Robert C. Stebbins - A Natural History of Amphibians

A NATURAL HISTORY OF AMPHIBIANS

A NATURAL HISTORY OF AMPHIBIANS

Robert C. Stebbins and

Nathan W. Cohen

Illustrated by the Authors

PRINCETON UNIVERSITY PRESS PRINCETON, NEW JERSEY

Copyright 1995 by Princeton University Press

Published by Princeton University Press, 41 William Street,

Princeton, New Jersey 08540

In the United Kingdom: Princeton University Press, Chichester, West Sussex

All Rights Reserved

Library of Congress Cataloging-in-Publication Data

Stebbins, Robert C. (Robert Cyril), 1915

A natural history of amphibians / Robert C. Stebbins and

Nathan W. Cohen; illustrated by the authors.

p. cm.

Includes bibliographical references (P. ) and index.

ISBN 0-691-03281-5 (cl)

ISBN 0-691-10251-1 (pbk)

1. Amphibians. I. Cohen, Nathan W., 1919-. II. Title.

QL667.S84 1995

597.6dc20 94-43931

eISBN: 978-0-691-23461-8

R0

Preface ________________________________________

THIS BOOK has been written for a general audience, for the pleasure and edification of anyone, anywhere, interested in learning about the ways of amphibiansthe frogs, toads, salamanders, and caecilians (tropical snakelike amphibians) that grace our planet. Topics discussed follow closely the format of lectures given by the senior author over a period of thirty-three years of teaching vertebrate natural history and herpetology. They were selected because they related to the field experience of the authors and their students and were found to arouse student interest in amphibian natural history. An exception is the last chapter on declining amphibians. The apparent worldwide collapse of many frog and toad populations has only recently come to the attention of scientists and, we believe, serves as an appropriate subject with which to end the book. The declining amphibian story is open-ended and represents a frame in an ongoing process, the outcome of which is uncertain. Some parts of it are speculative. However, it exposes the reader to the scientific processthe gathering of data, development of hypotheses, the importance of basic knowledge concerning the subject under study, and its ultimate integration with other fields of knowledge. All that has gone before in the book helps set the stage for understanding and evaluating the processes and events set forth in the chapter on declining amphibians. Its ecological message should be of concern to all of us.

We began our investigation of apparent amphibian declines in the spring of 1993, late in the writing of our book. In view of the international alarm among amphibian biologists over amphibian declines and what they might portend for the future of these and other animals, we felt we should include some information on the subject in this book. However, we were not fully prepared for the outcome. The results of our survey proved so disturbing that, upon its completion, we decided the topic warranted a full chapter in the book, even though many field studies were underway and new information was being reported almost daily in an international effort to assess the damage and its causes.

After nearly two lifetimes of devotion to the study, artistic representation, and protection of our esteemed subjects and our present effort to set forth their secrets for all to enjoy, we were profoundly sobered by the information we had obtained. If the senior author were now to redraw the distribution maps in his A Field Guide to Western Reptiles and Amphibians (Peterson series, 1985), he would be required to show many ranges with major gaps, sprinkled with question marks. Many of the gaps appear to represent outright extinction of populations over large areas of former ranges.

It is our hope that by setting forth these findings in detailas they existed, incomplete, at the time of our survey (spring 1993 to summer 1994) against the backdrop of amphibian natural history information as presented in this book, amphibian conservation efforts will be promoted and studies of the causes of declines will be further stimulated. We fervently hope that the last chapter of the book will not become an epitaph for many members of a remarkable group of living beings.

Topics discussed in the book apply to amphibians worldwide and deal with many important aspects of their lives. These draw upon the personal experiences, knowledge, and interests of the authors, who have studied many of these animals, both in the laboratory and field, for nearly a lifetime, and on the studies of many other biologists, extensively cited throughout the text. We have usually followed closely the wording of cited passages to avoid misconstruing the sense of the authors and have identified the sources of information that are not our own. Some information is considered to have become common knowledge and therefore citations are not included. Considerable older literature is included to provide historical perspective.

Scientific literature, including that on amphibians, grows exponentially, so we have had to be highly selective in our choice of references. We have made an effort to maintain a streamlined account for the general reader, but there is much in the book that will be useful to more advanced readers as well. At the end of some sections, additional references will guide readers who are interested in pursuing the subject under discussion in greater depth.

Often there are disagreements among scientists in their attempts to explain natural phenomena. This results from the nature of the scientific process. We have included a number of such controversies in the book to make clear the ongoing, self-correcting process that is the hallmark of science.

Conservation of wildlife is assuming a high priority as human pressures accelerate the process of wildlife decline and extinction. Amphibians have not escaped. In fact, they may be in the vanguard of decline (see ). It is our hope that the book will help further wildlife conservation goals by providing basic information on amphibians that is useful to government agencies that care for the land, to environmentalists, to the concerned public, scientists, developers, politicians, and to others who are addressing land-use issues.

Our selection of the title of the book, A Natural History of Amphibians, reflects our interest in individual animals and their populations, their taxonomic relationships, how and where they live and reproduce, how they interact with one another and their environment, and the evolutionary processes that have made them what they are and that continue to shape their future. A natural history approach involves looking at not only the details of nature, but also seeing those details, perhaps often subconsciously, against the total backdrop of nature. It is this comprehensive worldview that now risks being blurred or lost in an age of scientific specialization and preoccupation with the needs and desires of humanity. Yet paradoxically, it is just such a broad view that is crucial to the present and future well-being of society.

In recent years teaching and research in natural history have declined in popularity, and greater focus is being given to cellular and molecular studies at many colleges and universities. On some campuses, natural history studies have never existed or have been eliminated completely. While the importance of studies at the level of molecules and cells is unquestioned, it is equally important to study life at the other end of the spectrum of biological organizationwhole organisms and their interactions in nature. To paraphrase George Gaylord Simpson, knowing all there is to know about a lions molecules and cells will not tell you why a lion roars. Like the science of ecology, this is what good natural history studies doobtain direct, on-site knowledge of what is going on outdoors among diverse life forms, often including humans, and the environment. However, natural history studies tend to emphasizeperhaps more than ecological investigationsspecies identification, systematics and distribution, opportunistic observations of species behavior and interactions in nature, and observational techniques.