Orang-Utan Behavioural Ecology in the Sabangau Peat-Swamp Forest, Borneo

ORANG-UTAN BEHAVIOURAL ECOLOGY IN THE SABANGAU PEAT-SWAMP FOREST, BORNEO by Helen Celia Morrogh-Bernard This dissertation is submitted to the University of Cambridge for the degree of Doctor of Philosophy. Wildlife Research Group, Anatomy School, University of Cambridge. Wolfson College, Cambridge. February 2009 Jupiter kiss squeaking Mozart looking out for the approach of a flanged male Contents CONTENTS i TABLES AND FIGURES viii PREFACE xiii ACKNOWLEDGEMENTS xiv SUMMARY xvii CHAPTER 1: INTRODUCTION 1 1.1 OVERVIEW 1 1.2 ORANG-UTANS 2 1.2.1 Taxonomy 3 1.2.2 Distribution, density and effects of disturbance 6 1.2.3 Life history and social structure 9 1.2.4 Feeding ecology 12 1.3 THREATS TO ORANG-UTANS 13 1.3.1 Habitat loss 13 1.3.2 Hunting 21 1.4 TROPICAL PEAT-SWAMP FOREST 23 1.4.1 Peatlands 24 1.4.2 Importance of tropical peat swamp forest 25 1.4.3 Threats to tropical peat-swamp forests 26 1.5 PROJECT DESIGN 28 1.5.1 Previous research / 28 1.5.2 Justification for research 30 1.6 AIMS AND OBJECTIVES 31 1.6.1 Aims 31 1.6.2 Objectives 32 CHAPTER 2: STUDY AREA AND METHODS 33 2.1 STUDY AREA 33 2.1.1 Location 33 2.1.2 Habitat types 36 2.1.3 Fauna 38 2.1.4 Climate 39 2.1.5 Human disturbance 41 i Contents 2.2 METHODS 42 2.2.1 Habituation 42 2.2.2 Age/sex class classifications 45 2.2.3 Follow protocol 47 2.2.4 Data collection 47 2.2.5 Behaviour activities 49 2.2.6 Feeding bouts 54 2.2.7 Home range 55 2.2.8 Long calls 55 2.2.9 Social interactions 55 2.2.10 Assessing urinary ketones as a proxy for orang-utan energy 56 balance 2.2.11 Genetic analysis 56 2.2.12 Disturbance 57 2.2.13 Vegetation plots 57 2.3 RESEARCH PERIOD AND ACCOMPLISHMENTS 59 2.3.1 Grid system 59 2.3.2 Field research 59 2.3.3 Study animals 60 2.4 DATA SET AND ANALYSES 61 2.4.1 Data set 61 2.4.2 Analyses 63 CHAPTER 3: FOREST COMPOSITION, SEASONALITY AND 66 PRODUCTIVITY 3.1 INTRODUCTION 66 3.2 OBJECTIVES 68 3.3 METHODS 68 3.3.1 Forest composition 69 3.3.2 Fruiting, flowering and new-leaf phenology. 69 3.3.3 Fruit and flower productivity levels 71 3.3.4 Degree of synchrony 72 3.4 RESULTS 73 3.4.1 Forest composition 73 3.4.2 Reproductive phenology 77 ii Contents 3.4.3 Fruiting and flowering stems. 82 3.4.4 Productivity levels 83 3.4.5 Degree of synchrony 84 3.5 DISCUSSION 87 3.5.1 Species composition and forest structure 87 3.5.2 Fruit and flower production and seasonality 87 3.5.3 Fruiting events 89 3.5.4 Fruiting cycles 90 3.6 CONCLUSION 92 3.7 SUMMARY 93 CHAPTER 4: ORANG-UTAN DIETARY DIVERSITY AND EFFECTS 94 OF FOOD AVAILABILITY 4.1 INTRODUCTION 94 4.1.1 Diet and food availability 94 4.1.2 Food availability and energy balance 96 4.2 OBJECTIVES 97 4.3 METHODS 98 4.3.1 Diet composition 98 4.3.2 ‘Food’ availability and effects on diet 98 4.3.3 Comparison with other sites 100 4.3.4 Species eaten, importance and preference in the diet 100 4.4 RESULTS 102 4.4.1 Dietary composition 102 4.4.2 ‘Food’ availability and its effect on dietary composition and 107 energy balance 4.4.3 Site differences in diet 113 4.4.4 Species eaten 116 4.5 DISCUSSION 121 4.5.1 Dietary composition and site comparisons 121 4.5.2 ‘Food’ availability and energy budgets 122 4.5.3 Species importance and preference 124 4.6 CONCLUSION 126 4.7 SUMMARY 127 iii Contents CHAPTER 5: ORANG-UTAN ACTIVITY PATTERNS 128 5.1 INTRODUCTION 128 5.1.1 Activities 128 5.1.2 Comparative studies 129 5.2 OBJECTIVES 130 5.3 METHODS AND ANALYSIS 132 5.3.1 Active period and activities 132 5.3.2 Sabangau 132 5.3.3 Comparison with other sites 134 5.3.4 Analysis 135 5.4 RESULTS 136 5.4.1 Active period start and finish time. 136 5.4.2 Active period length 138 5.4.3 Activity budgets 140 5.4.4 Changes in activity budgets in response to changes in ‘food’ 144 availability. 