April 11, 2026, 10:19 pm
Earlier, they held hands with each other; now, they raise them to kill one of their own. Ngogo chimpanzees, the world’s largest known group of wild chimpanzees who were once a close-knit community have been engaged in an eight-year-long vicious ‘civil war’ as per a recent research published in the journal Science. The group has burst into a fatal conflict between two sects with one killing their former group mates on the other side, revealed the study carried out over a period of 30 years. The event is rare, shocking and surprising as scientists estimate that chimpanzee communities split on average, every 500 years.Lead author of the study Aaron Sandel, an anthropologist from the University of Texas in US and co-director of the Ngogo Chimpanzee Project said chimpanzees are “very territorial” and have “hostile interactions with those from the other groups.”However, over the past several decades, the nearly 200 Ngogo chimpanzees in Uganda’s Kibale National Park had been living in harmony. They groomed each other, shared food and moved in units, but now they are divided into two sets, known to researchers as Western and Central.
In a conversation with the Science podcast, Sandel said he first noticed them polarising in 2015 when the Western group ran away and was chased by the Central members. Calling the animals “melodramatic” he shared that they could be “screaming and chasing” one moment and grooming and cooperating the other. However, after this particular dispute, researchers observed a six-week avoidance period between the two sets with interactions dying down. When they did interact, the instances were “more intense” and “more aggressive.”By 2018, two distinct groups emerged and the Western group, which is smaller yet more aggressive, began attacking the Central chimpanzees. Through the 24 attacks since the split, at least 7 adult males and 17 infants have been killed by the Western chimps, while the researchers believe the actual number of deaths to be higher.
In a conversation with National Geographic, Sandel described the instance of the death of a 36-year-old chimp named Basie. He woke up in his nest surrounded by other dozing chimpanzees, swung between branches for some time, and snacked on ripe figs for a meal. But soon, a patrol group of about 13 adult chimps from the Western faction arrived near sunset. Three adults surrounded Basie and 10 attacked him on the ground, piling and biting. “In the moment, I felt like a war correspondent. I wanted to be there, I wanted to witness it, to document it, and try to understand what’s going on,” said Sandel. “Once I’d written up my notes and shared them with colleagues, that’s when the emotions hit me.”Basie’s death was the second casualty in the new war, but it was the one that made researchers question how a group connected so closely could be pushed to kill each other brutally.
Why the sudden turnaround? The researchers believe numerous factors such as group size, subsequent competition for resources and ‘male-male’ competition for reproduction, could be some factors to blame. However, scientists believe three events to be the catalysts. It is the presence of adult leaders who kept the groups bonded socially.
Similar to their ancestral cousins, chimpanzees have had instances of civil wars before and this is not the first. In the mid-1970s, the late primatologist Jane Goodall witnessed a four-year war, caused by a lethal split between a chimp community at Tanzania’s Gombe Stream National Park. In her memoir, ‘Through a Window’ Goodall described the years as the “darkest” in Gombe’s history. “For several years I struggled to come to terms with … a dark side to their nature.”During Goodall’s time and Sandel’s observations, some things remained common. Scientists documented a series of social disturbances that preceded the conflict. These included a change in leadership structure, the death of key individuals that connected chimp neighbourhoods and a disease outbreak.“When you stop coming together, it’s possible to stop seeing yourselves as part of the same group,” said co-author Jacob Negrey, a primatologist at the University of Arizona. “That can lead to violent consequences in a shockingly short period of time.”
“The war is ongoing— it’s not finished yet,” said Negrey. Chimpanzees are one of humanity’s closest living relatives and this civil war between animals who are not divided on the ideals of religion, politics, ethnicity or other ideals, has made scientists question just how war between humans conspires. “Relational dynamics may play a larger causal role in human conflict than often assumed”, they added.
