Mammals of Montana: Second Edition

By Kerry R. Foresman and Alexander V. Badyaev

Mammals, named after the presence of mammary glands, nurse their young and have fur, but that's where their similarities end. Some dig underground homes, some live in social groups, some hunt underwater, some fly through the night skies. This comprehensive guide details the taxonomy, ecology, behavior, reproductive biology, and distribution of all

• Language: English
• Publisher: Mountain Press Publishing Company
• Release date: Mar 14, 2014
• ISBN: 9780878426294

Book preview

Mammals of Montana

SECOND EDITION

Kerry R. Foresman

Photographs by Alexander V. Badyaev

2012

Mountain Press Publishing Company

Missoula, Montana

© 2012 by Kerry R. Foresman

First Printing, July 2012

All rights reserved

Front cover photo by Alexander V. Badyaev

Back cover photos: Deer mouse, red fox, and coyote by Alexander V. Badyaev

Spotted skunk by Julie Larson Maher © Wildlife Conservation Society

Photos © 2012 by Alexander V. Badyaev and Kerry R. Foresman unless otherwise credited

See extensive photo and illustration credits on following pages.

This project sponsored in part by the Montana Natural Heritage Program, a

program of the Montana State Library operated by the University of Montana.

Library of Congress Cataloging-in-Publication Data

Foresman, Kerry Ryan.

  Mammals of Montana / Kerry R. Foresman ; photographs by Alexander V. Badyaev. — 2nd ed.

      p. cm.

  Includes bibliographical references and index.

  ISBN 978-0-87842-590-7 (pbk. : alk. paper)

1. Mammals—Montana—Identification. I. Title.

  QL719.M9F667 2012

  599.09786—dc23

2012012648

PRINTED IN HONG KONG

P.O. Box 2399 • Missoula, MT 59806 • 406-728-1900

800-234-5308 • [e-mail]

www.mountain-press.com

I dedicate this work to my parents, Kenneth and Louise Foresman, who encouraged me to pursue my goals throughout my life, whatever they might be. My parents were the first to introduce me to the wonders of the woods and I am forever grateful. Also to my wife, Deana Pedersen, who endured my writing of the first edition and has persevered through the second, allowing me to sit behind the computer for months on end or run into the field at a moment’s notice. The greatest gift anyone can give someone is the freedom to pursue their dreams and to support them in those efforts.

A special dedication, in memoriam, goes to Philip L. Wright, mammalogist and ornithologist, teacher and friend, who lit the spark in me to the field of mammalogy. P. L. taught me mammalogy, as he did thousands of other students during his forty-six years at the University of Montana. His stories are surely missed but not forgotten.

To the next generation of budding Montana naturalists

Illustration and Photograph Credits

Page number and position of images: top(T), middle(M), bottom(B), right(R), left(L)

ILLUSTRATIONS

Illustrations on 115, 123, 125TL: Redrawn with permission from University of Missouri Press from The Wild Mammals of Missouri (1959) by Charles W. Schwartz and Elizabeth R. Schwartz.

Illustration on 53B: Reprinted with permission from Canadian Museum of Nature from Handbook of Canadian Mammals, Volume 1 (1983) by C. G. van Zyll de Jong.

Illustration on 240T: Reprinted with permission from Elsevier from Comparative Biochemistry and Physiology Part A: Physiology 43(3), Wang, L. C. H., Circadian body temperature of Richardson’s ground squirrel under field and laboratory conditions: A comparative radio-telemetric study, pgs. 503–10.

Illustration on 183: Reprinted with permission from MacArthur, R.A., and M. Aleksiuk, Journal of Mammalogy 60:151. American Society of Mammalogists, Allen Press, Inc.

Illustration on 13T: Reprinted with permission from Christopher Hill.

All pen-and-ink drawings by Rex L. McGraw, II

PHOTOGRAPHS

W. C. Alden, USGS: 30T

Courtesy of the Arizona Historical Society, Tucson (AHS# PC10F417_5929): 34

Dave Ausband: 270T, 270B, 271T, 278T, 278B

Allison Begley, Montana Fish, Wildlife & Parks: 200, 201, 202

Milo Burcham: 36T, 119, 141M, 144, 157, 162, 164, 169, 172, 176, 184, 185, 186, 189B, 191, 218B, 244, 256, 281R, 286, 304, 322, 332, 342L, 342R, 365, 370, 373, 374, 378, 381, 384, 389

Todd Caltrider: 68T

© Mark A. Chappell: 152, 154, 155B

Jessie Cohen, Smithsonian’s National Zoo: 331B

Jeff Copeland: 302

Coburn Currier, Montana Natural Heritage Program: 88B (with Bryce Maxell)

