Ngogo chimpanzee war

The Western and Central factions of chimpanzees have been engaged in a violent conflict in the Ngogo hill region of Kibale National Park, Uganda, since 2015. The conflict involves one-sided killing and violence of the Western group against the Central group. Due to the Ngogo chimpanzees formerly constituting a single peaceful community that violently split apart, this conflict has been described as a "civil war". The New York Times said the conflict was the bloodiest among chimpanzees ever recorded.

This is the second major conflict between chimpanzees observed in primatology, after the Gombe Chimpanzee War of the 1970s in Tanzania. Bloody, brutal attacks and mutilations are part of the conflict.

The chimpanzee community initially consisted of about 200 members living in relative cohesion for 20 years in the densely forested Ngogo region of Kibale National Park. Though various cliques existed, they generally cooperated and defended their territory together from other chimpanzee communities. Social cohesion began to break down, however, after several individuals of the Ngogo community, who had helped to "bridge" the gaps between the cliques, died from disease in 2014. Furthermore, a new alpha male rose in the community, furthering tension.

The large canine teeth of a chimpanzee in Kibale. These are used for dominance displays and fighting.

In 2015, tension among the Ngogo chimpanzees caused low-level violence, with two rival factions emerging. These were described as the Western and Central Ngogo chimpanzees by researchers. By 2018, the division had become complete, and the violence escalated in intensity. The Western faction, despite being numerically inferior, launched coordinated lethal raids into the Central Ngogo chimpanzees' territory, seeking out and killing rival male adults. The raiders often ambushed isolated chimpanzees, overwhelming their targets with numbers. From 2021, the Western raiders also began to target and kill infants. The Western faction's attacks were so successful that the conflict has been described as a "one-sided rout", with the Westerners growing in numbers from 76 to 108, while the population of the Central faction suffered a "stepwise decline".

By 2026, at least 28 chimpanzees, including 19 infants, had been killed in the conflict. All casualties had been of the Central faction.

The Ngogo community was the primary subject of the 2023 Netflix docuseries Chimp Empire. Directed by James Reed and narrated by Mahershala Ali, the series brought global attention to the "Western" and "Central" factions just as their conflict was escalating. Reed also directed the film Rise of the Warrior Apes before the split between the two factions.

In April 2026, major international outlets including the BBC, The New York Times, and The Guardian reported on a definitive study published in Science. These reports highlighted the war as the first rigorously documented "permanent fission" and subsequent civil war in wild chimpanzees without human intervention.

• Killer ape theory, proposed by Raymond Dart in 1953

• Sandel, Aaron A.; et al. (9 April 2026). "Lethal conflict after group fission in wild chimpanzee". Science. 392 (6794): 216–220. doi:10.1126/science.adz4944.

• Sandel, Aaron A.; Watts, David P. (2021). "Lethal Coalitionary Aggression Associated with a Community Fission in Chimpanzees (Pan troglodytes) at Ngogo, Kibale National Park, Uganda". International Journal of Primatology. 42 (1): 26–48. doi:10.1007/s10764-020-00185-0. PMC 8277110.

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