The Behaviour of Pinnipeds

Transcription

1 The Behaviour of Pinnipeds

2 The Behaviour of Pinnipeds Edited by Deane Renouf Professor, Department of Psychology and Ocean Sciences Center, Memorial University of Newfoundland, Canada S SPRINGER-SCIENCE+BUSINESS MEDIA, B.V.

3 First edition Springer Science+Business Media Dordrecht Originally published by Chapman and Hall Ltd in 1991 Softcover reprint ofthe hardcover lst edition 1991 Typeset in 10/12pt Trump Mediaeval by Mayhew Typesetting, Bristol ISBN lO AlI rights reserved. No part of this publication may be reproduced or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, or stored in any retrieval system of any nature, without the written permission of the copyright holder and the publisher, application for which shall be made to the publisher. The publisher makes no representation, express or implied, with regard to the accuracy of the information contained in this book and cannot accept any legal responsibility or liability for any errors or omissions that may be made. British Library Cataloguing in Publication Data The behaviour of pinnipeds. 1. Mamrnals: Seals 1. Renouf, Deane I S B N I S B N ( e B o o k ) D O I / Library of Congress Cataloging-in-Publication Data The Behaviour of pinnipeds I edited by Deane Renouf. - 1st ed. p. cm. Includes bibliographical references and index. ISBN lO Pinnipedia - Behavior. 1. Renouf, Deane, QL737.P6B '5-dc CIP

4 To Bora, Tustin, Luke, Colin and Laura who encourage the intrusion of projects like this into the otherwise smooth running of a family. To Meem, facilitator and peace-maker.

5 Contents Contributors Preface Acknowledgements Foreword xi xiii xv xvii 1 Determinants of mating systems in the Otariidae (Pinnipedia) Introduction Overview of current theory Types of mating system among Otariids Variation in the form of Otariid mating systems Conclusions 31 Acknowledgements 34 References 35 2 Pinniped mating system on land, ice and in the water Emphasis on the Phocidae What do we expect in pinnipeds and other mammals? What do we find in mammals? What determines the distribution of females and the degree of polygyny? Do the unique features of pinnipeds give an advantage to one sex and affect the form that mating systems take? What are the consequences of mating on land verses in the water? Conclusions 58 References 59

6 viii Contents 3 Behavioural ecology of pinniped neonates Introduction Life history characteristics The lactation period Weaning Behaviour and diet of weaned pups Discussion 114 Acknowledgements 117 References Communication in pinnipeds, with special reference to non-acoustic signalling Introduction Signal structure and variation Some concepts in communication Combat behaviour and the communication of threat Ecological variation and time/activity budgets Evolutionary patterns Concluding comments 213 Acknowledgements 215 References Physiology of behaviour in pinnipeds Introduction The physiology of reproductive behaviour Maternal behaviour Motor development and play Immune system Diving Metabolism Activity patterns Thermoregulation Moult Orientation Conclusion 285 Acknowledgements 286 References Reproductive and foraging energetics of pinnipeds: Implictions for life history patterns Introduction Reproductive biology Maternal investment Foraging behaviour 327

7 Contents ix 6.5 Summary and conclusions 337 Acknowledgements 338 References Sensory reception and processing in: Phocidae and Otariidae Introduction Methodological caveats in psychophysical threshold measurement 7.3 Vision 7.4 Hearing 7.5 Tactile sensation: Vibrissae 7.6 Chemoreception 7.7 Magnetic reception 7.8 Discussion 7.9 Umwelten: Beyond the receptor References Index 396

8 Contributors Burney J. Le Boeuf Department of Biology and Institute of Marine Sciences, University of California, Santa Cruz, California, USA Daryl J. Boness Department of Zoological Research, National Zoological Park, Smithsonian Institution, Washington, DC, USA W.D. Bowen Bedford Institute of Oceanography, Department of Fisheries & Oceans, Dartmouth, Nova Scotia, Canada B2Y 4A2 Daniel P. Costa Joseph M. Long Marine Laboratory, Institute of Marine Sciences, University of California, Santa Cruz, California, USA Edward H. Miller Biology Department, University of Victoria, P.O. Box 1700, Victoria, British Columbia, Canada V8W 2Y2 and Royal British Columbia Museum, Victoria, British Columbia, Canada V8V lx4 Deane Renouf Ocean Sciences Centre, Memorial University of Newfoundland, St. John's, Newfoundland, Canada AlB 3X9 Douglas Wartzok Department of Biological Sciences, Indiana University-Purdue University, Fort Wayne, IN, USA 46805

9 Preface We teach our students of behavioural science that one first defines a research problem, and then the most appropriate animal is selected to investigate hypotheses. The reverse order of events is improper: a particular class of animals should not be studied for its own sake. In the case of the Pinnipeds (seals, sea lions, fur seals and walruses) the organism and the problem are essentially the same. The research questions presented in this volume in one way or another relate to survival in two worlds, the ocean for foraging, and the terrain at its edge or frozen above it for breeding. The evolution of Pinniped behaviour and the mechanisms which underlie it are a consequence of having to cope with two seemingly incompatible sets of environmental constraints. The physiological adaptations for concomitant functioning in two media with very different physical characteristics have produced correlated behavioural modifications. The energetic demands of reproduction and foraging are idiosyncratic because each activity occurs on opposite sides of the air/water interface. As a result, the mating system must reconcile aquatic design for such functions as locomotion and thermoregulation, with the terrestrial requirements for successful pupping. Similarly, the ecology of this dual habitat prescribes the rules governing the behaviour of the neonate and its interactions with its mother. Sensation, perception and cognition * and consequently the vehicle for communication must operate properly in air and underwater either by using different mechanisms in each medium, or by modifying systems which are designed for use in one medium to operate effectively in the other. Throughout the chapters which follow, whenever possible the This volume was to have a chapter entitled 'Learning and cognition in pinnipeds: a quarter century of research' by Ronald J. Schusterman, but at the eleventh hour he was unfortunately unable to provide it.

