Study reveals that female chimpanzees team up to retaliate against male aggression

In 2003 and 2004, Dr Newton-Fisher studied a community of eight adult male and 21 adult female East African chimpanzees in Budongo Forest, Uganda. He observed that the females were subject to frequent aggression by adult males that was at times severe. However, between October and December 2003, he observed females retaliating in direct response to this aggression.

In almost half of his observed retaliations, the females formed coalitions of two to six members and retaliated with vocalisations, threatening gestures, and direct pursuit. Females were also witnessed physically attacking males that were aggressive to other females, and on several occasions were seen to solicit the support they then received.

Until Dr Newton-Fisher’s study, there have been no reports of female cooperative retaliation to such aggression from the wild despite more than four decades of detailed behavioural study across a number of populations and its occurrence among captive female chimpanzees.

Dr Newton-Fisher said, ‘Female wild chimpanzees form coalitions as a strategy to counter male aggression. This strategy may reduce the incidence, severity or effectiveness of male aggression. Why they do this is still unclear but the levels and forms of cooperative retaliation that I observed among the chimpanzees in Budongo Forest may be because these females tend to be more gregarious than in other populations of East African chimpanzees, as other work studying the same population has suggested.

‘Also, the absence of similar reports from wild populations suggests that females may be able to form coalitions only under appropriate conditions – such as ecology, demography or local tradition. If groups of females are able to spend time together because of the way food is distributed in the habitat, then they are ‘on-hand’ to provide support and form coalitions. Whether they do this simply because they are present when another female is threatened by a male, or because they have previously formed a supportive relationship, are questions for future research.’

Dr Newton-Fisher’s report is published in the International Journal of Primatology.