Ecology of Bats This limited facsimile editian has been issued for the purpose of keeping this title avaiJable to the scientific community. Ecology of Bats Edited by Thomas H. Kunz Boston University Boston, Massachusetts Plenum Press • New York and London Library of Congress Cataloging in Publication Data Main entry under title: Ecology of bats. Indudes bibliographical references and index. 1. Bats-Ecology. 2. MammaIs-Ecology. I. Kunz, Thomas H. QL737.C5E33 1982 599.4'045 82-10157 ISBN-13: 978-1-4613-3423-1 e-ISBN-13: 978-1-4613-3421-7 001: 10.1007/978-1-4613-3421-7 AACR2 This limited facsimile edition has been issued for the purpose of keeping this title available to the scientific community. 10987654 © 1982 Plenum Publishing Corporation Softcover reprint of the hardcover 1s t ed ition 1982 233 Spring Street, New York, N.Y. 10013 All rights reserved No part of this book may be reproduced, stored in a retrieva! system, or transmitted, in any form or by any means, electronic, mechanieal, photocopying, micromming, recording, or otherwise, without written permission from the Publisher To Margaret, Pamela, and David Contributors Hans G. Erkert Institut für Biologie III der Universität Tübingen. D-7400 Tübingen I, Federal Republic of Germany M. Brock Fenton Department of Biology. Carleton University, Ottawa KIS 5B6. Canada James S. Findley Department of Biology, University of New Mexico. Albu querque. New Mexico 87131 Theodore H. Fleming Department of Biology. University of Miami, Coral Gables. Florida 33124 E. Raymond Heithaus Department of Biology, Kenyon College. Gambier. Ohio 43022 Thomas H. Kunz Department of Biology, Boston University, Boston, Mas sachusetts 02215 Adrian G. Marshall Department of Zoology, University of Aberdeen. Aber deen AB9 2TN. Scotiand Brian K. McNab Department of Zoology. University of Florida, Gainesville, Florida 32611 P. A. Racey Department of Zoology. University of Aberdeen, Aberdeen AB9 2TN, ScotIand Diane Stevenson Vertebrate Division, Milwaukee Public Museum, Mil waukee, Wisconsin 53233 Merlin D. Tuttle Vertebrate Division, Milwaukee Public Museum, Mil waukee, Wisconsin 53233 Don E. Wilson U.S. Fish and Wildlife Service. National Museum of Natural History, Washington, D.C. 20560 vii Preface Among living vertebrates bats and birds are unique in their ability to fly, and it is this common feature that sets them apart ecologically from other groups. Bats are in some ways the noctumal equivalents of birds, having evolved and radiated into a diversity of forms to fill many of the same niches. The evolution of flight and echolocation in bats was undoubtedly a prime mover in the diversification of feeding and roosting habits, reproductive strategies, and social behaviors. Bats have successfully colonized almost every continential region on earth (except Antarctica), as weIl as many oceanic islands and archipelagos. They comprise the second largest order of mammals (next to rodents) in number of species and probably exceed all other such groups in overall abundance. Bats exhibit a dietary diversity (including insects, fruits, leaves, flowers, nectar and pollen, fish. other vertebrates, and blood) unparalleled among other living mammals. Their reproductive pattems range from seasonal monestry to polyestry, and mating systems inelude promiscuity, monogamy, and polygyny. The vast majority of what we know about the ecology of bats is derived from studies of only a few of the approximately 850 species, yet in the past two decades studies on bats have escalated to a level where many important empirical pattems and processes have been identified. This knowledge has strengthened our understanding of ecological relationships and encouraged hypothesis testing rather than perpetuated a catalog of miscellaneous observations. More than ever before, there is an urgent need to intensify efforts to study the ecology of these unique mamrnais, both in temperate and tropical regions. The tropical regions of the world support the highest diversity of bat faunas known, but uniess steps are taken to decelerate or reverse the current rate of loss of tropical habitats to altemate land-use pattems, the ecological diversity of this fauna may never be fully known. The objective in organizing this volume was to provide a balanced and authoritative account of major topics on the ecology of bats. Each of the ten chapters has been prepared by one or more acknowledged experts. The range of topics treated is by no means exhaustive; rather, the subjects are representative of ix x Preface a sizable Iiterature and have not been treated in reeent works. The authors were eneouraged to develop ehapters in an ecologieal framework based on subjects of their own interest and expertise, to emphasize empirical studies as well as theory, and, where appropriate, to inelude discussions of adaptations and evolutionary trade-offs. It is my hope that this volume will provide points of departure for more rigorous study by ecologists and ethologists interested in bats and encour age others to consider ecological adaptations of bats as models for comparative study. An attempt has been made to organize the sequence of chapters so that most of them are presented in a logical progression; otherwise they are grouped to gether by related subjects. An inevitable consequence of a multiauthor volume of this scope is that it leads to some redundancy in subject matter. Where appropri ate, cross-references are made to relevant chapters. As in any discipline, new viewpoints emerge that will not always be received with universai agreement. This is as it should be, and consequently I have tried not to interfere with presentarions of unorthodox ideas and interpretations, for the sake of encourag ing further dialogue. The following comments provide an introduction to the topics included in this volume. Roosts play a dominant role in the life history of bats, but there have been few attempts to integrate roosring habits, foraging behavior. social behavior. morphology, and energetics as factors influencing the roosting ecology of bats. Taking this approach in preparing Chapter 1, I (Kunz) have summarized the diversity of roosting