Biodiversity Response to Climate Change in the Middle Pleistocene The publisher gratefully acknowledges the generous contribution to this book provided by the General Endowment Fund of the University of California Press Associates. Biodiversity Response to Climate Change in the Middle Pleistocene The Porcupine Cave Fauna from Colorado Edited by ANTHONY D. BARNOSKY UNIVERSITY OF CALIFORNIA PRESS Berkeley Los Angeles London University of California Press Berkeley and Los Angeles, California University of California Press, Ltd. London, England © 2004 by The Regents of the University of California Library of Congress Cataloging-in-Publication Data Biodiversity response to climate change in the middle Pleistocene : the Porcupine Cave fauna from Colorado / edited by Anthony D. Barnosky p. cm. Includes bibliographical references and index. ISBN 0-520-24082-0 (cloth : alk. paper) 1. Vertebrates, Fossil—Colorado—Park County. 2. Paleontology— Pleistocene. 3. Paleoecology—Colorado—Park County. 4. Paleo- ecology—Pleistocene. 5. Climatic changes—Environmental aspects— Colorado—Park County—History. 6. Animals, Fossil—Colorado— Park County. I. Title: Porcupine Cave fauna from Colorado. II. Barnosky, Anthony D., 1952– QE881.B535 2004 560′.1792—dc22 2003059592 Manufactured in the United States of America 13 12 11 10 09 08 07 06 05 04 10987654 321 The paper used in this publication meets the minimum requirements of ANSI/NISO Z39.48-1992 (R 1997) (Permanence of Paper). To Don Rasmussen, who with his son Larry found the fossil deposits in Porcupine Cave, and whose unfailing enthusiasm for discovery, excavation, and working with other scientists and volunteers was essential in moving the project from concept to reality. CONTENTS PREFACE ix 5 The Geology and Speleogenesis 12 The Early and Middle ACKNOWLEDGMENTS xi of Porcupine Cave 51 Pleistocene Avifauna from LIST OF CHAPTER APPENDIXES xiii Robert G. Raynolds Porcupine Cave 127 LIST OF FIGURES xv Steven D. Emslie 6 Magnetostratigraphic Constraints LIST OF TABLES xix on the Age of Pleistocene ABBREVIATIONS AND DEFINITIONS xxi 13 The Carnivora from Porcupine Fossiliferous Strata in Porcupine Cave 141 Cave’s DMNH Velvet Room Elaine Anderson PART ONE Excavation 57 The Discovery and Distribution S. Julio Friedmann and 14 Middle Pleistocene (Irvingtonian) of Fossils Robert G. Raynolds Ochotona (Lagomorpha: 7 Age and Correlation of Key Fossil Ochotonidae) from 1 Climate Change, Biodiversity, Sites in Porcupine Cave 64 Porcupine Cave 155 and Ecosystem Health: The Past Anthony D. Barnosky and Jim I. Mead, Margarita Erbajeva, as a Key to the Future 3 Christopher J. Bell and Sandra L. Swift Anthony D. Barnosky 8 Biology of Wood Rats as Cave 15 Leporidae of the DMNH 2 The Pleistocene Fossils of Dwellers and Collectors 74 Velvet Room Excavations Porcupine Cave, Colorado: Robert B. Finley Jr. and Mark’s Sink 164 Spatial Distribution and Colleen N. Baxter Taphonomic Overview 6 9 Paleopathology and Taphonomic Modification of Mammalian Bones Anthony D. Barnosky, 16 Identification of Miscellaneous from Porcupine Cave 82 Christopher J. Bell, Robert G. Mammals from the Pit Locality: Raynolds, and Louis H. Taylor C. Suzane Ware and Including Soricidae, Leporidae, Elaine Anderson 3 The Modern Environment, Geomyoidea 169 Flora, and Vegetation of Anthony D. Barnosky and South Park, Colorado 27 PART TWO Samantha S. B. Hopkins David J. Cooper Systematic Accounts of Taxa 17 Systematics and Faunal 4 The Historical Context of 10 A Summary of Fossilized Species Dynamics of Fossil Squirrels Porcupine Cave: American in Porcupine Cave 95 from Porcupine Cave 172 Indians, Spaniards, Government H. Thomas Goodwin Anthony D. Barnosky Surveyors, Prospectors, Ranchers, Cavers, and Paleontologists in 11 Synopsis of the Herpetofauna 18 Fossil Wood Rats of South Park, Colorado 39 from Porcupine Cave 117 Porcupine Cave: Tectonic Geraldine J. Rasmussen, Kirk Christopher J. Bell, Jason J. Head, or Climatic Controls? 193 Branson, and John O. McKelvy and Jim I. Mead Charles A. Repenning 19 Arvicoline Rodents from 24 Stable Carbon and Oxygen Porcupine Cave: Identification, Isotope Analysis of Marmot Spatial Distribution, Taxonomic Cheek Teeth from the Pit Assemblages, and Locality 327 Biochronologic Significance 207 Robert S. Feranec Christopher J. Bell, 25 Assessing the Effect of Middle Charles A. Repenning, Pleistocene Climate Change and Anthony D. Barnosky on Marmota Populations from 20 Pliocene and Pleistocene Horses the Pit Locality 332 from Porcupine Cave 264 Anthony D. Barnosky, Matthew Eric Scott H. Kaplan, and Marc A. Carrasco 21 Pleistocene (Irvingtonian) 26 Effect of Climate Change on Artiodactyla from Porcupine Terrestrial Vertebrate Biodiversity Cave 280 Anthony D. Barnosky 341 Jim I. Mead and Louis H. Taylor LITERATURE CITED 347 PART THREE LIST OF CONTRIBUTORS 371 Effect of Environmental Change INDEX 373 on the Porcupine Cave Fauna 22 Irvingtonian Mammals from the Badger Room in Porcupine Cave: Age, Taphonomy, Climate, and Ecology 295 Alan B. Shabel, Anthony D. Barnosky, Tonya Van Leuvan, Faysal Bibi, and Matthew H. Kaplan 23 