1Department of Human Evolutionary Biology, Harvard University, 2Department of Evolutionary Anthropology, Duke University
April 16, 2016 , Atrium Ballroom A/B
Primates expend significantly less energy than would be expected for a placental mammal of their body size, yet they show no deviation from other mammals in basal metabolic rates. Although previous explanations for this trend have focused on primates’ slow life histories lowering their energy expenditure, we propose that another important variable may be primates’ increased ability to escape from predators in arboreal environments, relative to ground-dwelling mammals. Much of mammalian predator escape is dependent upon anaerobic burst speed, which scales positively with body temperature. Thus, we predict that body temperature positively correlates with evolutionary dependence on predator escape bursts.
We used energy expenditure and BMR data from the Pontzer et al. 2014 PNAS dataset, data on body temperature and other physiological functions from the International Species Information System’s database of Physiological Reference Values, and ecological data from the PanTHERIA database.
Arboreal mammals had lower body temperatures than terrestrial ones (F[1,273]=7.614; p=0.00618), providing support for the decrease in probable predator escape energy expenditure among arboreal primates. Primates also had lower body temperatures than expected for their relative ratio of total energy expended to BMR (t[21.519]=3.2902; p=0.003409), providing further evidence of primates’ exceptionally low body temperatures among mammals. With lower than expected body temperatures, primates should have lower than expected BMRs, which they do not. Among the metabolic functions that may account for this deficit in BMR are not only the energetic demands of maintaining growth over a slow life history, but also those of maintaining strong immune function throughout life.
CMM was supported by the NSF Graduate Research Fellowhip Program under Grant No. DGE-1144152.