Deep in Kibale National Park, one of the world’s largest communities of wild chimpanzees has descended into a rare and deadly internal conflict, shocking scientists and reshaping understanding of animal behaviour.
What was once a tightly bonded group of about 200 chimpanzees known as the Ngogo community has, over the past decade, split into two rival factions that are now engaged in sustained, organised violence against each other.
Researchers say the conflict, which began around 2015, represents the first clearly documented case of a single chimpanzee community breaking apart and waging prolonged war-like attacks on itself.
“This is the first clearly documented example of a group of wild chimpanzees splitting into two separate factions, with one launching a series of coordinated attacks against the other,” scientists noted in findings published in the journal Science.
For decades, the Ngogo chimpanzees lived in relative harmony, grooming, feeding, and defending their territory together. But that cohesion began to unravel following the deaths of key individuals and shifts in leadership, weakening the social bonds that held the group together. By 2018, the split had hardened into two camps commonly referred to as the Western and Central factions—marking the beginning of violent territorial raids.
Primatologist Aaron Sandel described the brutality of the attacks, saying, “Biting, pounding the victim with their hands, dragging them, kicking them… mostly adult males, but sometimes adult females participate in the attacks.”
The violence has since escalated into coordinated ambushes, with chimpanzees patrolling borders, isolating rivals and killing them behaviour that closely resembles organised conflict in humans.
At least 28 chimpanzees, including infants have been confirmed killed, though researchers believe the true number may be higher as some individuals have simply disappeared. Strikingly, many of the attackers and victims once lived side by side.
“It is hard… to wrap my head around the fact that yesterday’s friend turned into today’s foe,” said primatologist John Mitani. “Males in the two groups grew up with each other… and cooperated and collaborated.”
Scientists are still investigating the exact trigger of the split, but several factors are believed to have contributed. Researchers point to the unusually large size of the group, which may have increased competition for food and mates, as well as the death of key “bridge” individuals who helped maintain unity. Changes in dominance and leadership are also thought to have played a role, alongside possible environmental pressures that may have strained resources.
“Maybe they were no longer facing such an abundance of resources and became too large a group to maintain cohesion,” Mitani suggested.
Other researchers say the conflict highlights the fragility of social systems, even among highly intelligent animals. When groups begin to fragment, and individuals stop interacting regularly, the sense of shared identity can erode, making violence more likely.
While experts caution against drawing direct comparisons with human wars, the parallels are striking. The chimpanzees have demonstrated organised raids, shifting alliances, and targeted attacks patterns that mirror aspects of human conflict and suggest that the roots of such behaviour may run deep in evolutionary history.
More than a decade after the first signs of division, the Ngogo conflict remains ongoing, making it one of the longest and most closely observed cases of sustained violence in wild primates. For scientists, it remains both a mystery and a powerful insight into how even the strongest societies can fracture with consequences that echo far beyond the forest.
