Evidence for an important social role of allogrooming in a platyrrhine primate.

Allogrooming behaviour was analysed in a wild group of tufted capuchin monkeys, Cebus apellain Iguazu National Park, Argentina. Evidence is provided that allogrooming in this platyrrhine species serves an important social function, as has been demonstrated for catarrhine primates. Using ad libitum sampling, 654 grooming sessions were recorded during 740 contact hours with one group. Seasonal variation was found in daily time allocation to allogrooming and the mean duration and reciprocity of sessions. Individual dominance rank was an important determinant of grooming relationships. The dominant male and female were the most actively involved in grooming. Among adults, dominant individuals were involved in more sessions than were subordinate individuals. The females maintained strong grooming relationships with each other and tended to reciprocate more within sessions than did males. Oestrous females engaged in more grooming bouts with adult males than did non-oestrous females. Females with newborn infants were attractive social partners for the remaining members of the group. A social function for allogrooming in Cebus is indicated by the close relationship between allogrooming, the social system and coalition formation, and by the changes in quantity and direction of grooming in response to oestrous behaviour and to the birth of infants.