5.4.5 Comparing activity budgets between sites 146 5.5 DISCUSSION 150 5.5.1 Active period 150 5.5.2 Differences in activity budgets between age/sex classes 151 5.4.3 Impact of ‘food’ availability on activity 153 5.5.4 Impact of habitat on activity 153 5.6 CONCLUSION 157 5.7 SUMMARY 158 CHAPTER 6: FOREST STRUCTURE AND ANTHROPOGENIC 159 DISTURBANCE: ON ORANG-UTAN USE AND BEHAVIOUR 6.1 INTRODUCTION 159 6.1.1 Selective logging 159 6.1.2 Effects of logging on orang-utans and other species 161 6.1.3 Impact of direct human disturbance 163 6.2 OBJECTIVES 165 6.3 METHODS 166 6.3.1 Habitat classification 166 6.3.2 Habitat scores 170 iv Contents 6.3.3 Habitat preference 172 6.3.4 Direct human disturbance 173 6.4 RESULTS 174 6.4.1 Habitat 174 6.4.2 Forest quality within the research area 177 6.4.3 Orang-utan habitat preference 178 6.4.4 Habitat preference for activities 180 6.4.5 Orang-utan activities in different habitat classes 182 6.4.6 Impact of active human disturbance 184 6.5 DISCUSSION 187 6.5.1 Habitat Classes 187 6.5.2 Orang-utan habitat preference 187 6.5.3 Effects of habitat disturbance on secondary activities 189 6.5.4 Implications for conservation 191 6.5.5 Response to active human disturbance 192 6.6 CONCLUSION 193 6.7 SUMMARY 194 CHAPTER 7: RANGING 196 7.1 INTRODUCTION 196 7.1.1 Home ranges 196 7.1.2 Day ranges 198 7.2 OBJECTIVES 200 7.3 METHODS AND ANALYSIS 201 7.3.1 Residency 201 7.3.2 Ranging 201 7.3.3 ‘Food’ availability 204 7.4 RESULTS 204 7.4.1 Residence status 204 7.4.2 Home ranges 206 7.4.3 Female range overlap 209 7.4.4 Core area 209 7.4.5 Day ranges 211 7.5 DISCUSSION 213 v Contents 7.5.1 Home range 213 7.5.2 Day ranges and ‘food’ availability 214 7.6 CONCLUSION 216 7.7 SUMMARY 217 CHAPTER 8: UNDERSTANDING ORANG-UTAN SOCIAL 218 ORGANISATION - GENETIC DIVERSITY AND DISPERSAL PATTERNS 8.1 INTRODUCTION 218 8.2 OBJECTIVES 221 8.2.1 Genetic diversity 221 8.2.2 Range overlap 221 8.3 METHODS AND ANALYSIS 222 8.3.1 Relatedness 222 . 8.3.2 Range overlap and social encounters 225 8.4 RESULTS 226 8.4.1 Genetic diversity and pedigree 226 8.4.2 Female range overlap and encounters 233 8.5 DISCUSSION 236 8.5.1 Genetic diversity and dispersal patterns 236 8.5.2 Range overlap 238 8.6 CONCLUSION 243 8.7 SUMMARY 244 CHAPTER 9: REPRODUCTIVE STRATEGIES AND MALE 245 DOMINANCE 9.1 INTRODUCTION 245 9.1.1 Mating strategies. 245 9.2 OBJECTIVES 247 9.3 METHODS 247 9.4 RESULTS 249 9.4.1 Associations 249 9.4.2 Male-male encounters 251 9.4.3 Matings 253 9.5 DISCUSSION 253 vi Contents 9.5.1 Male-male encounters 253 9.5.2 Mating strategies 254 9.5.3 Overall reproductive strategy 257 9.6 CONCLUSION 258 9.7 SUMMARY 258 CHAPTER 10: CONCLUSIONS 259 10.1 MAJOR RESULTS 259 10.1.1 Behaviour in Sabangau 260 10.1.2 Differences between Sabangau and other research sites 260 10.1.3 Impact of these differences on orang-utan behaviour 261 10.2 IMPACTS OF DISTURBANCE AND IMPLICATIONS FOR CONSERVATION 263 10.2.1 Impact of disturbance 263 10.2.2 Recommendations 263 REFERENCES 265 APPENDICES 290 vii Contents TABLES CHAPTER 1 Table 1.1 Mortality rates for different age/sex classes in various habitat types 21 (from Singleton et al., 2004). CHAPTER 2 Table 2.1 Types of human disturbance. 41 Table 2.2 Total hours followed. 59 Table 2.3 Orang-utans identified and followed during my study. 60 Table 2.4 Sex ratio. 61 Table 2.5 Number of habituated follows on each individual 62 CHAPTER 3 Table 3.1 Number of species, genera and families identified in the phenology 73 plots. Table 3.2 Family dominance within the phenology plots. 75 Table 3.3 Density of the 20 commonest species in the Sabangau. 76 Table 3.4 The number of trees in six tree size classes. 76 Table 3.5 Synchronous and asynchronous species of trees 85 CHAPTER 4 Table 4.1 Productivity classes for orang-utan foods only. 99 Table 4.2 Predicted means from regression model. 106 Table 4.3 Food types in the diet against ‘food’ availability. 109 Table 4.4 Orang-utan diet (%) during three different levels of ‘food’ availability. 110 Table 4.5 Pair-wise comparisons for food-types in the diet against food 111 availability Table 4.6 Number of individuals sampled each month. 112 Table 4.7 Orang-utan diet at eight sites, expressed as percentage of total feeding 115 time. Table 4.8 Number of plant families, genera and species eaten by orang-utans 116 Table 4.9 Number of species fed on by food parts.

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