© Kristi DuBois Photo: 54, 73R, 74, 75T, 75B, 76, 78T, 81B, 91B, 93T, 93B, 96, 99L, 99R, 101, 178T, 231, 274T, 281L

Steve Gniadek: 319

© Bob Gress: 121, 122, 148, 150, 166, 168, 192

Lou Hanebury, USFWS: 330B

Diane Hargreaves.com: 330T, 336B

Paul Hendricks, Montana Natural Heritage Program: 66, 88T, 111, 112T, 224

Mary Jo Hill: 48

Shannon Hilty: 107T, 116, 117T, 313, 318

Jake Ivan: 312T

David Jachowski: 204, 205T, 205B, 206, 207T, 207B

Benjamin Jimenez: 301T, 301B, 343, 344T, 344B

Neil Kadrmas, USFWS: 284T, 284B, 285

Jack Kirkley: 325

Hal S. Korber: 42 (as per Merritt)

Michel T. Kohl: 167

Susan Lenard, Montana Natural Heritage Program: 70B, 77, 82 (with Bryce Maxell), 83 (with BM), 94B, 97B, 112BL, 112BR, 113

Peter Lesica: 22B, 23T

Rick Mace, Montana Fish, Wildlife & Parks: 349

Julie Larsen Maher © Wildlife Conservation Society: 298

Randy Matchett: 328, 329T, 329B, 331T

Gary Matson: 345T

Bryce Maxell: Montana Natural Heritage Program: 67T, 82 (with Susan Lenard), 83 (with SL), 88B (with Coburn Currier)

Tom Meier, National Park Service: 11

Joseph F. Merritt (Photo permission granted to JFM by H. S. Korber): 42

L. Scott Mills: 32T, 32B, 33, 118, 120R

Darin Newton: 305T, 306, 308T, 309T

Michael Patrikeev, Wild Nature Images, Inc.: 260

Dean E. Pearson: 189T, 198

© 2011 Dale Pedersen: 300

© Roger A. Powell: 314, 316T, 316B

Blase Reardon, USGS: 30B

Tonie E. Rocke: 336T

© Nate Schwab: 95B

Clio Smeeton, Cochrane Ecological Institute: 35B, 276

John Squires: Rocky Mountain Research Station, Northern Rockies Lynx: 288T, 288B, 289T, 289B, 290L, 290R

Bruce D. Taubert: 69

Richard Throssel Collection, American Heritage Center, University of Wyoming: 321, 379

Dana K. Vaughan Ph.D., University of Wisconsin, Oshkosh: 246L, 246M, 246R

Ray Vinkey: 37, 315, 317

John W. Weisel: 307M, 307B

Keaton Wilson: Montana Natural Heritage Program: 73L

Alex Badyaev: iii, vi, x, 3, 4T, 4B, 6B, 7, 24T, 31, 38/39, 46, 52, 53, 57, 58, 60/61, 72, 84, 87, 90, 92, 98, 102/103, 106, 107B, 110, 114, 124, 125T, 125B, 127, 128/129, 134, 135, 136, 137B, 180, 182, 188, 191, 194, 209, 211T, 211B, 216, 220, 223, 229, 232, 233, 235, 238, 240B, 242, 247, 248, 249, 250, 252, 254, 262/263, 268, 269, 272, 274B, 275L, 275R, 279, 280T, 280B, 282, 291, 292, 293, 294, 297, 305B, 309B, 334, 335T, 335B, 338, 339, 340, 341TL, 341TR, 341BL, 341BR, 345M, 346, 347L, 347R, 348, 350/351, 356, 359, 360, 364, 367B, 369B, 376, 382T, 382B, 383, 387T, 387M, 387BL, 387BR, 391T, 392T, 393, 396, 402, 405, 430B