Faunal Dynamics of Small Mammals through the Pit Sequence 318 Anthony D. Barnosky PREFACE Since fossil vertebrates were first discovered at Porcupine Cave scientific and recreational purposes over the past 20 years. on the rim of South Park, Colorado, in 1981, the site has be- The book endeavors to highlight the importance of the frag- come the world’s most important source of information about ile but irreplaceable paleontological resources to be found in animals that lived in the high elevations of North America in caves. the middle part of the ice ages, between approximately one The book is divided into three parts. The chapters in part 1 million and 600,000 years ago. Beginning in 1985, teams of articulate some scientific questions that the data from the scientists and volunteers from three major research institutions cave can help answer; document the location, modern envi- —the Carnegie Museum of Natural History, the Denver Mu- ronment, and geological setting of the site as a context in seum of Nature and Science, and the University of California which to interpret the fossil data; and relate the history of the Museum of Paleontology—spent some 15 field seasons exca- discovery of Porcupine Cave, the spatial distribution and age vating and studying tens of thousands of fossil specimens that of the fossil deposits, and the cause of the accumulation of so have opened a window onto past evolutionary and ecological many fossils. Part 2 documents the identification and occur- adjustments. This window into the past allows us to visualize rence of various taxonomic groups from the many different how ongoing global change could affect our living commu- localities within the cave. Part 3 synthesizes the information nities. This book reports the results of nearly two decades of presented in the other two parts into a series of analyses de- research and has been written to appeal to three overlapping signed to explore the implications of the Porcupine Cave fauna audiences. for understanding how terrestrial mountain ecosystems react The first target audience is made up of scholars, students, and in the face of environmental change, how climate change others interested in paleontology and in how paleontological affects patterns of biodiversity in mammals, and, in light of data are applied to solving ecological and evolutionary ques- these processes, how we might expect ecosystems to respond tions. The second audience consists of ecologists and conser- to human-induced global warming. vationists concerned with understanding and preserving Given the astounding numbers of fossils that Porcupine biodiversity and other natural ecological dynamics. To serve Cave has produced—more than 20,000 specimens have been these first two audiences, the book strives to illustrate the identified, and many times that number are stored in mu- critical role paleontology plays in understanding ecosystem seum drawers awaiting identification—it is impossible to ex- dynamics, such as the maintenance of biodiversity, and to plore all their implications in a single publication. This book document carefully the scientific data from Porcupine Cave should be viewed as a foundation for further research rather so that this unique data set can be used now and in the future than the final word on the matter. We hope that the data and to illuminate ecological processes. ideas presented herein stimulate debate and provide impetus The third audience is the caving community, which has for a new cohort of scholars to continue the work we have just increasingly used Porcupine Cave and others like it for both begun. ix ACKNOWLEDGMENTS Excavating, analyzing, and publishing the Porcupine Cave Hazel Barton led the cartographic efforts to produce detailed data has been an arduous task that has taken nearly 20 years maps of the cave, and I thank her for making her beautiful and involved more than 30 scientists, more than 100 field map available. hands, and the cooperation of the three major museums where As editor, my job was made easier by the contributors to this specimens reside: the Carnegie Museum of Natural History book, many of whom waited patiently after submission of (CM), the Denver Museum of Nature and Science (DMNH), their manuscripts for the whole package to come together. and the University of California Museum of Paleontology Special thanks are due to Chris Bell, who has been with the (UCMP). Thanks are due to all who lent a hand, and especially project since the early 1990s and who picked most of the ma- to the following individuals and institutions. trix from the Pit. Several scientists gave of their time in pro- The kindness of Frank and Connie McMurry (McMurry viding detailed reviews of various chapters: Elaine Anderson, Land and Livestock Company) in allowing us to excavate in Jill Baron, Chris Bell, Annalisa Berta, Doug Burbank, Jim their cave and spend field seasons at their cow camp made the Burns, Emmet Evanoff, Bob Feranec, Tom Goodwin, Fred whole project possible. I am deeply indebted to them. The Grady, Elizabeth Hadly, Bill Harbert, Art Harris, R.