al. 2018, 2020) and these areas served as the first places animals, including black-tailed deer, colonized from refugial areas. There is evidence of black-tailed deer on Vancouver Island and Haida Gwaii, British Columbia dating to around 12,000 YBP and other deer remains farther north in southeast Alaska dated only as far back as 9,200 YBP (Heaton and Grady 2003; C. Lindqvist, University at Buffalo, unpublished data). The estimates of timing of demographic population expansion of the dominant black-tailed deer mtDNA haplogroup is 19,000 YBP (Latch et al. 2009:table 1), which is not substantially different from the timing of the first emergence of ice-free areas

10 available for colonization (17,000 YBP). These kinds of refugial dynamics undoubtedly played out through many glacial cycles. Perhaps black-tailed deer were trapped, released, and retrapped in glacial refugia repeatedly during the Pleistocene (2.5 million–11,700 YBP). There were areas thought to have remained ice free even during the last glacial maximum (26,000–17,000 YBP) on various islands and coastal areas in the Alexander Archipelago of southeast Alaska (Cook et  al. 2006, Carrara et  al. 2007), but recent work dating exposure of rocks and remains of cave fauna indicates at least some of these areas were not ice free until about 17,000 YBP (Lesnek et al. 2018). There is no evidence from cave deposits of black-tailed deer occupying coastal refugia in southeast Alaska or coastal British Columbia before 13,100 YBP (Lesnek et  al. 2018), but if they did and have been thus far undetected, that could explain the genetic and phenotypic differences between Columbian (O. h. columbianus) and Sitka (O. h. sitkensis) black-tailed subspecies. A coastal Alaska refugia on the west edge of the Cordilleran ice sheet, in addition to the western Washington-Oregon refugia documented by Latch et  al. (2009), would provide the isolation needed to explain the divergence of 2 black-tailed subspecies. Latch et al. (2009) concluded 1 or more locations in western Washington-Oregon provided refugia for black-tailed deer because of the high haplotype diversity they found there (0.719–0.983). Prince of Wales Island (0.751) and Vancouver Island (0.879), however, also had relatively high haplotype diversity; hopefully future genetic work will reveal whether this is an artifact of sample size or a cryptic genetic signal of another northern refugial population. Phenotypic and nDNA differences between white-tailed, black-tailed, and mule deer arose in separate refugia, probably at different times, but the enigmatic relationship of mtDNA among them remains to be resolved. If we assume all 3 types of deer started with very similar mtDNA, several mechanisms could explain why black-tailed deer mtDNA is different. The isolation (or repeated isolation) of black-tailed deer in relatively small, fragmented populations along the coast and from island to island could have caused black-tailed deer mtDNA to diverge through genetic drift, founder effect, progressive and leading-edge colonization, gene surfing, and high-density blocking (Waters et  al. 2013). All of these processes could result in cumulative genetic differences on the periphery of black-tailed deer range (Lohr et  al. 2011), but it is not clear if they would have resulted in this much genetic change (7% divergence) starting with the same mtDNA. Under this scenario, it is also difficult to explain how white-tailed deer and mule deer mtDNA remained remarkably similar during that time despite their nearly complete reproductive isolation. One mechanism that could explain the unusual relationships of mtDNA in Odocoileus found in all 3 theories is the wellestablished concept of incomplete lineage sorting, or hemiplasy, where incongruent gene phylogenies can arise because they sort into lineages at different rates (Avise and Robinson 2008). It is not uncommon for inferred relationships among mtDNA lineages to be incongruent with the true evolutionary phylogeny of an organism because mtDNA is inherited as a single locus (Avise et  al. 1983; Cronin 1991a, 2003; Mende and Hundsdoerfer 2013). The ancestral Odocoileus stock may

James R. Heffelfinger and Emily K. Latch have had a variety of mtDNA polymorphisms, including those present today in black-tailed deer, mule deer, and white-tailed deer. As white-tailed deer and a primitive form of blacktailmule deer diverged, they carried with them that diversity of shared polymorphisms. Over time, some polymorphisms were lost in each lineage, leaving, by chance, very similar mtDNA genotypes in mule deer and white-tailed deer and distinct ones in black-tailed deer (Avise et  al. 1983; Avise 1986; Cronin 1991b, 1993; Carr and Hughes 1993). This disconnect between deer and their mtDNA phylogenies resulting from incomplete lineage sorting has been used to explain the confusing and disparate relationships between mtDNA, nDNA, and phenotype arising from all 3 theories discussed above. There are no simple straightforward explanations of mule deer origin that are free of serious contradictory evidence. There is no way to reconstruct deer distributions in all the various ice advances and retreats in the last 5 million years that white-tailed, black-tailed, and mule deer ancestors have been around, periodically interacting with one another. These theories above are also not mutually exclusive; for example, mtDNA capture could occur in refugium, followed by phenotypic changes driven by environment during dispersal into unoccupied habitat. Ancient hybridization certainly happened throughout the evolutionary history of the genus Odocoileus, but this does not automatically lead to the mtDNA capture of 1 species by another. This summary of what we know about mule deer evolution is very much an incomplete picture. Future research will continually add pieces to the puzzle, but the answers we seek will be elusive without a geographically comprehensive analysis of this genus with not only mtDNA but also nuclear genomic data, Y chromosome markers, and other paternal markers. Hopefully future work on mule deer evolution will disprove some or all of these scenarios.

Taxonomy and Classification In 1758, Swedish physician and botanist Carl von Linnaeus finalized a system for naming plants and animals in a classification scheme he called Systema Naturae (Linnaeus 1758). This system is still called binomial nomenclature because it uses 2 names for each species; the first name is the genus and the second is the species. With this naming system each plant and animal in the world has a unique scientific name (Genus species) used by scientists in all countries regardless of their primary language. The subspecies category was not part of Linnaeus’ original system of nomenclature, but it was added later in an effort to describe regional variations. Historically, especially in the eighteenth and nineteenth centuries, taxonomic splitting was very common. There were very few specimens available and exploration of new lands resulted in new specimens that seemingly had unique characteristics. Many new categories were established based on only a few specimens. In some cases, a small and barely discernible difference resulted in the naming of a new species. For example, Merriam (1918) examined grizzly bear (Ursus arctos) skulls and declared there were 86 species of grizzlies in North America, with 27 species in Alaska alone.

11

Origin, Classification, and Distribution These early efforts at categorizing every variation in animals introduced much confusion and poor application of science into the taxonomic realm when further analysis of many more samples showed characters to be more continuous and often not diagnostic. Unfortunately, these myriad described taxa then become accepted in the literature, leaving the scientific community the burden of conducting a comprehensive morphologic, genetic, and ecological study throughout the animal’s entire range to properly evaluate its validity (Senn et al. 2014, Earp 2016). With a greater understanding of geographic variation, many of these early species of bears and other wildlife were later reduced to subspecies status or dissolved completely, resulting in a series of synonyms for many subspecies. For example, Nowak (1995) collapsed 24 subspecies of North American wolf (Canis lupus) to 5 based on a morphological analysis and that revision has withstood scrutiny. Deer are mammals in the class Mammalia (Table 1.1), which contains all warm-blooded animals that produce milk for their young, usually have fur, and 7 cervical vertebrae. Within the class Mammalia are 26 orders; 2 of which are groups of animals that walk on thick, modified toenails called hooves (Wilson and Reeder 2005). These animals are called ungulates from the Latin word unguis meaning claw or toenail (Gotch 1995). Ungulates with an odd number of toes (1, 3, or 5) on each foot belong to the order Perissodactyla (e.g., horses [Equus spp.], rhinoceros [Rhinocerotidae], tapirs [Tapiridae]), and the order Artiodactyla (artios = even, daktulos = toes) contains all even-toed ungulates (e.g., cattle, deer, goats [Bovidae], and pigs [Suidae]). Within Artiodactyla, there are many different taxonomic families that have been traditionally recognized, but only 4 occur naturally in North America: Bovidae (sheep [Ovis spp.], cattle, goats, bison [Bos spp.]), Antilocapridae (pronghorn [Antilocapra americana]), Tayassuidae (collared peccary [Pecari tajacu]), and Cervidae (deer, elk, moose, caribou; Nowak 1999). One of the most remarkable taxonomic discoveries in recent years is the well-supported placement of whales and dolphins (infraorder Cetacea) deep within the traditionally recognized order Artiodactyla (Geisler et al. 2007, Zurano et al. 2019). The earliest genetic work was rudimentary but showed whales were closely related to hoofed animals. These strange results were dismissed as erroneous, but as more sophisticated genetic analysis methods became available, the more solidly supported this relationship became to strengthen this connection (Zurano et al. 2019). Subsequently, the fossil foot TABLE 1.1 Classification of black-tailed and mule deer. Kingdom Phylum Class Order Suborder Family Genus Species

Animalia (animals) Chordata (animals with a backbone) Mammalia (mammals) Artiodactyla (whales and even-toed hoofed animals) Ruminantia (ruminants) Cervidae (deer family) Odocoileus (medium-sized North American deer) hemionus (black-tailed and mule deer)

bones of primitive whales were discovered to have a distinctive ankle bone (astragalus) found only in hoofed animals and other elements that supported their evolution from hoofed animals. Mammalogists now generally accept the strange fact that whales and dolphins are not just closely related to hoofed animals, but they are nested deep in the phylogenetic structure of Artiodactyla as a sister group to hippos (Hippopotamus amphibius; Geisler et al. 2007). This finding has caused some to refer to this unwieldy group of hoofed and finned relatives as order Cetartiodactyla (Geisler et  al. 2007); however, Prothero et al. (2022) provide a compelling argument for why Artiodactyla remains the correct name for this order.

Cervidae The deer family (Cervidae) is comprised of all animals that shed antlers annually, including moose, elk-red deer, caribou-reindeer, white-tailed and mule deer, and several Asian, European, and South American species. Only males have antlers, except for caribou-reindeer in which females bear a smaller version of the males’ antlers. Cervids, as members of the family are called, walk on the hooves (toenails) of the third and fourth toes, but no longer have the first digit (thumb or big toe). The second and fifth toes have been reduced and assume a non-functioning role in what are called dew claws. True cervids have a 4-chambered stomach like other ruminants but lack a gallbladder. Worldwide, there are 18 genera in the deer family (Groves 2007) containing at least 35 species (Marcot 2007). There is still a lack of clarity about the distinctiveness of some of these species and disagreement about what constitutes species-level versus subspecies-level differences. Taxonomic revision is a continual process as additional morphometric and especially genetic information become available. Regardless of the number of species, there is little doubt about the worldwide success of the deer family, which is native to all continents except for Australia and Antarctica. The family ranges from the 8.8-pound (4-kg) pudu (Pudu spp.) of South America to the 1,600-pound (725-kg) Alaskan moose, and occupies ecosystems from arctic tundra to tropical forest to desert. Chinese water deer are included in Cervidae even though this species lacks antlers. Rather than antlers, male Chinese water deer have the large protruding upper canine tusks reminiscent of several extinct cervids (Figs. 1.1, 1.2). Chinese water deer have been used as an example of a cervid that retained its ancestral form, but there are indications it may have had antlers in the past and reverted to an antlerless and tusked condition secondarily (Groves 2007). Support of this contention is that its closest genetic relative is the Eurasian roe deer. Two deer-like ruminants have been associated with the deer family at times but are not true cervids. The first is the diminutive mouse deer or chevrotain (Tragulus spp.) weighing about 5 pounds (2.3 kg). The chevrotain is a small antlerless animal that lives in the tropical forests of Africa and Southeast Asia. These solitary animals have upper canines, no antlers, and represent a very primitive form of ruminant. The musk deer is a 15.4–33-pound (7–15-kg) animal resembling the Chinese water deer with enlarged saber-like canines. This animal was originally considered a cervid, but some morphologic

12 differences, like the presence of a gallbladder and abdominal musk gland, have always been enigmatic. Sophisticated genetic work has recently revealed the musk deer is more closely related to the cattle family, Bovidae (Groves 2007). Separate taxonomic families are now used for the chevrotain (Tragulidae) and musk deer (Moschidae).

Odocoileus The genus Odocoileus includes 2 species of medium-sized deer whose distribution is centered in North America: whitetailed deer and black-tailed and mule deer. The suite of characteristics that set Odocoileus apart from other cervids include nonpalmate antlers, hairless muzzle, metatarsal glands, vomer dividing the posterior narial cavities, and the absence of upper (proximal) ends of the lateral metacarpals and upper canine teeth (Baker 1984, Jacobson 2004, Groves 2007). Many of these can occur in rare instances, but together they characterize this genus. This genus name was given by Constantine Rafinesque based on a few fossilized teeth given to him by a colleague who had broken them out of a jaw protruding from the wall of a limestone cave in Pennsylvania (Rafinesque 1832). Rafinesque returned to the cave in hopes of finding more material to examine but found none. Although he described the teeth in detail, he was unsuccessful in matching them to any living animal. Despite his prowess as a taxonomist, Rafinesque had not yet seen deer teeth for comparison. He gave his mysterious cave teeth the genus name Odocoileus, from the Greek words odous meaning tooth and koilos meaning hollow (Rafinesque 1832, Gotch 1995). It is not clear if his description “teeth well hollowed” referred to the crescent-shaped infundibula in the center of the chewing surface or that the fossil teeth were cracked open revealing the vacuity formerly filled with nerve tissue (Rafinesque 1832:109). In his haste to publish this specimen, Rafinesque (1832:109) simply left it for others to identify what kind of teeth they were to place them in the proper family, which he suspected was related to “goats or a dwarfish oxen.” Later taxonomists, using his detailed and accurate description of the teeth, realized these were from white-tailed deer and accepted this publication as the first to assign a valid genus name to these North American deer. The name Odocoileus was used widely without question, until Hershkovitz (1948) pointed out that it was wrong. The genus name Dama was used for white-tailed deer by Zimmerman (1780), 52 years before Rafinesque pondered the origin of his cave teeth. Under taxonomic rules, this makes Dama the correct genus name for white-tailed and mule deer in North America. Shortly thereafter, some sources began to use Dama hemionus for mule deer (Hall and Kelson 1959). This caused considerable confusion in the taxonomic community because Dama was already being used for European fallow deer (Dama dama) and that was subsequently also found to be an invalid name (Allen 1902). This necessitated finding a new genus name for fallow deer, which was Platyceros (Baker 1984). The cascading confusion of changing 2 well-established genera was deemed unacceptable and so the International Commission on Zoological Nomenclature used its plenary powers to issue Opinion 581. This decision

James R. Heffelfinger and Emily K. Latch acknowledged that although Dama is technically correct, Odocoileus would be recognized as the official genus name for white-tailed, black-tailed, and mule deer (International Code of Zoological Nomenclature 1960). In addition to Dama, other genera names one might see used in historical documents include Cariacus, Cervus, Dorcelaphus, Eucervus, Gymnotis, Mazama, Odocoelus, and Odontocoelus (Cowan 1936, Anderson and Wallmo 1984)

Odocoileus hemionus The mule deer was described by Rafinesque (1817a) based on a field journal originally attributed to Charles LeRaye but later found to be fraudulent (Woodman 2015a,b). The description of mule deer in the apocryphal LeRaye journal actually came from the journal kept by a member of the Lewis and Clark Expedition. Patrick Gass (1807) was the first to publish an account of the expedition and to describe these new deer they saw and harvested in Lyman County, South Dakota (Woodman 2015a,b). Even though Rafinesque (1817a) based his description on a fabricated and discredited source (the fake LaRaye journal), he did write it in accordance with the correct taxonomic rules and the plagiarized information about mule deer could be traced directly to its legitimate source (Gass 1807). On 17 September 1804, William Clark wrote in his journal, “Colter Killed a …curious kind of deer of a Dark gray Colt. more so than common, hair long & fine, the ears large & long, a Small reseptical under the eyes; like an Elk, the Taile about the length of Common Deer, round (like a Cow) a tuft of black hair about the end, this Speces of Deer jumps like a goat or Sheep” (Thwaites 1904:152). Later during the trip (10 May 1805), Clark wrote a more complete description of mule deer, but the 2-volume final expedition journal did not appear in print until 1814, 7.5 years after they returned. In scooping the others by 7 years, Gass (1807:33) was the first to publish a clear and accurate description of the mule deer harvested by John Colter in Lyman County, South Dakota (Woodman 2013) on 17 September 1804: “The black-tailed, or mule deer have much larger ears than the common deer and tails almost without hair, except at the end, where there is a bunch of black hair.” It is upon this description that Rafinesque (1817a) indirectly, and Say (1823) directly, formally named and described this species for science. The scientific species name hemionus comes from ancient Greek hēmíonos, which means half (hēmi) donkey (ònos), referencing the strikingly large ears that gave members of the Lewis and Clark expedition reason to refer to them in their journals as mule deer.

Subspecies and Ecotypes Infraspecific taxonomy has been a challenge in mule deer, in part because the species is geographically widespread and continuously distributed, occupying diverse habitats over 40 degrees latitude throughout every major biome except tundra. Mule deer translocations in some areas may have also complicated our understanding of geographic variation (Longhurst et al. 1952, Kamler et al. 2001, Heffelfinger and Webb 2010). This species has been divided into as many as

Origin, Classification, and Distribution 11 subspecies (Cowan 1956, Hall 1981) that roughly correspond to some of the major ecosystem transitions in North America. Mule deer exhibit extensive morphological and behavioral variation throughout their range, but efforts to develop a key to reliably differentiate subspecies have failed (Cowan 1936). How subspecies are classified can depend greatly on the definitions employed and the criteria used for determining whether biologically significant differences exist. As an extension of Linnaeus’ system of classification, subspecies have an official trinomen. Like all levels in the Linnaeus taxonomic system, subspecies classifications should be based on phylogenetic relationships; while specific definitions vary, most converge on the idea that subspecies are groups of populations that are geographically separated, are morphologically distinct, and have unique evolutionary potential (Wilson and Brown 1953, Mayr 1963, Haig et al. 2006, Coates et al. 2018, deQuieroz 2020). Using multiple lines of evidence (e.g., behavior, environment, genetics, geography, life history, morphology) is critical to appropriately define and evaluate subspecies taxonomy. A number of other classification systems exist that are potentially useful for conservation and management, including evolutionarily significant units (ESUs; Ryder 1986) and management units (MUs; Moritz 1994). Both emphasize genetic divergence; ESUs exhibit genetic uniqueness due to historical isolation (evolutionary independence), whereas MUs are characterized by restricted gene flow (demographic independence). They differ from subspecies in that they do not require phenotypic distinctiveness and thus do not consider adaptive divergence. These discrete units may have colloquial names and may be managed separately but lack the subspecies trinomen. Ecotypes are also a useful unit to consider for management (Williams 1972). Ecotypes emphasize phenotypic differentiation, presumably arising from environmental variation, without requiring phylogenetic distinctiveness. Clear delineation of well-supported subspecies and other subunits (ESUs, MUs, ecotypes) can be important for mule deer management, which typically operates at localized jurisdictional units (e.g., state or provincial). Ideally, management decisions would be enhanced by the phenotypic and ecological structure that exists across a species’ range. In addition, we are increasingly interested in preserving the unique genetic diversity harbored by different population segments as a means of maximizing a species’ evolutionary potential (i.e., capacity to evolve in response to changing environments; Frankham 2005, Sgrò et al. 2011, Harrisson et al. 2014). Subspecies and other infraspecific groupings, however, can become taxonomic entities with legal definitions enshrined in conservation law (United States Government 1988; O’Brien and Mayr 1991; Cronin 1997, 2007; Geist 1992, 1998). If subspecies, or any other groupings, are not based on phylogeny reflected by concordant phenotypic and genetic characters, they would be more appropriately called ESUs, MUs, or ecotypes. Subspecies in particular have been recognized as a subjective category (Wilson and Brown 1953; Cronin 1997, 2007; Ehrlich 2000), but with their trinomial designation they are often assumed to be discrete taxonomic classifications. Because evolution is a continuous and complex process, it can be challenging to

13 categorize taxa into discrete, hierarchical entities along the population-species continuum (Schaefer 2006). Genetic differences.—Genetic differences exist in a continuum, from populations that evolve independently but exchange migrants (and their genes) to species that exhibit complete reproductive isolation and are genetically distinct. Molecular techniques provide an increasingly accurate estimation of taxonomic relationships, in particular at levels of genetic differentiation below the species level. Clear delineation of subspecies has been challenging in mule deer, given their nearly continuous distribution and extensive morphological and behavioral variation throughout their range. Advances in genetics now allow scientists to evaluate differences between populations of mule deer across their range at high resolution, providing powerful data on the evolutionary component of subspecies delineation. The most consistent and pronounced genetic differentiation within the mule deer species complex (O. hemionus) occurs between black-tailed deer and mule deer. The genetic distinctiveness of mule deer and black-tailed deer lineages is unanimously supported by all genetic studies of the species, including those using mtDNA (Cronin et  al. 1988, Cronin 1991b, Carr and Hughes 1993, Cathey et al. 1998, Latch et al. 2009, Pease et  al. 2009), allozymes (Gavin and May 1988, Cronin 1991b), Y chromosome markers (Cathey et al. 1998), microsatellites (Carr et al. 1986, Latch et al. 2014), and single nucleotide polymorphisms (SNPs; Haynes and Latch 2012, Powell et al. 2016, Haines et al. 2019). These divergence patterns correspond to recognized lineages that are also supported by morphological (Taylor 1956, Wallmo 1981b) and behavioral (Müller-Schwarze and Müller-Schwarze 1975) data. The amount of genetic differentiation between mule deer and black-tailed deer can be measured for different genetic markers. Mitochondrial DNA divergence is 6–8%, among the highest infraspecific values reported for mammals. Nuclear markers exhibit less, though still notable, divergence between the 2 lineages (Gavin and May 1988, Cronin 1991a, Cathey et  al. 1998, Haynes and Latch 2012, Latch et  al. 2014). To some extent, this is due to the differences in evolutionary rates between mitochondrial and nuclear DNA. But it also reflects a discordance in the pattern of nuclear and mtDNA divergence in North American deer. At mitochondrial loci, mule deer are more closely related to white-tailed deer than to conspecific black-tailed deer, whereas mule deer and black-tailed deer are more closely related at nuclear loci. Disagreement in divergence patterns between nuclear and mitochondrial markers is not uncommon in phylogenetic studies, and can result from incomplete lineage sorting, selection, or ancient hybridization. Although ancient hybridization has been proposed to explain this mitochondrial-nuclear discordance in North American deer (Geist 1998), it is only one of several potential hypotheses (see above) and currently available data preclude further interpretation. The evolutionarily distinct mule deer and black-tailed deer lineages hybridize where they come into contact along the Cascade Mountain range in the Pacific Northwest. Observations of hybrids go back at least as far as Jackson (1921). Genetic data reveal clear evidence for extensive hybridization throughout Washington and Oregon, just east of the

14 Cascades ridgeline where there is a steep ecological transition from wet forest to dry scrub (Latch et  al. 2011, Haines et al. 2019). Hybridization occurs in both directions (mule deer males × black-tailed females and black-tailed males × mule deer females), and hybrids can mate with each other or backcross with either parental lineage. Over many generations, this has created a full range of hybrid types near the zone of contact, while distinct parental lineages are maintained farther away from the contact zone. Genomic studies suggest that this zone of hybridization is more likely maintained by many loci under weak selection, rather than a few loci under strong selection (Powell et al. 2016, Haines et al. 2019). At the southern edge of the black-tailed deer range in northern California, thorough studies of the hybrid zone have not been undertaken, but hybridization does appear to occur there (Pease et al. 2009, Latch et al. 2014). Within the black-tailed deer, there are 2 named subspecies, Sitka black-tailed deer and Columbian black-tailed deer. Phylogenetic analysis of mtDNA data suggests that at the time of the last glacial maximum (~18,000 YBP), blacktailed deer existed in an ice-free refugium in the Pacific Northwest. Upon glacial retreat, black-tailed deer may have recolonized northward along the coast of British Columbia and into southeast Alaska. Evidence for this pattern of postglacial recolonization comes from genetic diversity data; we see higher genetic diversity in refugia, where populations persisted, and reduced genetic diversity in more recently recolonized areas (Latch et  al. 2009, 2014). It is also possible that Sitka and Columbian black-tailed deer were already diverged at the time of the last glacial maximum, and that Sitka black-tailed deer persisted in a northern refugia in the Alexander Archipelago in southeast Alaska (Latch et  al. 2008). Some records indicate that portions of the Prince of Wales Island complex remained ice-free during Pleistocene glaciation (Carrara et al. 2007), and deer remains dating to the Wisconsin glaciation have been identified from caves near Prince of Wales Island (Heaton et  al. 1996). Higher and unique genetic diversity on Prince of Wales Island compared to neighboring islands lends support to the idea there may have been additional refugial deer populations north of coastal Washington and Oregon (Latch et al. 2008). Existing genetic data for contemporary populations of Sitka and Columbian black-tailed deer suggest that they are evolutionarily similar. More-advanced genetic markers including microsatellites and SNPs have the resolution to distinguish between these 2 types (Latch et  al. 2014; M. L. Haines, University of Wisconsin-Milwaukee, unpublished data). Yet, the differentiation we observe appears to be mostly due to a lack of genetic variation in sampled Sitka black-tailed deer, which have been sampled only from island populations including those introduced from a small number of founders (e.g., Kodiak Island; Latch et  al. 2008, 2014; Colson et  al. 2013). Island populations in general are expected to harbor less genetic variation than mainland populations because they are isolated, but it is unknown whether mainland Sitka blacktailed deer populations harbor similarly low levels of genetic variation. Sitka and Columbian black-tailed deer are thought to intergrade along the central British Columbia coast near Bella Coola (Shackleton 1999), so genetic characterization of

James R. Heffelfinger and Emily K. Latch deer from this region would help understand the magnitude and pattern of differentiation at the region of contact. Within Sitka black-tailed deer, low genetic variation within islands contributes to genetic differentiation among islands (Latch et al. 2008, 2014). Deer in the Alexander Archipelago harbor more genetic variation than deer on Kodiak Island, which was founded from only 25 deer from the Alexander Archipelago. Within the Alexander Archipelago, Prince of Wales Island harbors the most genetic diversity but also appears to be the most isolated (Latch et al. 2008, Colson et al. 2013). Movement of deer among other Alexander Archipelago Islands (Admiralty, Baranof, Chichagof) is likely. Within Columbian black-tailed deer, there is a similar pattern of low genetic diversity contributing to genetic structure of island populations on Vancouver Island and Gabriola Island (Latch et  al. 2009, 2014). This differentiation is also in line with expectations for island populations and does not indicate these island populations are evolutionarily distinct. Within the mule deer lineage, the most pronounced genetic differentiation also was seen on islands. Deer on Cedros Island (O. h. cerrosensis) and Tiburón Island (O. h. sheldoni) exhibit considerable genetic differentiation from the rest of the lineage and greatly reduced genetic variation (Latch et al. 2014, Alminas et al. 2021). In contrast to insular differentiation we observe in black-tailed deer, the reduced genetic variation and divergence from mainland populations we observe for Cedros and Tiburón islands deer is more pronounced, suggesting longterm isolation on a biogeographic scale. The genetic data are supported by cultural, archaeological, and phenotypic evidence supporting endemicity (Alminas et al. 2021). We urge caution in making taxonomic decisions based solely on patterns observed from a single molecular marker, but the total weight of genetic evidence supports the subspecies status of both Cedros Island and Tiburón Island mule deer. The rest of the mule deer lineage, including all mainland mule deer from Yukon, Canada to Sonora, Mexico, is best characterized by an overall gradient of genetic variation (Latch et  al. 2009, 2014). Termed isolation by distance, this pattern is observed when populations that are geographically proximate are more genetically similar than populations that are far apart. Strong isolation-by-distance patterns are consistent with the natural history of a widespread, highly mobile species, where gene flow prevents the emergence of population genetic structure. In mainland mule deer, discrete genetic boundaries between populations are absent at a broad scale, offering no genetic support for subspecies designations in this mule deer group, comprising the formerly recognized subspecies: California (O. h. californicus), burro or desert (O. h. eremicus), southern (O. h. fuliginatus), Rocky Mountain (O. h. hemionus), Inyo (O. h. inyoensis), and peninsula (O. h. peninsulae). Additionally, the desert subspecies name (O. h. crooki) was previously invalidated by Heffelfinger (2000b). The genetic and phenotypic variation we see at a broad scale across mainland mule deer is more continuous, grading from 1 form to another. These diffuse patterns are mostly influenced by historical biogeography (Latch et  al. 2014) and are more consistent with ecotypes. We observe some north-south genetic differentiation that roughly corresponds to the described break between

