Kibale chimpanzees in re-current big fights

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Two rival chimpanzee groups in Kibale National Park are engaged in what is being called a ‘civil war. “After years of tension, the world’s largest wild chimpanzee group has fractured into two rival factions, battling each other for eight years, according to researchers.

It is not clear exactly why the once close-knit community of Ngogo chimpanzees at Kibale are at loggerheads, but since 2018, the scientists have recorded 24 killings, including 17 infants, according to the latest study.

"These were chimps that would hold hands," lead author Aaron Sandel says, "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.

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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.

A community of around 200 chimpanzees living in Uganda's Kibale National Park has fractured into two warring factions, with one group launching a years-long campaign of lethal attacks against the other.

The Ngogo chimpanzees have been studied continuously for three decades, but in recent years, scientists have watched as a violent split unfolded in slow motion.

From around 2015, what had been a single cohesive group began to polarise. Social ties frayed, neighbourhoods within the community hardened into distinct factions, and shared territory became a contested border. By 2018, the break was permanent.

What followed was remarkable – and troubling. The smaller of the two groups – the Western chimps – began making targeted raids into the territory of the larger Central group. Over the next six years, they killed at least seven adult males and 17 infants.

And that figure is likely an undercount. A further 14 adolescent and adult Central males disappeared or died unexpectedly between 2021 and 2024, none of whom showed any signs of illness beforehand.

Today, the Western group has surpassed its rival to become the dominant force in the jungle.

The findings, published in Science, have prompted comparisons to civil war. Unlike inter-group conflict between strangers, what happened at Ngogo involved former companions, groomers, and long-term social partners turning on one another.

The scientists behind the study estimate such conflict occurs only once every 500 years.