Department of Anthropology, University of California, Davis, Graduate Group in Ecology, University of California, Davis, Animal Behavior Graduate Group, University of California, Davis
Saturday 2:15-2:30, Ballroom A
The high diversity of vertebrate frugivores in many tropical forests raises the possibility that interspecific competition for fruit may play an important role in structuring communities of tropical vertebrates. An important step in assessing the role of such competition is to characterize the extent of niche overlap among sympatric species and determine whether they are able to mitigate the potential for competition by habitat switching or utilization of distinct foods during periods of fruit scarcity. I present an analysis of vertebrate feeding observations gathered over a five-year period along a series of 14 established transect routes in seven forest types at Gunung Palung National Park, West Kalimantan, Indonesia. These independent, unbiased observations permitted a quantitative assessment of the degree of niche overlap among 24 families encompassing five mammalian and seven avian Orders. Concurrent monthly phenological monitoring in all seven forest types enabled examination of the effects of spatial and temporal variation in food availability on patterns of niche overlap. There were high degrees of overlap among many taxa, especially hornbills, primates, and squirrels. Generally, the diets of vertebrate frugivores diverged significantly during periods of low fruit availability (with interesting exceptions), indicating that some, but not all, taxa reduced the potential for inter-specific competition during periods when resources were scare. In contrast, habitat switching (e.g., by orangutans and hornbills) did not affect general patterns of dietary overlap. These results provide insights into the ecological forces currently influencing communities of tropical frugivores, and inform hypotheses about the evolution of diverse mammal communities.
This study was kindly supported by the University of California, Davis, the Hellman Foundation, the Orangutan Conservancy, and the Leakey Foundation.