Gibbons (eBook)

THE GIBBONS 2
Foreword 6
Acknowledgments 9
Contents 10
Contributors 13
Part 1: Introduction 17
The Diversity of Small Apes and the Importance of Population-Level Studies 18
Gibbon Diversity 19
Gibbon Socioecology: Flexibility 20
The Limits of Flexibility 22
The True Neglected Apes? 23
References 24
Part 2: Biogeography 26
Evolutionary Relationships Among the Gibbons: A Biogeographic Perspective 27
Introduction 27
Taxonomy 27
Geographic Distributions 31
Phylogenetic Inter-relationships 36
Biogeography 40
Paleontological Record of Gibbons 40
Paleoenvironmental History of Southeast Asia 41
The Radiation of Gibbons in Southeast Asia 44
Conclusions 46
References 46
Genetic Differentiation of Agile Gibbons Between Sumatra and Kalimantan in Indonesia 51
Introduction 51
Samples and Identification 52
Chromosomes 54
DNA Analyses 57
Discussion 59
References 62
Vocal Diversity of Kloss’s Gibbons (Hylobates Klossii) in the Mentawai Islands, Indonesia 64
Introduction 64
Materials and Methods 66
Field Methods 66
Data Collection 67
Kloss’s Gibbon Song Structure 67
Male Song Structure 68
Female Song Structure 68
Sample Size of Tape-Recorded Gibbon Songs 69
Acoustic Analysis 70
Statistical Analysis 70
Discriminant Function Analysis 70
Multidimensional Scaling 71
Results 71
Discriminant Function Analysis 71
Multidimensional Scaling 75
Vocal Versus Geographic Distance 75
Discussion 77
Appendix: List of Vocal Variables 80
Trill Phrase of the Male 80
Great Call Phrase of the Female 81
References 81
Phylogeography of Kloss’s Gibbon (Hylobates Klossii) Populations and Implications for Conservation Planning in the Mentawai Islands 85
Introduction 85
Methods 87
Sampling 87
DNA Sequencing 88
Phylogenetic Inference 88
Phylogenetic Species Concept 89
Population Genetics 90
Results 90
Discussion 94
Recent Gene Flow 95
Historical Gene Flow 96
Incomplete Lineage Sorting 96
Implications for the Other Mentawai Primates 96
Conservation Planning 97
References 98
Individual and Geographical Variability in the Songs of Wild Silvery Gibbons (Hylobates Moloch) on Java, Indonesia 102
Introduction 102
Methods 105
Study Animals 105
Recording and Analysis Equipment 105
Acoustic Analysis 105
Statistics 109
Results 110
Variability Within and Between Individuals 110
Variability Between Populations 113
Possible Taxonomic Boundary 115
Discussion 115
Conclusions 117
References 117
The Fossil Record of Gibbons 122
The Nature of the Fossil Record of Gibbons and Gibbon-Like Primates 123
The Distribution of Fossil Gibbons in Relation to Changing Sea Levels and Landforms 124
Life History, Diet, and the Evolution of Gibbons 134
Summary and Conclusions 137
References 138
Part 3: Diet and Community Ecology 142
Hylobatid Diets Revisited: The Importance of Body Mass, Fruit Availability, and Interspecific Competition 143
Introduction 143
Hylobatid Ecology 143
The Effects of Body Mass on Hylobatid Energetics 144
Competition Between Hylobatid Species 144
New Ways to Understand Hylobatid Diets 146
Methods 148
Data Collection 148
Statistical Analyses 149
Descriptive Statistics and Mann-Whitney U tests 149
Regression Analyses 149
Discriminant Function Analyses 151
Results 151
How Folivorous Are Siamangs Relative to All Other Hylobatids? 151
How Well Is Folivory Linked to Body Mass in Gibbons? 153
How Do the Diets of Small-Bodied Gibbons Compare When Living Sympatrically vs. Allopatrically with Siamangs? 155
What Is the Relationship Between Resource Availability and Hylobatid Diets? 155
What Is the Impact of Interspecific Competition on Gibbon Diets? 158
