Chimpanzees in Uganda are in a ‘civil war,’ and researchers are unsure how it will end

Aaron Sandel can pinpoint when it all started.

co-director Ngogo Chimpanzee Project I was observing a group monkeys On June 24, 2015, he noticed that the chimpanzees suddenly became silent in Uganda’s Kibale National Park, where the project is located. Some began to grimace; It was a facial expression that showed they were nervous. Others began touching each other for reassurance.

More chimpanzees could be heard in the distance, but this was nothing unusual. For at least two decades, Ngogo chimpanzees had formed a group. a pretty big communityThe harmonious coexistence of more than 200 individuals has reached its peak.

But when Sandel saw more chimpanzees showing up, the primates did not regroup with the typical loud screaming, patting their backs and holding hands. Instead, some chimpanzees started running, leaving Sandel and fellow researcher John Mitani confused. The once close-knit group of chimpanzees suddenly began to treat each other like strangers.

“I asked John, ‘What’s going on?’ I remember asking. He said, ‘I don’t know,'” Sandel recalls. “And it struck me, too, because he’s one of the world’s experts on chimpanzees. He’d been studying these chimpanzees for twenty years. But we were seeing something new.”

Sandel sees the day when the large group began to organize into two groups, now known as Western and Central chimpanzees, as the beginning of the split. “I think this planted the seeds of polarization that led to the collapse of the group,” said Sandel, who is also an associate professor of anthropology at the University of Texas at Austin.

Since then, violence between the two groups has increased; raids resulted in fatal attacks on adults and infants several times a year. Now a new study documents a rare event that researchers consider a “civil war” in chimpanzees, estimated to occur every 500 years and only observed once before.

findingsThe research, published April 9 in the journal Science, provides a unique perspective on how shifting social bonds can lead to conflict between groups of nonhuman animals, a phenomenon that is difficult to understand in the wild but may still highlight the role of interpersonal relationships in conflicts between humans, researchers say.

‘Civil war’ among primates

Chimpanzees are naturally territorial. On a regular basis, a group of individuals (usually men) come together and perform. patrols controlling rival group members near borders. If they find any stranger from outside, they will attack and sometimes kill the other chimpanzee.

The Ngogo Chimpanzee Project was founded in 1995 by John Mitani, now professor emeritus of anthropology at the University of Michigan. Experts have been debating all along whether the unusually large group of chimpanzees should split up. Researchers initially did not believe they would do this, as there were no signs of fracture at the time. Lead author Sandel said the forest was also well equipped to support the large group because the protected area they occupied was rich in food and trees.

But after that day in 2015, chimpanzees quickly divided themselves into Western and Central clusters; These clusters are named after the territories divided by chimpanzees. They now patrol to keep each other away.

Western chimpanzees are more aggressive than Central chimpanzees; The group conducted up to 15 patrols every four months between 2018 and 2024, killing an average of one adult and two infants per year from the Central group, according to the study. Western chimpanzees appear to have an advantage over Central chimpanzees, possibly due to their early adaptation, Sandel said.

The first fatal attack occurred in 2018 on a young adult male named Errol. The chimpanzee was attacked by five Western adult males feeding in a fig tree near the middle of the Ngogo region. Errol was about 10 years old when Sandel joined the project in 2012 and was the subject of his thesis.

Sandel said that before the division, chimpanzees were able to cross the entire territory, but now their territory has been divided in two, with the border closer to the center. He added that the boundary is always changing, and it appears that Western chimpanzees are currently managing to push the boundary eastward.

The second fatal attack in 2019 occurred while Sandel and other researchers were observing several chimpanzees feeding in a large tree. A group of Western chimpanzees rushed over, surprising them and causing chaos to ensue.

While Western chimpanzees climbed trees, Central chimpanzees dispersed. Unaware at the time that the group had been permanently split, the researchers watched as three adult males cornered and attacked a chimpanzee from the Central group. Sandel immediately recognized the victim as Basie. 33 year old member From the Ngogo group.

As the chimpanzees swarmed over him, adult female chimpanzee Aretha tried to protect Basie from the attackers, but Basie was quickly pushed away. When the chimpanzees finally relented, Basie returned home, accompanied by a male chimpanzee named BF, over 50 years old, who had apparently been close to Basie over the years. Basie died the next day.

According to the study, the death toll in the Central cluster so far includes seven adult and 17 baby chimpanzees; Also missing are 14 chimpanzees who may have been victims of deadly attacks.

“It’s absolutely sad to see these chimpanzees killing each other, especially chimpanzees that I know so well, being killed. Sometimes I feel like a war correspondent,” Sandel said. He added that while the researchers are currently studying acts of violence, they are also getting opportunities to study chimpanzees’ other emotions, such as empathy, as well as acts of heroism and friendship.

“I feel like we’re touching on something that’s at the core of being a chimpanzee,” Sandel said. “By seeing these relationships change so dramatically, we gain an understanding of chimpanzees that we wouldn’t normally get through observation alone, opening a window into their minds and emotions.”

What can chimpanzees teach us about war?

late primatologist Jane Goodall He observed the first known chimpanzee ‘civil war’ during his research on chimpanzees in Tanzania’s Gombe National Park in the 1970s. During the darkest period in Gombe’s history, which Goodall and his colleagues called the “Four Years’ War,” chimpanzees that grew up together were suddenly splitting up and killing each other.

Although Ngogo researchers aren’t sure why war broke out among their group, they have a few theories. Similar to Goodall’s chimpanzee group, the community experienced a change in dominance hierarchy, which immediately affected the chimpanzees’ interactions with others, Sandel said. Ngogo researchers suggest that the deaths of large numbers of chimpanzees for unknown reasons in 2014, the change in the alpha male in 2015, and the respiratory epidemic in 2017 led to the weakening of social bonds and the fragmentation of the group.

“Careful documentation of this rare event with long-term data over many years provides invaluable insight into intergroup conflict,” said Katie Slocombe, a comparative psychologist and professor of psychology at the University of York in the United Kingdom. Slocombe was not involved in the new study.

“This was the largest known chimpanzee community, so maintaining effective relationships with so many individuals may have become challenging for community members,” Slocombe said in an email. He added that this new information about the chimpanzee group could contribute to our understanding of how interpersonal relationships and other environmental factors contribute to human conflict.

The study’s authors argued that chimpanzees do not have cultural markers, such as religion or ethnicity, that are largely thought to drive human warfare, and that studying chimpanzees could be useful for learning more about our own species and the role of relational dynamics in human warfare, Sandel said.

Sandel added that there are two possible possibilities for how the war will end. First, the Central group will be better organized to defend its territory and borders against the Western group, and lethal attacks will occur less frequently. The second possibility is similar to what Goodall observed in Gombe: the stronger group will kill all members of the weaker group.

“There is a third event that seems extremely unlikely, but there could be some reunification between the groups,” Sandel said. “From everything I know about chimpanzee behavior, I don’t see how this is possible, but at the same time, I know enough about chimpanzees to never be that surprised at what they can do.”

Taylor Nicioli is a freelance journalist based in New York.

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