SOCIAL BONDS AND THE COHERENCE OF MOUNTAIN BABOON TROOPS

Abstract

Abstract Female chacma baboons (Papio cynocephalus ursinus) in the Drakensberg mountains, experiencing neither predation nor within-group competition, structure their social relationships with other females in order to sustain reciprocated grooming (Henzi et al., 1997b). To do so, they cap, where time constraints demand, the size of their grooming cliques. From this we have assumed that the social orientation of mountain baboon females is primarily towards other females and that fission is a consequence of the increasing differentiation of cliques, leading to one or a few females following a male 'friend' when he departs. An alternative argument (Barton et al., 1996) is that, where predation or within-group competition do not occur, neither should female-bonded groups. In this view, females under such conditions should be 'cross-bonded' to males, each group male associating with a few females in the manner of hamadryas baboons (P. c. hamadryas). We test this prediction of 'cross-bonding' at both troop and individual level and find no evidence to support it. We then present data on fission events which argue for fission in the Drakensberg being due to the departure of small one-male units. However, the data do not support, unequivocally, the proposal that females leave with male 'friends'. They do, however, always leave with a male who has fathered at least one of their non-adult offspring.