Overview
- The peer-reviewed study, published Thursday in Science, reports a permanent split in Uganda’s Ngogo chimp community and a years-long campaign of lethal raids.
- Once a single group, the chimpanzees polarized between 2015 and 2018 into Western and Central factions, with the Western group killing at least seven adult males and 17 infants from 2018 to 2024.
- Researchers say the toll is likely higher because many healthy Central chimpanzees disappeared without explanation, and they document coordinated gang attacks and frequent infanticide starting in 2021.
- The team cites possible contributors—including an unusually large group size near 200, the 2014 deaths of key adult males, a 2015 alpha-male change, and a 2017 respiratory outbreak—while stressing the cause remains unresolved.
- Permanent fissions in chimpanzees are estimated to be extremely rare, roughly once every 500 years, and the long-term Ngogo record offers a rare window into how shifting relationships can fuel collective violence among close human relatives.