A ‘chimp civil war’ has erupted in Uganda with around 28 apes killed so far in the vicious conflict said to be so rare that it only happens ‘once in every 500 years’
World War Three is here – but not in the way you may expect.
In a jaw-dropping “chimp civil war” so rare scientists say it happens only once every 500 years, a staggering 28 chimpanzees have now died as former friends turned into deadly enemies.
A deadly “civil war” has broken out among the largest group of wild chimpanzees known to scientists, resulting in a permanent split in to two camps. Researchers say it is the first clearly documented permanent fission in wild chimps and the sustained intergroup violence that followed. The study drew on three decades of field observations of the Ngogo chimpanzees in Kibale National Park, Uganda.
Chimps are one of the two closest living relatives to humans, and the Ngogo population has featured in the Netflix documentary series Chimp Empire.
Scientists say their findings, published in the journal Science, show that shifting social ties alone can beak up a once unified group and ignite sustained, deadly conflict among former allies.
The research team estimate such ‘chimp wars’ occur only once every 500 years – making the scale and ferocity of this conflict all the more extraordinary.
They say that, at beginning around 2015, the Ngogo chimpanzee community began to rapidly split from a single cohesive group into two distinct polarised clusters – a social “rupture” that was matched by spatial and reproductive separation.
By 2018, the split was complete and enduring, with no remaining ties between the two groups dubbed “Western” and “Central” by scientists – with separate territories. As the division solidified, aggression between the two groups escalated.
Following the 2018 split, the Western group launched “sustained and coordinated attacks” on Central, marking a clear shift to lethal conflict among former group members. The raids resulted in multiple killings of adult males and, beginning in 2021, expanded to frequent infanticide, averaging several deaths per year.
Between 2018 and 2024, researchers observed or inferred with high confidence seven attacks on adult males and 17 on infants. The research team believe that the true toll of the violence is likely higher than observed, as many individuals disappeared without clear cause, suggesting additional unrecorded attacks – bringing the estimated death toll in this brutal chimp war to 28.
Chimpanzees who had long cooperated and bonded turned on one another after the split, which the scientists say indicates that group identity can be redefined beyond mere familiarity.
Study lead author anthroplogy Professor Aaron Sandel, from The University of Texas at Austin, said: “What’s especially striking is that the chimpanzees are killing former group members. The new group identities are overriding cooperative relationships that had existed for years.”
The research team describe their findings as a “challenge” to the hypothesis that human warfare, including civil war, is driven primarily by cultural markers of group identity such as ethnic or religious differences.
A rare case of prolonged internal violence among chimpanzees documented in the study may have been driven by leadership changes and a breakdown in social cohesion within the group, a primate expert said.
Dr. Tamar Federman, founder and director of Israel’s Monkey Sanctuary, said in an interview that such internal aggression is highly unusual.
“Chimpanzees live in complex social groups based on family ties and very intricate relationships,” she said. While they are often aggressive toward neighbouring groups, violence within the same group is rare because of reconciliation mechanisms that help maintain stability.
Federman said one possible factor behind the case was a change in leadership, noting that dominant individuals play a key role in maintaining group cohesion. “Leaders have a very important role in keeping the group together, and it depends on their character,” she said.
She also pointed to the loss of key individuals who may have acted as intermediaries between subgroups. “There were individuals in the group who had the ability to bridge between different parts of the community,” she said. “Once they were gone, there was no one to connect those individuals, and gradually the subgroups drifted apart.”
Over time, chimpanzees that had once cooperated began to perceive one another as members of rival groups, leading to escalating violence between the factions.