Discussion 160
Siamangs Are as Folivorous as Other Hylobatids 160
Folivory Is Poorly Linked to Body Mass in Gibbons 161
Small-Bodied Gibbons Living Sympatrically vs. Allopatrically with Siamangs Do Not Differ in Diet and Interspecific Competition Does Not Significantly Impact Gibbon Diets 162
There Is a Significant Relationship Between Resource Availability and Hylobatid Diets 163
Morphological Consequences of Large Body Size 163
Conclusions and Future Perspectives 164
Other Modes of Niche Segregation 164
Gibbons Within the Larger Southeast Asian Community 165
References 166
Competition and Niche Overlap Between Gibbons (Hylobates albibarbis) and Other Frugivorous Vertebrates in Gunung Palung National Park, West Kalimantan, Indonesia 170
Introduction 170
How Specialized Are Gibbon Diets? 171
Which Taxa Are the Major Competitors of Gibbons? 172
How Similar Are the Feeding Niches of Gibbons and Their Major Competitors? 173
Methods 175
Study Site and Subjects 175
Vertebrate Feeding Observations 175
Fruit Phenology 177
Primate Density Transects 177
Analyses 178
Results 179
How Specialized Are Gibbon Diets? 179
Which Taxa Are the Major Competitors of Gibbons? 182
How Similar Are the Niches of Gibbons and Their Major Competitors? 185
Discussion 187
How Specialized Are Gibbon Diets? 188
Which Taxa Are the Major Competitors of Gibbons? 190
How Similar Are the Niches of Gibbons and Their Major Competitors? 190
References 192
The Seed Dispersal Niche of Gibbons in Bornean Dipterocarp Forests 198
Introduction 198
Methods 199
Study Area and Gibbon Groups 199
Bornean Frugivores 200
Quantity: Selection of Food Plants 201
General Fruit Types 202
Patch Size 206
Quality: Primary Seed Shadow and Post-Dispersal Processes 207
How Seeds Are Deposited 207
Where Seeds Are Deposited 209
What Is the Seed Dispersal Niche of Gibbons? 210
Appendix 212
References 213
Part 4: The Relationship Between Ecology and Social Organization 217
Ecology and the Social System of Gibbons 218
Introduction 218
Grades of Explanation 220
Ecological Explanations 220
Caring for Young: Parental Investment Theory 220
Mate Competition Theories and the Trivers-Wrangham Model 221
Guarding Mates and Young 222
Gibbon Ecology and Foraging 222
Foraging and Food Patch Size 223
Knowledge of the Territory 223
Parental Investment Theory 227
Types of Investment 227
Territorial Resource Defense 228
Guarding Against Predators 230
Grooming 230
Play 231
Infant Carrying 231
Protection Against Infanticide 231
Is Territorial Defense Mate- or Infant-Guarding? 232
Evidence for Resource Territoriality 234
Mate Competition Theory 235
Asymmetry of Parental Investment and Mate Competition 235
Are Female Mates ‘‘Resources’’? 236
Territoriality and Resource Competition in Males and Females 237
Can Mate-Guarding by Males Promote Monogamy? 238
Unanswered Questions 239
What Is Territorial Behavior? 239
Is Food Limiting? 239
Does Territoriality Increase Feeding Efficiency? 240
Conclusions 240
References 241
The Ecology and Evolution of Hylobatid Communities: Causal and Contextual Factors Underlying Inter- and Intraspecific Variation 247
Introduction 247
Ecological Bases for Variation and Flexibility 250
Distribution and Habitat Characteristics 250
Patterns of Resource Use 251
Examples of Variation Among the Four Hylobatid Genera 252
Hylobates 252
Symphalangus 255
Nomascus 256
Hoolock 257
Comparison Between Genera: Hylobates and Symphalangus 258
From Ecological Variation to Variable Social Organization 259
Human Impacts, Social Organization, and Population Viability 260
