DefinePK

Abstract

ABSTRACT Grooming behaviours have a functional role, keeping animals clean. However, the social dimension of grooming has attracted more attention in research. According to biological market theory, grooming can be traded as currency for other commodities or exchanged for reciprocal grooming. Based on this theory we can roughly rank females, according to the reciprocity index of grooming. Yunnan snub-nosed monkeys (Rhinopithecus bieti) are a polygynous species, and the female individuals have to compete for access to a single male in their unit to get pregnant. We collected data on grooming in the mating and birthing seasons. We suggest that females directed more grooming to males in the mating season than in the birthing season, especially ‘non-mother’ females. After the mating season, female individuals redirected their attention to focus on babies in the birthing season, and correspondingly the proportion of grooming given to babies was higher than in the mating season. For ‘mother’ females, there was no significant difference in the grooming given to males between the two seasons. Another remarkable phenomenon was that R. bieti individuals groomed the anogenital area more frequently before the mating season than on the two other periods, and compared with the birthing season, the rate of grooming on the anogenital region was also higher in the mating season. In conclusion, females made use of grooming as a currency to exchange for valuable resources, and during the mating season grooming was traded for copulation. Meanwhile, grooming is essential to maintain a complex social network for the female R. bieti.