Kerry R. Foresman: 5, 6T, 8, 9TL, 9TR, 9BL, 9BR, 10T, 10TM, 10BM, 10B, 12, 13B, 14, 15T, 15B, 16, 17, 18T, 18M, 18B, 19T, 19B, 20T, 20B, 21, 22T, 22M, 23B, 24B, 25T, 25B, 26T, 26BL, 26BR, 27TL, 27TR, 27B, 28T, 28M, 28BL, 28BR, 29TL, 29TR, 29BL, 29BR, 35T, 36B, 40T, 40BL, 40BR, 43, 44, 45, 47, 55T, 55B, 59, 62, 65TL, 65TR, 65BL, 67B, 68B, 70T, 71, 78B, 79, 80L, 80R, 81T, 81M, 85TL, 85TR, 85BR, 86T, 86B, 89L, 89R, 91T, 95T, 97T, 104TL, 104TR, 104BL, 104BR, 108T, 108M, 108BL, 108BR, 109TL, 109TR, 109BL, 109BR, 117B, 120L, 126, 131TL, 131TR, 131BL, 131BR, 137T, 137M, 138, 139, 140L, 140R, 141T, 141B, 142, 145, 146, 151, 153, 155T, 156, 158, 159T, 159B, 160, 163, 165T, 165B, 170T, 170B, 171, 173L, 173R, 174, 175L, 175R, 177, 178M, 178B, 179, 181T, 181M, 181B, 190T, 190B, 193L, 193R, 195, 199L, 199R, 203, 208, 210, 212, 213L, 213R, 214, 217, 218T, 221, 226, 227L, 227R, 228, 230, 234, 237, 239T, 239B, 243, 245, 251L, 251R, 253, 255, 257, 258L, 258M, 258R, 265TL, 265TR, 265M, 265BL, 265BR, 271B, 295, 296T, 296B, 299, 303, 307T, 308B, 310, 312B, 320, 323, 326L, 326R, 327, 337, 342B, 345B, 352TL, 352TR, 352M, 352BL, 352BR, 353L, 353R, 357T, 357B, 358, 361, 362T, 362B, 363, 367TL, 367TR, 368T, 368B, 369T, 371, 372T, 372B, 375, 377T, 377B, 380T, 380B, 385L, 385R, 386T, 386B, 390, 391BL, 391BR, 392B, 430T

Life is a party for Montana’s state animal.

Contents

Preface and Acknowledgments to the Second Edition

Acknowledgments to the First Edition

Introduction

Mammalian Characteristics

Physiography of Montana

Observing Mammals in Montana

Global Climate Change and Its Effect on Montana’s Mammal Populations

Extirpation and Reintroduction of Species

Order Soricomorpha

Family Soricidae—Shrews

Order Chiroptera

Family Vespertilionidae—Vespertilionid Bats

Order Lagomorpha

Family Ochotonidae—Pikas

Family Leporidae—Hares and Rabbits

Order Rodentia

Family Castoridae—Beaver

Family Erethizontidae—Porcupine

Family Geomyidae—Pocket Gophers

Family Heteromyidae—Heteromyids

Family Muridae—Mice, Rats, and Voles

Family Sciuridae—Squirrels

Family Zapodidae—Jumping Mice

Order Carnivora

Family Canidae—Canids

Family Felidae—Felids

Family Mephitidae—Skunks

Family Mustelidae—Mustelids

Family Procyonidae—Raccoons

Family Ursidae—Bears

Order Artiodactyla

Family Antilocapridae—Pronghorn

Family Bovidae—Bovids

Family Cervidae—Cervids

Potential Occurrence of Selected Species

Checklist of Montana Mammals

Scientific Names of Plants Mentioned in Text

Glossary

Bibliography

Index

Preface and Acknowledgments to the Second Edition

Mammals encompass one of five taxonomic classes of vertebrates in the world, the others being fishes, amphibians, reptiles, and birds. In Montana, we are fortunate to have a rich diversity of species in the class Mammalia, in large part due to our geologic history. Montana is a story in extremes, from the semidesert environment in the Pryor Mountains of the southeast to the alpine tundra of the Beartooth Plateau in the south-central region and the higher elevations of Glacier National Park to the north. Mammals are found throughout and have developed in concert with these environments.

This book was originally published in 2001 as a Special Publication for the American Society of Mammalogists, a professional national organization formed for the study of this taxonomic class. Until this time, no such book had been written for the state of Montana. This book, as presented here, is a revision of this original work. The need for such a revision, after only ten years, is due in large part to a focused interest on mammals by state and federal agencies (Montana Fish, Wildlife & Parks, the Montana Natural Heritage Program, the USDA Forest Service, the U.S. Fish and Wildlife Service, and Glacier National Park) as well as continued research by the author and his graduate students at the University of Montana. One new species (the short-tailed shrew, Blarina brevicauda) has been recorded in the state during this period and a wealth of additional information has been obtained on the ecology and distribution of the others as a result of statewide field surveys initiated by Montana Fish, Wildlife & Parks and the Montana Natural Heritage Program, and focused studies on some of the least known species in the state, notably the lynx, wolverine, fisher, mountain lion, swift fox, wolf, and grizzly bear. Agency working groups have also been created in the past several years to focus attention on little-known taxonomic groups (for example, the Bat Working Group and the Prairie Dog Working Group in Montana Fish, Wildlife & Parks), and reintroduction efforts for species such as the wolf, fisher, and swift fox (the latter two by the author’s lab) have taken hold. Our own research on these latter two species as well as porcupines, northern river otters, and others has also greatly expanded our understanding of lesser-known species in the state. Several extensive studies and reviews on game species, notably for bighorn sheep (Conservation Strategy, 2010), black bear (Research and Management 2011 Report), grizzly bear (Management Plan, 2006), mountain lion (Garnet Mountain Lion Study, 2011), and elk (Statewide Management Plan, 2004) have also been completed by Montana Fish, Wildlife & Parks. Last, but surely not least, the opportunity to work with a new publisher whose commitment to making this information readily available to the public in such a rich manner settled this decision.

