Bonobos are often depicted as relatively peaceful. This view derives, in part, from studies conducted at Wamba during the past 50 years. Prior and ongoing field research there indicates that members from different groups typically affiliate instead of behaving aggressively to each other. Here I report some observations that indicate this has not always been the case. An explanation for these observations remains elusive and highlights the fact that our understanding of bonobos continues to be far from complete.

Exerpt

[...] Some researchers hypothesize that several factors, including female social dominance, reduced male mating competition, and the consistent formation of large parties that are similar in size contribute to the lack of intergroup aggression in bonobos. Female dispersal leading to female kin residing in neighboring groups is also likely to mitigate intergroup aggression. The aggressive intergroup encounters that I observed between bonobos, however, were reminiscent of those that occur between chimpanzees. In chimpanzees, the number of participants play a decisive role in determining the outcome of intergroup encounters; the group with the most individuals typically dominates its opponent. In 1991, P group, consisting of 45 individuals, was much larger than E1 with only 30 bonobos, and members of the former always chased away those in the latter. By contrast, the number of bonobos in each group were more balanced during Idani’s earlier research; E1 group had 33 individuals while P group contained 39. In 1991 when there was a clear asymmetry in the number of individuals between groups, bonobos in E1 group also avoided those in P when they heard the latter calling in the distance, and more than once, E1 bonobos fell silent when P group was nearby. Finally, bonobos at Wamba are no longer provisioned, but as is the case with chimpanzees, who were fed during the early years of research at Gombe and Mahale National Parks, Tanzania, it is unclear whether and how artificial feeding influenced their behavior and the observations described here. [...]