1Anthropology, University of Colorado - Boulder, 2Anthropology, Hunter College of CUNY, 3New York Consortium in Evolutionary Primatology
April 16, 2016 , Atrium Ballroom A/B
Arguments for Cercopithecinae evolutionary and ecological success often center on adaptations selected for during periods of climate change, when shortages of energy exacerbated feeding competition. Although phenotypic adjustment is an à priori expectation under these circumstances, few specifics regarding physiological plasticity in response to variation in food availability/quality are known. We evaluate plasticity in digestion and measure how mean retention times (MRT) vary as a function of diets differing in nutrient density (ND) and digestible energy. Baseline caloric requirements of Macaca mulatta (9 male; 9 female) was determined for 3 months and animals habituated to 1 of 3 dietary treatments: D1 = High ND (3.8kcal/g Dry Matter [DM]) fed at 70% caloric requirement; D2 = High ND fed at 100% caloric requirement; D3 = Low ND (2.8kcal/g DM) fed at 100% caloric requirements. Animals were administered 40 inert markers over two feeding trials and all fecal samples screened for markers (6 days). A Mixed Effects model (R v 2.9) indicated no significant effect of caloric restriction on MRT (X2=0.0001; P>0.9) when fed high ND diets (D1 MRT 64.2h SD=19; D2 MRT 69.2h SD=13.11). However, low ND (D3 vs D1+D2) reduced MRT dramatically (MRT 26.6h; X2=19.711, P>0.001). Results suggest that cercopithecines adjust MRT in response to ND rather than caloric intake: as food quality declined, MRT shortened, presumably to maximize food intake rate. This suggests greater selective pressure for digestive plasticity in response to nutritional balance rather than energetic status.