FORAGING STRATEGIES, DIET AND COMPETITION IN OLIVE BABOONS Robert A. Barton A Thesis Submitted for the Degree of PhD at the University of St. Andrews 1990 Full metadata for this item is available in Research@StAndrews:FullText at: http://research-repository.st-andrews.ac.uk/ Please use this identifier to cite or link to this item: http://hdl.handle.net/10023/2767 This item is protected by original copyright FORAGING STRATEGIES, DIET AND COMPETITION IN OLIVE BABOONS Robert A. Barton Thesis submitted for the degree of Doctor of Philosophy, University of St. Andrews, 1989. _ ACKNOWLEDGEMENTS- This thesis has seen the light of day only through the great help, support and encouragement I have received from many quarters. I would particularly like to thank Liz Anderson, who has helped in so many ways and provided emotional, intellectual and practical support throughout the last four years. Andy Whiten has been the most patient, diligent and generous of supervisors, and has headed off innumerable crises with typical pragmatism and skill, while I flapped and floundered. I would also like to thank both Andy and Susy Whiten for the warm hospitality they have extended to me on so many occasions. The fieldwork would simply not have been possible without the assistance of Shirley Strum, who kindly allowed me to join the Uaso Ngiro Baboon Project, gave me ideas for data-collection, and provided vital logistical support throughout. I also thank Shirley for welcoming my dishevelled, field-weary self into her home on my visits to Nairobi, and for stimulating discussions about baboons, philosophy, and soul music. My second supervisor, Dick Byrne, has been instrumental in sharpening up some of my ideas and prose, and has given over much time to sorting out all the little wrangles and administrative details that have inevitably arisen. Josiah Musau and Hudson Oogh helped in crucial ways in the field, and kept me going at the beginning when it all seemed impossible. Debbie Lochhead helped with the collection of demographic and ecological data, and tolerated my little domestic foibles and oddities at Geoffrey's House. A number of other people have helped along the way. In particular, David and Anne Perrett have shown incomparable kindness and hospitality, which I have shamelessly exploited for far too long. Mary English conducted the phytochemical analysis, and computing assistance was given by Alan Milne, Phil Benson, Phil Robertson and Darryl Davies. Useful comments on research proposals and drafts of the thesis have been provided by Shirley Strum, Robin Dunbar, and Jeff Graves. I thank the Office of the President, Kenya, for granting me permission to conduct research in that country, and the Institute of Primate Research, Nairobi, to whom I was affilited during the period of fieldwork. Jim Else was a particular help in sorting out administrative details. Financial support was provided by a studentship from the Science and Engineering Council of Great Britain: Finally, I would like once again to thank my parents, Catherine Peters and Anthony Storr, who have provided the secure base and encouragement which have enabled me to keep going through dissapointments and lean times. ABSTRACT Savannah baboons are amongst the most intensively studied taxa of primates, but our understanding of their foraging strategies and diet selection, and the relationship of these to social processes is still rudimentary. These issues were addressed in a 12-month field study of olive baboons (Papio anubis) on the Laikipia plateau in Kenya. Seasonal fluctuations in food availability were closely related to rainfall patterns, with the end of the dry season representing a significant energy bottleneck. The distribution of water and of sleeping sites were the predominant influences on home range use, but certain vegetation zones were occupied preferentially in seasons when food availability within them was high. The influence of rainfall on monthly variation in dietary composition generally mirrored inter-population variation. Phytochemical analysis revealed that simplistic dietary taxonomies can be misleading in the evaluation of diet quality. Food preferences were correlated with nutrient and secondary compound content. The differences between males and females in daily nutrient intakes were smaller than expected on the basis of the great difference in body size; this was partly attributable to the energetic costs of reproduction, and possibly also to greater energetic costs of thermoregulation and lower digestive efficiency in females. A strongly linear dominance hierarchy was found amongst the adult females. Dominance rank was positively correlated with food ingestion rates and daily intakes, but not with time spent feeding or with dietary quality or diversity. In