# A lethal incident during an intergroup encounter in bonobos

## TL;DR

A lethal incident occurred during a bonobo intergroup encounter, where an infant was taken and later died after its mother was attacked.

## Contribution

This study documents a rare lethal outcome in bonobo intergroup interactions involving infant acquisition and aggression.

## Key findings

- A coalition from one bonobo community aggressed an adult female from another community.
- The infant of the attacked female was taken by unrelated individuals and died the next day.
- The case highlights the lethal and complex nature of bonobo intergroup encounters.

## Abstract

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.

The online version contains supplementary material available at 10.1038/s41598-026-40297-w.