By Jon Cohen (science.org)

Chimpanzees regularly fight viciously over food, mates, and rank, but only rarely do these brawls spill over into a broader civil war. Now, a study tracing 30 years of chimp behavior in Kibale National Park in Uganda reveals how and why such internecine violence erupts. The study, described today in Science, shows how in chimps—and perhaps humans—tensions in once-peaceful groups can grow into deadly violence, even without resource shortages or cultural divisions to fuel them.

“This study demonstrates beautifully the analytical power gained through sustained research,” says Roman Wittig, a primatologist at the Max Planck Institute for Evolutionary Anthropology who studies chimps in Ivory Coast’s Taï National Park. Primatologist Richard Wrangham, who in 1987 kicked off his own study of a neighboring chimp community in Kibale, says the new study is “terrific” and both clarifies motivations for human warfare and spotlights how we differ from one of our closest relatives.

Researchers in 1995 began to study the Kibale chimpanzees in a densely forested area called Ngogo, carefully tracking their movements and social networks. At one point, there were more than 200 individuals, the largest community of chimps ever studied. They lived in two main social groups, designated as Central and Western, that peacefully intermingled, with many cross-group matings.

But on a fateful day in June 2015, some chimps from the two clusters met up near the center of their territories, and the Central chimps chased the Western ones away. Afterward the two clusters avoided each other, and reproduction between the groups stopped. Western males regularly began to patrol in Central territory, looking to expand their domain.

Read the full article: https://www.science.org/content/article/what-plunged-these-chimps-civil-war-new-study-traces-breakdown

Infos about the study “Civil war among wild chimpanzees” – https://www.science.org/doi/10.1126/science.aeg6719