In this revised edition, an effort has been made to not only update the information but to also present it in a more useable manner. Detailed accounts for all 109 species are presented with distinguishing species characteristics highlighted to help with field identification; nearly five hundred new photographs have been added, along with many from the original version, primarily those of Milo Burcham, who now works for the USFS and resides in Cordova, Alaska, all in full color. The exquisite color photographs provided in large number by Alexander V. Badyaev, who received his Ph.D. from the University of Montana and still conducts research in this state, have been incorporated to not only illustrate the beauty of these species but to highlight some of their unique behaviors. Copious additional color photographs by a large number of biologists, most of whom are friends I have worked with over the past twenty-eight years, offered up their works for the good of the project, showing Montana’s mammals at their best. Foremost among these is Milo Burcham, another University of Montana alumnus. Special thanks to professional photographers Mark A. Chappell, Bob Gress, Julie Larsen Maher, Dale Pedersen, and Bruce D. Taubert, all of whom I have never met but who readily and unselfishly agreed to help me in this endeavor.

Others who have added to this new effort include graduate students Ray Vinkey, David Ausband, Nathan A. Schwab, Katie Eaton, Steve Carson, and Darin Newton; undergraduate students Ryan Kovach, Todd Caltrider, and Shannon Hilty; and GIS technician Michael Krebs. Many of those acknowledged in the first edition have continued to help with this revision through thoughtful conversations and the sharing of data. Thanks again Milo, Kristi, Randy, Dean, and Paul, and new thanks to Jeff Copeland, John Squires, Nick DeCesare, Ben Jimenez, and Susan Lenard. The excellent editorial skills of Jennifer Carey and the design skills of Jeannie Painter, both at Mountain Press Publishing, kept this project on track and delivered a beautiful product.

For those needing very detailed information on skull and dental morphology for species identifications, a revised and updated companion taxonomic key, Key to the Mammals of Montana, is available through the University of Montana Bookstore in Missoula, Montana. We live in this remarkable state in part because of its wildlife; I hope this offering will enhance your enjoyment while in the field.

Acknowledgments to the First Edition

A project like this can be accomplished only with the support of a large number of persons. I would first like to thank the many undergraduate and graduate students who have worked with me in the field collecting new information on the mammals of this state. The specific efforts of David J. Worthington, Dean E. Pearson, Scott Gillingham, Karl Stanford, Scott Tomson, Jo Ann Dullum, Jake S. Ivan, Kimberly S. Heinemeyer, Karen E. McCracken, Jay F. Shepherd, Morris Myerowitz, Ralph D. Pratt, and Ron E. Jensen, Jr. are greatly appreciated. The technical lab support provided by R. Daniel Long and additional field support provided by Michael T. Maples kept much of my research running smoothly while I tried to juggle one-too-many projects. I would like to thank Diane K. Boyd for the use of some of her as yet unpublished data on Montana’s wolves. Peter M. Rice and Matthew P. Harrington were instrumental in bringing their computer expertise to bear on the development of the distribution maps, as was Patrick Munson. Tom Tompson helped with several other maps, as did the Montana State Library through their Natural Resource Information System. David L. Dyer and Cathy Seibert provided access to Montana’s university museum collections. Cedron Jones and Paul Hendricks provided access to the Montana Natural Heritage Program’s database, for which I am grateful. Elizabeth Madden and Neil Perry provided access to specimens and information on the arctic shrews they recently caught, the first records for this species in the state.

Robert Henderson, Montana Fish, Wildlife & Parks, answered many questions I had concerning the state’s efforts for wildlife management. Randy Matchett introduced me to the world of black-footed ferrets and black-tailed prairie dogs at ferret camp—C. M. Russell National Wildlife Refuge, Bowdoin National Wildlife Refuge, and the miles in between; truly unique species in an even more unique environment. Discussions held with many faculty over the years provided additional insight into the wonders of these mammal species; in this regard, I would particularly like to thank Bart O’Gara, Daniel H. Pletscher, Chris Servheen, Donald P. Christian, and Robert W. Seabloom. The many hours spent in the field with Colin B. Henderson have been rewarding, especially listening as the chipmunks sang the evening away.

The pen and ink drawings by Rex L. McGraw, II, throughout this text I think finely illustrate my points and it is hoped will make this information that much more useful.

Sophie Craighead’s interest in this project and the financial assistance provided by the Charles Engelhard Foundation is truly appreciated.

Joseph F. Merritt encouraged me to consider using the American Society of Mammalogists’ Special Publication series as the venue for this manuscript and provided editorial support along the way. The additional editorial skills and continued encouragement of Meredith J. Hamilton, Virginia Hayssen, and especially David M. Leslie, Jr., brought this project to completion.