Conclusion 264
References 265
Seasonal Home Range Use and Defendability in White-Handed Gibbons (Hylobates lar) in Khao Yai National Park, Thailand 271
Introduction 271
Methods 272
Study Site and Animals 272
Resource Abundance and Rainfall 272
Behavioral Data Collection 273
Data Analysis 273
Results 274
Resource Abundance and Rainfall 274
DPL and Home Range Size 275
Defendability 277
Discussion 277
Variation in DPL 277
Defendability 277
Maximum Number of Defendable Females 278
References 280
Part 5: Mating Systems and Reproduction 282
Monogamy in Mammals: Expanding the Perspective on Hylobatid Mating Systems 283
Introduction 283
Definition of Monogamy 284
Incidence of EPC and EPP 290
Proximate Mechanisms Maintaining Monogamy 293
Ultimate Causation 294
Paternal Care 295
Ecology 298
Infanticide 300
Other Factors 300
Social Structure and Mating Patterns 301
Flexible Grouping and Mating 301
Relatedness Within Groups 304
Broader Social Networks 304
Future Directions 305
Appendix 306
References 309
Monitoring Female Reproductive Status in White-Handed Gibbons (Hylobates lar) Using Fecal Hormone Analysis and Patterns of Genital Skin Swellings 316
Introduction 316
Methods 317
Subjects and Study Sites 317
Fecal Sample Collection 318
Hormone Analysis 319
Genital Swelling Score 319
Results 321
Hormone Profiles and Concentrations in Relation to Female Reproductive Status 321
Changes in Genital Skin Swelling 323
Effect of Storage Procedure on Hormone Concentrations 324
Discussion 324
References 327
Patterns of Infant Care in Wild Siamangs (Symphalangus syndactylus) in Southern Sumatra 329
Introduction 329
Methods 331
Study Site and Animals 331
Behavioral Data Collection and Analysis 332
Results 333
Lactation 333
Female Time Spent Carrying Infants Declined Consistently Over Time 334
Male Time Spent Carrying Infants Varied Between Groups and Individuals 335
Adults Spent Little Time in Social Play with Infants 336
Adults Spent Little Time Grooming Infants 337
Female Time in Close Proximity with Infants Declined Over Time 337
Some Males Spent Most of Their Time in Close Proximity with Older Infants, Even When Not Directly Providing Care 338
Infants in Polyandrous Groups Received Less Male Care than Infants in Monogamous Groups 339
All Study Infants Survived at Least Two Years 339
Discussion 340
References 343
The Social Organization and Mating System of Khao Yai White-Handed Gibbons: 1992-2006 348
Introduction 348
The Flexible Social Organization of Khao Yai Gibbons 351
Mo Singto - Klong E-Tau Study Site 351
Mixed Species Groups 352
Social Groups 354
Data Collection 354
Individual Recognition 355
Field Key to Identify Social Groups and Solitary Individuals 355
Social Organizations in Khao Yai gibbons 357
The Variable Mating System of Khao Yai Gibbons 358
Sexual Behavior Data Collection 358
The Data Set of Adult, Sexually Active Gibbons in the Population 360
Mating Strategies of Khao Yai Females and Males 363
Variable Social Organization and Mating System in Khao Yai Gibbons 364
Multimale Polyandry, Resource Distribution and Territorial/Female Defense 369
Sociosexual Flexibility and Advanced Cognitive Abilities 371
Appendix 1: Multimale Single-Female Groups 373
Appendix 2: Multimale Single-Female Group ‘‘A’’ 375
Appendix 3: Multifemale Single-Male Group ‘‘J’’ 376
Appendix 4: Mixed-Species Multimale Multifemale Group ‘‘E’’ 377
References 378
Part 6: Conservation Biology 386
Status and Conservation of Yellow-Cheeked Crested Gibbons (Nomascus gabriellae) in the Seima Biodiversity Conservation Area, Mondulkiri Province, Cambodia 387