Origin, Classification, and Distribution formerly recognized Rocky Mountain mule deer and desert subspecies (Latch et al. 2009, 2014). The boundaries, however, are indistinct; for example, based on mtDNA a desert ecotype might include the southern half of California, whereas nDNA may not include California mule deer in the desert group at all. Both data types would likely put the boundary between these ecotypes a little farther north than is currently described, including all of New Mexico and Texas and areas south of the Grand Canyon in Arizona. Such a genetically defined delineation, however, would conflict with phenotypic differences and lacks concordance with ecological conditions. Mule deer on the mainland Baja Peninsula also have been described as distinct subspecies (formerly southern and peninsula) but do not appear to be endemic. Genetic data suggest that deer likely expanded down the Baja Peninsula from southern California along the coast (Latch et  al. 2014, Alminas et  al. 2021). In California alone, 5 mule deer subspecies have been described (California, burro, southern, Rocky Mountain, Inyo). Comprehensive sampling throughout California did find support for regional differentiation among southern California mule deer but suggested that the divergence was recent and mediated by ecological factors (Pease et al. 2009). This conclusion is supported by Latch et al. (2009, 2014) and Cronin and Bleich (1995) and suggests that phenotypic differences in this region are not phylogenetically based and would be more appropriately considered as ecotypes. In continuously distributed species, adaptation to local environmental conditions can influence adaptive divergence even with ongoing gene flow at non-functional loci (including microsatellites and neutrally evolving SNPs). Functional variation has not been directly assessed in mule deer rangewide adequately enough to quantify any ecologically based structure that might have emerged through local adaptation. Physical differences.—Throughout the geographic range of black-tailed and mule deer, there is considerable variation in body size, coat color, antler shape, behavior, and other attributes. The physical variation in mule deer led early naturalists to collect a deer from 1 location and another from someplace else and designate them as different species or subspecies because of slight differences they described (Rafinesque 1817a; Mearns 1897, 1907; Lydekker 1898). Some of these physical differences are taxonomically meaningful, but others simply reflected the variation one might see within a single population of deer. From this sparse collection of deer specimens 90–200 years ago, the geographic ranges of mule deer subspecies were drawn on a map (Cowan 1936, 1956). Without a robust sampling of deer from many different areas, it is not possible to accurately describe the true physical variation of this species across western North America. This variation among subspecies originally was described based solely on physical attributes of specimens because genetic analyses were not available. Given that subspecies was a trinomial extension of the Linnaean binomial nomenclature, these physical differences were thought to reflect underlying phylogenetic relationships, but we now know that is not always the case. Physical characteristics of all types are environmentally plastic and subject to differences in nutrition the animals have access to their whole life, and maternal and epigenetic effects (Monteith et al. 2009, Linnell and Zachos 2011, Putnam

15 and Flueck 2011). Aragon et  al. (1998) illustrated that skull length in roe deer varied geographically, not along latitude, longitude, or elevation but in relation to primary productivity of the habitat. They suggested this geographic variation was better described as a series of ecotypes and not taxonomic subspecies because the differences were mostly the result of environmental influences. Aragon et  al. (1998) cautioned against defining phylogenetic taxonomic categories using characters influenced mostly by environment, which is advice that holds important relevance to Odocoileus hemionus taxonomy. No comprehensive rangewide morphological analysis has been conducted on mule deer physical characteristics, but there is ample evidence for strong environmental effects on deer phenotype (Mech et  al. 1991, Geist 1998, Monteith et  al. 2009, Michel et al. 2016a; Chapter 4). Keeping environmental and epigenetic effects in mind, an objective review of black-tailed and mule deer physical characteristics is overdue. Of the 11 subspecies of mule deer that have been described, 2 stand out as substantially different from the rest. In addition to the stark mtDNA differentiation (Latch et al. 2009, 2011), Sitka and Columbian black-tailed deer differ physically from the rest of the species. The Sitka black-tailed deer in southeast Alaska and coastal British Columbia is the most divergent phenotype of all the putative black-tailed and mule deer subspecies. Overall, it is the smallest subspecies, with a darker pelage and more brown on the sides of their face making lighter-colored eye rings more prominent than their conspecifics (Shackleton 1999; Chapter 3). The fur on the edges of the preorbital glands is white, which is distinctive and unique in this subspecies (Figs. 1.3A, 3.1C). The presence of 2 white throat patches is iconic in black-tailed deer, compared to the single patch in mule deer. Their rump markings are the most subdued of all conspecifics, with very little white visible on either side of a flat flap-like tail that is brown on the upper half and then black to the tip, consistent with their occupying thick dark forest rather than open areas (Geist 1998). Their ears are the shortest of all black-tailed or mule deer (Table 3.2). Sitka black-tailed deer also have the shortest metatarsal glands (1.5–2 inches [38–51 mm]) that, unlike mule deer, are often circumscribed with white fur (Fig. 3.2C; Table 3.2; Cowan 1956). Antlers of this small coastal rainforest deer are correspondingly smaller with 2 or 3 points/side (excluding brow tines) common in mature males, but some individuals develop miniature versions of the classic 4×4 mule deer configuration. The second phenotypically supported subspecies is the Columbian black-tailed deer, which inhabits the coastal Pacific Northwest from southern British Columbia southward to northern California. This subspecies looks more like a mule deer than do Sitka black-tailed deer, but it is still smaller, darker, and with shorter ears than mule deer (Table 3.1, 3.2). The Columbian black-tailed deer has a more obvious rump patch than do Sitka black-tailed deer with some white visible on either side of the tail, but the patch is still much more subdued than in mule deer (Fig. 1.3). The tail of this subspecies is mostly black for the length of the dorsal surface, but it is often narrower and brown at the base, or upper 25%, of the tail (Shackleton 1999; Table 3.1; Fig. 3.1C). As with all black-tailed deer, the base of the ventral surface of the tail is not naked as in mule deer (Cowan 1936). The double throat patch occurs

16

James R. Heffelfinger and Emily K. Latch

FIGURE 1.3  Physical differences among black-tailed and mule deer subspecies and ecotypes: A) Sitka black-tailed deer, B) Columbian black-tailed deer, C) mule deer - California ecotype, D) mule deer - desert ecotype, E) mule deer - Rocky Mountain ecotype. Illustration by Randall Babb, based on Geist (1990).

on Columbian black-tailed deer but is often absent. Metatarsal glands in this subspecies are larger than in Sitka but still are about half the length of mule deer (Cowan 1956, Shackleton 1999; Fig. 3.2C; Tables 3.1, 3.2). Although they are more likely to produce a classic 4×4 antler configuration than Sitka blacktailed deer at maturity, the antlers are smaller and less massive than those of mule deer. Some have reported black-tailed deer on certain islands along the coast of British Columbia and southeast Alaska with large variations in body mass, antler configuration, or pelage color (Cowan 1936, Cowan and Raddi 1972). These local variations can be intensified in closed island populations, but these are not taxonomically different kinds of deer. Body mass can vary much more dramatically in relation to density of deer and nutritional resources on an island at the time than phylogenetically in this area. Likewise, it would be unwise to put too much credence on differences in subtle skull measurements (Cowan 1936, 1956) from small sample sizes for the same reason. Although the 2 black-tailed deer subspecies are supported as sufficiently different phenotypically and genetically, they do blend together at the point their distributions meet  along the coast of British Columbia. At the southern extent of blacktailed deer distribution, there is some uncertainty where blacktailed deer transition into mule deer. The deer between San Francisco and San Luis Obispo County, California, were at one time designated as a southern black-tailed deer (O. columbianus scaphiotus) with a type specimen collected in 1898 in the Gabilan Range of San Benito County, California (Merriam 1898, Sheldon 1933). Although it was described as a form of black-tailed deer because of the black on the dorsal surface of the tail, many of the characters Merriam (1898) described are consistent with mule deer. Genetic methods were unavailable at the time to determine whether deer in this region were mule deer or black-tailed deer, and samples from this area were unfortunately not included in the more recent genetic analyses

of black-tailed and mule deer secondary contact (Latch et al. 2009, 2011). This leaves some uncertainty as to the taxonomic status of deer in this area, but phenotypically they tend more toward the California mule deer ecotype than Columbian black-tailed deer. California Department of Fish and Wildlife (CDFW) considers these deer to be mule deer for management purposes (D. S. Casady, CDFW, unpublished data). There are 2 subspecies that have been described with discrete ranges confined to their respective islands. Tiburón Island is in the Sea of Cortez between Sonora on the Mexican mainland and Baja California. The island itself is 464 miles2 (1,201 km2) and separated from the mainland by Channel Infiernillo (Alminas et  al. 2021), a channel with strong tidal currents that varies 1–5 miles wide (1.7–8 km). Mule deer have been documented swimming between the island and mainland, but genetic patterns indicate it is not common (Alminas et al. 2021). There are no records, or local lore, of deer being translocated onto or off the island, which has been separated from the mainland for 11,000–10,000 years (Wilder 2014, Alminas et al. 2021). Stories written in the language of the native Seri people support the endemism of mule deer on Tiburón Island (Wilder 2014). The deer on Tiburón Island are classified as threatened by the Secretaría del Medio Ambiente y Recursos Naturales (SEMARNAT 2010) and the United States Fish and Wildlife Service (1975). Mule deer on Tiburón Island are morphologically similar to (but genetically distinct from) their conspecifics on the mainland of Sonora (Alminas et al. 2021) with some morphological variation in color and reported dental and skull measurements (Goldman 1939, Cowan 1956). Overall body size, shape, and coloration of the tail are typical of other mule deer inhabiting desert environments, although possibly smaller. The body pelage, however, is consistently darker and sometimes fades to a brown-reddish hue in mature animals with the white ventral surfaces tending toward buff instead of white in many

Origin, Classification, and Distribution

FIGURE 1.4  Mature Tiburón Island mule deer harvested on Tiburón Island. Photo by Derick Lopez.

individuals (Goldman 1939, Cowan 1956). Besides the darker overall color, the presence of a dark dorsal stripe from the upper neck to the tail is more common than in mainland desert mule deer (Goldman 1939, Cowan 1956; Fig. 1.4). Goldman (1939) reported the skull of Tiburón mule deer as broader and shorter (nasals, toothrow, individual teeth) than mainland desert mule deer, but this was based on a very small sample of skulls and confounded with environmental plasticity (Cowan 1936). The antlers of mature males on this island more commonly have extra points when compared to those on the mainland and are very dark in color. The color of the antlers, of course, is not of taxonomic significance because it comes from the Torote plant (Bursera spp.) upon which they rub their antlers (Johnson 1992; Wilder et al. 2008; D. D. López, Derick López Outfitting, personal communication). Cedros Island is 134 miles2 (348 km2) in size and 14.9 miles (24 km) northwest of the nearest mainland at Punta Eugenia, Baja California. This island has been isolated in the Pacific Ocean off the west coast of Baja California for 12,000–10,000 years (Des Lauriers 2006, Alminas et al. 2021). Cedros Island mule deer are listed as endangered by SEMARNAT (2010, 2018) and conservation efforts are underway. Physical evidence of mule deer on the island stretches back to 2,500 YBP (Des Lauriers 2009), but most archaeological work has been done along the coast where Indigenous peoples focused on plentiful marine resources for sustenance (Des Lauriers 2005, 2006, 2009). Although coastal sites lacked evidence of deer prior to 2,500 YBP, Des Lauriers (2005) reported the discovery of large, biface and shouldered projectile points similar to those used for hunting large game on the mainland and urged caution in assuming deer were not present earlier. The mule deer on Cedros Island have been referred to as island dwarfs (Geist 1990, 1998) and pygmy deer (Des Lauriers 2005, 2009) because of their smaller size (Merriam 1898, Cowan 1936, Pérez-Gil Salcido 1981). Smaller stature for large mammals on islands is an established relationship and not surprising (Foster 1964, Lomolino 2005). The lack of funding, remoteness of the island, and endangered status of the deer make capture and collection of morphological data difficult; however, Pérez-Gil Salcido (1981) indirectly estimated

17

FIGURE 1.5  Young male mule deer on Cedros Island with lack of brow tines, buff color instead of white undersides, and dark dorsal stripe. Photo by José Antonio Soriano.

the height at shoulder of these mule deer to be 73% (40–55 inches [103–140 cm]) that of mainland mule deer. Overall pelage color differs in that insular deer are darker and more reddish-brown with a dark dorsal line down the back of the neck to the tail (Merriam 1898, Cowan 1956, Pérez-Gil Salcido 1981). Metatarsal glands are typical for desert mule deer but at the shorter end of the normal range of variation (Merriam 1898, Cowan 1956). On most animals, a dark line runs along the ventral chest between the front legs that appears more pronounced than in other mule deer. Cedros Island deer have a very small rump patch with buff or cream-colored hairs where white is normally seen in other mainland mule deer (Cowan 1936, Pérez-Gil Salcido 1981, Povilitis and Ceballos 1986; Fig. 1.5). Likewise, the throat patch, ventral surfaces, and inside of legs are subdued with a more-uniformly buff and brown color instead of white (Merriam 1898). Tails appear to have longer hairs than other mule deer subspecies, again with buff color replacing the typical white of most other mule deer (Pérez-Gil Salcido 1981). It is very common for Cedros Island mule deer to have a dark stripe down the dorsal surface of their tails as in some mainland forms. Cowan (1936) reported smaller skull measurements from deer on Cedros Island, which was confirmed by Pérez-Gil Salcido (1981) who reported Cedros Island skulls smaller in all dimensions measured. There are other skull measurements mentioned as different in the literature (Cowan 1936, 1956; Pérez-Gil Salcido 1981), but the same caution as above is warranted. When sample sizes are small, individual variation and environmentally induced phenotypic plasticity is not accounted for (Wallmo 1981b). As in the deer on Tiburón Island, the antlers of Cedros Island mule deer also are very dark brown, likely from rubbing on a local plant species. Antlers can reach a relatively large size, but Cowan (1936) and Pérez-Gil Salcido (1981) reported they never grow brow tines, which are common in mule deer on the nearby Baja California (A. Tapia-Landeros, Autonomous University of Baja California, unpublished data). The lack of browtines appears to hold true as a unique characteristic of this subspecies, although a few mature males may produce small bumps in place of brow tines, so it is likely not absolute.

18 There are mule deer on San Jose Island off the Mexican coast in the Sea of Cortez (Huey 1964), but they have never been described or investigated. Alminas et al. (2021) included 2 mule deer samples from this island in their analysis and they differed slightly from mule deer on the adjacent Baja California mainland, but not enough samples were available from either San Jose Island or nearby Baja California to evaluate properly. Along the North American mainland, mule deer populations are distributed and interconnected from the Yukon and Northwest Territories in the north to Zacatecas, Mexico in the south and from the southern Pacific Coast east to the central Great Plains. Throughout the range of mule deer on the mainland, we see variations in tail color, rump color, body size, antler shape, metatarsal gland length, pelage coloration, skull shape, and the amount of contrasting coloration on the face and neck (Cowan 1936, 1956; Wallmo 1981b; Geist 1994). These variations in physical characters occur as gradients across geographic space and are best described as clines (Huxley 1939, Geist 1990). For example, a physical feature such as tail coloration gradually changes from one end of mule deer range to the opposite end. It is common to have a character change across a gradient from north to south (e.g., body size), while another varies along an east-west axis (e.g., tail coloration). None of these geographically varying characteristics are very different from one another in adjacent populations but can be dramatically different when distant populations are compared. It is not easy to disentangle the causes of these geographical differences in physical characteristics, whether from underlying phylogenetic histories or the influence of current environmental pressures shaping and maintaining those differences. If genetic analyses of the appropriate resolution fail to reveal phylogeographic patterns concordant with geographic patterns in physical differences, then it is reasonable to assume this geographic variability is primarily the result of environment. Clines can be uniform gradients from one end to the other or may contain steps along the cline where characteristics change more abruptly. It may be tempting to draw lines through steps in clines to differentiate subspecies, but without genetic support for phylogenetically based distinctions, these steps are more appropriately thought of as divisions between ecotypes maintained by environmental forces. There are several clines or step clines recognized throughout the range of mule deer. Body size generally follows a north-south axis with the largest average body mass and size in Canada and the smallest of the mainland mule deer in the Southwest Deserts (Cowan 1936, 1956; Wallmo 1981b; Bowyer and Bleich 1984a; Geist 1998; Table 3.1). This cline follows a gradient of net primary productivity of the vegetative community, from more productivity and seasonality in the north to less in the southwestern parts of mule deer range. Pelage coloration also occurs along a cline with lighter coloration in arid areas and darker, more contrasting coloration as humidity increases (Cowan 1936, 1956). Mule deer tails change in coloration geographically in a stepped cline (Huxley 1939), with deer throughout the northern majority of mule deer range (excluding black-tailed deer) uniformly having the typical white rope-like and black-tipped tail. In central California, this typical mule deer tail form gives way to tails

James R. Heffelfinger and Emily K. Latch that usually have a dark stripe down the dorsal surface. The stripes on mule deer tails in California are also found sporadically elsewhere in populations throughout the southern part of mule deer range (Hoffmeister 1962; J. R. Heffelfinger, Arizona Game and Fish Department, unpublished data). In extreme southern California and northern Baja California, Mexico, the black stripe becomes somewhat wider (R. A. Botta, California Department of Fish and Wildlife, personal communication) before returning to a predominately typical mule deer tail in Baja California Sur, and the Mojave, Sonoran, and Chihuahuan deserts of the American Southwest and northern Mexico. Metatarsal gland length is also arranged in a northsouth cline with an increasing length as one moves northward from Baja California and Sonora, Mexico to Canada (Cowan 1936, 1956; Hoffmeister 1962), in the same latitudinal gradient as described in white-tailed deer (Brokx 1972a). In the past, the geographic variation of these physical characteristics has been partitioned into discrete taxonomic subspecies, each with their own geographic range and scientific name creating an impression there are several different mutually exclusive kinds of mule deer on the mainland of North America, each with their own uniform characteristics (formerly identified as California, desert, burro, southern, Inyo, and peninsula). Researchers and managers have been repeating these names even as they recognize they are not supported by physical or genetic characteristics that would hold up to a comprehensive evaluation with adequate sample size and distribution (Wallmo 1981b; Geist 1990, 1998; Kucera and Mayer 1999; Heffelfinger 2006). There is no hierarchical identification key that will accurately differentiate these kinds of deer based on physical characteristics described, in some cases, >200 years ago (Anderson and Wallmo 1984). The Inyo mule deer was first defined by Cowan (1933) as a new subspecies of deer in eastern California, but its validity has been questioned ever since (Wallmo 1978, Geist 1990, Kucera and Mayer 1999, Kie and Czech 2000, Mackie et al. 2003). Later, in letters to O. C. Wallmo, Cowan himself questioned the validity of this subspecies (Wallmo 1981b). Subsequent data collected on Inyo mule deer show no evidence they meet the criteria for subspecies nomenclature; morphological differences are slight and grade into nearby forms, they are not geographically separated, and there is no evidence for phylogenetic distinctiveness indicating unique evolutionary potential. One obvious example of the continued use of subspecies distinctions for what should be recognized as ecotypes is the case of desert versus Rocky Mountain mule deer (Hoffmeister 1962, 1986). Subspecies maps indicate that deer in the Yukon, Canada are the same as those in central Arizona, whereas mule deer in southern Arizona represent a different taxonomic entity (Wallmo 1981b). There is no meaningful line that could be drawn between desert and Rocky Mountain mule deer on either physical or genetic bases; bigger, darker, northern deer gradually change to lighter, smaller deer in the Southwest Deserts. The desert mule deer subspecies is a good example of the confusion created over designating new subspecies based on 1 or a few specimens from 1 location in the face of ample individual variation. In 1892, Edgar Mearns shot a deer in

Origin, Classification, and Distribution southwestern New Mexico and described it for science as Crook’s black-tailed deer (Dorcelaphus crooki; Mearns 1897), a new species of black-tailed deer based on its similarity to the Columbian black-tailed deer. No other deer with similar characteristics were collected at or near that locality and no true black-tailed deer are found within 900 miles (1,448 km), leading many to suspect this type specimen might be a hybrid between white-tailed and mule deer (Lydekker 1898, Seton 1929, Bailey 1931, O’Conner 1939). Goldman and Kellogg (1940), however, evaluated this specimen in detail and classified it as a desert mule deer (Dorcephalus hemionus crooki). In the same publication Mearns (1897) described the burro deer or desert mule deer (Dorcelaphus hemionus eremicus) based on a deer collected in 1895 by W. J. McGee in the Sierra Seri, Sonora, Mexico. McGee did not keep the skull but processed the hide as a deer skin rug (Goldman 1939). A few fragments trimmed from the skin were deposited in the United States National Museum (USNM) until Mrs. McGee sold the deer rug to USNM in 1902 (Poole and Schantz 1942). The formal description of this subspecies was based on the few scraps of fur in the museum (USNM 63403) and 2 sets of antlers from different deer: 1 from Sonora, Mexico (USNM 59910) and the other from Black Butte, 15 miles (24 km) northwest of Yuma, Arizona (USNM 60855). Using the corrected genus name, Odocoileus (=Dorcelaphus), Hoffmeister (1962) reported it was not possible to discern exactly what the characteristics of O. h. eremicus were because of the lack of adequate specimens and suggested the valid subspecies name for desert mule deer was O. h. crooki (= eremicus). Subsequently, Heffelfinger (2000b) showed that Mearns’ black-tailed deer-like type specimen representing O. h. crooki was actually a whitetailed deer × mule deer hybrid, invalidating the use of that name. According to the rules of binomial nomenclature, O. h. eremicus had to be resurrected as the next available name for desert mule deer. Merriam (1901) also described another type of desert mule deer (Odocoileus hemionus canus) based on a single male (USNM 99361) from Sierra en Medio, Chihuahua, Mexico despite this location lying only 25 miles (40 km) southwest of the type locality for O. h. crooki in New Mexico. Later, O. h. canus was synonymized with O. h. crooki, which was then found to be invalid, forcing the use of O. h. eremicus. This desert mule deer example illustrates how neither science nor conservation is advanced when taxonomic categories of mule deer are based upon a foundation of misidentification, nonexistent or insufficient specimens, near-arbitrary range maps, and descriptions of assumed phylogenetic relationships based on morphological assessment of only a few specimens.

Summary of Geographic Variation in Odocoileus hemionus Black-tailed and mule deer subspecies originally were defined and described morphologically in ways that would never satisfy even a basic standard of science today. Subsequently, some of these subspecies have been confirmed as valid with additional morphological and genetic studies (Cowan 1956; Latch et al. 2009, 2011; Alminas et al. 2021). Others, however, have been continually perpetuated in publications even when it is clear the rigid range maps and subtle differences in a few

19 skull measurements or pelage color fail to accurately describe the geographic variation of the species. Subspecies designations, with their trinomial Linnaean nomenclature, imply an infraspecific division that arose from a unique phylogenetic history. For example, geographic groupings of a species that were isolated in separate glacial refugia might be the foundation for a subspecies designation depending on other data. These phylogenetic histories should be detectable with genetic analyses of appropriate resolution. Without evidence that variations in phenotype reflect phylogenetic differences, it is likely they are caused by environmental influences and are not appropriately defined by trinomial scientific names. There is phenotypic, and nuclear and mitochondrial genetic, support for 2 subspecies in the Pacific Northwest: Sitka and Columbian black-tailed deer (Cowan 1956; Cronin 1991b; Cathey et al. 1998; Latch et al. 2009, 2014). Additionally, there are 2 subspecies confined to Tiburón and Cedros islands in Mexico that are supported by genetic data (Alminas et  al. 2021) and some morphological differentiation (Merriam 1898; Cowan 1936, 1956; Goldman 1939; Wallmo 1981b). Further morphometric analyses are needed on the 2 insular subspecies, but their genetic differences and isolation from mainland mule deer populations for >10,000 years warrant recognition as distinct taxonomic entities. These subspecies have independent phylogenetic histories and future evolutionary trajectories that will remain separate barring anthropogenic interference. In the meantime, it is imperative that all possible conservation measures be implemented to conserve these important units of genetic diversity. None of the remaining mainland types of mule deer that have been referred to as subspecies are geographically separated from other adjacent types. In fact, they are genetically indistinguishable at a broad scale and freely interbreed as an interconnected population with no pronounced phylogenetic pattern (Latch et al. 2009, 2014). Local ecological influences can maintain distinct regional phenotypes as young dispersers remain in familiar vegetation communities or ecological conditions and populations adapt to the local environment. This is why one might see physical differences at the boundaries of vegetation associations and ecological discontinuities (Pease et al. 2009, Latch et al. 2014). Ecologically based differences with no phylogeographic support would be more appropriately categorized as ecotypes shaped more by environment than evolutionary descent (Geist 1990, Aragon et  al. 1998). The formerly recognized mule deer subspecies (California, desert, burro, southern, Inyo, and peninsula) on the mainland North American continent should be recognized as 1 subspecies under the nomenclaturally correct trinomen O. h. hemionus (Rafinesque 1817a). Mule deer ecotypes that are somewhat differentiated physically and ecologically can, and should, still be recognized as non-taxonomic entities. There is no reason to discontinue the use of local references such as desert, California, Inyo, southern, peninsula, San Diego County, and Rocky Mountain mule deer. Those are useful terms for communicating among biologists, deer enthusiasts, and possibly as units of conservation; they just do not represent taxonomic divisions of evolutionary descent in the Linnaean system. Records books that recognize

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James R. Heffelfinger and Emily K. Latch

TABLE 1.2 Subspecies of black-tailed and mule deer currently supported by the weight of ecological, morphological, and genetic evidence. Common name

Scientific name

Sitka black-tailed deer

Odocoileus hemionus sitkensis

Columbian black-tailed deer Mule deer

Odocoileus hemionus columbianus Odocoileus hemionus hemionus

Cedros Island mule deer Tiburón Island mule deer

Odocoileus hemionus cerrosensis Odocoileus hemionus sheldoni

Range West of the Coast Mountains on the Pacific Coast from approximately Bella Coola, British Columbia, Canada, northward to Haines, Alaska, USA, with translocations farther north to the Kodiak Archipelago and Prince William Sound. Northwestern California from San Francisco northward, west of the Cascade Mountains along coastal Oregon and Washington, USA, to approximately Bella Coola, British Columbia, Canada. Continental North America from Yukon, Canada, and Alaska, USA, south to Zacatecas, Mexico, and from the central Great Plains in the east to the southern Pacific Coast and the crest of the Cascade and Coast mountain ranges. Includes the geographical distribution of formerly recognized subspecies: Rocky Mountain, California, desert, burro, southern, Inyo, and peninsula. Cedros Island, Baja California, Mexico Tiburón Island, Sonora, Mexico

different categories of animals have proven useful in collecting regional data of conservation relevance and for generating interest and advocacy for some populations (Monteith et  al. 2013a; LaSharr et  al. 2019; A. Tapia-Landeros, unpublished data). These nonscientific categories should be encouraged because they promote and focus conservation of mule deer in certain parts of their range that may otherwise be neglected. These ecotypes—especially at the periphery of their range— represent important pockets of phenotypic and genetic variation that should be preserved to provide the raw material for adaptation to changing future conditions (Aragon et al. 1998). Taxonomy continues to evolve as more information is gathered about these deer. Genetic methods are rapidly evolving and will continue to do so. Comprehensive evaluation of morphology, especially the characteristics that have been used in the past to categorize subspecies, would be most useful. Given the totality of all the evidence, we find support for 5 subspecies of black-tailed and mule deer: Sitka black-tailed deer, Columbian black-tailed deer, mule deer, Cedros Island mule deer, and Tiburón Island mule deer (Table 1.2; Fig. 1.6).