Listen up

Introduction

Mammals of Montana, Second Edition is intended to be used by everyone who enjoys Montana’s outdoors, whether for family outings, hunting trips, or professional activities of the forester, range manager, or wildlife biologist. In this second edition, I made a special effort to keep this material user-friendly and yet provide a detailed and scientific approach to the subject. Toward this end, even the size and format of the text was considered, the intention being to provide a guide that can be thrown into one’s day pack so that it is always readily available in the field.

The following section, titled Mammalian Characteristics, provides the reader with a clear understanding of the physical characteristics of this broad animal group, the mammals, and how these attributes have contributed to the evolution of the group as a whole. Immediately following is a section on the physical attributes of Montana, including such topics as climate, topography, and habitat, qualities that determine the presence or absence of the species at hand. The introduction also discusses the potential effects that our changing climate may have on Montana’s species, the extirpation of species, and recent or proposed reintroduction efforts.

The true focus of this book, of course, is the 109 species of mammals found in the state. The species are organized by the taxonomic order within which they occur, and photographs of the skull of a representative species in the order are provided to illustrate diagnostic characteristics. Additional line drawings illustrate diagnostic skull characteristics for each taxonomic family within each order. Species accounts within an order are organized by family. For example, the black bear and grizzly bear are within the family Ursidae in the chapter about the order Carnivora, the carnivores. For a detailed illustrative key for the identification of all Montana species, the reader should refer to the companion text, Key to the Mammals of Montana, by this author.

Each species account begins with a discussion of the species’ unique distinguishing characteristics, followed by its distribution and status in the state and throughout North America. Information on the general ecology, requisite habitat associations, life history traits, and reproductive patterns has been summarized from the literature and my own research. Extensive use has been made of Mammalian Species accounts, and literature cited therein, published by the American Society of Mammalogists, although additional references are included, particularly those pertaining to Montana research or information that is more recent. Readers are encouraged to review these species accounts for more detail.

Distribution Maps. Montana distribution maps for each species have been updated based upon the author’s and his graduate students’ work in the field over the past many years, and the work of other professional biologists both from within Montana and out of state. This information details the occurrence of each species on a county-by-county basis, information that reflects actual museum collection records, harvest records in the case of game species, or verified sightings by professional biologists. Distribution maps, by their very nature, are problematic. Their accuracy reflects collection efforts, so gaps are not uncommon. Rather than simply fill in the gaps where the likelihood of occurrence is high, but for which no verification exists, I have chosen to designate such counties as probable occurrence. Thus, counties shown as dark orange reflect those in which specimens have actually been collected or recorded. Those that are shaded lighter orange reflect the probable occurrence of the species based upon broader, generalized North American range distributions described by other authors, and habitat availability. Lastly, those counties shown in yellow indicate that to the best of our current knowledge, the species is probably not to be found there. In some instances, for example the lynx (Lynx canadensis), grizzly bear (Ursus arctos), and swift fox (Vulpes velox), the distribution presented reflects some historical museum records; disappearance of such species from some portions of the range described is highly likely. Given this approach, I hope to stimulate additional collection or sighting efforts, which will provide verification of occurrence in counties now listed as probable, and evidence for disappearance from previously occupied counties.

All attempts have been made to identify and incorporate any substantive Montana materials held within museums in the United States. The holdings of the National Museum of Natural History at the Smithsonian Institution, Washington, D.C.; the Museum of Natural History at the University of Kansas, Lawrence; the Museum of Zoology at the University of Michigan, Ann Arbor; the Bell Museum of Natural History at the University of Minnesota; and the museums of the University of Montana, Missoula, and Montana State University, Bozeman, have been particularly beneficial. Museum records, the author’s private collections, and records from research in which animals were captured, identified, and released now number over thirty-two thousand. Additional distribution data also have been included from Montana Department of Fish, Wildlife & Parks records for game species hunted or trapped. Continuing discussions with professional field biologists working throughout the state have been included in this database. Within each species account, the habitat with which each is associated is provided in as much detail as our current knowledge allows. This information, coupled with the discussion of habitat categories in the section on physiography, will allow the reader to determine whether or not a particular species may be expected in any given locality.

Status. The sidebar containing a species’ measurements also contains its current known status in Montana and in the United States. Species of Concern are defined by the ranking criteria adopted by the Montana Natural Heritage Program. As of 2011, twenty-eight mammals in Montana were listed as Species of Concern. Eight additional species are Potential Species of Concern.

