Deadly Civil War Observed in the World’s Largest Chimpanzee Group

The long-term study of the largest group of wild chimpanzees revealed a clear split as well as violent and sometimes deadly clashes, pushing some scientists to speak of a “civil war”.

Deadly Clashes

Relying on three decades of behavioral and statistical analyses, these new findings indicate a relatively recent shift among the chimpanzees in Kibale National Park in Uganda. Previously tightly knit, the Ngogo community began to fragment in 2015, with members avoiding one another both geographically and reproductively. A scenario potentially linked to the death of several key males in that community a year earlier.

In 2018, two groups of primates emerged, and, unlike other documented cases, the situation has only worsened since. Comprising 83 individuals, the western group began to physically attack the central group (107 individuals), with attacks initially targeting adults and then juveniles starting in 2021. Observations suggest at least three fatalities per year over the period 2018–2024.

“What is particularly striking is that chimpanzees kill former companions,” notes Aaron Sandel, a researcher at the University of Texas and the lead author of the study, published in the journal Science. “The new group identities largely take precedence over the cooperative dynamics that had existed for years.”

Potential Implications for Our Understanding of Human Conflicts

In the 1970s, primatologist Jane Goodall was the first to label the bloody split of a Tanzanian chimpanzee group as a “civil war.” While Sandel acknowledges similarities, he also notes several differences, including the absence of a “cultural system.”

“The fact that relational dynamics alone can drive polarization and deadly conflicts in chimpanzees devoid of speech, ethnicity, or an ideological system also suggests that these markers could be eclipsed by something more fundamental in humans,” the researcher notes.

“Thus, perhaps the small everyday gestures of reconciliation and rapprochement between individuals offer the best chances for peace.”

Previously, a study had shown that even after decades of separation, chimpanzees and bonobos could recognize their old friends.