Patterns of coalition formation and social bonds of female bonobos at Wamba, DR Congo (#31)
Although chimpanzees and bonobos are closely related, the roles of females within each species’ society are markedly different. Female bonobos (Pan paniscus) have higher social status compared to female chimpanzees. In chimpanzees, all males are dominant over all females, but the social status of female bonobos is equal to or higher than that of males. Both chimpanzees and bonobos have male-philopatric social systems wherein females are generally not related, however, female bonobos, unlike chimpanzees, establish strong social bonds and form coalitions in attacks against males. One hypothesis purports that frequent supportive behaviour between females is important for acquiring and maintaining high social status. We investigated patterns of female coalition formation and social bonds in a group of wild bonobos at Wamba, Luo Scientific Reserve, DR Congo. We recorded all aggressive interactions during party follows. Coalition was defined as simultaneous aggression directed by two or more individuals against a common target. The direction of agonistic support was recorded when possible. We recorded grooming interactions and proximity to neighbors by scan sampling method to examine the strength of social bond of each dyad. Female-female dyads formed coalitions significantly more frequently than male-male and male-female dyads. All of the targets of female coalition were male(s). Female coalitions were often triggered by a male’s aggressive behaviour. We did not find a significant relationship between strength of social bond and frequency of coalition formation of the dyad. Agonistic support was not significantly reciprocal: older females often supported younger females, but younger seldom supported older. There was no evidence that female bonobos used grooming or proximity to develop alliance partnerships. Coalitions might be a protecting behaviour provided by older females to younger against male harassment.