adaptations, emphasized factors affecting roost fidelity and daily time budgets, and provided the first comprehensive treatment of night roosting ecology. Roost availability. roost dimensions. energetic considerations. and risks of predation appear to be major determinants of roost use. In recogniz ing the importance of roosts to successful reproduction. Racey (Chapter 2) draws extensively from the literature and upon his own work to identify factors control ling reproduction in bats. Environmental factors affecting reproductive cyeles. rates of embryonic development, and the timing and sequence of births are examined in bats from both temperate and tropical regions. He emphasizes that food supply during laetation and weaning is the single most important evolution ary factor in the timing of reproductive cyeles. Plasticity appears to be one of the IJlost prevaJenr features of growth and survival in bats. Tuttle and Stevenson (Chaptef 3) draw from an extensive litera ture and point out that both the litter size and developmental state at birth vary with biological and environmental factors. They note that successful growth of pre- and postweaned young varies among species and is markedly affected by feeding success and roost temperatures. In their anaJyses of bat survival they caution the reader on the limitations of sampling procedures and statistical treat ments in published studies. Preface xi The imponance of body size, food habits, and environmental conditions are emphasized by McNab's treatment of bat energetics and water balance in Chap ter 4. Drawing extensively from his own work on the physiological ecology of temperate and tropical bats, he discusses factors influencing energy expenditure in bats, the eeological significanee of energetics (including endotherrny and the relationship between metabolie rate and life span), energy budgets, and the evolution ofbat energetics. He argues that the distributionallimits to bats may be imposed by food habits and an energy eeonomy imposed by small body size. In Chapter 5 Erken summarizes an extensive literature on aetivity pattems of bats and, drawing from his own experimental work, interprets the periodicity of aetivity rhythms as adaptations to environments subjected to a 24-hr rhythm. He suggests that the flight and foraging activities of different speeies are influ enced by the plastieity of a circadian system, the inhibitory aetivity of light, and the sensitivity of the circadian system to meteorologieal faetors. The central thesis of Chapter 6, by Findley and Wilson, is that morphologieal traits used by systematists are valid ecological indices. Findley and Wilson emphasize the value of multivariate morphologieal analyses for quantifying the ecological niches of bats and in making comparisons of speeies within and among different ecological communities. Fenton (Chapter 7) integrates field studies of bat echolocation with proper ties of insect prey in the interpretation of the feeding ecology of insectivorous bats. He suggests that the hearing ability of insects may influence the design of echolocation calls used by bats when feeding. He notes that most insectivorous bats are dietary opponunists. Because of extensive overlaps in habitat use and foraging time and morphological similarities among sympatric species, Fenton argues that there is no convincing evidence that insectivorous bats compete for and thus panition available food resources. Foraging strategies of plant-visiting bats are the subject of Chapter 8, where Aeming examines the imponance of food availability and roosting behavior to foraging strategies (including foraging group size and föraging distance). He compares the foraging strategies of four well-studied species of Neotropical plant-visiting bats and emphasizes the impor tance of integrating studies on roosting behavior, socialorganization, and feed ing behavior to the ultimate understanding of the foraging strategies of bats. Most mutualistic interactions between plants and planr-visiting bats are unique to tropical regions, and in Chapter 9, Heithaus synthesizes a diverse botanicaI literature and integrates it with current knowledge of the foraging behavior of plant-visiting bats. He develops a model for coupled speciation between bats and plants. summarizes their complex coadaptations. and discusses the ecological and evolutionary consequences of bat-plant interactions. He sug gests that one should avo id assuming that mutualism between bats and plants is coevolved, since preadaptations characterize several modem bat-plant systems. Preface In spite of the pote!ltial importanee of parasitism in the lives of bats, rela tively little research has been published on this topie. Ecologically, the best known group of parasites associated with bats is the eetoparasitie inseets, whieh Marshall treats in Chapter 10. He draws from the literature and from his own work on life eycIes, host associations, and population dynamies to provide insight into some rather eomplex host-parasite adaptations unique to these flying mammals. This ehapter includes an appendix with suggestions for eolleeting ectoparasitie insects for ecological smdy. I am grateful to the authors of this volume for enthusiastieally aeeepting the ehallenge to eontribute their time and ideas and for tolerating my impatienee in meeting deadlines. The staff of the Plenum Publishing Corporation has been extremely helpful in all phases of produetion. I owe special thanks to Kirk Jensen, who initially agreed to embark upon this venture and to Alan Winick and Daniel Jaul for their indulgenee in my inexperienee as an editor. I want to thank my most reeent and present graduate smdents, Edythe Anthony, Pete August, Christopher Bumett, Marty Fujita, Karen Hoying, Al Kurta, and Holly Stack. for their assistance in proofreading and in the preparation of indices, and Nancy Tinnel and Christine Zotter, who assisted in elerieal matterso Karl F. Koopman kindly verified the famiIial and species nomenelature of the Chiroptera. Finally, I want to acknowledge my graduate mentor, J. Knox Jones. Jr., who encouraged me to pursue my ecological interests in bats. Thom"as H. Kunz Boston. Massachusens