Distribution Black-tailed and mule deer occur in all biomes of western North America from central Mexico north to, but not including, the arctic tundra (Anderson and Wallmo 1984). Sitka black-tailed deer occupy coastal rainforests west of the Coast Mountains along the Pacific coast of southeast Alaska and British Columbia (Fig. 1.6). Sitka black-tailed deer currently occur as far north and west in Alaska as Prince William Sound and the Kodiak Archipelago as a result of historical translocations. Columbian black-tailed deer occupy northwestern California from San Francisco northward, on the west side of California’s Central Valley and west of the Cascade Mountains along coastal Oregon and Washington, to the central British Columbia Pacific coast. The changes in physical and genetic characteristics between Sitka and Columbian black-tailed deer are likely a transition with the approximate center near Bella Coola, British Columbia. Both black-tailed deer subspecies

occur from sea level up to alpine elevations in the summer (Chapter 10). Sitka black-tailed deer in particular are capable swimmers and often swim between coastal islands and the mainland. The Cedros Island mule deer is confined to that island off the Pacific coast of Baja California, Mexico with no known natural or anthropic interchange. Mule deer on Tiburón Island, Sonora, Mexico, have been reported to swim to and from the mainland, but genetic analyses indicate it must be rare because they are genetically distinct. Both of these Mexican insular subspecies have been separated from the mainland for most of the last 10,000 years and are genetically distinct, supporting their subspecific status as valid (Alminas et al. 2021). The mule deer on mainland North America are found as far north as the Alaska-Yukon border, south to nearly Zacatecas, Mexico and from the central Great Plains in the east to the southern Pacific Coast and the crest of the Cascade and Coast mountain ranges (Table 1.2; Fig. 1.6). Mule deer range overlaps that of Columbian black-tailed deer along the crest of the Cascade Mountains in California, Oregon, Washington, and the Coast Mountains of British Columbia (Shackleton 1999). This subspecies contact zone represents a well-documented bidirectional hybrid swarm (Latch et al. 2011, Haines et al. 2019). At the species’ northern extreme, distribution and abundance of mule deer in northern Saskatchewan, Alberta, and British Columbia is affected by winter severity and habitat disturbance, with no clear trend of expansion or contraction (J. D. Gilligan, Alberta Fish and Wildlife Division, personal communication; T. E. Perry, Saskatchewan Ministry of Environment, personal communication). At the southern part of mule deer distribution, they occur in the desert grasslands of eastern Chihuahua, northeastern Durango, and western Coahuila, Mexico, north through West Texas and the Texas Panhandle. The only large and irregular gaps in mule deer distribution are extreme southwestern Arizona, southeastern California, and southwestern Nevada. In addition to those natural gaps in distribution, mule deer are rare or absent in the Central Valley of California because of intense development, agriculture, and human presence (Kucera and Mayer 1999).

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Origin, Classification, and Distribution

FIGURE 1.6  Geographic range and subspecies of black-tailed and mule deer in North America. Cartography by Sue Boe.

Peripheral Observations, Natural Expansions, and Contractions Mule deer first appeared in the Yukon in the 1930s and have been recorded as far north as Chapman Lake (Hoefs 2001). Mule deer distribution at its northern extent in the Yukon appears to expand and contract with trends in winter severity. Expansion to the north in milder periods seems to be facilitated by major roadways and their corridors; mule deer are not often seen in more remote areas during surveys for other species (S. M. Czetwertynski, Yukon Department of Environment, personal communication). Mule deer are not native to Alaska, but occasional sightings have been reported in the eastern Interior since at least the 1970s. These animals are rare dispersers from the Yukon, occasionally resulting in mule deer sightings well outside their historical range. These incursions into interior Alaska seem to be more common recently, with 3 reported north of Delta Junction in 2013. During the winter of 2016–2017, a male was killed by a car near Fairbanks,

Alaska (specimen UAM:Mamm:134827 housed at University of Alaska). In recent years, mule deer also have been seen more commonly around Skagway and Haines, Alaska (K. R. McCoy, Alaska Department of Fish and Game, personal communication). There is no self-sustaining population of mule deer in the Northwest Territories. There have been 2 recorded sightings (1979 and 2003) of mule deer in the last 4 decades and both were in the southeastern corner of the Nahanni National Park (Mule Deer Working Group 2021). In addition, there was 1 unrecorded sighting in 2018 from a wildlife officer working for the Government of the Northwest Territories of 2 mule deer just north of the British Columbia-Northwest Territories border near the Liard River (Mule Deer Working Group 2021). Mule deer were occasionally observed in the Northwest Territories from the 1920s to late-1960s, but the area has not supported a viable population. Mule deer occasionally are reported in Iowa, Wisconsin, and Minnesota even though these states are not within their normal

22 distribution. In 1954, a hunter harvested a yearling mule deer near the town of Leon in south central Iowa (Sanderson 1956). Subsequently, 2 additional mule deer were harvested during hunts the following 2 years, 1 in the northwestern and another in the southwestern part of the state (Kline 1959). In total, Bowles (1975) provided documentation of 7 mule deer in western Iowa. Bowles et al. (1998) reported being told that a mule deer was harvested in western Iowa about every third year up to 1998. Erickson and Bue (1954) documented many early confirmed occurrences of mule deer in Minnesota (1941, 1947, 1948, 1952, 1953) as deer populations recovered under modern deer management practices. Mule deer were historically more numerous in Minnesota (Hazard 1982); the USNM mammal collection contains a male mule deer specimen (USNM 120310) collected in Marshall County, Minnesota in November of 1892. Today, mule deer only show up in the harvest at a cadence of about 1 every 3 years, including 1 near Rochester in the southeastern part of the state (L. Cornicelli, Southwick Associates, personal communication). Mule deer have been documented in Wisconsin even though they have to travel through Minnesota to get there. The first known mule deer harvested in Wisconsin was during the 1988 gun season in Grant County, followed by another in Polk County in 2015, about 350 miles (563 km) from the nearest mule deer population. In 2011, Wisconsin Department of Natural Resources biologists received a trail camera photo of a young mule deer in Vernon County. Despite efforts to confirm the origin of the Polk and Vernon county records, it is unclear if it was wild, a captive escape, or transported as a fawn into the state (K. B. Wallenfang, Wisconsin Department of Natural Resources, personal communication). With the increased deployment of trail cameras, it should be easier to document these extralimital occurrences. Populations in the central Great Plains are receding westward in some states (Mule Deer Working Group 2021). The Texas Panhandle has experienced an expansion of mule deer distribution in the last 70 years. After translocations from West Texas to the Texas Panhandle (1949–1968), mule deer distribution increased gradually from 11 panhandle counties at that time to 49 counties by 2000 (Kamler et al. 2001). The shortgrass prairie of the Texas Panhandle lacked adequate cover for mule deer historically, but with the enrollment of agricultural fields in the Conservation Reserve Program starting in 1986, many fields provided food and cover in the form of tall dense grasses. The southern extent of mule deer distribution in Mexico once reached farther east in Coahuila, southwestern Nuevo León, northern San Luis Potosí, northern Zacatecas, and a small part of western Tamaulipas (Leopold 1959, Ceballos 2014, Gallina-Tessaro et al. 2020). That range has retracted on its southern and eastern edges in Mexico so that they no longer exist in wild, free-ranging populations in Tamaulipas, Nuevo León, San Luis Potosí, and eastern Coahuila, and may only exist in a small area of northern Zacatecas (Sánchez-Rojas and Gallina 2007, Gallina-Tessaro et al. 2020).

Extralimital Translocations Alaska.—Alaska has a long history of translocating wildlife starting in 1750 with the Russians releasing foxes (Vulpes

James R. Heffelfinger and Emily K. Latch spp.) on Alaskan islands (Paul 2009). In 1917–1923, Sitka black-tailed deer were captured from the Sitka, Alaska area and released in Prince William Sound on Hinchinbrook and Hawkins islands (n = 24). These deer spread throughout Prince William Sound and the mainland, allowing them to be hunted for the first time in 1935 (Paul 2009, Westing 2018). Harvest can vary quite a bit from year to year, but this area (Game Management Unit 6D) yielded >2,000 deer harvested in 2019 (Westing 2018). A small number of Sitka black-tailed deer were captured in the Hoonah area in 1920 and released nearby on Willoughby Island in Glacier Bay, where they are still periodically seen. Three years later (1923), more deer from Sitka, Alaska were translocated to Homers Spit (n = 7), but that release failed. The Kodiak Archipelago stands as the best-known translocation of Sitka black-tailed deer far north of their normal distribution with more than 5,000 deer harvested in 2019 (Svboda and Crye 2020). Deer were captured near Sitka (1924, n = 14) and Prince of Wales Island (1930, n = 2), and released on Long Island. Additional deer were captured in Rocky Pass between Kupreanof and Kuiu islands (1934, n = 9) and released on Kodiak Island (Paul 2009). Deer subsequently dispersed to other islands in the Kodiak Archipelago, including Afognak, Sitkinak, and Tugidak islands (Svboda and Crye 2020). The current population of Sitka black-tailed deer in Yakutat Bay is the result of only 12 animals (5 males, 7 females) also captured in Rocky Pass in 1934. Translocation of ≥13 black-tailed deer to Lynn Canal in 1951–1952 and 1956 were not very successful, with very few subsequent black-tailed deer sightings in the Skagway area and only very low numbers of black-tailed deer in the Haines and western Lynn Canal mainland areas (Paul 2009; K. R. McCoy, unpublished data). The release of 8 additional deer on Sullivan Island in Lynn Canal (1951–1954), however, was successful and deer persist at low to average densities as documented by pellet-group surveys and hunter harvest (Sell 2020). Kupreanof Island received 10 Sitka black-tailed deer from Admiralty Island in 1979 in an attempt to accelerate recovery of deer populations following a severe winterkill (Paul 2009). British Columbia.—The first Sitka black-tailed deer known to be translocated was a group of 8 released on Haida Gwaii (formerly Queen Charlotte Islands) in 1878. Although the archaeological record confirms deer occupied Haida Gwaii 12,000 YBP (Fedje et al. 2011), this island complex was devoid of deer at the time of the 1878 translocation. It is not clear if the first translocation was successful, but additional animals captured on Porcher Island and released in 1911 (n = 41), 1912 (n = 6), 1913 (n = 7), and 1925 (n = 3) resulted in an overabundant deer population on the island (Paul 2009, Martin et al. 2010). California.—As with many states and provinces, California has vague mentions of undocumented translocations, some of them across the ranges of different subspecies and ecotypes. Longhurst et al. (1952) mentions translocations of mule deer with a Rocky Mountain ecotype into the ranges of Columbian black-tailed deer, southern mule deer, and California mule deer ecotypes. Undoubtedly, poorly documented movements of deer like this further complicates our understanding of geographic variation in this species. To increase hunting opportunities, 1 male and 2 female mule deer from Modoc County were introduced to Santa Catalina Island in 1929. Catalina

23

Origin, Classification, and Distribution Island is a 75-mile2 (194-km2) island located 25 miles (40 km) south of coastal Los Angeles (Manuwal and Sweitzer 2008). These first 3 animals were augmented with 19 more from 1930–1932 (Longhurst et  al. 1952). By 1949, they were estimated to number 2,000 and were already causing problems by eating gardens and ornamentals. Recent estimates by the Catalina Conservancy place the current population estimate between 1,000 and 2,500 deer. Mule deer captured on Arizona’s Kaibab Plateau in 1930 were released on Santa Rosa Island. This island is 83 miles2 (215 km2) and 1 of the Channel Islands northwest of Los Angeles, California. Thirty (15 males, 15 females) mule deer from the Kaibab Plateau were released there by the Vail family who owned the entire island (Heffelfinger and Webb 2010). The descendants of those 30 mule deer grew and fluctuated between 400–700 deer for many years. This island was the center of controversy after Vail and Vickers, who had owned the island since 1901, sold it to the United States government for $30 million (USD) in 1986. The island is now part of the Channel Islands National Park. One of the stipulations of the original sale was that all mule deer had to be removed by the end of 2011, which was largely accomplished. Hawaii.—In 1961, 10 (5 males, 5 females) Columbian blacktailed deer from Oregon were released into Pu`u ka Pele Game Management Area on the island of Kaua`i, Hawaii (Long 2003, Hess 2008). Those releases were supplemented with 10 (2 males, 8 females) in 1962, 5 more females in 1965, and 15 (2 males, 13 females) in 1966 (Long 2003). These 40 deer released on Kaua’i in the 1960s grew in number to occupy both sides of Waimea Canyon, including Köke`e State Park and are considered a non-native invasive species (Hess 2008). The population was estimated to be 950–1,050 in 2017 (Mule Deer Working Group 2021). New Zealand.—Long (2003) reported the release of 11 mule deer near Mercer and Piako in the Waikato District on the North Island, New Zealand, in 1877, but all were later shot. In 1905, 5 mule deer from Santa Fe, California were released on the eastern side of the North Island at sites near Runanga Lake in the Ngaruroro Valley in Hawkes Bay Province, or near Tarawera. These deer increased in number at least through 1915, before dying out by the 1940s (Wellwood 1968). Wodzicki (1950) reports 9 mule deer were released in 1905 into Rees Valley on the South Island which drains into Lake Wakatipu, but Banwell (2006) presents a credible argument that this is a mistake and that only whitetails (n = 9) were released there that year. The misunderstanding apparently comes from Cuthbertson (1929) listing the 9 deer as blacktailed Virginia deer released in Rees Valley in 1905; clearly a misunderstanding of his confusing terminology. Unlike most of the non-native cervids released in New Zealand, mule deer did not persist. United Kingdom.—Mule deer reportedly were released into the woods near Woburn Park in Berkshire England in 1910 and apparently flourished for a short while before disappearing before World War II (Long 2003). There are other reports that 1 male and 3 females were observed in a park in South Berwickshire in 1900, and that a male was shot by a farmer in 1947 in Northumberland (Long 2003). The details of these

records have been lost to time, but this species does not occur today in the wild in the British Isles. Russia.—A group of 20 mule deer were translocated from North America to Russia in December 2014, but neither the source location nor the destination are known (A. P. Aksyonov, The Center for Parasitology at the A. N. Severtsov Institute of Ecology and Evolution of the Russian Academy of Sciences, personal communication). These deer likely were released into a captive facility in the Moscow area (Aksyonov et al. 2017).

Ecoregions Of the 60 types of potential natural vegetation west of the 100th meridian identified by Kuchler (1964), black-tailed and mule deer occupy almost all of them (Wallmo 1981b). Large differences in recruitment, cause-specific mortality, and other population characteristics have been measured in mule deer populations across these vegetation associations (Heffelfinger et al. 2003). These widely varying ecological conditions lead to quite different population structures and management regimes. Because of this, managers have categorized the overall range of black-tailed and mule deer into 7 ecoregions to better recognize and address the diverse relationships between regional vegetative structure, climatic effects, and population dynamics (Heffelfinger et  al. 2003). Within these ecoregions, ecological relationships between deer and their habitat have relevant commonalities, and thinking in terms of ecoregions helps managers and researchers in different jurisdictions communicate and collaborate on black-tailed and mule deer conservation (Heffelfinger et al. 2003). Chapters 9–15 identify and discuss the major influences on deer population dynamics in each of these 7 ecoregions.

Summary The deer family arose out of the Miocene from a group of early hoofed animals in Eurasia. The large tusk-like canines of these primitive deer gradually gave way to the development of antlers that were replaced annually. Later, well-developed cervids entered North America through Beringia, across what is now Alaska 7–5 million YBP. The earliest deer in North America are represented by 3 forms that appear nearly simultaneously in the fossil record about 5 million YBP. One of those forms was the genus Odocoileus, which includes 2 species of medium-sized deer whose distribution is centered on North America: black-tailed and mule deer and the white-tailed deer. The subsequent origin and differentiation of black-tailed and mule deer is complex and fraught with contradicting evidence from genetics, physical characteristics, and geographic range. There are 3 theories of the origin of mule deer that are not exclusive to one another: dispersal theory, hybrid origin theory, and glacial refugia theory. Infraspecific taxonomy has been a challenge in mule deer, in part because the species is geographically widespread and continuously distributed. This species has been divided into as many as 11 subspecies, but efforts to develop a key to reliably differentiate subspecies have failed. Subspecies and other infraspecific groupings, however, can become taxonomic

24 entities with legal definitions enshrined in conservation law. If subspecies, or any other groupings, are not based on phylogeny reflected by concordant phenotypic and genetic characteristics, they are more appropriately called ecotypes. There is phenotypic and nuclear and mitochondrial genetic support for 2 subspecies in the Pacific Northwest referred to as Sitka and Columbian black-tailed deer. Additionally, there are 2 subspecies confined to Tiburón and Cedros islands in Mexico that are supported by genetic data and some morphological differentiation. None of the remaining mainland types of mule deer that have been referred to as subspecies are geographically separated from other adjacent types. In fact, they are genetically indistinguishable at a broad scale and freely interbreed as an

James R. Heffelfinger and Emily K. Latch interconnected metapopulation with no pronounced phylogenetic pattern. Given the totality of all the evidence, we find support for 5 subspecies of black-tailed and mule deer: Sitka black-tailed deer, Columbian black-tailed deer, Cedros Island mule deer, Tiburón Island mule deer, and mule deer on the mainland. Overall, the distribution of black-tailed and mule deer has been fairly stable with some retraction to the north and west in Mexico at the southern tip of distribution, and a recession to the west in Central Plains states. Extralimital translocations have established new populations in coastal Alaska and British Columbia and on 3 islands in the Pacific Ocean (Santa Catalina, Santa Rosa, and Kaua’i).

2 Historical Trends in Black-tailed Deer, Mule Deer, and Their Habitats William F. Jensen, Vernon C. Bleich, and Donald G. Whittaker CONTENTS Introduction..................................................................................................................................................................................... 25 Exploration of Western North America (1800 to 1850).................................................................................................................. 26 Railroads and the Exploitation of the West (1850 to 1890)............................................................................................................ 27 Hitting the Bottom (1890 to 1930)................................................................................................................................................. 30 Restoration of America’s Wildlife, and Habitat Management (1930 to 1980)............................................................................... 31 Predator Control......................................................................................................................................................................... 32 Fire Suppression........................................................................................................................................................................ 32 Excessive Herbivory (Livestock, Feral Animals, Native Ungulates)......................................................................................... 37 Invasive Species......................................................................................................................................................................... 39 Forest Management.................................................................................................................................................................... 39 Water Development.................................................................................................................................................................... 39 Energy and Mineral Development............................................................................................................................................. 40 Human Encroachment................................................................................................................................................................ 40 Saving the Pieces (1980 to 2020).................................................................................................................................................... 40 Summary......................................................................................................................................................................................... 41

Introduction Explorers that wrote about their early travels through mule deer (Odocoileus hemionus) country primarily focused on Indigenous Peoples, bison (Bison bison), and grizzly bears (Ursus arctos). Most only gave passing attention to deer and other wildlife, and when they did mention deer, it is often not clear which member of the deer family they were referencing. For example, white-tailed deer (Odocoileus virginianus) had been called bannertail, common, Virginia, longtail, or fallow deer, and elk (Cervus canadensis) had been called Canada stag, gray moose, red deer, round-horned elk, or wapiti. Adding to the confusion, as recently the early 1900s it was believed by many that another member of the deer family, the rare and diminutive gazelle or fantail deer, existed in the West, and its range extended into the northern Great Plains (Seton 1927). It also is noteworthy that Coues white-tailed deer (O. v. couesi) of the Southwest were also referred to as fantails (Kellogg 1961). In the past, mule deer also had been referred to as jumping deer, bounding deer, burro deer, donkey deer, hill deer, and hill blacktail. Blacktailed deer had been referred to as Cascade, coast, Columbia, sound, true blacktail, western, or black-tailed fallow deer (Seton 1927). Interpretation of these early accounts also must consider that these travelers primarily stuck to the river corridors and less-rugged terrain, avoiding the rougher country that mule deer prefer. Finally, many of these accounts were DOI: 10.1201/9781003354628-3

retold or written down years after specific events or observations occurred; Meriwether Lewis was chronically late in making journal entries, and his final report on the 1804–1806 Corps of Discovery Expedition did not appear until 1814, 5 years after his death. Among the first systematic reports on the life history, abundance, and distribution of mule deer and black-tailed deer was that of Audubon and Bachman (1854). In 1843 Audubon had trouble obtaining specimens of mule deer near Fort Union in present day North Dakota because skin hunters may have suppressed local populations. In their classic work, Roosevelt et  al. (1903) provided life-history information and then-current distributional maps. The target audience for this book, however, was big game hunters, and most of the text revolved around hunting and hunting trips. Like Roosevelt et al. (1903), Seton’s (1927) work primarily was geared to the hunting public but also included range distribution maps and population estimates. The classic work of Ely et al. (1939) also was geared to the hunter but, in addition, provided current range maps and subspecies descriptions. Taylor (1961) is among the first texts on deer written primarily for biologists, and thereby provided a consolidated source of reference material on black-tailed deer and mule deer. Later, Wallmo’s (1981a) book served as the primary source of information about black-tailed and mule deer for biologists and managers for >40 years. Since publication of that work, much has been learned about the ecology and management of 25

26 these deer. In this chapter we look back over the previous 220 years to explore how black-tailed deer and mule deer, and the habitats that support them, have fared up to this point in time. The chapters that follow will bring together current research findings, management experiences, and a look into the future of these valuable members of the deer family.

Exploration of Western North America (1800 to 1850) In 1800, few permanent European settlements were found in or along the periphery of black-tailed and mule deer range; at the time, they consisted largely of Spanish missionary settlements in the Southwest and fur-trading posts in what were to become the state of Washington and the Canadian provinces of British Columbia, Alberta, Saskatchewan, and Manitoba. Overshadowed by bison, mule deer were treated as a secondary source of protein by Indigenous Peoples over much of the range. The journal of a fictional French fur trader, Charles Le Raye, reported seeing mule deer at the mouth of the Big Sioux River near what is now Sioux City, Iowa. This fraudulent journal has now been shown to have been derived primarily from the published journal of Patrick Gass (1807), a member of the Lewis and Clark Corp of Discovery (Dollar 1982; Woodman 2013, 2015a). Gass’ (1807) description of these deer provided Rafinesque (1817b) with the information used for naming the species hemionus, or half mule. The Lewis and Clark expedition sightings of black-tailed and mule deer, however, are undisputed. On 5 September 1804, Clark reports in his diary that, “One of our hunters Shields, informed that he Saw Several black-tailed Deer” near the mouth of the Niobrara

William F. Jensen, Vernon C. Bleich, and Donald G. Whittaker River, in what is now Knox County, Nebraska (Mohler et al. 1951, Burroughs 1995:131), and on 17 September 1804, Clark records “Colter Killed a Goat, & a Curious kind of Deer, a Darker grey than Common the hair longer & finer, the ears verry large & long a Small rescepitical under its eye its tail round and white to near the end which is black & like a Cow in every other respect like a Deer, except it runs like a goat. Large” (Moulton 1987:82; Fig. 2.1). This mule deer was harvested along Corvus Creek (American Crow Creek) near the present-day town of Oacoma (43o48’N, 99o22’W) in Lyman County, South Dakota (Burroughs 1995, Woodman 2013). On 12 May 1843, near the mouth of the Little Sioux River in present day Harrison County, Iowa, Audubon (1897:484) reported “On going along the banks bordering a long and wide prairie, thick with willows and other small brush-wood, we saw four Black-tailed Deer;” this appears to be the farthest eastern observation recorded of mule deer during the early 1800s. Additional early sources reported mule deer in eastern Nebraska (Mohler et al. 1951). On 19 November 1805, Clark again noted “Some curious Deer on this Course darker large boded Shorte legs Pronged horns & the top of the tale black under part white as usial” (Moulton 1990:68). This deer, and the deer killed in subsequent days, served as the type specimens of black-tailed deer (Odocoileus hemionus columbianus). They were harvested near an abandoned Chinook village on Baker’s Bay, now present-day Fort Columbia Historical State Park (46o15’N, 123o55’W) in Pacific County, Washington (Cowan 1961a, Burroughs 1995, Nicandri 2009:196). Seton (1927) estimated the primitive abundance of mule deer and black-tailed deer at 10 million and 3 million animals, respectively, but those estimates were based on coarsely drawn distribution maps and local density estimates derived from conversations with a handful of sources. Consequently, some

FIGURE 2.1  The first mule deer described for science was based on a deer shot 17 September 1804 by a member of the Lewis and Clark expedition and subsequently described by Gass (1807). Illustration by Randall Babb.

