1Department of Anatomy, Midwestern University, 2Departments of Biology and Anthropology, Penn State University, Altoona, 3Curator of Primates, Philadelphia Zoo
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Maximum Ingested Bite Size (Vb) is the volume of the largest bite of food an animal ingests whole. Our ongoing studies have demonstrated that Vb scales isometrically with body mass in a broad sample of strepsirrhines. To begin to test whether this trend pertains to all primates, we collected Vb on three anthropoid species at the Philadelphia Zoo (Hylobates lar, Trachypithecus obscurus, and Saimiri sciureus). Foods from the captive diet were selected for their range of material properties and all could be cut into relatively homogeneous cubes. Material properties data were collected on all foods for comparison with our previous work. We hypothesized that although small anthropoids might have similar Vb to small strepsirrhines, the largest anthropoids would have relatively small Vb compared to the largest strepsirrhines. The competing hypothesis, isometry of Vb, implies unrealistically large foods for the largest living primates. Despite the small species sample for anthropoids, we found clear separation between the strepsirrhine and anthropoid data. All three species of anthropoids had small Vb for their body size, especially the large-bodied species. This might be due to a lack of very large, three-dimensional foods in primate environments, thus reducing the advantage of gape adaptations at larger body sizes. Currently we are gathering data on several more species of captive anthropoids to test the universality of this trend.
This study was funded by NSF grant BCS-0962692.