1Department of Anthropology, The University of Texas at San Antonio, 2Department of Anthropology, Hunter College of the City University of New York
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Cheek pouches are found ubiquitously among Cercopithecinae species. Unlike other mammals exhibiting this trait (e.g., Rodentia), cercopithecines feed gregariously, suggesting potential for feeding competition as an important selective pressure on this trait. Earlier work (Lambert 2005) demonstrated that Lophocebus albigena and Cercopithecus ascanius in Kibale National Park, Uganda, are more likely to use cheek pouches when consuming fruit, when distance among feeding animals is low (<5m), and with increasing density of feeding neighbors. Here we test the hypothesis that if cheek pouches increase feeding efficiency by reducing competition over contestable foods, then foods higher in energetic or nutrient density are more likely to be cheek-pouched than lower-quality foods. To test this hypothesis, we used standard nutritional methods and near infrared reflectance spectroscopy to measure fat, total non-structural carbohydrates (TNC), crude protein (CP), and neutral detergent fiber (NDF) of foods cheek-pouched by L. albigena and C. ascanius (n = 19) versus immediately swallowed foods (n = 18). Total energy (TE) and non-protein energy (NPE) were calculated with no assumptions of energy yielded from fermentation. Results indicate that the average fat, TNC, CP, and NDF of cheek-pouched foods are 10.2, 39.1, 26.0, 38.5, and non-cheek pouched foods are 11.7, 38.9, 26.6, and 41.5, respectively (% dry matter basis). TE and NPE of cheek-pouched foods were higher (412.0, 307.8) than in non-cheek pouched foods (392.9, 286.5). These data suggest that nutrient density influences oral processing behavior and may shed light on the natural selection of morphology related to competition over contestable foods.
This research was funded by the University of Texas and the National Science Foundation, MRI/SES 0922709.