a provisioned group, high-ranking females occupied central positions, while low-ranking females were more peripheral and were supplanted more frequently. In the naturally-foraging group, the intensity of competition was related to the pattern of food distribution, but not to food quality, and was greater in the dry season than in the wet season. The number of neighbours and rates of supplanting were correlated with rank, and evidence was presented that high-rankers monopolised arboreal feeding sites. CONTENTS PAGE CHAPTER 1: INTRODUCTION 1 CHAPTER 2: STUDY SITE AND METHODS 11 Geography 11 Geology, topography and vegetation 11 Climate and seasonality 15 Fauna 16 Livestock and human activities 18 Baboons at Chololo 19 Methods 20 CHAPTER 3: VEGETATION, FOOD AVAILABILITY AND HABITAT USE 44 Introduction 44 Relative abundance of habitat types 47 Seasonal variation in food availability 49 Implications of seasonality for baboons 54 Spatial distribution patterns of food and the problem of patchiness 58 Patterns of ranging and habitat use 64 CHAPTER 4: FEMALE DOMINANCE RELATIONS, REPRODUCTIVE PROFILES AND BODY CONDITION 101 Introduction 101 Social organisation among females 104 Reproduction and body condition 128 CHAPTER 5: DIET SELECTION 136 Introduction 136 Phytochemistry 139 Diet 153 Phytochemical determinants of dietary preferences 176 CHAPTER 6: NUTRIENT INTAKES 196 Introduction 196 Effects of month, sex and reproductive state 198 Seasonal variation 200 Sex differences 207 The influence of reproductive state 212 Nutrient intakes in comparative perspective 216 The influence of dominance rank amongst females 222 Discussion 224 CONTENTS, cont. CHAPTER 7: THE DYNAMICS AND SEASONALITY OF FEEDING COMPETITION 244 Introduction 244 Competition and spatial deployment: an experiment 245 Seasonal variation in the intensity of competition 252 The influence of food quality and distribution 256 Dominance rank, spatial deployment and supplanting 261 Discussion 266 CHAPTER 8: CONCLUDING DISCUSSION 279 Ecological contrasts between males and females 279 Feeding competition, predation and social evolution 287 APPENDICES: SPECIES LIST OF MAMMALS SIGHTED LIST OF FOODS PROXIMATE COMPOSITION OF CHOLOLO PLANTS 1 CHAPTER 1: INTRODUCTION Ye. The study of primate social behaviour has been characterised by something of a thematic schism. On the one hand, many researchers have been interested in the relationship between animals' environments and their mating systems and demography, an area of study known generally as socioecology. This was chiefly stimulated by pioneering comparative work on birds by Orians (1961) and, in particular, by Crook (1964), who later extended the approach to primates (Crook and Gartlan, 1966). On the other hand, some researchers, notably Robert Hinde and colleagues, have carried out extensive investigations into the complex nature and dynamics of social interactions and relationships (Hinde, 1969, 1976, 1979, 1983a; Hinde and Simpson, 1975; Hinde and Stevenson-Hinde, 1976; Datta, 1981), and into the relations between inter-individual processes and social structure (Seyfarth, 1977, 1978; Colvin, 1982). A little more recently, some attempts have been made to integrate these two disparate trends, in order to produce coherent models of primate social evolution (Wrangham, 1979, 1980, 1983; Dunbar, 1988; van Schaik, 1989). The aim of this thesis is both to advance the study of primate ecology, and, specifically, to continue the trend of interpreting social relationships from an ecological point of view. The Papio baboons have been perhaps the most intensively studied of all primate genera (e.g. Zuckerman, 1932; DeVore and Washburn, 1963; Crook and Aldrich-Blake, 1968; Rowell, 1966; Altmann and Altmann, 1970; Smuts, 1985; Strum, 1987). To some, it might therefore seem difficult to justify further 2 studies; do we not know all we want to know? In fact, the - advanced state of our knowledge about some aspects of baboon behaviour makes continued study all the more interesting, because it enables us increasingly to interrelate social, life-history, demographic and ecological variables. By integrating such information, it may eventually be possible to construct a socioecological model for the genus which is unique in its completeness. The Papio baboons inhabit a wide range of habitats (mainly in sub-Saharan Africa, but extending north as far as Saudi Arabia in the case of P.hamadryas), including forest, swampy woodland, savannah, desert, and high montane slopes (DeVore and Hall, 1965; Rowell, 1966a; Kummer, 1968; Altmann and Altmann, 1970; Jouventin, 1975; Hamilton et al., 1976; Stammbach, 1987; Norton et al., 1987; Whiten et al., 1987; Dunbar, 1988). This has contributed to their reputation as ecological generalists, a reputation