Historical Trends in Black-tailed Deer, Mule Deer, and Their Habitats have suggested that 5 million or fewer black-tailed and mule deer is more realistic (Mackie 1987). The geographic ranges of black-tailed deer and mule deer in 1800 appear to have been much the same as their current distributions. Mule deer range, however, has contracted to the west on the northern Great Plains and to the north in Mexico but has expanded farther north into Alberta and British Columbia (Cowan 1961a, Wallmo 1981b; Fig. 1.4). Mule deer first appeared in the Yukon in the late 1930s or early 1940s, and by the 1980s they had reached the latitude of Dawson City (64o N). The most northerly record of a mule deer in Yukon has been a sighting at Chapman Lake along the Dempster Highway (64o 50’N, 138o 25’W; S. M. Czetwertynski, Yukon Department of Environment, personal communication). Mule deer have also expanded their range from the Yukon Territory into Alaska (K. R. McCoy, Alaska Department of Fish and Game, personal communication), perhaps as early as the 1980s (S. M. Czetwertynski, personal communication). Vagrant mule deer occasionally are reported in the Nahanni-Liard area in the Northwest Territories (Lamontagne 2020). In 1800, probably fewer than 20 European settlements had been established in or along the periphery of black-tailed and mule deer range in North America. These settlements were established primarily to spread the faith or search for gold in the southwestern United States, and to collect furs in the northern Great Plains and along the Pacific coast. Subsistence hunting depressed big game populations around those settlements. Even around the permanent earth-lodge villages of the Mandan and Hidatsa people in what is now North Dakota, deer numbers were suppressed. Indeed, William Clark—while wintering with the Mandan and Hidatsa peoples—described a hunting expedition that ran from 3 to 12 February 1805 (Moulton 1987:285), “…our provisions of meat being nearly exorsted I concluded to Decend the River on the Ice & hunt, I Set out with about 16 men 3 horses & 2 Slays Descended nearly 60 miles Killed and loaded the horses back, & made 2 pens which we filed with meat, & returned on the 13th we Killed 40 Deer, 3 Bulls 19 elk, maney So meager they were unfit for use”. Additionally, it has been argued that the territorial boundaries of tribes of Indigenous Peoples on the northern Great Plains, when combined with the introduction of the horse in the 1700s and trade for rifles in the early 1800s, have played positive and negative roles in the distribution and abundance of big game. Game refuge habitat between warring tribes on the northern Great Plains also points to the value of the horse for hunting (Martin and Szuter 1999, 2002), but the theoretical role of game refuges and game sinks has been questioned (Lyman and Wolverton 2002). Whatever the cause, early explorers reported that deer were scarce in many parts of the West (Bolton 1950, Ogden and Elliott 1909, Smith and Merriam 1923, Burroughs 1995), and mule deer may only have become abundant in the Great Basin in the twentieth century (Mackie 1987). Between the early and mid-1800s, big game on portions of the northern Great Plains began to decline in numbers. John Luttig was the clerk and chronicler for Missouri Fur Company’s 1812 expedition up the Missouri River, during which the Fort Manuel trading post, near what is now the North Dakota-South

27

Dakota border, was established (Oglesby 1984). Fresh meat was a scarce commodity, with hunters sent out nearly every day to feed the crew of more than 20 men, and often relying on everything from catfish (Ictalurus spp.) to turtle eggs (Luttig 1920). During the 48 days between passing what is now the southern boundary of Nebraska and reaching what became Fort Manuel, hunters brought in 52 deer (presumably mostly white-tailed deer), 4 bison, 3 bear (Ursus americanus), 3 elk, 2 pronghorn (Antilocapra americana), and a smattering of fish, birds, and small mammals (Luttig 1920). Once arriving at the future site of Fort Manuel, deer became much less prominent in their diets, with only 10 deer brought in by hunters between 9 August 1812 and 5 March 1813 (Luttig 1920), suggesting deer were common along the river, perhaps at low densities, but had been nearly extirpated near the settlement. In the 1800s, leather was the plastic of the day for industry; in addition to clothing, hides were needed for the factory belts that kept the industrial age functioning and for covering everything from books to sleighs. Thus, commerce also may have played an early role in reducing big game populations near trading posts. As an example, Prince Maximilian of Wied noted that the American Fur Company at Fort Union (near present-day Williston, ND) exported 20,000 to 30,000 deer hides in 1833 (Thomas and Ronnefeldt 1982). By 1867, Charles Larpenteur, a fur trader at Fort Buford, 2 miles (3 km) east of the then abandoned Fort Union, reported trading only 1,800 deer hides (Larpenteur 1898). In the mid-1800s, subsistence hunting was a common practice in the gold fields of California and Nevada. Nevertheless, the effect of market hunting appears to have been less pervasive among coastal deer populations than those occupying the harsh, northern Great Plains (Seton 1927). Other than around the scattered permanent settlements or along trade corridors, deer numbers and habitat conditions in the West likely saw little change during this period.

Railroads and the Exploitation of the West (1850 to 1890) Prior to 1850, logging and timber production in the West was tied to local markets. With the expansion of gold mining in California, a steady supply of timber was needed. By 1850, there were 37 sawmills operating in the Pacific Northwest, primarily near the mouths of the Columbia and Willamette rivers, where transportation of logs by water was readily accomplished (http://www.nwcouncil .org/​repor​ts/Co​lumbi​a-riv​er-hi​ story​/logg​ing, accessed 17 Aug 2020). Although not all wildlife may have benefited, opening of the forest canopy resulted in greater forage production, and deer were beneficiaries of these changes (Cowan 1961b). Mule deer occupying the northeastern portion of their range, however, suffered from effects of logging. The current eastern boundary of mule deer range in the southern Great Plains appears to be congruent with what existed prior to European settlement, but such is not the case in the northern Great Plains. Indeed, historical range maps suggest that the distribution of mule deer extended much farther to the east prior to arrival of settlers (Roosevelt et  al. 1903, Seton 1927, Ely et al. 1939). For example, the type specimen of

28 the now subsumed subspecies of brush deer (Cariacus virgultus) was collected in Kittson County, Minnesota (Seton 1927, Anderson and Wallmo 1984). While discussing deer within the Red Lake Refuge in northwestern Minnesota, Leopold et al. (1947) stated that the area had formerly been mule deer range and that white-tailed deer moved into the region after it was cleared by loggers in the late 1800s. Mule deer also occupied southwestern Manitoba (Seton 1927) and western Iowa (Audubon 1897) in the past but since have been classified as a threatened species in Manitoba and may number fewer than 500 animals along the western border with Saskatchewan (R. R. Davis, Manitoba Agriculture and Resource Development, personal communications). Mule deer have been extirpated from Minnesota (Ernst and French 1976) and Iowa, and are uncommon or rare in the eastern Dakotas (Seabloom et  al. 2020). It appears that logging and habitat changes associated with settlement of vast regions of the Northern Plains allowed white-tailed deer to expand westward. Concomitantly, the distribution of its obligate parasite, the meningeal worm (Parelaphostrongylus tenuis), also has expanded. Anderson (1972) reviewed the relationship between meningeal worm, its usual host the white-tailed deer, and the effect the parasite could have on other native cervids because of northern and western range expansions of white-tailed deer. In conclusion, Anderson (1972:308) noted, “We still know nothing about the relationships between white-tailed deer, mule deer, and meningeal worm. White-tails are replacing mule deer as the main species in many regions west of Ontario. This is usually attributed to the higher reproductive rate and

William F. Jensen, Vernon C. Bleich, and Donald G. Whittaker greater adaptability of the former species.” Nonetheless, mule deer have been infected experimentally with P. tenuis, resulting in severe neurologic disease and death (Tyler et al. 1980). Thus, circumstantial evidence indicates that logging, fire suppression, and other anthropogenic changes to the landscape have allowed the meningeal worm and its obligate hosts (terrestrial gastropods and white-tailed deer) to expand westward on the northern Great Plains, making the region unsuitable for sustainable mule deer populations (W. F. Jensen, North Dakota Game and Fish Department, unpublished data). Readers are referred to Chapter 6 for additional discussions about diseases and their effects on mule deer. Additional changes in the West began to occur with passing of the Homestead Act in 1862. For a fee of $18, any adult citizen—or an adult intending to become a citizen—was eligible after 5 years to receive 160 acres (65 ha) or, after 6 months and minor improvements, could purchase up to 160 acres (65 ha) for $1.25 per acre ($3.09 per ha). The legislation was written so ambiguously, however, that it invited fraud and more than 80% of the 500 million acres (200 million ha) authorized went to speculators, cattlemen, miners, lumbermen, and railroads. The lumber barons, miners, and ranchers needed railroads to get their commodities to market and building these rail lines was accomplished with remarkable speed; by 1869, the 1,912-mile (3,077-km) Transcontinental Railroad was completed. Canada followed shortly by completing the Canadian Pacific Railroad in 1885. Once the tendrils of new rail lines spread into the heart of the continent, effects on mule deer and other wildlife soon followed (Fig. 2.2).

FIGURE 2.2  Building of railroad lines in the United States between 1850 and 1890 opened the West to farming, ranching, logging, and mining. Between 1860 and 1890, the total railroad mileage in the region west of the Mississippi River increased from 2,175 miles (3,500 km) to 72,389 miles (116,500 km), thus ushering in the exploitation of, and forever changing, western North America. This illustration depicts the 1879 construction of a temporary winter bridge crossing the ice of the Missouri River, Dakota Territory. F. Jay Haynes, artist; image courtesy of State Historical Society of North Dakota 0714-00001.

Historical Trends in Black-tailed Deer, Mule Deer, and Their Habitats

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FIGURE 2.3  Unregulated hunting decimated big game populations across the West in the late 1800s. This 1886 hunting party, in what is now the North Dakota badlands, harvested 11 mule deer (3 fawns, 4 adult females, and 4 adult males), and 4 bighorn sheep; (1 lamb, 1 adult female, and 2 adult males). By 1905, mule deer were becoming a rare sight and bighorns had been extirpated from the state. Osborn Photo Studio, Image courtesy of State Historical Society of North Dakota 0119-00001.

Most settlers heading west carried a shotgun to be used for protection and procurement of game. Filled with shot, it could kill ducks, geese, and grouse; loaded with buck or ball, it could kill a deer (Fig. 2.3). Across the West, cowboys with free time during fall and winter supplemented their wages by markethunting (Seton 1927, Knue 1991). Additionally, there exists a long history of deer hides being used as a medium of exchange (Young 1961); in northwestern Montana, even as recently as 1900, deer hides were considered legal tender and were worth 50 cents each (Allen 1971). The cumulative effects of unregulated subsistence hunting, market-hunting, and the rush of European settlement in the 1870s and 1880s, when combined with resulting conversion of much of the arable land to agriculture, had severe implications for large herbivores, and western North America. These activities resulted in the near extirpation of all large herbivores, and many of their predators, throughout the Great Plains (South Dakota Game Fish and Parks 1959, Jones 1964, Hardy 1967, Webb 1967, Allen 1971, Knue 1991), the Great Basin, and even the deserts of the southwestern United States and Mexico. The California Gold Rush of 1849 resulted in major effects on many species, but not necessarily because of habitat changes associated with agricultural activities. Millions of acres (ha) of government land, much of it desert, was not arable; instead of agriculture, primary activities affecting mule deer centered around other activities associated with rail lines, including ranching and mining. Indeed, railroad companies were encouraged to expand into the Southwest by transfer of 2

sections of federal land per township to the various companies. These enticements resulted in the construction of railroads throughout much of the Southwest, and enabled shipment of goods from east to west, and products such as ore, coal, and meat to markets in the East. To feed mining camps and others moving westward to take advantage of new-found opportunities, unregulated market-hunting bode an onerous future for mule deer and other wildlife. At the same time, cattle grazing and, eventually, sheep grazing altered the vegetation composition of much of the West, with resultant effects on mule deer and other species. In California, livestock grazing on climax vegetation, particularly native perennial grasses and forbs, coupled with introduction of comparatively more palatable and digestible exotic plants, increased the carrying capacity of the range for deer (Longhurst et al. 1976). But benefits associated with these habitat changes to early successional stages were suppressed by unregulated harvest. Vegetation responses to livestock grazing have varied greatly throughout the West (Julander and Low 1976). Effects of excessive grazing pressure and logging are covered in chapters 8 and 10, respectively. Winter storms also played a role in reducing deer numbers on the northern prairie; the winters of 1883–1884 and 1886– 1887 were particularly severe (Webb 1967), and overstocked ranges led to massive cattle die-offs during these winters. In the Dakotas and in Nebraska, severe storms during winters of 1880–1881, 1886–1887, and 1896–1897 killed cattle and deer through starvation and caused deer to seek food in towns

30 and farmsteads where they fell easy victims to pistol or club (South Dakota Game Fish and Parks 1959, Jones 1964). One storm event stands out in particular. On 12 January 1888, a rapidly moving Arctic front rolled down from Canada across most of the northern Great Plains, reaching as far south as Texas. This massive blizzard dumped upwards of 40 inches (102 cm) of snow, produced winds of >60 miles/hour (>100 km/hr) and killed at least 250—and perhaps as many as 500— people across the prairie. Now known as the School Children’s Blizzard, that storm is credited with wiping out nearly all pronghorn in eastern South Dakota (South Dakota Game Fish and Parks 1959); other game species, including mule deer, probably shared the same fate. Following realization that fish and wildlife resources warranted some protection, it was during this period that the first state conservation agencies were established (Organ and McCabe 2018). Massachusetts and New Hampshire established fisheries commissions in 1866, and California did so in 1870 (Trefethen 1975). By 1880, all existing states had established game laws (Organ and McCabe 2018). Such laws were not taken seriously, however, and were simply disregarded by some hunters or anglers (Swanson 1940). Despite this slow beginning, an important outgrowth of this period of exploitation was the establishment of state wildlife agencies, the history of which has been described thoroughly by Trefethen (1964, 1975), Organ and McCabe (2018), and others.

Hitting the Bottom (1890 to 1930) By the late 1800s, it was becoming obvious that there were limits to the natural resources the continent had to offer. But, changing the attitude that exploitation at any cost was not in our nation’s long-term interest required educating the public. This job had fallen to people like George P. Marsh, George Bird Grinnell, John Burroughs, John Muir, and Theodore Roosevelt, who did this by writing essays for the popular press. They were the conservation bloggers of the nineteenth century. During this period, dozens of hunting, conservation, and scientific organization emerged. In 1887, a group of eastern patrician hunters organized the Boone and Crockett Club, an organization that promoted fair chase hunting and laid the basis for what later would become the North American Model of Wildlife Conservation. Slowly, western states and provinces began to pass game laws (Fig. 2.4). The first such legislation occurred in California in 1854 (Young 1961), and in 1913 British Columbia, Canada became the last jurisdiction to do so (McCabe and McCabe 1984). During this period, enforcement of game laws was spotty at best, and usually addressed only season dates and wanton waste (McCabe and McCabe 1984). Game protection laws on the books meant little, however, if they were not enforced, and years often passed before the various states provided funds to hire game wardens. Because of those delays, game of all types became increasingly scarce. Rather than recognizing that declines in big game were a result of unregulated hunting and loss of habitat, a more convenient solution was to target particular groups of people, and predators. Hornaday (1913), infamously blamed declines in wildlife on the guerrillas of

William F. Jensen, Vernon C. Bleich, and Donald G. Whittaker

FIGURE 2.4  Writings of Theodore Roosevelt, John Muir, and others helped change public attitudes regarding wildlife and conservation, leading to the development of the North American Model of Wildlife Conservation. Image courtesy of United States Biological Survey Collection, United States Fish and Wildlife Service Museum and Archives.

destruction (i.e., meat shooters, ethnic groups, and plumehunters), and the unseen foes of wildlife (i.e., domestic cats, dogs, and all manner of 4-footed predators). In 1898, the North Dakota legislature joined most other states and initiated a bounty on wolves (Canis lupus) and coyotes (Canis latrans), even though wolves had been all but extirpated from the state by 1887 (Bailey 1926). Yet, game numbers continued to decline and, by the 1920s, North Dakota was paying bounties on everything from rattlesnakes (Crotalus viridis) to magpies (Pica pica). As popular writers continued to educate the public about the problems that we, as a nation, were creating for ourselves, the status quo of widespread exploitation slowly began to change. In Canada, the western provinces of Alberta and Saskatchewan enacted game protection and management legislation in 1906, followed by British Columbia in 1913, and in Mexico, Miguel Angel de Quevedo was advocating for conservation of Mexico’s forests (Brown 2013). But it was not just game species that were suffering; clear-cutting practices by lumber companies left abundant wood slash and resulted in massive forest fires, unchecked mining practices were despoiling river systems, and excessive grazing by sheep and cattle were threatening the long-term viability of western rangelands. In 1908, Gifford Pinchot, first chief of the United States Forest Service, convinced President Roosevelt to call the Governor’s Conference and conduct a national inventory to document the condition and state of America’s natural resources. These collective efforts resulted in a series of important laws designed to reverse the sins that had been brought upon the land. Bailey’s (1926:43) assessment for the future of mule deer in North Dakota was, “a few in public parks or on private game

Historical Trends in Black-tailed Deer, Mule Deer, and Their Habitats farms are all we can hope to save in open country, but in the steep and rugged mountain areas farther west, where the game and recreational value of extensive tracts is greater than its agricultural value, a strong effort is being made to preserve mule deer as a permanent part of the wild life of the country.” Seton (1927) estimated mule deer to number about 400,000 in 1909; no estimate was given for black-tailed deer, but we postulate that the continental population of mule deer and black-tailed deer might have been about 1 million. Hill (1961) estimated big game numbers had increased about 4 times between 1921 and 1950; using Robinette’s (1961) estimate of about 1.9 million mule deer around 1950, we suggest a rough estimate of 490,000 mule deer and more than 216,000 black-tailed deer occurred around 1920. During this period, mule deer numbers were rebounding in the Southwest (Mackie 1987). Range distributions receded little except along the eastern Great Plains. The history of mule deer in Mexico is similar to that described above, and mule deer have undergone periods of abundance, local extirpations, and constant exploitation (Harveson et al. 2019). Mule deer have been subjected to an abundance of land-use practices, and Leopold (1959) concluded that the socioeconomic situation in Mexico would prevent most populations of mule deer from reaching carrying capacity of their habitat, in large part because of unregulated subsistence hunting by Indigenous Peoples, rural residents, or prospectors (Tinker 1978). Mule deer, however, now are recognized as a valuable commodity, and many owners of large ranches or estancias recognize the economic value of large desert mule deer (Harveson et al. 2019). Benefits to mule deer conservation have been realized by the transfer of some ejidos (i.e., rural communes) to the private sector (Stoleson et al. 2005), and those private landowners recently have played an important role in protecting mule deer from illegal hunting or other losses (Rosas-Rosas et al. 2003, Valdez et al. 2006, Valdez and Ortega-S 2019). Chapters 7, 19, 20, and 21 will provide greater detail on several of these issues.

Restoration of America’s Wildlife, and Habitat Management (1930 to 1980) The 1930s yielded 2 positive events for wildlife management and conservation: a plan, and the money to fund it. Leopold (1933) published the first science-based volume describing how wildlife professionals could implement change. Leopold’s (1933) book was not only a techniques manual for wildlife management but also included discussions on ethics and the administration of wildlife policies. Later, his essays about a land ethic inspired and helped change the way Americans valued charismatic big game and all wildlife—even the chickadee (Parus atricapillus; Leopold 1949; Fig. 2.5). The second gift of the 1930s was a funding source for management of wildlife. The 1937 Federal Aid in Wildlife Restoration Act (i.e., Pittman-Robertson Act) has been described as the “blue-collar worker among federal wildlife laws” (Williamson 1987; Fig. 2.5). Federal taxes on guns and ammunition and cost-sharing of those revenues with states, allowed agencies to fund biologists and land managers, develop habitat projects, and implement research. Rather than the hit-and-miss

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FIGURE 2.5  Aldo Leopold (A) gave wildlife managers the textbook for managing mule deer and other wildlife. Carl Shoemaker (B) drafted the Federal Aid in Wildlife Restoration Act, and Senator Key Pittman (NV; C) and Representative A. Willis Robertson (VA; D) sponsored the Act that provided states with a funding source to put wildlife management on the ground. Images courtesy of the Aldo Leopold Foundation and University of Wisconsin-Madison Archives, National Wildlife Federation Collection, United States Fish and Wildlife Service Museum Archives, and United States Senate Historical Office.

practices of the past, steady progress began to be made by state wildlife agencies that were growing into their new roles of managing and conserving wildlife. During this period, the Dust Bowl and the Great Depression also profoundly influenced public attitudes. Civilian Conservation Corps and Work Progress Administration projects poured money and labor into repairing environmental damage done during the previous 75 years, and brought urban youth to rural public lands to experience firsthand what was at stake. Brown (2013) and Organ and McCabe (2018) provide a complete description of the history of wildlife conservation in North America. After protection from unregulated hunting, mule deer numbers began to rebound quickly. As noted earlier, mule deer numbers increased from a low of 400,000–500,000 around 1920, but large portions of former range remained unoccupied (Trippensee 1948). Mule deer increased to 1.9 million by the early 1950s in the United States (Robinette 1961), and 7.5 million black-tailed and mule deer together occupied Canada and the United States by the early 1960s (Mackie 1987). Based upon Connolly (1981a), and reports in mule deer working group proceedings, we postulate North American

32 black-tailed and mule deer populations in 1950 and 1960 to total about 3 million and 6.5 million, respectively. The protective management strategies implemented during the 1920s and 1930s led to deer exceeding the carrying capacity of the land in areas like the Kaibab Plateau of Arizona. Attempts to deal with overpopulation by winter feeding were ineffective and results were questionable (Mackie 1987). In part, recovery may have been a result of widespread grazing, logging, and burning that resulted in more diverse range and forest vegetation, increased availability of more palatable and nutritious foods, predators being extirpated or severely controlled, decreased competition with other large herbivores, or combinations of these (Mackie 1987). In the 1930s, deer management options primarily were limited to law enforcement, predator control, designation of game refuges, and in some cases translocations. Following World War II, the G.I. Bill provided veterans an opportunity to attend college. Many individuals enrolled in newly developed wildlife management programs. The Federal Aid in Wildlife Restoration Act provided state agencies the funds to hire these technically trained biologists to study game animals, including deer populations. Early researchers determined that overpopulated ranges resulted in habitat damage, crop depredation, low fawn production, and, potentially, starvation; additional research underscored the need to increase hunter-harvest to keep deer numbers within the carrying capacity of the land (Mackie 1987). Science-based research led to the creation of deer management units and standardized methodologies to assess deer population trends or habitat condition, and informed the public of the need to harvest both sexes to control populations. North American mule deer and black-tailed deer numbers were thought to be between 6.5 million and 7.5 million in the early 1960s (Mackie 1987). Between 1950 and 1961, the annual number of mule deer and black-tailed deer harvested jumped from about 400,000 to nearly 1 million (Mackie 1987). In the 1970s, wildlife biologists gained access to and began using computers and radio-telemetry, new tools that were developed during the race to land a man on the moon. Computers allowed a new generation of biologists to develop predictive models of deer populations. Population modeling allowed biologists and managers to systematically explore and evaluate new and changing management strategies in response to demands by the public. Radio-telemetry allowed field researchers to obtain more intimate insights as to how deer used the landscape, survival rates, and primary mortality factors. Following the peak populations of mule deer and blacktailed deer during the 1960s, numbers declined slowly until about 1975, at which time Connolly (1981a) estimated mule deer and black-tailed deer numbers in North America at less than 3.5 million and 1.6 million, respectively (Tables 2.1, 2.2, 2.3). Factors causing mule deer population declines varied from region to region. In proceedings of the mule deer workshops of 1983 (Ziegler and Myers 1983) and 1993 (Doyle et al. 1993), the primary factors limiting mule deer populations identified by state and provincial biologists were habitat loss (AB, CO, ID, NV, OR, WA, WY), winter weather (AB, BC, CA, CO, MT, SK, UT), drought (AZ, NM, UT), forage quality and quantity (CA, CO, NM), hunting (TX, UT), predation (BC,

William F. Jensen, Vernon C. Bleich, and Donald G. Whittaker CA), and domestic livestock (CO). Black-tailed deer, however, seemed to be less affected by these factors (Gill 1990). Like many other species, mule deer have been introduced to areas outside their historical range; some introductions have been successful, but others have not. Introductions to England, New Zealand, and Argentina have failed; however, introductions to several islands off the coasts of Alaska and British Columbia, and to the Channel Islands of California have been successful (Long 2003). Between 1960 and 1966, about 40 black-tailed deer were introduced to Kauai in the Hawaiian Islands for the purpose of sport hunting (Long 2003). This herd currently numbers between 700 and 1,000, and some habitat damage has been reported (Hess 2008). In 2014, mule deer were introduced into central Russia near Moscow, but little information is available on their current status (Aksyonov et al. 2017). During the 50 years between 1930 and 1980, several anthropogenic factors influenced habitat quality, with resultant changes for black-tailed and mule deer populations in the West. These factors did not occur everywhere at the same time, nor did they necessarily have the same effects, and some produced unintended or unanticipated consequences or interactions between biotic and abiotic factors. During this period, the following were important factors influencing deer populations and habitat.

Predator Control When talking about hunting dogs in the Northern Plains, Roosevelt (1899:71) stated that, “… it is next to impossible to keep hunting-dogs very long on the plains. The only way to check in any degree the ravages of the wolves is by the most liberal use of strychnine, and the offal of game killed by a cattle-man was pretty sure to be poisoned before being left, while the ‘wolfer,’ or professional wolf-killer strews his bait everywhere” (Fig. 2.6). Attitudes began to change about the role of predators in the ecosystem with books by Murie (1940) and Leopold (1949). Bounty payments on predators began in the West in the late 1800s but were abandoned in many states in the late 1950s and early 1960s as evidence mounted that bounties were largely a waste of tax dollars. Use of poisons to kill predators continued, however, and was ubiquitous across the West into the 1970s. Common methods included the use of compound 1080 (sodium fluoroacetate) and coyote getters (explosive shells filled with cyanide pellets). In 1972, President Nixon signed executive order 11643, which prohibited the use of chemical poisons on all public lands (Brown 2013). A review of deer-predator relationships (Ballard et  al. 2001) reported that coyotes, mountain lions (Puma concolor), and wolves may be substantial mortality factors in some areas under certain conditions, but large herbivores at, or near, carrying capacity do not exhibit strong responses to predator removal, as emphasized recently by Bowyer et al. (2005, 2014, 2020).

