1Anthropology, University of Wisconsin-Madison, 2Physiology, University of the Witwatersrand, 3Psychology, University of Lethbridge, 4ABEERU, University of South Africa, 5Anatomy, Physiology and Human Biology, University of Western Australia
April 14, 2016 2:30, A 602
A strong case has been made that the primary function of grooming is hygienic. Nevertheless, its persistence in the absence of hygienic demand, and its obvious tactical importance to members of primate groups, underpins the view that grooming has become uncoupled from its utilitarian objectives and is now principally of social benefit. We identify improved thermoregulatory function as a further benefit of grooming and so broaden the utilitarian function of this behavior. Deriving the maximum thermal benefits from the pelt requires that it be kept clean. Grooming is an obvious way to achieve this. In a series of wind-tunnel experiments, we measured the heat transfer characteristics of vervet monkey (Chlorocebus pygerythrus) pelts in groomed and ungroomed conditions. Our data indicate that simulated grooming improves the thermal performance of the pelt, offering significantly better insulation than ungroomed pelts (t=-12.80, df=6, P<0.001) and, hence, better protection from the cold. Groomed pelts also experienced significantly lower radiant heat loads compared to ungroomed pelts (t=6.56, df=6, P<0.001), providing improved protection from the heat. Such thermal benefits therefore furnish grooming with an additional practical value to which its social use is anchored. Given the link between thermoregulatory ability and energy expenditure, our findings suggest that grooming for thermal benefits may be an important explanatory variable in the relationship between levels of sociability and individual fitness.
Research funded by: Claude-Leon Fellowship, ASAB and Faculty research grants to R.M; NSERC Discovery grants to S.P.H. and L.B; NRF grants to S.P.H; Canada Research Chair Program to LB.