Scientific Discovery. Each species account ends with a description of how, and by whom, the species was first described in the scientific community. Historically, Montana has played a significant role in the identification of many species. The derivation of the scientific nomenclature applied to the species is provided, information determined in large part through the use of Jaeger’s (1959) text, A Source-Book of Biological Names and Terms. The taxonomic classification scheme proposed by Baker et al. (2003) in their Revised Checklist of North American Mammals North of Mexico, 2003 has been adopted for this text unless otherwise noted. This taxonomic listing, updated roughly every three to five years, provides the most current and accepted rendition of North American mammalian systematics available. In addition, a recent article summarizing systematics of the mustelid-skunk families has been adopted. Taxonomy, by its very nature, is a dynamic scientific discipline. Our understanding of the relationship between one species and another, at every taxonomic level, can, and has, change(d) as we broaden our studies and apply ever more sophisticated methods to our analysis. The material presented herein is hopefully an accurate representation of the current state of our knowledge in this respect.

One of the primary interests in this new edition has been to provide high-quality color images for most of the 109 species, chosen for their ability to not only illustrate key characteristics and behaviors but also to display the unique beauty of each species.

An appendix shows the possible occurrence of heretofore unknown species in the state. The first edition identified the short-tailed shrew (Blarina brevicauda) as possibly occurring in the northeastern portion of the state though none had ever been seen or captured. Concerted collection efforts in this region, most likely in response to this suggestion, proved fruitful in 2005, thus providing Montana with its 109th species. Other species will surely follow.

A current checklist of all Montana mammals is provided at the back of the text so that readers may keep track of the species they have seen. This will also serve as encouragement to the reader to work toward observing all 109 species, a noble goal and surely a notable achievement if attained (the author even admits to being several species short of this goal at the time of this publication). Finally, the detailed glossary should answer any questions on terminology used throughout this text, and an extensive bibliography is provided for those who wish to learn more about a particular species.

Mammalian Characteristics

Mammals are classified based on the presence of mammary glands for the production of milk to nourish the newborn and the presence of hair. No other taxonomic class of animals possesses these characteristics, so they define the group and are worth considering in detail.

Mammary Glands. Mammary glands are exocrine glands specialized for the production of colostrum. The number of mammary glands that form is species-specific. Primates, for example, typically produce two, while some marsupials may have as many as twenty-four (and hence have the ability to accommodate larger numbers of offspring). Because most mammals develop in the uterus and are born in a relatively immature state, they require an immediate source of nourishment before they develop the physical ability and the behavioral skills to search for food on their own. Mammary glands provide this nourishment.

Composition of the secretions, or milk, produced by the mammary tissue is complex and species-specific. Water content can vary from as little as 32 percent in seals to as much as 91 percent in many marsupial species, such as the kangaroos. Fat content also varies widely, from approximately 4.5 percent in humans to over 53 percent in seals. Remaining components consist of a mixture of carbohydrates, proteins, and minerals.

Hair. Hair, the other strictly mammalian characteristic, functions in a multitude of ways. It is used as 1) a primary source of insulation, 2) to provide physical protection from abrasion, 3) in tactile sensations such as the whiskers in felids (cat family), 4) as a means of protective coloration, 5) to provide buoyancy in aquatic species, 6) for protection from predation, as with quills and bony plates, 7) for locomotion, and 8) in a variety of behavioral activities.

Lunch break

Red fox (Vulpes vulpes) with a dense winter pelt

Long whiskers of a deer mouse (Peromyscus maniculatus) used to sense its environment in the dark

Cardiovascular and Respiratory Systems. The cardiovascular and respiratory systems of mammals also have become highly specialized and variable throughout the course of evolution. Mammals possess a four-chambered heart, with complete separation of oxygenated and nonoxygenated blood, providing an efficient delivery system for required nutrients and gases. The respiratory system is highly partitioned into blind-ending sacs, or alveoli, giving the lungs a tremendous surface area for gaseous exchange. Many mammals maintain a constant body temperature and are thus referred to as homeothermic, or warm-blooded. However, these metabolic parameters can be adjusted by many species to offset energetic demands created by colder temperatures. Many Montana mammals can, and do, exhibit either torpor or true hibernation when winter sets in. The ability to alter body temperature is referred to as heterothermy. Here, heart and respiratory rates are allowed to drop, placing the animal in a reduced metabolic state. In true hibernation, the animal’s body temperature may actually drop to near ambient temperatures of 33°F (1°C). Hibernation has become most highly developed in rodents, among which marmots, ground squirrels, and chipmunks demonstrate the greatest ability. Some bats, and both bear species, also demonstrate this physiological modification, though their body temperature may be only slightly lowered.

Torpor, a condition in which the temperature of the body falls to a lesser extent than in hibernation (generally a few degrees to nearly 68°F [20°C]), still provides a significant reduction in metabolic costs to the animal. This metabolic adjustment occurs in many Montana species, particularly many rodents and bats, and at least one mustelid, the American marten (Martes americana).

