Chimpanzees in Uganda Engaged in Ongoing 'Civil War', Researchers Claim

Fri Apr 10 2026 21:26:15 GMT+0000 (Coordinated Universal Time)

A new study reveals the Ngogo chimpanzees in Uganda have been in a violent conflict for the past eight years, raising questions about social dynamics and the roots of conflict.

Scientists report that a split in the Ngogo chimpanzees, the world's largest group of wild chimpanzees, has led to lethal aggression and killings over resources and dominance. The study underscores the potential parallels between chimpanzee behavior and human conflict, suggesting social dynamics may play a bigger role than previously thought. Researchers observed at least 24 killings since 2018, including many infants, with several factors identified as triggers for this rise in violence.

The world's largest known group of wild chimpanzees has split and been locked in a vicious civil war for the last eight years, according to researchers.

It is not clear exactly why the once close-knit community of Ngogo chimpanzees at Uganda's Kibale National Park are at loggerheads, but since 2018 the scientists have recorded 24 killings, including 17 infants.

These were chimps that would hold hands, lead author Aaron Sandel said. Now they're trying to kill each other. The study, published in the journal Science, says the intensity and duration of the violence may inform how early human conflict developed.

Sandel, an anthropologist from the University of Texas in the US, and co-director of the Ngogo Chimpanzee Project, says chimpanzees are very territorial, and have hostile interactions with those from other groups. [It's] like a fear of strangers, he told the Science podcast.

But over several decades, Sandel said the nearly 200 Ngogo chimpanzees had lived in harmony. They were divided into two sets - known to researchers as Western and Central - but they had existed overall as a cohesive group.

Sandel said he first noticed them polarising in June 2015, when the Western chimpanzees ran away and were chased by the Central group. Chimpanzees are sort of melodramatic, he said, explaining that following arguments there would ordinarily be screaming and chasing and then later, they would grooming and co-operating.

However, after the 2015 dispute, the researchers observed that the duration of avoidance periods between the two sets increased, leading to infrequent and intense aggressive interactions. Following their final separation in 2018, members of the Western group started attacking the Central chimpanzees.

In the 24 targeted attacks recorded, at least seven adult males and 17 infants from the Central chimps have been killed, though researchers believe the actual number of deaths could be higher. Factors such as group size, competition for resources, and male-male competition for mating opportunities may play a role, but three specific events are considered likely catalysts:

The deaths of five adult males and one adult female in 2014, potentially disrupting social networks.
A change in the alpha male in 2015, following which aggression increased.
A respiratory epidemic in 2017 that killed 25 chimpanzees, also severing connections between the groups.

Sandel and his colleagues argue that their findings prompt a reevaluation of human conflict and warfare. The Ngogo chimpanzees represent a striking example of how social networks can dissolve leading to violent behavior based solely on group affiliation.

As James Brooks, a researcher at the German Primate Center pointed out, this study serves as a reminder of the dangers that group divisions pose to human societies, urging a learning perspective from studying the group dynamics of other species, be it in war or peace.