title: Thermal consequences of increased pelt loft infer an additional utilitarian function for grooming.
abstract: 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 previously unexplored benefit of grooming and so broaden our understanding of the utilitarian function of this behavior. Deriving the maximum thermal benefits from the pelt requires that it be kept clean and that the loft of the pelt is maintained (i.e., greater pelt depth), both of which can be achieved by grooming. In a series of wind-tunnel experiments, we measured the heat transfer characteristics of vervet monkey (Chlorocebus pygerythrus) pelts in the presence and absence of backcombing, which we used as a proxy for grooming. Our data indicate that backcombed pelts have improved thermal performance, offering significantly better insulation than flattened pelts and, hence, better protection from the cold. Backcombed pelts also had significantly lower radiant heat loads compared to flattened pelts, providing improved protection from radiant 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. Am. J. Primatol. 78:456-461, 2016. © 2015 Wiley Periodicals, Inc.
authors.affiliation: Brain Function Research Group, School of Physiology, University of the Witwatersrand, Johannesburg, Gauteng, South Africa.|Department of Anthropology, University of Wisconsin-Madison, Madison, Wisconsin.
authors.forename: Richard
authors.initials: R
authors.lastname: McFarland
authors.affiliation: Department of Psychology, University of Lethbridge, Lethbridge, Alberta, Canada.|Applied Behavioural Ecology and Ecosystems Research Unit, University of South Africa, Pretoria, Gauteng, South Africa.
authors.forename: S Peter
authors.initials: SP
authors.lastname: Henzi
authors.affiliation: Brain Function Research Group, School of Physiology, University of the Witwatersrand, Johannesburg, Gauteng, South Africa.|Department of Psychology, University of Lethbridge, Lethbridge, Alberta, Canada.
authors.forename: Louise
authors.initials: L
authors.lastname: Barrett
authors.affiliation: School of Anatomy, Physiology and Human Biology, University of Western Australia, Crawley, Perth, Australia.
authors.forename: Anuradha
authors.initials: A
authors.lastname: Wanigaratne
authors.affiliation: National Metrology Institute of South Africa, Pretoria, Gauteng, South Africa.
authors.forename: Elsie
authors.initials: E
authors.lastname: Coetzee
authors.affiliation: Brain Function Research Group, School of Physiology, University of the Witwatersrand, Johannesburg, Gauteng, South Africa.
authors.forename: Andrea
authors.initials: A
authors.lastname: Fuller
authors.affiliation: Brain Function Research Group, School of Physiology, University of the Witwatersrand, Johannesburg, Gauteng, South Africa.
authors.forename: Robyn S
authors.initials: RS
authors.lastname: Hetem
authors.affiliation: Brain Function Research Group, School of Physiology, University of the Witwatersrand, Johannesburg, Gauteng, South Africa.|School of Anatomy, Physiology and Human Biology, University of Western Australia, Crawley, Perth, Australia.
authors.forename: Duncan
authors.initials: D
authors.lastname: Mitchell
authors.affiliation: Brain Function Research Group, School of Physiology, University of the Witwatersrand, Johannesburg, Gauteng, South Africa.|School of Anatomy, Physiology and Human Biology, University of Western Australia, Crawley, Perth, Australia.
authors.forename: Shane K
authors.initials: SK
authors.lastname: Maloney
keywords: fitness; heat transfer; pelt characteristics; sociability; thermoregulation; vervet monkeys