The 85th Annual Meeting of the American Association of Physical Anthropologists (2016)

Plastic digestive response to variation in dietary nutrient density and energetic status


1Anthropology, University of Colorado - Boulder, 2Anthropology, Hunter College of CUNY, 3New York Consortium in Evolutionary Primatology

April 16, 2016 , Atrium Ballroom A/B Add to calendar

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.