Introduction 387
Methods 388
Study Site 388
Intensive Study Plots 390
Site Population Trends 391
Site Population Estimates 392
Results 394
Intensive Study Plots 394
Timing of Duets 394
Seasonality and Weather Conditions 395
Calling Probability 397
Site Population Estimates and Trends 397
Population Trends 397
Population Estimates from Listening Posts 397
Population Estimates from Line Transects 399
Discussion 399
Vocal Behavior 399
Habitat Requirements 400
Site Population Trends 402
Site Population Estimates 403
References 405
The Distribution and Abundance of Hoolock Gibbons in India 409
Introduction 409
Distribution of the Western Species (H. hoolock) 409
Distribution of the Eastern Species, H. leuconedys 410
Status of Hoolock Gibbons 411
Methods 412
Direct Sightings 412
Indirect Methods 412
Survey Area 413
Estimation of Population Size 413
Results 415
The Distribution of Hoolock Gibbons in Protected Areas 415
Distribution of the Western Species Outside the PAs 416
First Possible Record of the Eastern Species in India 416
Altitudinal Distribution 421
Group Size and Composition 421
Population Estimates for the Western Hoolock Gibbon in the State of Assam 422
Priority Conservation Landscapes in Assam 423
Discussion 423
Appendix 426
References 432
Census of Eastern Hoolock Gibbons (Hoolock leuconedys) in Mahamyaing Wildlife Sanctuary, Sagaing Division, Myanmar 434
Introduction 434
Hoolock Gibbons and Protected Areas in Myanmar 435
Study Area 438
Methods 438
Workshop and Training Exercises 438
Census Methods 440
Mapping and Density Determination 440
Assessment of Forest Condition 442
Results 442
Density of Groups 442
Mean Group Size 444
Gibbon Population Size 444
Forest Canopy in 1-ha Plots 445
Relationship Between Density and Forest Condition 445
Discussion 447
Conclusions and Recommendations 448
References 449
The Population Distribution and Abundance of Siamangs (Symphalangus syndactylus) and Agile Gibbons (Hylobates agilis) in West Central Sumatra, Indonesia 451
Introduction 451
Study Sites and Methods 452
Study Sites 452
Methods 454
Results 455
Detection Distance and Estimated Strip Width (ESW) 455
Maximum Reliable Animal-to-Trail or Perpendicular Distance 455
Maximum Reliable Animal-to-Observer or Direct Distance 455
Siamang and Agile Gibbon Densities 456
The Distribution of Gibbons in and around KSNP 456
Gibbon Group Sizes 457
Biomass of Gibbons 459
Discussion 459
Main Conclusions 461
References 462
Canopy Bridges: An Effective Conservation Tactic for Supporting Gibbon Populations in Forest Fragments 464
Introduction 464
Methods 465
Study Area 465
Hoolock Activity Budgets and Diets at Borajan 467
Hoolock Ranging Behavior at Borajan Prior to the Construction of Canopy Bridges 467
Placement of Canopy Bridges 469
Results 469
Use of Canopy Bridges 469
Discussion 470
References 472
The Role of Reintroduction in Gibbon Conservation: Opportunities and Challenges 473
Introduction 473
Rehabilitation and Reintroduction 475
Global Outlook on Rehabilitation 475
Determining the Success of Reintroduction 476
Primate Case Studies 476
Why Is Rehabilitation of Gibbons so Difficult? 479
Wild vs Rehabilitant Gibbons: The Resource Allocation Dilemma 480
Avoiding the Problems of the Past 481
Behavioral Assessment Prior to Release 482
Selecting a Suitable Site for Release 483
Post-Release Monitoring 485
Discussion 487
Summary and Conclusions 487
References 489
Saving the Small Apes: Conservation Assessment of Gibbon Species at the 2006 Asian Primate Red List Workshop 493
References 495
Index 496