Digestive System. Mammals can be grouped readily into three categories based upon their feeding habits and anatomy of their digestive system. In Montana, we have representatives of all three: herbivores, carnivores, and omnivores. Herbivores are vegetarians. Their teeth and digestive capabilities are highly specialized to process plant materials. Ungulates (hoofed mammals) fall into this category, as do most rodents and all lagomorphs (rabbits and hares). Carnivores, species that eat meat almost exclusively, have many anatomical modifications evolved for this feeding strategy. Canids (dog family), felids (cat family), and mustelids (weasel family) fall into this category, as do the soricids (shrew family) and vespertilionids (bat family). That leaves omnivorous species, which are more generalists than specialists, capable of, and preferring, a mixture of both vegetation and meat. The black bear (Ursus americanus) and grizzly bear have adopted this strategy, as has the raccoon (Procyon lotor), though all are taxonomically carnivores.

Black bear looking for grubs

A bison (Bison bison), a classic herbivore, eating a variety of sedges and grasses

The badger (Taxidea taxus), a typical carnivore, feeding on a small mammal

Reproductive Biology. All mammals in Montana are placentals, or eutherians, exhibiting internal fertilization and development in the uterus. The reproductive biology of Montana’s mammals is characterized by the timing of mating activity, length of gestation, number of young born, and number of litters/year. These parameters vary greatly among the state’s 109 species.

Most species of mammal in Montana mate during a particular time of the year, defined as the mating season, and are thus referred to as seasonal breeders. Mating during this time takes place when the female is behaviorally and physiologically receptive to the male. A few species do not display seasonal mating and are reproductively active year-round. Many of Montana’s species that produce multiple litters come into estrus (heat) immediately after giving birth, a condition known as a postpartum estrus. Thus, they are capable of becoming pregnant while they are lactating.

Bears mating in early summer

Skeletal and Dental Systems. For the purpose of species identification, skeletal and dental characteristics are probably of most importance. These tissues, particularly teeth, are the hardest of body structures and are capable of fossilizing. For this reason, they are more commonly found and available for identification. Over the course of evolution in some species, the mammalian skeleton has become stronger through the reduction in number of bones and the fusion of many that have remained.

The most significant diagnostic characteristics used for taxonomic purposes are the structure of the skull and its associated teeth. A typical adult mammalian skull contains approximately thirty bones. Size and conformation of these bones and the nature of the dentition are used extensively in taxonomic keys for species identification. A great deal can be learned about an animal and its feeding habits from a study of these structures.

Teeth. Mammalian teeth are characteristically described based upon the function they perform. In the broadest of categories they can be used to either cut food or to grind and crush it. All mammals in Montana have heterodont dentition, where not all of the teeth are of a similar size and shape. These differences in tooth structure provide for differences in function. The front teeth, called incisors, are for nipping: herbivores use these to cleanly cut vegetation; carnivores use them to strip muscle from bone. Immediately behind the incisors lie the canine teeth, numbering a total of four (one on each side above and below). This form of tooth can be greatly enlarged, as in the family Canidae (the dog family, hence the name), and can be specialized for grasping, puncturing, and tearing meat. They serve not only for feeding but for protection. All carnivores possess enlarged canines; reduced forms may be present and less functional in some artiodactyls, notably elk. The remaining teeth in the skull may or may not be easily distinguished in the adult, although they are developmentally different. These teeth are referred to as the molariform teeth and can be divided into premolars and molars.

Premolars lie between the canines and the true molar teeth within the cheek. They are generally smaller, with a less complex root system and cusp pattern. They also are deciduous, which means that they are replaced during the animal’s life; often they are described as milk teeth because they are replaced after the newborn is weaned. True molar teeth are characterized by being larger, possessing a more substantial root system and often more complex and numerous cusps, and by being nondeciduous (they remain and are not replaced). Surfaces of these teeth also are important for identification purposes. Molar teeth primarily serve the function of grinding and crushing food, although in some species, notably members of the families Felidae and Canidae, they can be highly specialized. In these families both premolar and molar teeth are interspaced between the upper and lower jaws so that the teeth interdigitate rather than coming into crushing contact with one another when the jaw is closed. Also, the last upper premolar (PM4) and the first lower molar (m1) are slightly displaced side-by-side so that they produce a shearing surface specialized for cutting food when the jaw closes. Such a tooth relationship is termed carnassial and is shown in the dental plates for the order Carnivora. Detailed photographs of dental differences between Montana’s mammals are shown at the beginning of each taxonomic order’s description.

