An adult male chimpanzee bares his teeth in Kibale National Park, Uganda.image: IMAGO / imagebroker
Science News
How do neighbors become enemies? A study reconstructs in detail how a group of chimpanzees split into two hostile camps. We humans can learn a lot from this.
April 9, 2026, 8:00 p.mApr 9, 2026, 8:44 p.m
Polarization, mutual avoidance, ultimately deadly violence: For the first time, researchers have documented over decades how a chimpanzee community splits into two camps, which then fight each other. The detailed reconstruction of this escalation in the journal “Science” also sheds light on the emergence of wars in humans – and their avoidance.
Since 1995, researchers in Uganda’s Kibale National Park have been observing around 200 animals By far the largest group of wild common chimpanzees (Pan troglodytes). For comparison: All other known groups contain – in some cases significantly – fewer than 100 animals. Roman Wittig from the research organization CNRS in Lyon, who was not involved in the study, gives a reason for the unprecedented group size: “From 1999 to 2010, the Ngogo chimpanzees almost completely wiped out a neighboring group and integrated many of the remaining females.”
Alliances, friendships and hierarchies before discord
By 2015, the team led by Aaron Sandel from the University of Texas at Austin recorded changing alliances, friendships and hierarchies in the group – as in other chimpanzee groups. The team observed the first indication of a rift in 2015: two camps met in the center of the territory – one from the western area, the other from the central area.
The western chimpanzees fled, pursued by the others. “A six-week phase of avoidance followed,” writes the team. This led to increasing polarization, and later both groups used separate areas. The violence then escalated, with all attacks observed coming from the smaller group.
In seven cases the attacked male was killed, The next escalation level followed in 2021: Now young chimpanzees were also targeted. As of 2024, western chimpanzees killed 17 young. In addition, 14 other chimpanzees from the central group disappeared.
Permanent splits in chimpanzee groups are very rare
According to Sandel and colleagues, genetic studies indicate that permanent splits in chimpanzee groups are extremely rare. In a “Science” commentary, James Brooks from the German Primate Center in Göttingen reports on a split in a community of bonobos (Pan paniscus) almost 50 years ago in the Democratic Republic of Congo – but without escalating violence: both bonobo groups still coexist today. (sda/dpa)