Intra- and Inter-Sexual Aggression by Bonobos in the Context of Mating

Previous work on bonobos (Pan paniscus) has focused on the role of aggression in the context of conflict resolution in captive groups. This study investigates events of aggressive behaviour of wild bonobos to evaluate its significance in the context of mating. Temporal association (15 minutes) between aggression and mating was used to assume functional relationship. The proportion of events that were found to be related to mating activity was highest for female-female aggression followed by male-male, male-female, and female-male aggression. The results suggest that intrasexual aggression is used to manipulate the mating success of competitors: Males competed for access to oestrus females, aggression between males was high on mating days, and aggressors had higher mating rates than targets. Harassment by females disturbed mating attempts of targets, the rate of aggression increased with the number of oestrous females per party and following harassment, aggressors tended to mate more often with the male partner of the target female. Unlike intrasexual aggression, support for the predicted functions of inter-sexual aggression in the context of mating was weak. Aggression by males against females was rare and was almost never followed by mating between aggressor and target. Female aggression against males occurred frequently but appeared to be independent of mating behaviour. The results did not support the female-defence alliance hypothesis (Parish, 1996). However, when males and females engaged in close association, the rate of aggression tended to be lower and rates of mating were higher than during control periods. We suggest that male intersexual aggression is incompatible with intersexual bonding and propose that the potential benefits that males derive from affiliative long-term association with females prevent males from being aggressive against females.