Mammals are bilaterally symmetrical, which means that when divided along the midline from head to toe they have right and left sides that are mirror images of one another, left and right hands for example. This symmetry is evident in the development of the tooth rows; the jaw or cranium contains equally paired teeth, half of which appear on the right side and half on the left. Rather than write a formula that denotes every tooth present in a particular species, mammalogists developed a shorthand method that identifies the type of tooth present (incisor, abbreviated i; canine, c; premolar, p; molar, m) and the number of each type on one side of the head. As an example, the dental formula for the mountain lion (Puma concolor) would be written: incisors 3/3, canines 1/1, premolars 3/2, molars 1/1 (or i 3/3, c 1/1, p 3/2, m 1/1, total 30). This indicates that on each side of the head are three incisors in the skull (denoted left of the backslash) and three in the jaw (denoted right of the backslash). Similarly, one canine occurs in the upper jaw and one in the lower jaw, and so forth (a 0 on either side of the backslash would indicate that particular type of tooth was not present in the species as an adult). The total number of teeth for the mountain lion would thus be thirty, two times the sum of the dental formula, to reflect both sides of the head. By convention, capital letters (I, C, P, M) indicate teeth in the skull, and lowercase letters (i, c, p, m) indicate teeth in the jaw. Often, as is the case of marmots (Marmota spp.) or shrews, it is quite difficult to distinguish between types of teeth, premolars and molars in the former group, incisors, canines, and anterior premolars in the latter. In this situation, the dental formula may reflect this fact either by simply combining both types of teeth or by designating a more generalized type. In the case of marmots, premolars and molars may be combined and the formula written as I 1/1, C 0/0, P+M 5/4, total 22. In shrews, it is not even entirely clear what the developmental history of the single-cusped teeth is; here the choice has been to designate such teeth as unicuspids and group them together. For the pygmy shrew the formula would be written I 3/1, U 5/0, P 1/2, M 3/3, total 36. Many additional pattern variations exist that are beyond the scope of this book. For a more detailed discussion, refer to the companion text: Key to the Mammals of Montana.

Frontal skull view. Red dotted line identifing bilateral symmetry with right and left sides

Lateral skull view

Lateral jaw view

Ventral skull view. Dashed white line identifying hidden, very small molar M3 [Mountain lion shown]

Dorsal jaw view; I (i) = incisors, C (c) = canines, P (p) = premolars, M (m) = molars

Common External Measurements. When specimens are captured or collected, five body measurements are commonly taken: total length, tail length, length of the hind foot, ear length, and body mass.

Measurement of a long-tailed weasel (Mustela frenata)

Total length (TL): Distance from tip of nose to end of vertebral column in the tail (excluding the extended hairs)

Tail length (Ta): Distance from base of tail to end of vertebral column (excluding the extended hairs)

Length of hind foot (HF): Distance from heel to end of longest claw

Ear length (E): Distance from base of notch in ear to tip (excluding any hairs)

Mass (M): Presented in either grams (g) or kilograms (kg). Small mammals can be weighed in a handling bag as shown in the section on mammal observations; large species, such as the grizzly bear shown here, may be hung from a scale supported by a tripod.

Such standard field measurements, obtained from museum records and field studies, are provided for each species. Where possible, values from a representative sample of ten adults were averaged. Measurements of males and females were combined, where similar; if sexual dimorphism occurs (males and females are consistently different sizes), measurements for both sexes are given. Attempts were made to provide measurements from Montana specimens, but where not available, measurements from other regions were used.

Physiography of Montana

Montana is a land of contrasts. It is the fourth largest state in the union, relinquishing honors only to Alaska, Texas, and California, with a land mass of 147,042 square miles (380,848 km²), nearly 94 million acres (38 million ha). It lies between 45° and 49° north latitude, placing it squarely within the montane coniferous forest biome. Of this acreage, one-fourth, nearly 2.3 million acres (9.3 million ha), is forested. The remaining three-fourths of the land is dispersed among four other climatic zones: alpine, subalpine, grasslands, and semidesert. An elevational gradient within the state runs from 1,800 feet (550 m) in the northwest corner, where the Kootenai River enters Idaho, to the 12,799-foot (3,902 m) summit of Granite Peak in the Beartooth Mountains of south-central Montana.

The state is characterized by mountainous terrain, a majority of which lies in the western one-third of the state and serves as the backbone to the Continental Divide. The Rocky Mountain chain that runs through Montana formed toward the end of the Cretaceous Period of the Mesozoic Era, 70 to 90 million years ago. Several mountain ranges, such as the Bears Paw, Big Snowy, and Crazy mountains, however, are isolated in the central part of the state. These latter mountain ranges formed more recently, about 50 million years ago, during the Eocene Epoch of the Tertiary Period.

East Front Range west of Augusta

As these central mountains were forming, Montana was experiencing one of several major dry spells. The combination of uplifting of the continental crust, and sedimentation brought on by soil erosion and the inability of weakly flowing streams to carry suspended materials away, led to filling of the valley floors. Many mammalian species became isolated on these mountain ranges, unable to disperse across the intervening wide-open,