1Department of Biological Sciences, Dartmouth College, 2Department of Anthropology, Dartmouth College
Saturday 8:45-9:00, Galleria South
Tarsiers are exemplary faunivores, consuming a wide array of invertebrate and vertebrate prey. The anatomy and behavior associated with this faunivorous diet has attracted much attention in part because it can inform competing hypotheses focused on primate origins. Yet the role of interspecific foraging competition is seldom addressed. Throughout their distribution, tarsiers appear to compete with scops owls (Otus bakkamoena) for resources. The functional similarities of the species include extremely large and forward-facing eyes, acute directional hearing for detecting prey, a flexible cervical spine, specialized feeding morphology for immobilizing prey, and efficient sit-and-wait ambush tactics. Accordingly, Niemitz (1985, 2010) proposed a high degree of food competition between tarsiers and scops owls. Here we report on the isotopic ecology of these sympatric faunivores to test the hypothesis that dietary overlap under nocturnal conditions has favored convergent visual adaptations. We measured the δ13C and δ15N of hair samples from tarsiers and feather fragments from scops owls with overlapping distributions in Borneo and the Philippines. Carbon isotopes vary as function of canopy cover, and thus understory habitat use, whereas nitrogen isotopes vary as a function of trophic level and can distinguish subtle differences in the proportion of insect and vertebrate prey. The findings from this study are expected to inform hypotheses not only on how the visual systems of vertebrate predators evolve under dim light conditions, but also on how dietary overlap and competition for insect resources might have shaped the functional anatomy and evolution of early primates.
This study was funded by Sigma Xi and the David and Lucile Packard Foundation.