TRADE-OFFS BETWEEN FEEDING COMPETITION AND PREDATION RISK IN BABOONS by Guy Charles Cowlishaw Dissertation submitted to the University of London for the degree of Doctor of Philosophy. University College London, Gower Street, London WCIE 6BT August 1993 ProQuest Number: 10017741 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. uest. ProQuest 10017741 Published by ProQuest LLC(2016). Copyright of the Dissertation is held by the Author. All rights reserved. This work is protected against unauthorized copying under Title 17, United States Code. Microform Edition © ProQuest LLC. ProQuest LLC 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106-1346 For Sanjida ACKNOWLEDGEMENTS This work owes a great deal to many people. Without their kind and generous help this thesis would not have been possible. Thanks go to Peter Henzi (of the University of Natal), for suggesting Namibia as a possible study site in the first place; Chris Brown and Eugene Joubert (of the Ministry of Wildlife, Conservation and Tourism), for organizing and granting permission for me to conduct research in Namibia at very short notice; Alisdair MacDonald (of the same Ministry), for suggesting possible study sites; Joris Komen and Eugene Marais (of the Windhoek State Museum), for taking me along on a site visit (and also for checking out second-hand vehicles with me); Coleen Mannheimer, for finding my study site; Douglas Reissner (of the Namibia Nature Foundation), for all his time and effort in helping me to raise funds for a vehicle in Namibia; Herta Kohlberg (of the National Herbarium), for identifying my plant specimens; and Willem Kongombe, for his help in habituating baboons. In particular, I would like to thank Andre Retief and Coleen and John Mannheimer for their friendship and hospitality. Coleen and John were extremely kind hosts during my first month in Namibia, and remained firm friends thereafter. I am indebted to August Juchli for granting me permission to conduct this study at Tsaobis Leopard Park, and also to Winston Retief, Mr Behrends and Mr Snyman for allowing me to follow the baboons onto their land when they travelled out of the boundaries of Tsaobis. In the U.K., I would like to thank Louise Barrett and Nilofer Ghaffer for supplying me with scientific papers while out in the field. In addition, I am grateful to Dawn Hartley for a crash course in SPSS and John Pearson for a similar course in Fig-P while writing-up. My funding came primarily from a Natural Environment Research Council (NERC) Studentship. However, contributions were also received from the University of London Central Research Fund and the Boise Fund (Oxford). In addition, the Namibia Nature Foundation, together with Rossing Uranium, Trail-A-Quip and Sun Alliance, kindly donated money towards the purchase of a second-hand vehicle in Namibia. To all these organizations, I am extremely grateful. My greatest thanks go to those people who became crucial to the success of this work: Peter and Desiree Bruce were my hosts at Tsaobis Leopard Park; they provided me with a neverending supply of help and friendship during my year there. Yvonne Cowlishaw, my mother has aided and abetted me throughout all stages of this work. Jon Davies assisted me in my fieldwork for four of the first six months; his company and practical contribution to the project were invaluable. Robin Dunbar, my supervisor, has been a constant source of friendship, intellectual stimulation, and moral and logistical support; his infectious enthusiasm and good humour have been indispensable. Rob Simmons and Phoebe Barnard were great friends and a tremendous source of advice, help and support during all stages of my work in Namibia; they made me feel at home in a foreign country as soon as I arrived, and continued to do so for the rest of my stay. The contribution that each of these individuals has made to this work cannot be understated. I am indebted to all of them and consider myself very lucky to have had their participation in this work. Finally, my most heartfelt thanks go to Sanjida O’ Connell. Sanjida worked with me in Namibia for the last three months of the study, during which time she collected half of the baboon data presented in this volume. In addition, she has had the misfortune to suffer the entirety of the interminable write-up. Sanjida’s contribution to this work has been very special. My thanks are equally so. ABSTRACT This study investigates the influence of feeding competition and predation risk on the behaviour and ecology of baboons. Four groups of chacma baboons ipapio cynocephalus ursinus) were habituated and studied over 12 months between 1990-91 in the Pro-Namib desert region of Namibia. Each group differed in size and composition (with 1-6 adult males occupying groups of between 22-55 members), but their ranges overlapped extensively. Additional data were collected describing (1) food quality and availability and (2) biologically relevant measures of predation risk. The results suggest that contest competition for food or safety was minimal both within and between groups in this population. However, scramble competition for food did occur, despite high levels of food availability. Female reproductive state had little influence on feeding or anti-predator behaviour. Females and individuals in small groups were shown to be at the greatest risk of predation, and responded as predicted by exhibiting the highest levels of anti-predator behaviour. Habitat use reflected a trade-off between food availability and the reduction of both diurnal and nocturnal predation risk. Individual spatial position within groups was influenced by male reproductive strategies and predation risk, although social constraints might also have been present. Vigilance in males reflected reproductive strategies while in females vigilance was aimed at predator detection. Trade-offs between foraging and predation risk were suggested in the patterns of home range habitat composition, the use of habitat in the home range, the presence of scramble feeding competition, the choice of feeding site and the choice of diet. In addition, large groups reduced feeding competition at the expense of increased predation risk. Finally, points of special interest included the reduction of predation risk by both (1) the active use of "rest" time and (2) the defensive behaviour of male group members. TABLE OF CONTENTS Title page ....................................................................................................................................... 1 D edication ....................................................................................................................................... 3 Acknowledgements ....................................................................................................................... 5 Abstract ..........................................................................................................................................7 Table of contents .............................................................................................................................9 1. INTRODUCTION ...................................................................................................................15 1.1. Theoretical background ..................................................................................................... 16 1.1.1. Types of competition ..............................................................................................16 1.1.2. Determinants of competitive ability ......................................................................17 1.2. Competition for limited resources ........................................................................................ 18 1.2.1. Male reproductive strategies ................................................................................ 18 1.2.2. Female feeding competition ................................................................................ 19 1.2.3. Competition for safety ...........................................................................................20 1.3. Interaction between feeding competition and predation risk ..............................................21 1.3.1. Non-primates ........................................................................................................22 1.3.2. Primates ................................................................................................................22 1.4. Structure of thesis ...................................................................................................................23 2. BABOONS, PREDATORS AND PREDATION R IS K ......................................................25 2.1. Introduction ...........................................................................................................................25 2.2. Quantifying instantaneous predation r is k ..............................................................................25 2.3. The predators of baboons ..................................................................................................... 27 2.3.1. Candidates ............................................................................................................. 27 2.3.2. Tsaobis