A lethal incident during an intergroup encounter in bonobos

Although neighbouring bonobo communities often display tolerance and cooperation when associating together, aggression is also commonly observed during intergroup encounters. Here, we describe an observation at the Kokolopori research site (DRC) in which a coalition of individuals from the neighbouring Kokoalongo community aggressed an adult female from the Ekalakala community. This happened during an ongoing intergroup encounter that had begun earlier as the two communities travelled and foraged together. Shortly after the attack, the 52-day-old infant of the attacked female was carried by two immatures of Kokoalongo. The infant showed signs of distress before being taken by an adult Kokoalongo female, the mother of the immatures. The infant died the following day, and the adult female continued to carry the corpse for two additional days. This unique case of infant acquisition by unrelated out-group individuals immediately following aggression against the mother underscores that bonobo intergroup encounters can have lethal outcomes. These events highlight the complexity and unpredictability of intergroup dynamics in this species.