Fire Suppression Prior to European settlement, the frequency of fire was highly variable in western North America, ranging from 1 to 3 years on the plains, and to ≥500 years in the Pacific Northwest

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Historical Trends in Black-tailed Deer, Mule Deer, and Their Habitats TABLE 2.1

Estimated numbers of mule deer in the United States, expressed in thousands of animals from 1950 to 1975 (Connolly 1981a:230). Trend data = increasing (I), decreasing (D), and stable (S). Small numbers of mule deer were reported to occur in Iowa, Minnesota, and Oklahoma. Because of the difficulty in obtaining population estimates and variation in methodologies, these estimates should be considered general trends. State Year

AZ

CA

CO

ID

1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975

225 (S) (D) 225 215 195 184 185 185 185 185 190 203 190 175 190 195 210 220 23b 127 128 128 132 130 120

600 625 500 540 590 575 520 520 520 520 520 520 (D) (I) (I) (S) (I) (D) (D)

275 299 292 300 330 325 (I) (D) (D) (I) (I) (I) (S) (S) (S) (D) (D) (I) (I) (S) (S) (S) (S) (S) (D) 365

70 120 129 130 240 260 260 260 315 (I) 325 (D) (D) (D) (D) 320 (S) (I) (S) (D) 300 (D) (D) (D) (S) 210

a b

(D)

KS

MT

NE

NV

NM

ND

OR

SD

TX

UT

WA

0.1 (I) (I) (I) (I) (I) 0.9 1.2 1.4 1.8 2.4 3 3.4 3.6 4 4.5 5 5.4 5.9 6.7 7.3 7.6

145 172 177 202 195 238 296 299 (I) (I) (I) (I) (I) (I) (I) (I) (I) (I) (S/I) (S) (S) (D) (D) (D) (D) (D)

14 13 18 13 12 60a 75a 75a 75a 75a 60a 75a 45 50 45 43 29 27 30 28 28

80 90 90 90 100 100 150 150 175 200 246 245 225 200 200 180 180 150 160 170 150 150 150 144 122 82

124 124 129 200 272 248 275 300 318 318 318 318 293 303 301 (I) (I) 405 (D) (I) (I) (D) (D) (D) (D) 276

2.5 3.5 5.5 7.7 4 6 10 (I) (S) 15 20 20 18 23 25 (S) 18 15 20 17 (I) 20 20 20 20 20

200 375 325 350 400 425 475 425 425 425 400 450 480 460 530 510 515 570 510 500 430 416 400 404 387 383

22 23 27 35 33 33 40 40 30 85 35 40 20 23 33 41 17 44 85 100 95 70 75 90 90 90

6.5 6 5 5 5 5 15 75 75 75 77 80 82 84 100 157 163 167 167 167 155 163 168 169 163 130

300 350 350 350 375 375 375 375 375 375 375 375 325 325 325 300 300 300 I I 325 (D) (D) (D) (D) (S)

100 105 120 130 170 160 110 115 135 150 155 175 175 185 175 160 165 175 185 120 130 120 120 150 150 150

WY 99a 139a 176a 200a 200a 222a 166a 282a 272a 262a 336a 368a 386a 311a 298a 277a 280a 312a 290 333 378 298 248 244 262 280

Numbers of mule deer and white-tailed deer combined. This value was published by Connolly (1981a:230) and appears to be a typographical error.

(Higgins 1986, Frost 1998). On the prairie, lightning-caused fires were highly variable, occurring at intervals ranging from 6.0 per year per 3,861 miles2 (10,000 km2) in the eastern North Dakota grasslands to 91.7 per year per 3,861 miles2 (10,000 km2) in pine savanna lands of western South Dakota (Higgins 1984). Similarly, in coastal California, lightning-caused fires also varied among the North Coast, Central Coast, and South Coast bioregions in terms of ignitions and acres (ha) burned, and that variation was substantial (Davis and Borchert 2006, Keeley 2006, Stuart and Stephens 2006). Nevertheless, blacktailed deer in the northern part of the state, and mule deer in the southern part of the state would have benefitted substantially from effects of those fires. Following the establishment of the United States Forest Service in 1905, fire suppression was actively encouraged. With the adoption of the iconic story of Smokey the Bear in the early 1950s, the addition of aerial tankers in 1958 (Longhurst et  al. 1976), and other newly developed technologies, efficient fire suppression became a cultural norm. This suppression resulted in closed forest canopies with severely reduced

palatable understory vegetation and encroachment of wooded species such as Rocky Mountain juniper (Juniperus scopulorum) in the Great Plains and pinyon pine (Pinus edulis, P. monophyla) in the Desert Southwest ecoregions (Fig. 2.7A, B). As a result, mule deer carrying capacity was reduced. In 1974, the United States Forest Service changed its policy from one of fire suppression to one of fire management (DeBruin 1974), but use of prescribed fire to enhance or maintain conditions suitable for large herbivores, including mule deer, are infrequent and, even if implemented, generally are limited to the area treated (Bleich et al. 2008, Holl and Bleich 2010, Holl et  al. 2012). The exception to the general benefit of fire to increasing forage for deer appears to be in the Great Basin where bitterbrush (Purshia tridentata), curl-leaf mountain mahogany (Cercocarpus ledifolius), and sagebrush (Artemisia spp.) are killed out by fire, whereas coastal chaparral species are adapted to fire and reseed or resprout after a burn (Keeley and Davis 2007) and yield high quality forage in the form of new growth (Biswell et al. 1952, Longhurst et al. 1976, Bleich and Holl 1982).

2008

115

1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007

120 118 121 133 143 155 158 158 151 138 126 124 127 128 119 118 111 108 103 106 113 112 120 110 110 107

AZ

Year

a

275

(S) (S) (S) (S) (I) (I) (I) (I) (I) (I) (I) (I) (I) (I) 425 441 410 486 345 377 285 343 302 259 285 340 322 281 237 327 215 245

CA

b

467

325 350 425 536 487 594 595 625 570 550 564 580 595 609 601 585 574 545 539 530 547 516 526 529 552 567 564 603 601 613 613 539

CO

c

245

(D) (I) (S) (S) (I) (D) (S) (S) (I) (I) 265 (I) (S) (I) (D) (S) (D) (D) (S) (D) (I) (D) (I) (S) (S) (S) (S) (S) 300 (I) 230 226

ID

d

62

8t (I) (I) (I) (I) (I) (I) (I) (I) (I) 50w (I) (I) (I) (I) (I) (I) (I) (I) (I) (I) (I) (S) (D) (D) (D) (D) (D) (D) (D) 42 43

KS e

335

315 344 347

265w

(I)

(D)t

MT f

(I)

(D) (I) (S) (I) (S) (I) (I) (I) 50w (D) (I) (I) (S) (S) (S) (I) (D) (I) (D) (I) (I) (D) (D) (S) (I) (D) (D) (I) (I) (I) (D)

NE g

108

95 113 122 113 126 136 140 120 130 156 180 220 240 212 202 180 184 148 115 118 120 125 132 134 133 129 108 109 105 107 110 114

NV h

(S)

(D) 262 (D) (D) 260 (S/I) (S/I) (S/I) (S/I) 250x 300w (S/I) (S/I) (S/I) (D) (D) (D) (D) (D) 224 (D) (D) (D) (D) 235 (D) (D) (D) (D) (D) (S) (S)

NM i

United States

22

10 13 14 11 13 17 17 16 18 15 16 14 16 15 13 12 12 15 14 12 10 15 14 16 17 24 16 17 20 24 21 23

ND j

227

274 300 306 265 252 249 249 270 285 302 245 258 254 263 235 216 232 235 244 260 268 257 268 265 254 247 244 240 234

400t

OR k

(S)

(I) (I) (D) (D) (D) (D) (D) (D) (S) (S) (I) (I) (I) (I) (I) (I) (S)

69w

SD l

193

249 204

245x

213w

149v

236v

151t

TX m

274

340 240 245 255 305 282 308 318 322 310 280 268 290 297 318 302

360x 500w

(I)t

UT n

(S)

(I) (S) (S) (D) (D) (S)

(I)

WA o

481

458 365 444 423 471 513 507 543 586 596 421 426 429 475 429 478 512 545 489 485 500 483 500 521 525

WY p

189

109 128 149 146 135 156 166 172 186

134

94 100 101 112 114

100 73 94 86 64 88

73

90u

AB q

(D)

(S) (S) (S) (S) (I) 30w (I) (I) (I) (I) (I) (D) (D) (D) (D) (S) (S) (S) (I) (I) (I) (I) (S) (S) (S) (D) (D) (D)

SKs

(Continued )

108-194

105-175

96-170

165

170

170

167

165w

BCr

Canada

Estimated number of mule deer in the United States and Canada, 1976–2020, expressed as thousands of animals. Population trends are expressed as increasing (I), decreasing (D), or stable (S). Small populations of mule deer occur in Oklahoma (~2,000) and the Yukon (~1,000), and vagrants are reported rarely in the Northwest Territories. Because of the difficulty in obtaining population estimates and variation in methodologies used, these figures should be viewed with caution.

TABLE 2.2

34 William F. Jensen, Vernon C. Bleich, and Donald G. Whittaker

y

x

w

v

u

t

s

r

q

p

o

n

m

l

k

j

i

h

g

f

e

d

c

b

a

100

90

AZ

272 248 268 301 363 334 387 350 299 282 275 277

CA

b

461 430 418 408 391 424 436 419 419 433 418

CO

c

247 270 280 250 256 282 303 318 331 318 267

ID

d

63 42 48 57 50 51 51 41 48 54 45

KS e

301 247 249 212 232 264 297 366 386 350 322 328

MT f

(S) (D) (D) (S) (D) (I) (I) (I) (I) (D) (D)

NE g

106 107 109 112 109 108 99 94 92 92 93 92

NV h

(S) (S) (S) (S) (S) (S) (S) 90 90 90 90 90

NM i

United States

20 19 14 11 13 15 19 22 26 25 20 21

ND j

221 214 220 211 227 231 228 219 200 191 171

OR

A. Munig, Arizona Game and Fish Department. D. S. Casady, California Department of Fish and Wildlife. A. A. Holland, Colorado Parks and Wildlife (post-hunt population estimate includes ~5% white-tailed deer). R. L. Ward Idaho Department of Fish and Game. L. A. Jaster, Kansas Department of Wildlife Parks and Tourism. L. A. Parsons, Montana Fish Wildlife and Parks. L. R. Meduna, Nebraska Game and Parks Commission. C. A. Schroeder, Nevada Department of Wildlife. O. V. Duvuvuei, New Mexico Department of Game and Fish. W. F. Jensen, North Dakota Game and Fish Department (post-hunt population estimate for just the Badlands). D. G. Whittaker, Oregon Department of Fish and Wildlife. A. J. Lindbloom, South Dakota Department of Game Fish and Parks. S. S. Gray, Texas Parks and Wildlife Department. C. D. Jones, Utah Division of Wildlife Resources. S. J. Hansen, Washington Department of Fish and Wildlife. W. Schultz and D. J. Thiele, Wyoming Game and Fish Department. J. Gilligan, Alberta Fish and Wildlife Division. A. B. D. Walker, British Columbia Ministry of Forests Lands and Natural Resources. T. Perry, Saskatchewan Ministry of Environment. Connolly 1981a. Bruns 1980. Western Deer Workshop Participants 1985. Gill 1990. Heath et al. 2001. Mule Deer Working Group 2020.

2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020

Year

a

k

(D) (D) (D) (D) (D) (S) (I) (I) (I) (I) 59

SD l

231 286 186 227y

188 168 198 188

177

TX m

302 294 286 319 333 356 385 374 364 376 319

UT n

(S) (S) (D) (S) (I) (S) (I) (D) (D) (S) (s) 90-110y

WA o

440 427 376 374 361 375 407 409 377 358 343

WY p

187 179 143 138 137 141 128 151 155 151 167

AB q

100-170y

100-170

100-168

115-205

BCr

Canada

(D) (S) (D) (D) (D) (S) (S) (I) (I) (I) (I) 65-85y

SKs

Estimated number of mule deer in the United States and Canada, 1976–2020, expressed as thousands of animals. Population trends are expressed as increasing (I), decreasing (D), or stable (S). Small populations of mule deer occur in Oklahoma (~2,000) and the Yukon (~1,000), and vagrants are reported rarely in the Northwest Territories. Because of the difficulty in obtaining population estimates and variation in methodologies used, these figures should be viewed with caution.

TABLE 2.2 (CONTINUED)

Historical Trends in Black-tailed Deer, Mule Deer, and Their Habitats 35

36

William F. Jensen, Vernon C. Bleich, and Donald G. Whittaker

TABLE 2.3 Estimated number of black-tailed deer from 1950 to 2020 in the United States and Canada expressed as thousands of animals. Information from 1950 to 1976 is from Connolly (1981a:230) unless otherwise noted. Information from 1977 to 2020 was provided by wildlife agency representatives or obtained from published sources, as indicated by footnotes. Trend data = increasing (I), decreasing (D), and stable (S). Because of the difficulty in obtaining population estimates and variation in methodologies used, these estimates should be viewed with caution. States and provinces Year 1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997

AK

a

BC

b

450 475 586 580 610 625 580 580 580 580 580 580 (D) (I) (I) (S) (I) (D) (D) (D) (D)

120 250 (I) 250 225 (S/I) 200 250 100 110 105 100 110 120 140 150

310g 170

180

(I) 350i (S) (I) (D)

CAc

220

180

(D) (D) (D) (D) (D) (D) (D) (D) (D) (D) (D) (D) (D) (D) 302 270 312 336 414 375 313 370

HI

0.01f 0.02f

0.12f 0.14f

0.35f

ORd

WAe

200 240 250 400 360 440 400 350 450 560 610 650 630 530 580 480 590 550 560 480 600 650 634 686 566 635 650

160 165 170 160 190 180 150 180 215 245 250 250 250 253 230 210 215 225 245 195 215 230 230 240 240 240

452 462 430 410 455 445 434 458 483 506 471 480 432 430 455 360 372 392 (D)

200h

173i

(Continued )

37

Historical Trends in Black-tailed Deer, Mule Deer, and Their Habitats

TABLE 2.3 (CONTINUED) Estimated number of black-tailed deer from 1950 to 2020 in the United States and Canada expressed as thousands of animals. Information from 1950 to 1976 is from Connolly (1981a:230) unless otherwise noted. Information from 1977 to 2020 was provided by wildlife agency representatives or obtained from published sources, as indicated by footnotes. Trend data = increasing (I), decreasing (D), and stable (S). Because of the difficulty in obtaining population estimates and variation in methodologies used, these estimates should be viewed with caution. States and provinces Year

AKa

1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020

(S) (D) (S) (S) (S) (S/D)

a b c d e f g h i j k l

(S) (I) (D) (I) (D) (I) (I) (D) (S) (I) (I) (I) (D) (S) 333–346l

BCb

93–168

115–200

98–166

99–155

98–157

98–155

CAc 283 272 251 255 235 253 218 301 203 193 244 217 189 179 186 196 191 250 218 197 188 183 184

HI

0.7k

1l

ORd

WAe

387 (D) (D) (D) (D) (D) 320 (S) (S) (S) (S) (S) (S) (S) (S) (S) (S) (S) (S) (S) (S) (S)

154j

(D) (I) (I) (D) (S) (S) (D) (S) (S) (D) (I) (S) (S) (I) (S) (D) (I) (S)

K. R. McCoy, Alaska Department of Fish and Game. A. B. D. Walker, British Columbia Ministry of Forests, Lands and Natural Resources. D. S. Casady, California Department of Fish and Wildlife. D. G. Whittaker, Oregon Department of Fish and Wildlife. S. J. Hansen, Washington Department of Fish and Wildlife. Long 2003. Gill 1990. Western States and Provinces Deer Workshop Participants 1991. Western States and Provinces Joint Deer and Elk Workshop Participants 1995. Deer and Elk Workshop Participants 1999. Hess 2008. Mule Deer Working Group 2020.

Excessive Herbivory (Livestock, Feral Animals, Native Ungulates) Livestock grazing results in effects on rangelands and wildlife species (Krausman et al. 2009). It can either decrease or improve the conditions for wildlife depending on the species or community attribute of interest (Bleich et  al. 2020). Domestic sheep and cattle began replacing bison and other native ungulates in the mid- to late-1800s, and throughout the West excessive livestock numbers led to significant overgrazing (Bahre 1991, Knue 1991). Excessive livestock grazing has led to changes in food and cover available to deer; under appropriate grazing regimes, however, cattle primarily eat

grass, if available, and have few effects on forbs and browse species (Jenks et al. 1996). Mule deer tend to avoid areas that have been heavily grazed by cattle (McIntosh and Krausman 1982, Yeo et  al. 1993), particularly during the fawning season (Loft et al. 1991). Excessive grazing can affect vegetation, particularly in riparian areas (Kauffman and Krueger 1984), by altering vegetative diversity and structure, and compacting soil with a concomitant effect on water infiltration rates (Jones 2000). These changes may occur rapidly but more often occur slowly over time and, thus, are not appreciated by local land managers (Peek and Krausman 1996, Bleich et al. 2020). There have been conflicts between ranchers and environmentalists on the issue of livestock grazing of federal lands

38

William F. Jensen, Vernon C. Bleich, and Donald G. Whittaker

FIGURE 2.6  Trapping, poisoning, and hunting with dogs have long been used as a means of predator control to protect livestock and game animals. This photograph is of wolfer Alfred Benson and his dogs and was taken in southwestern North Dakota around 1902. Image courtesy of State Historical Society of North Dakota 0227-00002.

FIGURE 2.7  Fire suppression throughout the West has led to significant vegetative changes. In the North Dakota Badlands, fire suppression has resulted in the dramatic expansion of Rocky Mountain juniper. These photographs were taken at the same photo-point in McKenzie County, North Dakota in 1962 (A) and in 2012 (B). Images courtesy of North Dakota Game and Fish Department.

for decades (Holechek and Hess 1994). A goal for publicland resource managers is to identify the acceptable level of livestock effects, apply appropriate standards and guidelines, monitor their effects, and adjust the level of grazing as necessary. Implementing management decisions to meet species and habitat objectives, and broader goals of ecosystem health on public rangelands, often are emotionally charged decisions

(Bleich et al. 2020). Although public-land grazers make up a small portion of the nation’s beef production, eliminating or altering federal-land grazing opportunities would severely harm some local economies and, further, would negatively affect wildlife if private land holdings were to be subdivided into ranchettes (Holechek and Hess 1994). Such considerations often involve reducing or eliminating livestock use in

Historical Trends in Black-tailed Deer, Mule Deer, and Their Habitats an area of concern for a period of time to allow recovery, and numerous case studies and demonstration areas have illustrated that these actions are effective in some rangelands, particularly riparian and aspen communities (Bleich et al. 2020). Developing and adapting public policy that meets the need of federal-land grazers and wildlife concerns will likely challenge decision-makers long into the future.

Invasive Species Among the most substantial non-native invasive plant species in western North America are cheatgrass (Bromus tectorum), field brome (Bromus arvensis), Japanese brome (Bromus japonicus), crested wheatgrass (Agropyron cristatum), Kentucky bluegrass (Poa pratensis), timothy (Phleum pretense), leafy spurge (Euphorbia esula), and saltcedar (Tamarix ramosissima). The single species that, perhaps, has had the most profound effect on mule deer and mule deer range is cheatgrass. Cheatgrass first arrived in North America sometime before 1860, and by 1900 was well-established throughout much of the West (Stewart and Hull 1949). Unlike perennial native grasses, cheatgrass is an annual that grows rapidly during the spring in dense stands (up to 10,000 plants/10.8 ft2 [m2]), and then dies off, depending on local precipitation patterns, between April and June, just in time to provide fuel for the western fire season. Sagebrush ecosystems throughout the West are not adapted to intense and frequent fires (Frost 1998); however, cheatgrass is and that, in turn, has resulted in 50–70 million acres (20–28 million ha) of western rangeland being dominated by cheatgrass (Pellant 2018). As a result, this cheatgrass-dominated landscape offers little palatable forage or cover for mule deer and other wildlife on a year-round basis. First introduced to what is now the United States in 1539, feral pigs (Sus scrofa) are one of the most widely introduced mammals on earth (Long 2003). Introductions were initially made to provide food, particularly on oceanic islands, and later for sport hunting. By 1982, feral pig populations were within black-tailed and mule deer range in 5 states (AZ, CA, NM, NV, TX). As of 2018, feral pigs have become established within black-tailed and mule deer range in 10 states (AZ, CA, CO, KS, NM, NV, OK, OR, UT, WA); populations have been documented in all but 1 county each in California and Texas (Animal and Plant Health Inspection Service 2020). As omnivores, feral pigs eat plants and any animal that cannot move quickly enough to escape, including deer fawns and groundnesting birds. Feral pigs have caused excessive damage to native vegetation and agricultural crops. With boars weighing >250 pounds (>113 kg), feral pigs can also pose a threat to humans. Feral pigs carry or transmit more than 30 diseases and 37 parasites to livestock, people, domestic pets, and other wildlife. It is estimated that >$1.5 billion is spent annually on feral pig damage and control (Animal and Plant Health Inspection Service 2013). Feral pigs are capable of withstanding very cold temperatures and are highly prolific; therefore, they will likely continue to become established in mule deer range of the northern Great Plains in Canada and the United States (BC, AB, SK, ID, MT, NE, ND, SD, WY) if permitted to do so.

39

Feral horses (Equus caballus) and feral ass (Equus asinus) are widely distributed across much of the western United States, particularly in the southwestern deserts and the Great Basin (McKnight 1958, Bureau of Land Management 2019, Stoner et al. 2021), and these species represent unique agents of disturbance in semi-arid ecosystems (Beever 2003). Feral equids affect mule deer and other native ungulates directly by competing for forage or water (Bleich and Andrew 2000; Marshal et  al. 2012a; Hall et  al. 2016, 2018), indirectly by altering the availability of food, water, or habitat and, thereby, reducing resource quality (Weaver 1959, 1974; Eldridge et  al. 2020), or through interference competition (Berger 1985, Ostermann-Kelm et  al. 2008, Hennig et  al. 2021). As of 2019, the number of feral horses and feral asses combined approached 100,000 animals on public lands set aside for their continued presence by Public Law 92-195, the Wild FreeRoaming Horses and Burros Act, and more than 3 times the Appropriate Management Level established for equids on public lands identified for their continued occupation (Bureau of Land Management 2019). Moreover, an average of 77% of Feral Equid Management Units (FEMUs) representing those lands designated as Wild Horse and Burro Territories by the United States Forest Service, or as Herd Management Areas by the Bureau of Land Management, are occupied by mule deer, and 97% of the FEMUs (n = 175) across 10 western states overlapped the distribution of mule deer (Stoner et al. 2021).

Forest Management Logging operations benefit deer and other wildlife by creating forest openings that allow forage production near the ground. The maximum benefits of increased deer forage production from logging usually occur 10–20 years after the cut, depending upon timber type, precipitation, and other factors; it is likely that the increases in mule deer numbers seen in California and other western states in the 1950s and 1960s were due in part to increased logging operations during the 1930s and 1940s (Longhurst et  al. 1976). Some forest management practices, such as large clear-cuts replanted to monoculture coniferous forests, removal of hardwood species, and use of herbicides, increase efficiencies of timber production but greatly reduce the benefits to mule deer and other wildlife. Variable-retention logging operations that create a planned series of patch cuts but leave old growth blocks appear to provide the best alternative to creating and maintaining diverse wildlife habitat (Franklin et al. 2019). With this method, deer receive seasonal benefits from the retention of patches of closed canopy or old growth forest (Yeo and Peek 1992, Armleder et al. 1994, Sullivan et  al. 2008, Franklin et  al. 2019). More research is needed, however, to understand the effects of timber harvest design, block size, edge effect, and consequences of habitat fragmentation on deer and other wildlife (Franklin et al. 2019).

Water Development Much of mule deer range falls within the desert and other areas characterized by semi-arid climate regimes. In these areas, water developments, big and small, are used by wildlife—including mule deer. Pregnant and lactating deer exhibit

40 increased demands for water (Short 1981) and, depending on how succulent their food sources are and the local precipitation rate, require access to surface water daily for milk production. This water can come from sources as small as hillside seeps in semiarid regions. Because of this need, water development in arid regions has been an integral part of habitat enhancement strategies for mule deer and other arid-land ungulates, is a widespread activity across the southwestern United States (Bleich et al. 2020), and is an important activity in northern Mexico (Harveson et al. 2019). Although development of small bodies of surface water in desert and other arid ecosystems likely benefits mule deer and has had a positive effect on populations, development of canals, aqueducts, or large reservoirs result in habitat loss, and may act as barriers to daily or seasonal movements (Reed 1981). Water supplementation is addressed in greater detail in Chapter 21.

Energy and Mineral Development Energy development affects mule deer through disturbance and habitat fragmentation (Sawyer et al. 2006, 2009a; Gamo and Beck 2017). Kolar et al. (2017) reported the probability of adult female mule deer in the North Dakota badlands selecting habitat within 2,000 ft (600 m) of a drilling rig was 22 times less likely than selecting areas farther from drilling rigs. Avoidance of oil and gas energy development infrastructure has been reported elsewhere (Fox 1989; Sawyer et  al. 2006, 2008; Hebblewhite 2008; Northrup et al. 2015), but the degree of avoidance varies among locations. For example, avoidance distances in the badlands of western North Dakota (Kolar et al. 2017) and in the Piceance Basin of Colorado (Northrup et al. 2015) were less than the avoidance distance in a flatter and more open wintering area on the Pinedale Anticline in Wyoming (Sawyer et  al. 2009a). Thus, topography and vegetative cover may influence how deer use the habitat in the presence of development, with deer in rougher terrain being less susceptible to line-of-sight disturbance. Other effects of energy development on mule deer include increased movement distances, and disruption of migration corridors (Lendrum et al. 2012). Two sectors of energy development that, to date, have received little attention are wind farms and solar farms (Webb et al. 2013a). These facilities often require daily visits by maintenance crews and can have a large footprint on the landscape (Lutz et al. 2011). In addition to energy development, although perhaps to a lesser degree, mining activities probably have affected mule deer. Large-scale mining operations have resulted in loss or modification of mule deer habitat (Merrill et  al. 1994). Further, increased mining activity, particularly in the western Great Basin, likely has affected habitat selection by, or movement patterns of, migratory mule deer, with potential consequences for energy expenditure by migrating animals (Blum et al. 2015). Direct losses of habitat from mining, however, may not be as severe as those associated with development of solar energy or wind energy projects, which involve massive areas (Lutz et  al. 2011). Initial effects of mining likely resulted in an increase in direct losses of mule deer, particularly in the western portion of their range, because of

William F. Jensen, Vernon C. Bleich, and Donald G. Whittaker uncontrolled harvest; currently, that is unlikely as a consequence of mining.

Human Encroachment As a society, we often think of human disturbance being limited to the building of roads or energy development, but such is not necessarily the case and recreational activities have been implicated as a concern (Wiedmann and Bleich 2014). The consequences of human encroachment through development of housing or ranchettes on important winter range, however, often is ignored and frequently is perceived as a problem only when deer or elk wander into new developments or feed on ornamental trees or shrubs. Between 1992 and 1997, Lutz et al. (2003) estimated that more than 5.4 million acres (2.2 million ha) of open areas were developed in the West, and much of that occurred in habitat occupied by mule deer. Development of roads and highways produces indirect costs to mule deer populations through avoidance of infrastructure (Ward et al. 1980) and direct mortality through increased deer-vehicle collisions; as many as 1.5 million deer-vehicle collisions of all species occur annually (Romin and Bissonette 1996, Schwabe and Schuhmann 2002). Further, recreational trail use and offroad use by all-terrain vehicles, snowmobiles, or mountain bikes create additional spatial and temporal displacement of wildlife. Even simple activities like searching for shed antlers during winter can have effects on northern deer populations already experiencing the energetic demands and stress of winter (Bates et al. 2021). These stressors each may be small but incrementally can lead to substantial cumulative effects on local populations.

