White-handed gibbons (Hylobates lar) alter ranging patterns in response to habitat type

Small apes are often characterized as inhabiting small home ranges and being dependent on evergreen forest due to their dietary specialization on ripe fruits. Yet few primate studies, particularly those with gibbons, have considered intraspecific variations in ranging behaviors in response to local ecological conditions. This study examines Endangered white-handed gibbon (Hylobates lar) ranging patterns in a heterogeneous landscape. We conducted 13 months of behavioral observations on four white-handed gibbon groups living in Huai Kha Khaeng Wildlife Sanctuary in western Thailand, and combine these data with group location and transect-based productivity data. We compare home range area, site fidelity, and microhabitat preferences. Home range (HR) area varied considerably among the four groups (17-61 hectares). Site fidelity was higher in one of the groups with more evergreen forest in the HR (0.72 ± 0.1) than one of the groups with very little evergreen forest in the habitat (0.47 ± 0.07). While groups with more evergreen forest in the HR preferred evergreen forest areas, groups with very little evergreen forest within the HR demonstrated less preference for evergreen forest areas. We conclude that gibbons at this site exhibit a considerable degree of behavioral variation in response to local ecological conditions. These findings suggest that while gibbons exhibit significant ecological flexibility, this flexibility may be limited by habitat type and key food resources.