Inside the chimpanzee 'civil war' that has locked a Ugandan forest in conflict
The clashes, known as the Ngogo conflict, are the focus of a major study published in April in the journal Science, based on three decades of research.
Researchers say the violence grew out of a single chimpanzee community that gradually divided into factions in Kibale National Park, a process that began in the late 1990s and became more pronounced around 2015.
The divide deepened after the birth of the last infant linking the two groups, after which they formed separate social circles and had less and less contact.
Scientists now identify the two sides as a “central group” and a “western group” – with both organising patrols across their territory.
Over time, the bonds within each group grew stronger as relations between them weakened – and the divide turned violent.
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Deadly rivalry
Between 2018 and 2024, the western group carried out 24 attacks on the central group, killing at least seven adults and 17 infants.
Several explanations are being explored, including changes in social ties, competition over food-rich areas and differences in the age of the male chimpanzees.
“There is no definitive answer at this point,” John Mitani, professor emeritus of anthropology at the University of Michigan, told RFI.
The community had reached an unusually large size, which increased competition between individuals as it grew.
New individuals joined the group and changed relationships, while a shift in the dominant male may have contributed to the tensions.
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Endangered species
The conflict adds to the pressure on the survival of chimpanzees, which are listed as endangered by the International Union for Conservation of Nature.
“The fact that they are killing each other certainly does not help us protect them, but other threats are more significant,” Mitani said.
Habitat destruction, disease outbreaks across Africa and hunting in Central and West Africa remain the biggest dangers facing the species.
Researchers say studying how social bonds evolve – and sometimes break down into violence – is uncommon in the animal world and offers valuable insight.
Chimpanzees have long been known to attack and kill neighbouring groups, even when those neighbours were once allies.
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Scientists hope to continue studying the conflict, but funding is uncertain.
“Science is under attack in the country,” Mitani said, referring to the United States. Funding for this kind of research could disappear, he warned, adding that he hopes studies can continue for another 30 years but fears this may not be possible.
Interest in the conflict has grown worldwide since the study was published.
Mitani added: “I challenge anyone to spend time with chimpanzees and not see a part of ourselves in them. It is impossible."
This story was adapted from the original version in French by Juliette Pietraszewski.