Saving the Pieces (1980 to 2020) In the 1980s, mule deer numbers once again were on an upward trend throughout the West, and increased interest in mule deer hunting helped spawn The Mule Deer Foundation in 1988. By the late 1980s, however, widespread drought ushered in another period of declining mule deer numbers, and by the mid-1990s mule deer were in an obvious decline throughout their distribution. The general trend in the continental black-tailed and mule deer population has been on a declining trajectory for the last several decades; we postulate that the number of black-tailed deer and mule deer in 2020 is about 1.2 million and 3.0 million, respectively (Tables 2.2, 2.3). This continental-scale decline could not be attributed to 1 or 2 factors; rather, it appeared to be the result of the multiple and cumulative human-induced factors that have influenced habitat quality for black-tailed and mule deer, as described above. Set against mule deer declines is the political backdrop of fractured interests and demands in western North America. In the early 1980s, the economy was in a recession. In most western states, large tracts of public land are administered by the Bureau of Land Management and the United States Forest Service, and much of this public land is habitat for mule deer or black-tailed deer. Struggling with the Great Recession, competing interest groups (i.e., ranching, forestry, energy, mining) wanted more input as to how these public lands were

Historical Trends in Black-tailed Deer, Mule Deer, and Their Habitats to be managed for economic development. At the same time, other groups such as the Sierra Club, Audubon Society, and The Wilderness Society demanded more land be devoted to recreational use and additional areas to be designated as wilderness, resulting in bitter disputes as how best to manage public lands. The Earth First! movement, some of whom engaged in environmental terrorism (e.g., spiking trees with nails, burning logging equipment, harassing hunters) took up their position on the far left. The Sagebrush Rebellion, or Wise Use Movement, called for private control of public lands, and established a position on the far right. At one point, the federal Office of Management and Budget recommended selling national parks, rangelands, and forests to balance the national budget (Brown 2013). This effort failed, but the divisions regarding best use of public lands still echo across the West 40 years later, and are the result of federal legislation that has confounded the management of public lands for decades (Bleich 2005). As a result of the confounding nature of much federal legislation, Jack Ward Thomas (2004:12)—a former chief of the United States Forest Service—wrote, “Taken one at a time, it is difficult to argue against...environmental laws. Taken in interactive total, they have produced a worsening impasse in federal land management—an impasse that Congress created with the best of intentions. It is an impasse that only Congress, with the best of intentions, can remedy.” Management and conservation of mule deer, and wildlife in general, are tied inescapably to the actions of Congress (Bleich 2005). Congressional action, much of it previously based on inadequate information and a clear lack of understanding of ecological processes by members of Congress, is needed to ensure the future of wildlife on public lands (Bleich 2005, 2016). Another challenge emerged in 1981 and 1985, when chronic wasting disease (CWD) was first detected in freeranging mule deer in Colorado and Wyoming, respectively. Prior to that time the disease was restricted to facilities housing captive elk, black-tailed deer, or mule deer. By the mid1990s, CWD had spread to captive facilities in Saskatchewan, Canada. This always-fatal disease of the nervous system soon spread to other members of the deer family and has been confirmed in captive or free ranging elk, mule deer, white-tailed deer, moose (Alces alces), and reindeer (Rangifer tarandus) in the United States, Canada, Finland, Norway, Sweden, and South Korea. This disease may, to date, be the greatest existential threat to deer hunting and deer management as it has been known. Chapter 6 provides more information about CWD. In the mid-1990s, as it became clear that mule deer were undergoing yet another decline across the West, neighboring states and provinces that always had shared information, realized there was no formal structure for regular meetings. The Western Association of Fish and Wildlife Agencies (WAFWA), an organization of 24 state and provincial agencies charged with managing fish and wildlife resources in the western United States and Canada, saw the need to act collectively. In 1997, WAFWA established the Mule Deer Working Group (MDWG), consisting of a representative from each western state and western Canadian province. Since 1997, the MDWG has met annually to address concerns about mule deer

41

and black-tailed deer shared by these agencies. The Working Group’s purposes are to begin to develop strategies to assist in managing declining mule deer populations throughout the West, improve communication among mule deer biologists, and provide a forum to respond to information needs from agency administrators. To date, the MDWG has produced and published extensive information (deVos et al. 2003, Wakeling et  al. 2015) and habitat guidelines for each the 7 ecoregions occupied by mule deer or black-tailed deer, and fact sheets on a wide variety of additional subjects. This book, in large part, is yet another product of the MDWG. In 1943, Leopold remarked, “Wildlife management is comparatively easy; human management is difficult” (Flader 1974:188), an observation that has withstood the test of time and, as a result, it remains, “… impossible to predict what the future holds in the world of wildlife management” (Bleich and Thompson 2018:88). Presently, and in the foreseeable future, denial of science and social tribalism will make wildlife management even more difficult. It would seem, therefore, that we need to identify the public concerns, explain the science in a nonthreatening manner, and broaden our base of support for sound management (Prot 2015). Conservation and management of mule deer and black-tailed deer face numerous challenges, and populations in each ecoregion are faced with different stressors. Only by accepting the history of how mule deer populations and habitat have changed over time, and the axiom that science-based management is the only meaningful way forward, can sustainable populations of mule deer and black-tailed deer be retained, and habitat be recovered. Acceptance of these points is important to biologists and managers, and probably is more so to policy makers and the general public, if we are to be successful.

Summary During the past 220 years, there have been dramatic changes to black-tailed and mule deer numbers and the habitats upon which they depend. Some of the changes to habitat are, for all practical purposes, irreversible, whereas others are not. As we are writing this chapter, western states have been experiencing the most devasting fire season in recorded history, and it seems likely that public policies regarding fire suppression and forest management will change in the coming years. But effective changes will require the public and decision-makers to have at least some basic understanding of the multiple ecological factors that are causing these changes, including those that are less obvious, such as the roles invasive plants and insects can play regarding fuel loads and fire regimes. Accomplishing this will require the same type of public education efforts that were used by George Bird Grinnell and others in the late 1800s, except via social media. Conserving threatened grassland and forest wildlife and habitat does not have to mean prohibition of grazing or logging; in fact, many species, including blacktailed deer and mule deer, can benefit from livestock grazing and timber management that is science-based. As stated above, probably the greatest existential threat to deer hunting and deer management is CWD, and it is not going away. Slowing the spread of this disease will require the hunting

42 public and big game biologists to rethink expectations; even management strategies emphasizing mature males may need to change (Miller et al. 2020). Dealing with these and other issues relating to mule deer management will require funding for research and for habitat management. The vestiges of the old, lingering wounds from the Sage Brush Wars can still be seen from time to time on the evening news. It is clear, however, that healing and reconciliation regarding public land management will require respectful discussions by all parties involved, among which are sportsmen, the public in general, public lands users,

William F. Jensen, Vernon C. Bleich, and Donald G. Whittaker agency administrators, non-governmental organizations, and politicians (Bleich 2005, 2016, 2018). In the absence of such, confounding legislation, bureaucratic inertia, public advocacy, political expediency, and budgetary constraints will bode poorly for the conservation and management of mule deer and black-tailed deer (Bleich 2017). The choices are clear: “We can wring our hands and do nothing about the destructive policies that harm the wild big-game populations of the world, or we can figure out how to modify or work around benighted government policies and economic imperatives” (Gabriel 2014:389–390).

3 Physical Characteristics Levi J. Heffelfinger and James R. Heffelfinger CONTENTS Introduction..................................................................................................................................................................................... 44 General Description........................................................................................................................................................................ 44 Size.................................................................................................................................................................................................. 45 Structural.................................................................................................................................................................................... 45 Mass........................................................................................................................................................................................... 50 Pelage.............................................................................................................................................................................................. 51 Molt............................................................................................................................................................................................ 51 Aberrations................................................................................................................................................................................. 54 Skin Glands..................................................................................................................................................................................... 54 Antlers............................................................................................................................................................................................. 56 Antlerogenesis........................................................................................................................................................................... 57 Timing of the Antler Cycle........................................................................................................................................................ 59 Factors Affecting Antler Size..................................................................................................................................................... 59 Growth Rate.................................................................................................................................................................................... 60 Fetal Development..................................................................................................................................................................... 60 Juvenile Growth......................................................................................................................................................................... 60 Adult Growth............................................................................................................................................................................. 60 Age and Lifespan............................................................................................................................................................................ 60 General Lifespan........................................................................................................................................................................ 60 Physical Characteristics of Age................................................................................................................................................. 61 Senses.............................................................................................................................................................................................. 61 Sight........................................................................................................................................................................................... 61 Hearing....................................................................................................................................................................................... 62 Smell.......................................................................................................................................................................................... 62 Taste........................................................................................................................................................................................... 62 Vomerofaction............................................................................................................................................................................ 62 Voice............................................................................................................................................................................................... 63 Mother to Offspring................................................................................................................................................................... 63 Alarm......................................................................................................................................................................................... 63 Mating........................................................................................................................................................................................ 63 Aggressive.................................................................................................................................................................................. 63 Contact....................................................................................................................................................................................... 64 Locomotion..................................................................................................................................................................................... 64 Energetic Expenditure................................................................................................................................................................ 64 Escape Behavior......................................................................................................................................................................... 64 Skeletal System............................................................................................................................................................................... 65 Dentition.................................................................................................................................................................................... 66 Digestive System............................................................................................................................................................................. 66 Circulatory System.......................................................................................................................................................................... 67 Internal Glands................................................................................................................................................................................ 67 Adrenal or Suprarenal................................................................................................................................................................ 67 Thymus...................................................................................................................................................................................... 68 Pineal......................................................................................................................................................................................... 68 Pituitary...................................................................................................................................................................................... 68 Reproductive System...................................................................................................................................................................... 68 Timing of Estrus and Spermatogenesis...................................................................................................................................... 68 DOI: 10.1201/9781003354628-4

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44

Levi J. Heffelfinger and James R. Heffelfinger

Ovulation................................................................................................................................................................................... 68 Receptivity of Females.............................................................................................................................................................. 68 Parturition.................................................................................................................................................................................. 69 Lactation.................................................................................................................................................................................... 69 Summary......................................................................................................................................................................................... 69

Introduction Species exhibit physical characteristics that are evolutionarily shaped by behavioral and physiological processes as they interact with their environment. Detailed knowledge of an animal’s physical structures is important for evolutionarily relevant taxonomic units that are foundational to proper management and conservation. Well-documented geographical differences in physical characteristics help biologists investigate which are environmentally plastic, and therefore useful for managing populations and their habitat, and which are strongly genetically based and may assist with understanding taxonomic units. Characteristics such as structural size, body mass, pelage, weaponry, senses, locomotion, and internal organ structure can all aid in understanding taxonomic differences and life-history characteristics of species. Specifically, physical characteristics are important to evaluate and monitor individual health, population performance, genetic differentiation, and environmental plasticity. A baseline of informative measurements is important to allow managers to evaluate individual animals in reference to others in the population and compare populations to other groups of conspecifics. Many physical measurements have been found to be useful in management to indirectly monitor population abundance in relation to habitat carrying capacity at that time. Our objective is to summarize the physical characteristics of black-tailed and mule deer throughout their geographical range in North America. We provide general descriptions of morphological features used in taxonomy and provide specific details in relation to various physical processes. External descriptions are provided including body size, pelage, locomotion, and antler formation; and internal attributes such as the reproductive, skeletal, circulatory, and digestive systems are covered in detail. We also summarize morphometric measurements across the range of black-tailed and mule deer. This summary will be a useful resource for future wildlife managers and researchers in the conservation of black-tailed and mule deer.

General Description Mule deer (Odocoileus hemionus) were first described for science by Rafinesque (1817a) based on a field journal kept by Patrick Gass (1807), a member of the Lewis and Clark expedition who described these new western deer they saw when they reached Kansas (Woodman 2013, 2015a). The scientific name means deer that is half donkey, referencing the strikingly large ears. The large ears of the mule deer range from 7.6–9.7 inches (19.4–24.6 cm) and average 8.6 inches (21.8 cm) when

measured from inside notch to tip (Fig. 3.1, Table 3.1). Blacktailed deer have shorter ears, with Columbian black-tailed deer (O. h. columbianus) averaging about 7.9 inches (20.1 cm) with a range of 7.8–8 inches (19.8–20.3 cm). Sitka black-tailed deer (O. h. sitkensis) have the shortest ears of the species averaging 5.6 inches (14.2 cm) and ranging from 5–5.8 inches (12.7–14.7 cm) rangewide (Fig. 3.1A–C; Table 3.2). White-tailed deer (O. virginianus) differ most obviously in tail, metatarsal glands, and facial and rump coloration (Fig. 3.1D). The rump patch and tail are probably the most distinctive feature setting mule deer apart from whitetails and their black-tailed conspecifics. Mule deer tails appear cylindrical, or rope-like, and are usually white with a distinctive black tip, all surrounded by a large, obvious white rump (Fig. 3.1A; Heffelfinger 2006). This contrasts with white-tailed deer, which have a wide triangular tail with white underneath and usually brown on the dorsal surface (Fig. 3.1D). Some mule deer in the Southwest Deserts and California Woodland and Chaparral ecoregions have a thin dark line down the middle of the tail. Black-tailed deer have tails that are less rope-like, with dorsal surfaces that are dark brown fading to black near the tip and white underneath (Fig. 3.1B, C). The tails of Columbian black-tailed deer are relatively longer than the Sitka blacktailed deer subspecies and generally appear wider at the tip. Sitka black-tailed deer have the shortest tails of any of the subspecies and are broad at the base forming a triangular shape. Facial coloration is yet another characteristic that helps differentiate black-tailed and mule deer from white-tailed deer. Mule deer have distinctive black foreheads, that contrast sharply with a mostly light gray face (Fig. 3.1A). The lighter facial coloration of mule deer means they do not have contrasting white eye rings and this helps differentiate them from whitetails with their brown faces and white around their eyes (Fig. 3.1D). Black-tailed deer, especially Sitka black-tailed deer, have more brown on the sides of their face, which creates less contrast between the typical black forehead and face (Fig. 3.1B, C; Cowan 1956). Mule deer metatarsal glands appear as a long tuft of fur on the upper half of the lower leg (metatarsus), which is distinct from that of white-tailed deer (Fig. 3.2). Mule deer metatarsal glands usually exceed 3 inches (76 mm) in length and are surrounded by brown hair. In contrast to mule deer, white-tailed deer metatarsal glands are usually 1.0 while conditions are favorable but may drop considerably in unfavorable conditions such as extended snow cover or lack of fall green-up for winter survival (Hurley et al. 2014). The combinations of demographic parameters that result in population growth are restricted (Figs. 5.3, 5.4). Furthermore, there is positive correlation between winter adult survival probability and juvenile survival probability (Lukacs et al. 2009). Therefore, a mule deer population has the potential to decline rapidly during unfavorable conditions, resulting in simultaneous declines in adult and juvenile survival.

Demographic Rates Survival Survival of mule deer has been thoroughly studied and some general patterns are unambiguous (Forrester and Wittmer 2013). Other chapters in this book provide demographic rates throughout black-tailed and mule deer range (Chapters 9–15); therefore, we present general patterns here. Early life stages of mule deer show variable survival. Forrester and Wittmer (2013) reviewed the literature and report average over-winter survival probabilities from 0.30–0.86. Lukacs et al. (2009) presented biological variation (process standard deviation) of 0.696 on the logit scale, which converts to approximately 0.13 on the probability scale. The large variation in juvenile survival suggests that parameter fluctuates widely from year to year depending on conditions. On the contrary, adult female survival shows almost no variation (Forrester and Wittmer 2013). Lukacs et al. (2009) report biological variation of 0.34 for 6-month adult female survival, which converts to a standard deviation of 0.03 on 12-month survival. Unsworth et al. (1999a) demonstrated similar variation in survival based on a shorter time scale but broader spatial extent. In fact, the variation in adult female survival is so small that a sample size of ≥120 radio-collars is required to return sampling variation that is as small as the process variation. The standard error from a sample of 120 radio-collars is 0.03, which is equal to the process standard deviation of adult female survival. Smaller sample sizes will result in sampling variation exceeding process variation. Therefore, single estimates of survival will not be informative about the actual biological process. Except in the most

Population Regulation The concept of population regulation is highly logical and almost certainly must exist (Mills 2013). Brook and Bradshaw (2006) provide evidence that density dependence is pervasive in an examination of time series data from nearly 1,200 species. Yet the authors did not find evidence for density dependence in the mule deer data they examined (Brook and Bradshaw 2006). This dichotomy shows the complexity of mule deer population dynamics and the challenge in measuring population regulation in wild, harvested populations (Bonenfant et al. 2009). Population regulation in mule deer is generally thought to occur through negative density dependence (Bergman et al. 2015a). Negative density dependence suggests that population growth rate declines as deer density increases. For negative density dependence to produce a population-level response, several factors must exist in the deer population. First, there must be a limiting resource. Often the limiting resource is nutrition (Chapter 5; Fowler 1987, Bartmann et al. 1992, Bishop et al. 2009b, Bergman et al. 2015a). Yet the limiting resource may also be competition for territories with lower risk of predation (Chapter 8; Hurley et al. 2020). Second, the demographic rate changing with density must have enough influence on growth rate to cause the growth rate to change (Mills 2013). In ungulates, density-dependent effects are expected to first appear in juvenile survival and reproductive rates, which also show low elasticity (Fowler 1987, Gaillard et al. 1998a, Bonenfant et al. 2009). Therefore, a density-dependent change in juvenile survival must be substantial to produce a population-level effect.

100 Population regulation in black-tailed and mule deer almost certainly results from a combination of density-dependent and -independent effects. Extensive study of other ungulates demonstrate these characteristics (Coulson et al. 2000, 2001; Bonenfant et al. 2009). The effects of density-dependent and -independent responses are similar across other species of ungulates, providing further evidence that we should expect similar responses in black-tailed and mule deer (Coulson et al. 2000, Bonenfant et al. 2009). White and Bartmann (1998a) reported evidence of density-dependent and -independent effects following the same patterns as other species. Many studies point to characteristics of a mix of regulatory processes on mule deer including weather patterns and nutrition (Marshal et al. 2002, Bishop et al. 2009b, Hurley et al. 2014); therefore, density-dependent and -independent factors are likely at play even if we lack time series data to demonstrate a mathematical relationship.

Inference to Population Dynamics Population dynamics of deer can be difficult to conceptualize in the face of imperfect data. Several factors weigh on our ability to make inference from multiple sources of data. These factors include sampling variation, spatial mismatch of data, and a lack of randomization. Each issue causes a different set of complications for inference to population dynamics. First, sampling variation, the variation caused by only observing a subset of the population, results in uncertainty in our estimates of parameters. In population dynamics, many parameters are probabilities or rates such as survival or fecundity. For those parameters, sampling variation exists even if we observe the entire population because we can only observe the outcome of the process (live or dead) rather than the process of survival. Therefore, we can never escape the presence of sampling variation. For example, we may estimate adult female survival to be 0.82 ± 0.08 (SE). The standard error measures sampling variation or how variable we expect a set of estimates to be based on observing different deer in each sample. Unfortunately, the process variation or standard deviation of adult mule deer survival probability is smaller than that standard error (Lukacs et al. 2009). When the standard error is larger than the standard deviation, then we are likely to see a wider range of estimated survival probabilities than actually occur in the wild population. Observing a wide range of point estimates provides the appearance of more variation and clouds our view of population dynamics. Therefore, we gain little if any new information from that one survival estimate on its own. Spatial mismatch affects our ability to compare estimates of different demographic rates directly. For example, we may seek to understand population dynamics of mule deer in a specific hunt unit. We estimate harvest by hunt unit in the fall and herd composition by hunt unit in the winter. If the deer that winter in the hunt unit of interest migrate to another hunt unit in the fall, then there will be a spatial mismatch of harvest estimates and herd composition. Spatial mismatch results in incongruent data entering a model. If the data entering the model do not arise from the same population of deer, there is little hope in the model performing well. Unfortunately,

Paul M. Lukacs and J. Joshua Nowak spatial mismatch of data and populations is far too common. Mismatch can occur when the management area is smaller than area covered by the biological herd. Mismatch regularly occurs at artificial boundaries such as state borders. Mismatch can also occur in more subtle ways in situations such as partial migration where subsets of the herd follow different behavioral patterns that expose them to different risks. Randomization is central to valid statistical inference. A lack of randomization in sampling design can lead to biased estimates and inappropriately small estimates of precision. Randomization requires first determining a sampling frame or geographical area from which to select samples (Cochran 1977). Then a set of sampling units must be drawn from that area, each with a known sampling probability (Cochran 1977). For example, deer herd composition surveys often prioritize observing large numbers of deer over randomly selected sampling units. Without randomization defining the sampling unit, there is no logical way to determine sample size and therefore standard errors are likely to be too small. Despite these shortcomings in data, we can still improve our understanding of population dynamics by making inference from imperfect data. To do so, we need to find the story that allows all of the data to agree—the overlapping consensus in the data. We need a method that combines multiple data sources and incorporates what we know about deer population dynamics. Although the topic of fitting population models could easily fill a book itself (King et al. 2009, Newman et al. 2014), we highlight important features of inference from population models. Integrated population models (IPM) provide a framework for combining multiple sources of data in a coherent manner and link them directly to demographic parameters. White and Lubow (2002) provided a foundational example of IPMs for mule deer using tools available in standard spreadsheets. Since then, broad development in the field has led to many technical advances and readily available software (Besbeas et al. 2002, Schaub and Abadi 2011, Eacker et al. 2017, Nowak et al. 2018). Integrated population models combine a process model describing the biology with observation models describing data collection. The process model for deer typically follows equation 1 (White and Lubow 2002, Nowak et al. 2018). The process model contains the links to survival, reproduction, and harvest. Extending the model presented in equation 1, the process model in an IPM also can include biological variation in demographic rates. The observation models follow the data collection methods and types of parameters of interest. For example, telemetry data for survival would likely follow a binomial capture-recapture framework (White and Garrott 1990). Integrated population models merge well with Bayesian inference methods (Kéry and Schaub 2011). Bayesian inference provides the architecture for key components of deer population modeling. Bayesian analysis is essentially a giant integration problem (here we use the definition of integration from calculus), which makes it perfect for handling the issues we face in population modeling (Link and Barker 2009). Efficient model-fitting algorithms, methods for handling missing data, direct incorporation of process variation, probabilistic results, the ability to incorporate prior information, and

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Modeling Population Dynamics of Black-tailed and Mule Deer straightforward prediction all emerge from the application of Bayesian inference to IPMs. Markov chain Monte Carlo (MCMC) model-fitting methods provide an efficient and effective technique for high dimensional problems (Link et al. 2002, Brooks et al. 2011). Because MCMC is a numerical integration method, it fits well with the multi-dimensional integrals required for IPMs. In addition, IPMs frequently employ hierarchical structures that also rely on integration. Although the mathematical details underpinning MCMC may be complex, modern software and computing languages allow for simple implementations of complex models (Kéry and Schaub 2011, Nowak et al. 2018). Markov chain Monte Carlo also provides a straightforward technique for projecting population models into the future while propagating variance along with those projections. Bayesian methods provide a mechanism for handling missing data. Missing data are ubiquitous in monitoring data sets because it is expensive and logistically challenging (impossible) to measure every demographic parameter in all locations every year. When data are absent, we must consider all the possible events that could have occurred and how likely each was to have occurred. For example, if a battery fails on a global positioning system (GPS)-collar, we do not know if the animal is alive or dead, but we can consider that the animal is alive following the survival probability and dead with the mortality probability (1 − survival probability) for each time interval since the battery failure. In thinking in that manner, we are taking a weighted average of all possible outcomes for the animal with the failed GPS-collar, where the weight is the probability of the outcome. Because the framework of Bayesian estimation is an integral (weighted average) over all possible outcomes, the Bayesian formulation handles missing data by integrating over the missing values. Markov chain Monte Carlo tools perform the integration in a seamless manner. Modern software such as JAGS (Plummer 2021) handles missing data values as if they were another parameter in the model (Kéry and Schaub 2011). Bayesian IPMs allow for direct incorporation of process variation in the model. Unlike standard matrix models that assume fixed demographic rates (Caswell 2001), the process model in an IPM easily incorporates hierarchical forms where demographic parameters are represented as a distribution. Instead of saying that adult mule deer survival probability is 0.85, we can represent the model as adult mule deer survival has a mean of 0.85 with a standard deviation allowing for variation. Including process variation allows more realism in the model and handles variation in rates from factors such as density dependence without providing a functional form for those factors. Bayesian methods produce posterior distributions (i.e., posteriors) as a product of the analysis (Gelman et al. 2013). The posterior describes the probability of all possible values for the parameter of interest. The posteriors provide the type of inference one would hope that a frequentist confidence interval would produce. Posteriors provide information about which values are more likely than others are and how much more likely (e.g., is survival of 0.85 more likely than 0.75?). Posteriors can also provide management-relevant information such as the probability that the deer population size is under (or over) objective. Bayesian inference provides answers in a

form that is useful for managers who must make a decision in the face of uncertainty. Bayesian methods provide a mechanism to incorporate all we know about deer biology into a population model. It would be naïve to consider a mule deer population as if we knew nothing about adult female survival when a lot of prior research exists (Forrester and Wittmer 2013). Prior distributions (i.e., priors) are part of the Bayesian architecture that defines what we know about a parameter before we collect data (Gelman et al. 2013). In the absence of data, priors allow us to simulate a population based purely on our current understanding of the system. As the volume of data increases, the data eventually overwhelm the prior distributions, resulting in data-driven inference. Given that biologists in wildlife agencies must make management decisions continuously and they can be updated through time, the Bayesian approach of prior distributions provides a bridge from data-free simulation to data-rich inference throughout the process. Bayesian methods in conjunction with MCMC algorithms provide a straightforward mechanism to make predictions about population dynamics into the future. Future values for demographic parameters can simply be viewed as unobserved data. Therefore, the mechanics of MCMC allows us to produce a weighted average of all possible outcomes for the population in future time steps. Model predictions also provide a mechanism for model selection. Model selection with simple selection criteria is often challenging in Bayesian analyses (Hooten and Hobbs 2015). For mule deer population dynamics models, many data sets exist across wildlife management agencies and researchers. Therefore, the opportunity exists for out-of-sample testing of model structures by predicting with a model fit to one set of data in another area or on future data. Predictive accuracy can provide the check on whether a model is sufficient. As with all methods, Bayesian IPMs present some shortcomings. First, the MCMC algorithms can be slow to converge in cases of sparse data or very complex models. The large numbers of parameters and frequency of missing data can increase the risk of convergence problems (Conn et al. 2018). Convergence diagnostics exist to help guide the user, but they are not infallible. Inference from model results that did not converge can be misleading. Moreover, the complexity of coding IPMs can increase the chance of errors. Coding errors are not always easy to diagnose. Carefully testing code is always advisable. In addition, strong prior distributions can mask sparse data, giving the appearance of more robust inference than would be possible without the prior distribution. Bayesian IPMs come with risks as all models do, but they offer many advantages as well.

Summary Our understanding of black-tailed and mule deer population dynamics leverages broader ecological principles and many empirical studies. Mule deer show high, constant adult female survival and variable juvenile survival. Those characteristics provide the basis for a tractable mathematical model of the population process. We can employ integrated population modeling to make inference and predictions to black-tailed and mule deer populations in the face of uncertainty and missing data.

