Study Documents Rare Chimpanzee Split and Years of Lethal Raids

Overview

• The Science study, published Thursday, reports the first clearly documented permanent split of the Ngogo chimpanzee community in Uganda.
• Social ties ruptured on June 24, 2015, and by 2018 Western and Central factions held separate territories and mating pools, a sharp break from chimp societies that usually mix and reunite.
• From 2018 to 2024 the smaller Western group carried out coordinated raids that killed at least seven adult Central males and 17 infants, with disappearances suggesting the toll is higher.
• The violence has been one-sided as Western numbers rose from 76 to 108 while the Central group shrank, raising concern among researchers that Central’s viability is at risk.
• Researchers drew on about 30 years of observations plus GPS and demographic records and point to an oversized community, the loss of key “bridge” males, an alpha change, and disease as likely triggers, with genetic evidence indicating such fissions are rare, roughly once every 500 years.