10 xiv Preface lines of distinction between Otariidae (sea lions and fur seals) and Phocidae (true seals) are clearly drawn. Too often, either inadvertently or as a result of a paucity of information, the behavioural literature has treated the two families collectively as if they were a single group. In fact the differences between phocids and otariids reflect variation in the extent of each family's re-adaptation to the marine habitat. Therefore, contrasts between the two groups illuminate aspects of adaptation. Behavioural investigations of the third pinniped family, the Odobenidae (walrus) are unfortunately few, but they are described when available. The intention of this collection is to examine the behaviour of Pinnipeds from the point of view of evolution and mechanism. The history of these two schools of thought is riddled with controversy, and in the 1960s could have been described as the American versus the European positions in what was a rather lively warfare. (Consider the battles in the scientific journals between the late Daniel Lehrman and Konrad Lorenz and their respective proponents.) Fortunately rapprochement has occurred since then, though occasionally one hears behavioural ecologists and physiologists/psychologists arguing from the floor of conferences, when in fact they are agreeing. This volume is a demonstration of this rapprochement, wherein the present and historical functions as well as the operating machinery of Pinniped behaviour are presented as mutually important components of its explanation. Unless stated otherwise, the nomenclature used in this book is that of Harrison and Ridgeways' 1981 Handbook of Marine Mammals, volumes 1 and 2. Where possible, all units have been changed to conform with the SI metric system.

11 Acknowledgements I am indebted to many people who assisted in various ways throughout the production of this volume, not the least of whom are the authors who agreed to participate, and thereafter put up with incessant nagging about their contributions. Bob Carling was remarkably patient while I nagged. Elizabeth Noseworthy ensured that my other duties were taken care of when the book took over my time. She moved into the library when required, and when necessary became illustrator and photographer. I am grateful for her steadfast competence. Mary Scott's assistance was similarly invaluable. I am thankful to Daryl Boness, Don Bowen, John Lawson, Elizabeth Perry, David Piggins, David Rosen, Mike Sherrick, and Jack Terhune for their insightful reviews and editorial assistance. Brenda Crewe and Bernice St Croix were exceedingly tolerant when I monopolized the services of the general office. I would like to give special thanks to Cherelyn Williams whose cheerfulness, skill and speed in the preparation of the manuscripts and accoutrements was always much appreciated.

12 Foreword People come to study pinnipeds from a diversity of scientific backgrounds. However, it is difficult to maintain a narrow disciplinary focus on these fascinating animals. Many active researchers on pinnipeds become generalists, ranging widely in their studies. Collectively, the authors in this book have done research at the molecular, individual (anatomical, physiological and behavioural), population and ecosystem levels of biological organization. This book is, of course, focused on behaviour, and the authors have been assigned particular tasks denoted by their chapter titles. But there is much creative lateral thinking in their analyses and syntheses of the enormous literature on seals. Not so many years ago a book on behaviour of a group of animals would have been grounded in experimental animal psychology, leavened somewhat by stirrings of ethology. In this book, behaviour is seen as part of the whole complex of anatomical, physiological, and life-history properties that determine the animal's fitness in challenging environments. It is worth noting that one of the first quantitative life-history analyses of a group of related animals was the study of seals by Laws (1960). It is also worth noting that one of the classics of behavioural ecology and sociobiology is the work of Bartholomew (1970) on pinniped polygyny. This book has strong roots in such approaches. Arguments about adaptiveness or optimality of behaviours are sometimes viewed with suspicion or even derision by those who prefer more readily testable hypotheses. There are two valid reasons for such suspicion. First, in the enthusiasm for I explanation', the phenomena to be explained can be poorly or even wrongly delineated. The chapters by Miller and Renouf bring the rigours of ethology and experimental psychology to bear on the description, measurement, naming and categorization of behaviours. Secondly, the 'naive pan selectionist' view that all phenotypic attributes of animals, including

13 xviii Foreword their behaviours, are closely adapted to the environment, fails to recognize such constraints as phylogeny, co-adaptations, and unpredictable environments. The authors in this book, with their diverse backgrounds, are fully alert to the complexity and contexts of behaviours. Of course biologists seek generalizations and patterns, but sometimes deviations and exceptions are equally informative. For example, in the last few years much has been written on the divergent patterns of maternal care by otariid and phocid seals: the former with prolonged lactation interrupted by feeding bouts at sea, and the latter with intense, uninterrupted lactation cycles. The chapters by Costa and Bowen, among others, enlarge upon this generalization and show that some animals are not all they should be. Boness, Wartzok and Le Boeuf deal extensively with mating systems of pinnipeds, about which there have been shaky generalizations and premature conclusions. The authors in this book have been privileged to carry out large, long-term programs of collaborative research. Yet much research on pinnipeds, especially on their behaviour, has been done independently and opportunistically by students and others, often motivated by the emotional appeal of these beautiful animals. Perhaps one of the greatest values of this book will be as an inspiration for future research on any scale. There remain explicit hypotheses to be tested, and there are guidelines to shape enquiries, even on seemingly trivial scales. In a charming little aside on methodology, Miller shows how observations on the position, horizontal or vertical, of a seal's head in water could be elevated into a more penetrating analysis of social behaviour. He also concludes with an eloquent appeal for the importance of such studies in a world where our companion species are increasingly threatened by those who seem not to see them. We must be grateful to Deane Renouf for organizing this broad focus on such fascinating creatures. Ian A. McLaren Halifax, Canada March 1990