6 Diseases and Parasites Margo J. Pybus, Mary E. Wood, Karen A. Fox, and Brandon A. Munk CONTENTS Introduction................................................................................................................................................................................... 103 Prion Diseases............................................................................................................................................................................... 104 Chronic Wasting Disease......................................................................................................................................................... 104 Viral Diseases................................................................................................................................................................................ 105 Viral Hemorrhagic Diseases.................................................................................................................................................... 105 Malignant Catarrhal Fever....................................................................................................................................................... 106 Deer Papillomavirus................................................................................................................................................................. 107 Bovine Viral Diarrhea Virus..................................................................................................................................................... 107 Bacterial Diseases......................................................................................................................................................................... 107 Necrobacillosis......................................................................................................................................................................... 107 Pasteurellosis............................................................................................................................................................................ 108 Infectious Keratoconjunctivitis (Pinkeye)................................................................................................................................ 108 Abscesses................................................................................................................................................................................. 109 Mycobacteriosis....................................................................................................................................................................... 109 Mycoplasma bovis...............................................................................................................................................................110 Parasites and Parasitic Diseases.....................................................................................................................................................110 Nematodes (Roundworms).......................................................................................................................................................110 Cestodes (Tapeworms)..............................................................................................................................................................114 Trematodes (Flukes).................................................................................................................................................................114 Protozoans (Sarcocysts)............................................................................................................................................................115 Flies and Fly Larvae..................................................................................................................................................................115 Lice...........................................................................................................................................................................................116 Ticks..........................................................................................................................................................................................117 Mites.........................................................................................................................................................................................118 Fleas..........................................................................................................................................................................................118 Zoonotic Diseases..........................................................................................................................................................................118 Anomalies......................................................................................................................................................................................119 Malnutrition...................................................................................................................................................................................119 Artificial Feeding and Disease...................................................................................................................................................... 120 Capture Myopathy and Capture-Related Injuries......................................................................................................................... 121 Toxins............................................................................................................................................................................................ 121 Toxic Plants.............................................................................................................................................................................. 121 Other Toxins............................................................................................................................................................................. 122 Additional Diseases of Interest..................................................................................................................................................... 122 Summary....................................................................................................................................................................................... 122

Introduction Understanding of diseases and parasites in wildlife has expanded over recent decades. Historically, many wildlife professionals regarded these as largely compensatory sources of mortality with limited population-level effects on black-tailed deer (Odocoileus hemionus columbianus, O. h. sitkensis) or mule deer (O. hemionus). An expanding body of science DOI: 10.1201/9781003354628-7

and experience now allows managers to see how emergent diseases like chronic wasting disease and locally introduced parasites like meningeal worm (Parelaphostrongylus tenuis) have potential to directly affect deer population performance. Distinguishing between pathogens with true implications for deer populations, those that have human or livestock health concerns, and those of limited overall consequence is fundamental to understanding deer health. 103

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The footprint of human population continues to expand, bringing people and livestock into greater contact with wildlife and increasing public awareness of diseases and parasites in wildlife species. Expanding urban areas along with increased agriculture, human populations, and movement of humans and other animals contribute to ecological fragmentation and increased potential for pathogen transmission. Health is increasingly understood as a function of the interconnectedness among humans, animals, and their environments. Rather than a true absence of diseases or parasites in a population, health refers more broadly to an individual or population in equilibrium with the surrounding environment. Therefore, understanding the occurrence and role of pathogens in deer is fundamental to a broader understanding of not only their health but also the health of their environments and other species that share the same landscapes. Indeed, deer can serve as reservoirs for diseases of concern to livestock and human health. Similarly, livestock harbor many diseases that are not native to deer, and spillover into deer can cause unexpected mortality or create new disease reservoirs that continue to be a disease risk for livestock. Wildlife managers are tasked with managing for healthy and sustainable populations. This includes an increasing need to identify and manage situations that impinge on the health of free-ranging deer populations. Increased awareness and concern for wildlife diseases and parasites led many wildlife management agencies to establish wildlife health programs that evaluate diseases, parasites, and their potential role in wildlife populations. To inform these efforts, wildlife health programs and associated partner groups undertake monitoring, surveillance, and investigation of pathogens in free-ranging wildlife. Such programs helped to advance our collective knowledge and understanding of diseases and parasites in deer. This chapter summarizes commonly recognized diseases, parasites, and non-infectious health risk factors of black-tailed deer and mule deer, and puts them in appropriate perspective for public and professional wildlife enthusiasts. Deer managers and the general public often ask a few key questions about diseases and parasites: What is it? How did it get there? Does

it harm the deer? These questions guide the content in this chapter.

Prion Diseases Chronic Wasting Disease Most wildlife professionals consider chronic wasting disease (CWD) to be the most significant infectious disease affecting long-term viability of deer populations across the United States and Canada (Gillin and Mawdsley 2018). This fatal disease of cervids is associated with structural, metabolic, and behavioral changes involving accumulations of abnormal, misfolded proteins called prions (EFSA Panel on Biological Hazards et al. 2017). It is part of a group of diseases known as transmissible spongiform encephalopathies (TSEs) that result in death of brain cells and the creation of vacuoles within the brain tissues, giving it a spongy microscopic appearance. The chronic wasting syndrome was first observed in the late 1960s in a captive research facility in Colorado but was not identified as a TSE until 1978 (Williams and Young 1980). Since then, both natural movements of free-ranging cervids and humanassisted transportation of captive cervids facilitated movement of CWD across a broad expanse of North America and beyond. Deer with CWD often show no clinical signs of disease for most of the time they are infected. They appear completely normal until the final stages prior to death. In some cases it may take over 2 years until the animal dies. Most hunter-harvested deer that test positive are in good body condition and hunters see no obvious signs of CWD. As the disease progresses, clinical signs typically change from subtle behavioral anomalies to loss of body condition, dull rough hair coat, increased salivation, increased drinking, pot-bellied appearance, general loss of awareness, and eventually death (Williams and Young 1980, Williams 2005; Fig. 6.1).These generic clinical signs can be associated with other pathogens or health concerns, thus confirmation of CWD requires laboratory testing of specific lymph nodes, brainstem tissue, or both. Infection with CWD

FIGURE 6.1  Three deer with chronic wasting disease (CWD). A) An apparently healthy deer as seen throughout most of the disease course: this deer tested positive for CWD on tonsil biopsy. B) A deer in the early terminal phase of the disease: flanks tucked up, enlarged fluid-filled rumen, abnormal ear position, prominent points of the shoulders and hips, and hair standing up. C) An emaciated deer consistent with end-stage disease. Photos by M.W. Miller, Colorado Parks and Wildlife (A and B); Justin Binfet, Wyoming Game and Fish Department (C).

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Diseases and Parasites also can lead to difficulties in swallowing and secondary aspiration pneumonia in late stages. Similarly, behavioral changes may result in increased risk of predation, vehicle collisions, or hunter harvest (DeVivo et al. 2017, EFSA Panel on Biological Hazards et al. 2017). Transmission of CWD is primarily through direct exposure to infectious animals (e.g., grooming, social behaviors, breeding behaviors), or indirect exposure to contaminated environments (e.g., sequential use of bed sites, rut behaviors at deer scrapes). Infectious prions are shed in feces, saliva, and urine for many months before an animal dies. In addition, carcasses of deer that die from CWD may serve as a source of environmental contamination. The prions may persist in the environment for years. Additional potential sources of transmission include human-related movement of infected carcasses, prioncontaminated hay or crops, or products containing contaminated cervid feces, saliva, or urine; however, there is no definitive documentation of these methods transmitting CWD in the field to date (Miller and Fischer 2016). The role of various sources of prions in the transmission, persistence, and spread of CWD is not well understood and may change over time as the disease becomes entrenched in deer populations. Data from surveillance programs typically demonstrate higher prevalence in male deer than females, with highest prevalence in prime-aged males (4–6 yr old; Miller and Conner 2005). The role of different species in the patterns of CWD occurrence is complicated. Where CWD is well-established (enzootic) in the eastern United States, the primary wild cervid on the landscape is white-tailed deer (Odocoileus virginianus). In contrast, in most western regions where the disease occurs, CWD can predominate in populations of mule deer or white-tailed deer, or may be similar in both. Furthermore, CWD occurs in wild elk (Cervus canadensis) populations and occasionally in freeranging moose (Alces alces). Currently, CWD is not documented in free-ranging black-tailed deer populations; however, they are susceptible to the disease (Williams and Young 1980). The overlap of multiple susceptible cervid species across western North America presents significant management challenges. Although cervid management often focuses on individual species management, a broader interspecies approach may offer greater opportunities for CWD suppression. Wherever the disease is established, CWD prevalence generally increases in the absence of management actions directly aimed at limiting the disease in wild populations (Jennelle et al. 2014, Miller et al. 2020). In local populations with a long history of CWD occurrence, there are measurable declines in population size and changes in the age structure associated with mature males becoming increasingly less common (Edmunds et  al. 2016, DeVivo et  al. 2017). Multiple jurisdictions have tried various management strategies including culling, harvest manipulations, and test and cull operations (Uehlinger et al. 2016). Although many of these strategies were either prematurely discontinued or had insufficient data to evaluate efficacy, some do show promise in reducing CWD (Mateus-Pinilla et al. 2013, Mysterud and Edmunds 2019, Miller et al. 2020). In contrast, a number of management practices may promote increases in CWD, including supplemental feeding, baiting, translocation of animals from enzootic areas, and managing for high male numbers or older age males (Gillin and Mawdsley 2018, Miller

et  al. 2020). Updated recommendations with guidance for experimental application offer renewed hope in finding effective means to suppress the disease (Western Association of Fish and Wildlife Agencies 2017a). Without effective management strategies for CWD, this disease may fundamentally alter deer population performance and hunting opportunities across wide areas of North America.

Viral Diseases Viral Hemorrhagic Diseases Outbreaks of viral hemorrhagic disease (HD) are some of the most common and significant disease events affecting deer. They are associated with 3 different viruses: bluetongue virus (BTV), epizootic hemorrhagic disease virus (EHDV), and deer adenovirus 1 (OdAdV-1; formerly cervid adenovirus or cervine adenovirus A). The diseases associated with these viruses are commonly known as bluetongue (BT), epizootic hemorrhagic disease (EHD), and adenovirus hemorrhagic disease (AHD), respectively. They have similar clinical signs and share many common features. As the name implies, bleeding or hemorrhage in various tissues are the classic signs of infection, but the outcome in an individual deer can range from sudden death to inapparent infection. All 3 viruses attack the cells lining blood vessels (endothelial cells) and can lead to leakage from blood vessels, hemorrhage, blood clots (thrombosis), and tissue death. Common clinical signs associated with HD can include excessive drooling, swollen muzzle, diarrhea (sometimes bloody), regurgitation, seizures, inability to rise, and death. Deer that die from HD often have heavy, wet lungs (pulmonary edema), clear or yellow- to red-tinged fluid in the chest or abdomen, and inflammation, hemorrhages, or ulcers anywhere in the alimentary tract (mouth, esophagus, rumen, intestines; Fig. 6.2).

FIGURE 6.2  Systemic deer adenovirus infection causing characteristic hemorrhagic disease lesions in the lungs of a black-tailed deer. Note the widened interlobular septae (walls) and the thickened, semi-opaque material over portions of the lung indicative of severe pleural edema. Multiple dark hemorrhages fill entire lung lobules and free fluid surrounds the dorsal and ventral margins of the lungs. Photo courtesy of California Department of Fish and Wildlife.

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Some infected individuals may exhibit no visible signs of disease or may recover after developing only mild to moderate disease. Alternatively, some mild forms of HD may ultimately lead to death through secondary infections or starvation and individual deer that survive can carry lasting evidence of previous infection (Howerth et al. 2001, Woods 2001). Multiple deer found dead in an area, frequently near water, are often the first indications of HD outbreaks, particularly those involving BT and EHD. Outbreaks of AHD usually involve young deer and a cluster of dead fawns in an area or at wildlife rehabilitation centers, often with bloody diarrhea, may be the first sign of a problem. A finding of 1 or more of the viruses in association with gross and microscopic evidence of HD is sufficient to confirm the type of outbreak (Howerth et al. 2001, Woods 2001). Following initial confirmation in 1 or more deer, monitoring the herd or population for additional mortalities consistent with HD often is adequate for documenting the extent of an outbreak. Bluetongue virus and EHDV are closely related viruses (genus Orbivirus, family Reoviridae) transmitted by culicoides biting midges (Maclachlan et al. 2019). Outbreaks of BT and EHD largely follow seasonal patterns of Culicoides sonorensis (Mayo et al. 2014, Ruder et al. 2017), but where climates are mild and Culicoides are active year-round, outbreaks could occur any time of the year. Most cases of AHD are detected between May and October (Woods et al. 2018). Odocoileus adenovirus 1.—Deer adenovirus 1 (OdAdV1) was first identified from a 1993–1994 outbreak of HD in California associated with at least 1,000 mule deer and blacktailed deer deaths from 17 counties (Woods et al. 1996). Prior to this, BTV and EHDV were thought to be the only causes of HD outbreaks in deer. Subsequent work using archived tissues detected OdAdV-1 in deer samples from high mortality events in California as early as 1981. It is possible that earlier outbreaks of HD in black-tailed deer and mule deer were caused by OdAdV-1, and in California, OdAdV-1 is believed to be the primary virus responsible for large epizootics of HD in mule deer and black-tailed deer (Woods et al. 2018). Since its initial discovery, OdAdV-1 has been detected in deer as far east as Colorado and as far north as British Columbia, though it remains unclear whether this is a true expansion of the virus range or a result of increased awareness and detectability of this virus. Deer adenovirus can result in either localized infection in 1 or 2 organs or broad systemic infection with distinct disease outcomes. Systemic AHD typically results in rapid mortality with pulmonary edema as the most consistent postmortem finding (Woods 2001). Localized AHD usually manifests as small erosions, ulcers, or abscesses in the mouth, throat, esophagus, or rumen. These may become secondarily infected with bacteria like Truperella pyogenes, Prevotella sp., and Fusobacterium necrophorum, which can lead to death. These bacteria may quickly take over and deflect diagnosis from the original OdAdV-1 because the virus usually is long gone by the time the bacterial infections are severe enough to cause death of the deer. Fawns, particularly black-tailed deer fawns, are at greatest risk for developing systemic and fatal AHD. Transmission of OdAdV-1 is by direct contact between infected and susceptible deer (Woods et  al. 1999), but other

routes of transmission may exist and could be important in maintaining the virus between outbreaks. Bluetongue and epizootic hemorrhagic disease viruses.— Despite recent information about the significance of OdAdV-1 in black-tailed deer and mule deer (Woods et al. 2018), BTV and EHDV remain common causes of HD in both deer species. Serologic surveillance (looking for antibodies in blood) for the 2 viruses shows widespread exposure in some deer populations (Dubay et al. 2006, Roug et al. 2012) and exposure is probable, at least seasonally, wherever Culicoides sp. vectors overlap with black-tailed deer and mule deer populations (Wirth and Jones 1957). It may be that BTV and EHDV cause more localized outbreaks of HD or chronic, sublethal, or inapparent infections throughout much of the range of blacktailed and mule deer. Outbreaks are rare in western Canada because of the absence of suitable vectors except when blown north from the northern states in late summer. Bluetongue virus and some strains of EHDV are associated with important livestock diseases and, if detected, it is (BTV) or may be (EHDV) mandatory to report cases to appropriate state and federal veterinary or animal health agencies in the United States and Canada. Clinical signs and lesions of BT and EHD are similar to those of AHD. Additional signs could include fever, reddened skin and mucous membranes, swelling around the eyes, weakness, and incoordination (Howerth et al. 2001). In addition to acute systemic HD, localized and chronic disease can occur with BTV and EHDV infections. Common signs include inflammation or hemorrhage where the hoof grows from the skin (coronary band) disrupting normal hoof growth and resulting in cracked or overgrown hooves, and damage to the lining of the rumen or other portions of the gastrointestinal tract that can disrupt nutrient absorption (Howerth et  al. 2001). These can lead to the slow nutritional decline of a deer and death long after the initial BTV or EHDV infection occurred. In addition, EHDV infection has been linked to testicular damage and resultant abnormal antlers (cactus buck; Fox et al. 2015). There are at least 26 BTV and 7 EHDV serotypes currently recognized (Rovid Spickler 2015, 2019) and at least 3 EHDV (Ruder et al. 2017) and 15 BTV serotypes have been documented in North America (Dubay et al. 2006, Maclachlan et  al. 2013). In part because of changing climate, there have been profound changes in the global distribution and biological behavior of BTV and EHDV, including emergence of novel strains in local areas, discovery of new strains, and evidence that some species-adapted strains can transmit through direct contact and through vectors (Maclachlan et  al. 2019). With continued changes in climate temperature and moisture regimes, the range of Culicoides sp. and detections of BTV and EHDV in various species are expanding northward in North America (Stallknecht et al. 2015, Vigil et al. 2018) and elsewhere. With ongoing continental changes, the biologic activity of these viruses and their vectors may continue to evolve with unknown outcomes for susceptible deer populations.

Malignant Catarrhal Fever Malignant catarrhal fever (MCF) is caused by several closely related ruminant herpesviruses. These viruses do not cause

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Diseases and Parasites significant diseases in species that are carriers but can cause serious and often fatal disease in other ruminant species. Ovine herpesvirus-2 (OHV-2) is the most commonly reported cause of MCF in North America. Healthy domestic sheep (Ovis aries) carry OHV-2 without showing clinical signs of disease but can pass the virus to other species. The OHV-2 virus causes MCF in a variety of captive and free-ranging cervids including black-tailed deer and mule deer (Jessup 1985, Vikøren et al. 2006, Schultheiss et al. 2007). In deer and other cervids, the clinical signs of MCF are variable but can include lethargy, separation from herd mates, cloudy eyes, bloody diarrhea, convulsions, blindness, and death (Vikøren et al. 2006, Schultheiss et  al. 2007, Palmer et  al. 2013a). Because MCF requires direct or indirect contact with the carrier species to produce disease (Li et al. 2014), infected deer are unlikely to transmit the disease to other deer; however, aerosol transmission from carriers is suspected to occur over long distances (≥5 km; Li et al. 2008). The presence of characteristic lesions and detection of the virus from lesions and lymph tissues can be used to confirm MCF. Tests for OHV-2 are readily available at most veterinary diagnostic laboratories, but other MCF-associated viruses may be under-recognized in cervids because of a lack of available tests (Cunha et al. 2009). For example, caprine herpesvirus-2 (CpHV-2) carried by domestic goats (Capra aegagrus hircus) causes MCF in captive and free-ranging cervids (Keel et  al. 2003, Li et  al. 2003a, Vikøren et  al. 2006), including mule deer, but is likely under-reported. Improved diagnostics may provide a better understanding of MCF in free-ranging wildlife. As a disease, MCF causes minimal concern in its primary livestock host but has significant effects in other species including deer. It typically occurs in a few individuals of a population, but it is unknown whether the disease can cause significant disease in wild populations when contact with domestic sheep or goats is extensive. Introduction of MCF into captive deer can result in considerable mortality, and MCF is considered one of the most significant viral diseases in captive cervids in major sheep-producing countries such as New Zealand.

Deer Papillomavirus Deer fibromas (often called warts) are common in free-ranging populations of black-tailed deer and mule deer. Although the disease is self-limiting with minimal concern for population health, the growths are highly visible and are often a source of concern to the public. Deer papillomavirus, previously known as deer fibromavirus (Groff and Lancaster 1985), causes wart-like growths on the skin of many cervid species, including black-tailed deer and mule deer. These growths can be pinpoint size to several inches in diameter and are typically dark-colored, hairless, firm, raised nodules, sometimes with an ulcerated surface. Growths may occur in clusters or singly, and large growths may hang from the attached skin. They are most common on the face, particularly around the eyes and on the neck, although they can occur anywhere on the body. Many terms can be used to describe the microscopic appearance of these benign tumors including fibroma, fibropapilloma, and papilloma, but they all

likely reflect the same disease (Lancaster and Sundberg 1982). The growths are typically self-limiting and resolve naturally. Young deer are most commonly affected and appear to retain lifelong immunity after infection. Spread of the virus is by direct skin-to-skin contact, shared scratching posts, or possibly biting insects. Because papillomaviruses are highly specific, there is no concern for transmission to people, pets, or livestock. Although they may appear large and unsightly, deer fibromas rarely require management actions. In very severe cases where the mouth, nose, or eyes are completely obscured, deer fibromas can interfere with normal foraging behavior and may warrant euthanasia of the affected individual.

Bovine Viral Diarrhea Virus Bovine viral diarrhea (BVD), caused by bovine viral diarrhea virus (BVDV), is an important disease of cattle (Bos taurus) associated with decreased reproductive success, milk production, and growth leading to serious economic losses. Serologic surveys demonstrate exposure to BVDV in free-ranging mule deer populations (Couvillion et  al. 1980, Roug et  al. 2012), although clinical cases in free-ranging deer have not been reported. Under experimental conditions, mule deer infected with BVDV showed no clinical signs of disease; however, they did shed the virus (Van Campen et al. 1997). One of the most important mechanisms of transmission of BVD in cattle involves persistently infected individuals that are exposed to the disease as a fetus and then shed large amounts of virus throughout their life. Experimental studies with white-tailed deer demonstrated that BVD infection can produce persistently infected fawns (Passler et al. 2009, 2010). Similarly, a free-ranging mule deer with persistent infection was detected in Colorado (Duncan et al. 2008). Although it appears that mule deer, and presumably blacktailed deer, can be infected with BVDV, there is no current evidence that infection results in clinical disease or population concern. The occurrence of persistently infected mule deer seems to be low in Colorado (Duncan et al. 2008); however, true prevalence has not been estimated across mule deer range. Although BVD is not considered a disease of significant concern to deer populations, the importance of the disease in cattle may lead to questions about the potential role of wildlife as reservoirs or sources of disease transmission.

Bacterial Diseases Necrobacillosis Necrobacillosis is a common occurrence in cervids and can be fatal. The disease is caused by the anaerobic bacterium Fusobacterium necrophorum (Leighton 2001). This bacterium is a normal inhabitant of the mouth, gut, and skin surfaces of deer. It cannot penetrate normal, healthy surfaces, but if these surfaces are broken or weakened, F. necrophorum and other bacteria can cause severe necrotizing (tissue-damaging) infections. Depending on where the bacteria enter an individual deer (mouth, foot, or rumen), F. necrophorum can be

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associated with a variety of diseases, collectively referred to as necrobacillosis. In the mouth, Fusobacterium necrophorum can cause various lesions, a condition known as necrotic stomatitis, following damage to the oral surfaces. When deer ingest sharp or thorny feed material, small puncture wounds can introduce bacteria into the deeper tissues of the mouth and tongue. In these tissues, the anaerobic bacteria proliferate and cause the cells to die (necrosis), leading to sloughing and ulceration of the overlying surfaces. If areas around the teeth are infected, the disease may extend to the underlying jaw causing necrosis, inflammation, and expanded bone, sometimes referred to as lumpy jaw. In very young deer, necrotic stomatitis may be associated with gum damage from tooth eruption. Animals with necrotic stomatitis may show excessive salivation and loss of body condition due to difficulty eating (Leighton 2001). Like most lesions, ulcerations of the mouth are not specific to any particular disease, and infections of OdAdV-1, MCF, or other ulcer-causing diseases with lesions localized to the mouth can look identical to or precede necrotic stomatitis. In the hoof, F. necrophorum can cause foot rot following damage to the skin surface. Extended exposure to wet or muddy conditions often leads to breakdown of the skin, allowing bacteria to invade through the damaged skin surface. The affected foot may have a crusted accumulation between the toes (pododermatitis) and be swollen due infection extending into nearby soft tissues and bone. Affected animals are often lame. Hoof rot is a general term for infections of the foot and can be caused by infections other than F. necrophorum. Other causes for foot rot should be considered, especially if multiple animals are affected. For example, outbreaks of hoof disease in elk are linked to infections with Treponeme bacteria (Han et al. 2019). In the rumen, F. necrophorum can cause significant necrosis (necrotizing rumenitis) following damage to the inner surface of the rumen. Damage to the rumen lining can be from sharp or thorny food items but is more often caused by acid burns from the contents in the rumen (rumen acidosis). Sudden changes in feed or a rapid shift to a high carbohydrate diet leads to increased acidity in the rumen that burns the rumen lining and creates an environment that favors growth of F. necrophorum and other pathogenic bacteria. Bacteria gain entry to the bloodstream through the damaged rumen and are delivered to the liver, often resulting in abscesses (hepatic necrobacillosis). Regardless of the point of entry, once F. necrophorum and other bacteria enter the bloodstream and spread to the liver and lungs, large abscesses can occur in these organs. Affected animals are typically in poor body condition and the disease may be fatal. Necrobacillosis is of limited population-level significance in black-tailed deer and mule deer; however, in Wyoming necrobacillosis is encountered routinely on elk feedgrounds, suggesting that crowding of animals may enhance transmission of the disease.

Pasteurellosis Bacteria of the family Pasteurellaceae are well-recognized causes of respiratory disease (bronchopneumonia) and bloodborne disease (hemorrhagic septicemia) in many free-ranging

and captive wildlife species (Franson and Smith 1988, Eriksen et  al. 1999, Miller 2001a, Mackintosh et  al. 2002). Species of Pasteurellaceae that commonly affect wild ruminants include Mannheimia hemolytica, Bibersteinia trehalosi, and Pasteurella multocida. At one time, these were all considered species of the genus Pasteurella but were reclassified and are now referred to collectively at the family level, Pasteurellaceae. Some species, such as Pasteurella multocida, are normal flora of the upper respiratory tract but cause disease if abnormal conditions allow them to invade the lungs or other tissues. This may occur secondary to other factors including malnutrition, stress, viral infections, and other bacterial diseases. In cases of hemorrhagic septicemia, bacteria ultimately enter the blood and become widespread throughout multiple organs. Signs of hemorrhagic septicemia are similar to other septic or hemorrhagic diseases with acute, rapid onset of disease, and lesions include hemorrhages and edema throughout the tissues. Pasteurellosis should be considered as a potential cause of bronchopneumonia and septic disease in black-tailed deer and mule deer, but pneumonia also is caused by a number of other bacteria and viruses, many of which are described elsewhere in this chapter. Noninfectious factors like aspiration of rumen contents into the lungs (as seen with CWD), or wounds penetrating the chest are other common causes of pneumonia. Some cases of pasteurellosis do not involve the lungs, or may affect atypical tissues like the brain or joints. Free-ranging mule deer fawns die occasionally from predatory bite wounds that are infected with Pasteurella multocida, normal bacteria in the mouths of carnivores. Similar situations occurred with caribou (Rangifer tarandus caribou) calves after lynx (Lynx canadensis) attacks (Bergerud 1971). These fawns and calves apparently survived the predation attempt but died from the infected wounds. Pasteurellosis is a good example of new data providing added perspective to the disease. Historical reports describe large-scale die-offs of deer with predominant findings of bronchopneumonia and septicemia associated with pasteurellosis; however, most of those reports predate currently available diagnostics (Quortrup 1942). Current understanding of Pasteurellaceae bacteria suggests they act more as opportunistic disease agents and other predisposing or contributing factors are likely present. What remains unclear is whether historical reports represented introductions of new or different strains of Pasteurellaceae into deer that resulted in primary disease or if there were other predisposing causes that went unidentified.

Infectious Keratoconjunctivitis (Pinkeye) Infectious keratoconjunctivitis (IKC), also known as pinkeye, involves inflammation of the tissues lining the eye and eyelids (conjunctiva). Affected eyes appear cloudy, often with a central ulcer. In severe cases, the iris may bulge out through a hole in the cornea, giving the appearance of a growth on the eyeball. The conjunctiva are red and swollen, with thick, yellow crusting around and under the eyes. Affected animals may appear blind and some walk in circles, although a cause for the circling is not apparent.

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Diseases and Parasites The disease often is encountered in young male mule deer in the late fall or winter, although females and males of any age can be affected during any season and at least 1 outbreak in mule deer primarily affected adults of both sexes (Taylor et  al. 1996). The reason for affecting mostly young males is uncertain. The disease is spread by direct contact with exudates from the infection, so rubbing on trees or shrubs during breeding season could contaminate these surfaces and cause scratches and abrasions that promote spread of the disease among males (Muñoz Gutiérrez et  al. 2018). Fall sparring between young males with small antlers may allow their faces to come close together and potentially spread the disease. The cause of IKC likely involves multiple disease-causing agents and environmental factors. These include bacteria such as Moraxella, Mycoplasma, and Chlamydia species, and viruses including a cervid alphaherpesvirus (Muñoz Gutiérrez et  al. 2018). Environmental factors such as dust, wind, flies, and sunlight may contribute to transmission and disease progression. Blind animals are easily spotted by the public and wildlife managers are frequently called to assess these cases. Although deer may recover from mild clinical signs (Taylor et al. 1996), the severity of disease typically warrants euthanasia. Although IKC can cause significant morbidity and mortality to individuals, IKC is not often a population-limiting disease in deer.

Trueperella pyogenes (previously known as Arcanobacterium pyogenes, Actinomyces pyogenes, and Corynebacterium pyogenes). Trueperella pyogenes is a normal inhabitant of the skin and mucous membranes, and most abscesses develop after a wound introduces bacteria through the skin or mucosal barriers into the underlying tissue. For example, a gore wound can push bacteria through the skin barrier and cause an abscess under the skin. In deer, abscesses usually are walled off from adjacent tissues and remain discrete with minimal spread; however, local extension into nearby tissues, and septic spread through the bloodstream, can occur (Turnquist and Fales 1998). Many other bacteria are found in abscesses besides T. pyogenes, including Fusobacterium spp., Corynebacterium spp., Staphylococcus spp., Streptococcus spp., and Pasteurellaceae species. Fusobacterium necrophorum is particularly important as the cause of necrobacillosis (see above). Corynebacterium pseudotuberculosis is the cause of caseous lymphadenitis, a disease characterized by multiple abscesses in various tissues, particularly lymph nodes, skin, and lungs. Often it is spread through exudates from ruptured abscesses in the skin or lungs. This disease occurs sporadically in deer but is a particularly significant management concern in domestic sheep and goats when a contaminated environment contributes to widespread disease in the herd.

Abscesses

Mycobacteriosis

Abscesses in deer generally are of limited consequence for the deer population but are a common source of concern for hunters. Hunters who encounter abscesses (also called pus pockets) while processing their animal often are concerned about possible bovine tuberculosis or other food safety issues. Although tuberculosis can occur in black-tailed deer and mule deer, it is an extremely rare disease in these species (see Mycobacteriosis below) and is not a significant concern beyond areas where the disease is well established in other species. Human health guidance regarding abscesses is typically based on the number and location of the abscesses. Hunters who find a single abscess under the skin, in the muscle, or in a lymph node are advised to discard the affected portion of meat and follow guidelines for thoroughly cooking the unaffected portions. If the carcass has multiple abscesses, or abscesses within internal organs, blood-borne spread of bacteria (sepsis) may have occurred and consumption of the carcass is not recommended. Intracranial abscesses (abscesses within the skull) in blacktailed deer and mule deer often are associated with skull fractures, particularly at the base of the antler. For this reason, cases are most common in males, and are particularly common in yearling males, presumably because of the lower density and increased fragility of the skull and antlers in young animals. Bacteria can enter through skin wounds, and associated skull fractures can allow invasion of the bacteria into the brain. Specific virulence factors may contribute to the extent of invasion by the bacteria (Cohen et al. 2018). Animals with intracranial abscesses tend to be circling, disoriented, or showing other abnormal neurologic behaviors. Abscesses are encountered frequently in black-tailed deer and mule deer, and often are caused by the bacteria

Mycobacteriosis refers to a wide range of diseases associated with bacteria of the genus Mycobacterium. The most notable mycobacterial disease in terms of implications for wildlife management is bovine tuberculosis, caused by Mycobacterium bovis. Tuberculosis carries significant health concerns for wildlife, domestic animals, and humans. In addition, there are considerable economic, regulatory, and international trade consequences when this disease is introduced into previously unaffected areas. Bovine tuberculosis has a limited distribution in the United States and Canada. In deer, the disease is established only in some free-ranging populations of white-tailed deer in parts of Michigan and Manitoba. In white-tailed deer, most infected individuals show no outward signs of the disease, although lesions in harvested animals may be encountered in otherwise normal deer. Typical lesions include variably-sized gritty nodules (granulomas) in the lymph nodes and lungs. These were observed in the lymph nodes of the head, chest, and abdomen of an infected free-ranging mule deer in Montana (Rhyan et al. 1995), although the disease is not currently established in free-ranging populations of mule deer or black-tailed deer. Most black-tailed deer and mule deer that have lesions suggestive of tuberculosis are ultimately diagnosed with infections from other abscess-producing bacteria (see Abscesses above) or infections from other insignificant nontuberculous species of Mycobacterium such as Mycobacterium avium hominissuis (Frayne et al. 2020). Another mycobacterium, Mycobacterium avium paratuberculosis, is the cause of Johne’s disease. This disease poses a significant health concern to domestic livestock in which it produces severe diarrhea and is difficult to eliminate from

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infected herds. Johne’s disease does occur in wildlife, but to date, there are no reports of Johne’s disease in free-ranging black-tailed deer or mule deer. Experimentally infected mule deer showed clinical signs of frequent soft feces and poor body condition. In these deer, lymph nodes were enlarged with multiple gritty foci (Williams et al. 1983). Although tuberculosis and Johne’s disease are expected to be extremely rare in black-tailed deer and mule deer, mycobacteriosis has considerable economic consequences for livestock species. If tuberculosis or Johne’s disease became established in free-ranging populations, infected deer could become a reservoir for reintroduction of diseases back into livestock. Therefore, continued passive surveillance for these diseases in black-tailed deer and mule deer is warranted.

Mycoplasma bovis Mycoplasma bovis is a well-known disease-causing bacterium of domestic cattle that can cause long-standing infection of the lungs (chronic bronchopneumonia), primarily in calves. Occasionally, Mycoplasma bovis spills over into free-ranging wild species, although observations of this disease in blacktailed deer and mule deer are limited. In farmed white-tailed deer fawns, Mycoplasma bovis can cause bronchopneumonia, lung abscesses, and infection of the surfaces inside the chest (pleuritis; Dyer et al. 2004). These findings are somewhat similar to those observed in captive bison (Bison bison), although other expected lesions (based on observations from cattle and bison) could include arthritis and middle ear infections (otitis media; Dyer et al. 2008, Janardhan et al. 2010). Recently, outbreaks of Mycoplasma bovis occurred in pronghorn (Antilocapra americana) in Wyoming, causing fatal bronchopneumonia in large numbers of animals (Jennifer Malmberg, University of Wyoming, personal communication). A few cases also occurred in mule deer in Colorado and Wyoming. Affected mule deer had pleuritis and multiple abscesses in the lungs, similar to bison and white-tailed deer. Because of the recent detection of Mycoplasma bovis in mule deer, much is still unknown about the potential significance of this disease at the population level.

Parasites and Parasitic Diseases Parasites are common, but their negative effect on health (parasitic diseases) are uncommon and reflect an imbalance in the normal relationships between species. Parasites living in or on other species are animals using other animals as available habitats. These species have inherent value and roles in functioning ecosystems. Most parasitic species are not obviously detrimental and often have negative effects only in conjunction with some change in intrinsic factors that affect either the parasite, the host that supplies the habitat, or both. Once the balance is tipped, parasites can lead to parasitic diseases. It is often the outlier situations resulting in overall negative effects on deer health that are of greatest concern to deer managers. A wide range of species live in or on black-tailed deer and mule deer (Table 6.1). The great majority are innocuous and benign.

Nematodes (Roundworms) Nematodes come in a variety of shapes and sizes and live in a wide range of tissues and organs. Generally, they are elongate, thread-like, fluid-filled animals with a relatively tough outer cuticle. The fluid is pressurized and thus provides the round contours of the body. They often are white and show up easily against the darker background of the habitats in which they live. Developmental stages follow a consistent pattern from egg, through 4 larval stages, to separate adult males or females. Life cycles may be direct—out of one individual, a period in the environment, and then into another individual of the same species as the first—or indirect—out of one individual, passed through one or more other species, and eventually back into the original species. Indirect cycles may or may not include some time spent free-living in the environment. Food habits, predator-prey interactions, and biting arthropods all play significant roles in life-history strategies of various helminth species. Gastrointestinal helminths.—Although often used in a broader context, gastrointestinal helminths (GIH) as used by parasitologists refers to a suite of nematodes that live in the digestive system and associated organs in cervids (and other ruminants) around the world. Most of these species share a general pattern of direct life cycles with dormant stages spending time on the ground or vegetation before being eaten by a deer. Eggs are passed in feces, and development to infective third-stage larvae occurs in the environment. Once eaten by a deer, infective larvae activate in the gut then continue development to adults. Gastrointestinal helminths occur in most, if not all, individual deer (Hibler 1981, Hoberg et al. 2001). They are part of the inherent suite of natural species that use available niches throughout the gastrointestinal tract; however, most of them occur in the abomasum and small intestine. Although they can occur in large numbers in individual deer and can be quite impressive when seen shortly after death of the deer, they rarely are associated with significant damage to the host tissues or organs. The relatively benign relationship among various GIH and their deer hosts implies a long-standing evolutionary history that serves the nematodes and the deer well. Population control mechanisms such as competition, spacing, and density limitations among the nematode species, age of the host, and acquired immunity in the host can act to reduce the abundance and diversity of GIH and thus avoid potential tissue damage in deer. Individual deer may be compromised if they are under nutritional, metabolic, competitive, or environmental stress that interferes with the inherent population control mechanisms that limit GIH. Young deer and older age classes of deer may be at increased risk of negative effects if the limiting factors do not regulate these nematodes. Previously, white-tailed deer managers tracked seasonal variation in eggs and larvae of abomasal nematodes (part of the GIH suite) in feces of deer as a measure of general herd health (Eve and Kellogg 1977, Demarais et al. 1983). But over time and with improved knowledge of the limitations and variations associated with these programs, the approach was largely discontinued. Limited opportunities for management actions to

Setaria yehi Taenia spp. Echinococcus canadensis Moniezia spp. Fascioloides magna

Dicrocoelium dendriticum

Sarcocystis hemionilatrantis

Sarcocystis mehlhorni Cephenemyia spp. Lipoptena, Neolipoptena Native species Exotic species

Abdominal worm Tapeworm larvae

Lancet liver fluke

Sarcocysts

Botfly larvae Louse fly Lice

a

Skin Skin Skin

Haircoat

Skeletal and smooth muscles As above Back of mouth Haircoat Haircoat Haircoat

Bile ducts of liver

Airways of lungs Airways of lungs Muscles throughout body Brain and spinal column Abdominal cavity Liver, muscles, lungs Lung, liver Intestines Liver

Digestive system Major blood vessels in head and neck

Location in host

Both Both Both

Both

Uncommon Uncommon Uncommon

Uncommon to Common

Common Common Uncommon to Common Common Locally common

BTD Both Both Both Both

MD

Inconspicuous, perhaps locally common Common

Both

Common Common Locally common Common Rare

Not in western regions

NO Both Both Both Both Both

Common Uncommon Common

Common Common

Occurrence

Both Both Both

Both Both

Hosta

Outcome

Benign Largely benign Benign Benign Debilitating mortality factor Benign on deer, potential vectors of pathogens Benign Benign on deer Benign

Benign

Debilitating leading to fatal Benign Benign Benign Benign Benign in deer, debilitating in moose Benign

Benign Benign in deer, debilitating in other species Benign Benign Benign

Both (occurs in black-tailed deer and mule deer); BTD (black-tailed deer); MD (mule deer); NO (not reported in black-tailed deer or mule deer).

Fleas

Mites

Ticks

Dermacentor spp., Otobius megnini, Ixodes pacificus Demodex spp. Psoroptes spp. Various species

Dictyocaulus Orthostrongylus macrotis Parelaphostrongylus odocoilei Parelaphostrongylus tenuis

Lungworms

Tapeworm adults Giant liver fluke

Various species Elaeophora schneideri

Scientific name

Gastrointestinal helminths Carotid worm

Common name

Overview of selected parasites of black-tailed deer and mule deer.

TABLE 6.1

No No No

No

No No No No Yes

No

No

No No No No No

Fatal

Rarely No Rarely

Rarely No

Individual concern?

No No No

No

No No No No Yes

No

No

Potential mortality risk No No No No No

No No No

No No

Population concern?

Diseases and Parasites 111

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affect the occurrence of GIH in free-ranging deer populations also may have played a role in abandoning the monitoring programs other than in specific herd health situations. Carotid worm.—Carotid (or arterial) worm (Elaeophora schneideri) is perhaps the single most significant nematode that commonly occurs in black-tailed deer and mule deer. Although relatively benign in mule deer, this species can lead to severe damage and individual mortality in other cervid species, bighorn sheep (Ovis canadensis), and domestic sheep and goats. High numbers of nematodes in the carotid arteries of mule deer can be associated with food impaction in individual deer (Couvillion et al. 1986). Pence (1991) and Anderson (2001a) provide excellent reviews of the biology, distribution, host range, and significance of carotid worms. Once considered a parasitic disease of management concern for elk and perhaps moose in the western United States (Hibler 1981), morbidity and mortality in these species appeared to decline even though they shared range with mule deer with relatively high prevalence of carotid worms. Many moose survive infection without evidence of clinical disease (LeVan et  al. 2013), although individual cases of affected moose continue to occur throughout the range of carotid worms (Grunenwald et al. 2018). Such unapparent infections hide the true mortality rate in free-ranging wildlife populations. As with many other wildlife parasites, development of live animal tests that could be applied in the field whenever animals are handled could improve our understanding of prevalence and significance of carotid worms in cervid hosts. Adult male and female carotid worms occur in major blood vessels of the head and neck, primarily the carotid artery. Microfilariae (mobile larvae) released directly into the bloodstream move to capillaries in the skin of the head where they are available to be picked up by biting tabanid flies (horse flies and deer flies). Larvae develop in the fly tissues, and newly formed infective larvae move into the salivary glands and are passed through the mouthparts when the fly bites again. Larvae in the bloodstream move to major arteries of the head and develop to adult males or females. Lungworms.—Perhaps the most conspicuous lungworms are those that live openly in the major airways of the lungs. In deer, these nematodes are Dictyocaulus viviparous. Originally, a parasite of cattle around the world, this nematode adapted to living in cervid lungs and now maintains populations in various free-ranging cervids. They are most visible in recently dead deer as they often migrate after death into the trachea. Dictyocaulus lungworms (Fig. 6.3) are common across the range of black-tailed deer and mule deer. Rarely are they associated with significant damage to the tissues or health of infected deer. A significant outbreak of dictyocauliasis occurred in 8 captive black-tailed deer fawns, although poor physical condition and adverse weather prior to confinement were perhaps contributing factors (Presidente et al. 1973). A similar pattern of high lungworm abundance following wet winters may occur in deer more broadly than currently documented. Of note, parasite infections, including D. viviparous, were seen in many black-tailed deer affected by hair loss syndrome (HLS) in Washington and Oregon (Bender and Hall 2004), although HLS was eventually attributed to exotic lice (Bildfell et al. 2004).

FIGURE 6.3  Dictyocaulus lungworms in mule deer lungs. Photo ­courtesy of Alberta Fish and Wildlife.

Unlike many lungworms, D. viviparous has a direct life cycle. Eggs released into the bronchi hatch in the trachea before they are coughed up and swallowed by the deer. First-stage larvae leave the deer in fecal pellets. Larval development continues in pellets on the ground. Third-stage larvae are hardy and can survive moderate freezing and dehydration. They are the stage that can establish infection in a deer. These larvae move away from the ground and up onto vegetation making them more available for grazing herbivores. Some larvae enter the spore-producing capsules of Pilibolus spp. fungi growing in the feces. When the capsules erupt, fungal spores and lungworm larvae can be scattered up to 9.8 feet (3 m) away from the pellets. Once ingested by a deer, the larvae move through the lymphatic system, into the blood stream, and eventually into the pulmonary airways. Adult Orthostrongylus macrotis (formerly Protostrongylus macrotis) occur in the bronchioles and bronchi of the lungs of infected deer. At less than 1 inch (25 mm, males) or 2 inches (50 mm, females) long, they are relatively inconspicuous and easily differentiated from the much larger D. viviparous. These small nematodes are not associated with significant damage to the lungs. Species of Parelaphostrongylus are classified in the lungworm group, but only the eggs and larvae pass through the lungs. Parelaphostrongylus odocoilei occurs throughout the range of black-tailed deer and mule deer along the west coast of Canada and United States (Lankester 2001) and can spillover into mountain goats (Pybus et al. 1984). Molecular diagnostic techniques, a powerful tool to identify and differentiate morphologically similar nematode larvae in deer feces, indicates broad distribution of P. odocoilei from Alaska to California (Jenkins et al. 2005). Individual deer may develop tissue damage when larvae migrate through the lungs, and there may be localized hemorrhage in the muscle tissues around adults (Pybus and Samuel 1984, Lankester 2001); however, significant population effects are not associated with P. odocoilei. A closely related species, Parelaphostrongylus andersoni, occurs in caribou throughout their range across northern Canada. Isolated pockets of P. andersoni also are documented

Diseases and Parasites in white-tailed deer in various locations in the United States and Canada (Asmundsson et al. 2008), including areas in the West where black-tailed deer and mule deer occur. Although experimental infections in mule deer were successful, there are no reports of this inconspicuous species occurring in wild black-tailed deer or mule deer (Lankester 2001). Parelaphostrongylus tenuis, also known as meningeal worm, is not known to occur in free-ranging black-tailed deer or mule deer in western jurisdictions. Meningeal worm occurs in white-tailed deer throughout eastern United States and Canada where it has no significant effect on deer populations but can have devastating effects on local moose and caribou populations (Lankester 2001). In these latter species, the larval nematodes undertake an abnormal migration and cause direct, often fatal, damage to the brain and spinal cord. Black-tailed deer translocated to eastern states also can develop neurologic disease and die if infected with meningeal worm. Distribution of meningeal worm appears limited by environmental conditions in the Great Plains of central North America. The eastern extent of mule deer distribution gradually ends along the eastern edge of the plains and may be a direct result of the lethal effects of meningeal worm from local white-tailed deer. States and provinces along this boundary line (e.g., Nebraska, North Dakota, Saskatchewan) report neurologic disease and mortality associated with meningeal worm in free-ranging mule deer and moose. These Parelaphostrongylus species all have a typical indirect life cycle. Eggs released into the blood stream are filtered out and hatch in the lungs. First-stage larvae move up the trachea, and are swallowed, pass through the gut and are excreted on fecal pellets. Larvae penetrate the foot of a terrestrial snail or slug and develop to second stage and then infective thirdstage larvae. Once ingested by deer, larvae are released from the snail tissues, penetrate the gut wall, and then migrate to muscles of the back and legs where they develop to adults (P. odocoilei, P. andersoni) or into the subdural space around the spinal cord and then migrate to the blood sinuses and subdural spaces around the brain (P. tenuis). Abdominal worm.—One of the most seen and easily recognized nematodes in deer is the abdominal worm Setaria yehi. This thin, white, cord-like nematode lives freely among the tissues and organs in the abdominal cavity, particularly on the mesenteric membranes or the surface of the liver. Adults range up to 9.8 inches (25 cm) long but less than 0.39 inches (1 mm) in diameter. They are relatively common and widespread throughout the ranges of black-tailed deer, mule deer, whitetailed deer, moose, and caribou. Prevalence is higher in fawns and yearlings than in adults (Weinmann et al. 1973), implying perhaps possible acquired immunity against these nematodes in older deer. There is little or no tissue damage associated with Setaria infections in deer. Mild inflammation, seen as small fibrin tags on the liver capsule, is present in some deer. Abdominal worms present an interesting variation on an indirect life cycle. From within the abdominal cavity, adult female Setaria spp. insert their tail into blood vessels and release microfilariae into the blood stream. Although not confirmed for S. yehi, closely related species use various species of mosquitoes as vectors of transmission. Microfilariae are ingested along with the blood, develop to infective third-stage

113 larvae in mosquito tissues, and then migrate towards the head. Infective larvae are regurgitated into the next deer fed on by the mosquito. Thelazia.—The eyeworm Thelazia californiensis is a small nematode (adults 0.39–0.78 inches [10–20 mm]) that often lives in the lacrimal (tear) ducts; however, these ducts are relatively small in deer so the nematodes occur under the third eyelid (nictitating membrane). They occasionally float out onto the surface of the eye (cornea) where they are readily visible in live or dead deer. This species is mainly a parasite of canids but occurs in various wildlife species. Closely related eyeworm species are common in cattle. There is limited zoonotic potential and T. californiensis has been associated with mild chronic conjunctivitis in a few humans (Knierim and Jack 1975, Doezie et al. 1996). Early literature (Hibler 1981) focused on reporting eyeworms in individual deer. More recently, aggregate data indicate eyeworms may be quite common in some local populations of mule deer and black-tailed deer. In the mid-1960s T. californiensis was seen in about 60% of deer in a population north of San Francisco, California; however, prevalence declined in the following years for unknown reasons (Weinmann et al. 1974). Beitel et al. (1974) found it in 33% of 64 black-tailed deer in northwest Oregon. They noted that all infected deer were from the valley bottom and none from foothill or mountain terrain. Prevalence increased with deer age and was higher in adult females than males. Dubay et  al. (2000) reported eyeworms in 15% of 60 and 8% of 38 mule deer harvested by hunters in Utah in 1994 and 1995, respectively. They also found them in 40% of 20 and 66% of 24 live deer captured in 1995 and 1996, respectively. They did not find eyeworms in 128 deer harvested in Wyoming in 1994 and 1995. There is little evidence of clinical disease associated with eyeworms in deer. Some reports include incidental mild irritation and conjunctivitis, including excessive or cloudy fluids from the tear ducts in a few deer. Although reported in conjunction with outbreaks of bacterial eye infections in mule deer (see IKC section), there is no definitive link with T. californiensis (Taylor et al. 1996, Dubay et al. 2000). In light of the gross visibility of eyeworms and the large number of mule deer heads examined for CWD in recent years, the lack of reports suggests that T. californiensis is not a significant deer management concern. Eggs released into eye secretions and tears are picked up when non-biting face flies of the genus Fannia feed on moisture and moist tissues around the eye. Larval development occurs within the fly tissues and infective larvae move to the head before leaving through the mouthparts when the fly feeds again. Onchocerca.—Legworms (Onchocerca cervipedis) live under the skin and in connective tissues of the foot and legs of various cervid species from Central America to the Arctic. Although common in black-tailed deer and mule deer, they are more of a curiosity than a concern. Adult females can reach 8 inches (20 cm) in length and are particularly visible in connective tissues of the lower leg. Legworms are found more often in front rather than back legs, and in older rather than younger deer. Adult females release microfilariae into tissues below the skin where they are available to biting flies, primarily

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blackflies (Simulidae). Development in blackfly tissues is followed by transfer of infective larvae when the fly bites a new individual.

Cestodes (Tapeworms) Most adult cestodes look alike. They are long, white, flat ribbons, with repeating segments through most of their length. One end has a small scolex (a head, of sorts) that often includes elaborate anchor structures that help keep the tapeworm in its favorite part of the gut. Cestodes do not have a digestive system, they simply absorb nutrients across their body wall. Each segment of the tapeworm contains complete male and female reproductive systems. Cross-fertilization from another worm is the norm, although self-fertilization can occur if there are no other individuals of the same species in the gut. Segments containing fertilized eggs detach from the posterior end of the tapeworm and pass out of the intestine with the feces. All cestodes are parasitic and most have complex indirect life cycles. Once the eggs leave in feces of their current host, subsequent larval stages may use 1 or 2 different species to get back into the original host species. Predator-prey relationships are a common component of these cycles and cervids are a primary target for larval cestodes on their way back into a carnivore. Adult cestodes generally are benign animals that live in the intestines surrounded by an abundance of food and protection. Tapeworms in deer rarely cause damage or concern, although long flat worms observed in the intestine may concern some hunters unsure of what they are looking at or whether it may infect them. Similarly, tapeworm larvae that occur as cysts in various deer tissues can be quite conspicuous when hunters field dress or process their deer. For the most part, adult and larval tapeworms in deer do not infect people. Taenia spp.—White fluid-filled larvae of various taeniid species occur in black-tailed deer and mule deer. These larvae are resting stages that mature into adult tapeworms in the intestines of foxes (Vulpes vulpes), wolves (Canis lupus), coyotes (Canis latrans), cougars (Puma concolor), or bears (Ursidae). The most common and conspicuous taeniid species in deer live in the liver, muscles, or lungs. These are Taenia hydatigena, T. ovis krabbei, and T. omissa, respectively. Adults of these tapeworms primarily live in wolves and cougars (for T. hydatigena); wolves, coyotes, cougars, black (Ursus americanus) and grizzly (Ursus arctos) bears (for T. ovis krabbei); and cougars (for T. omissa). Eggs in the environment are ingested accidentally by grazing deer. Eggs hatched in the intestines migrate through the intestinal wall and are carried in the blood to the liver. Larvae of T. hydatigena stay in the liver. Larvae of T. o. krabbei are transported through the liver and lungs and on to muscles throughout the deer. Larvae of T. omissa stay in the lungs. At their chosen site, larvae form cysts and wait to be eaten by a suitable carnivore. Once activated by chemical conditions in the carnivore stomach, each larva develops into an adult tapeworm in the intestines of the carnivore. Echinococcus.—Our understanding of tapeworms in the genus Echinococcus has been plagued by confusing taxonomy. Herein we take the approach that larvae using cervids

as intermediate hosts and canids as definitive hosts in North America all belong to E. canadensis (genomic strains G8 and G10; Thompson et  al. 2006, Thompson 2017). In North America, larvae of E. canadensis are more common in the lungs of elk and moose but also occur in mule deer, blacktailed deer, and white-tailed deer. These fluid-filled cysts contain small pale brown particles about the size of sand grains, called hydatid sand. These particles are protoscoleces (each one is a future scolex) that will develop into adult tapeworms in the intestines of wolves, coyotes, and dogs. Hydatid tapeworms do not pose significant risk to infected cervids or canids. Hunters may see them as they field dress their deer but need not worry. Neither the cysts nor the hydatid sand are infective to people; however, dogs and other canids that eat the cysts can develop adult tapeworms that produce echinococcus eggs. These eggs in canid feces are infective to humans and can develop into hydatid cysts in the lungs (alveolar hydatid disease). Eggs in canid feces persist in a wide range of environmental conditions for months. If they are eaten by a cervid, eggs hatch in the intestine, enter the blood stream, and are carried to the liver and lungs. Each hatched egg becomes a protective cyst that begins to produce hydatid sand—the future tapeworm heads. Hydatid cysts can survive in cervid tissues until eaten by a canid, in which they give rise to thousands of tiny adult tapeworms no larger than 0.4 inches (