Uganda Chimp 'Civil War': 24 Attacks Killed 7 Males, 17 Infants
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- Aaron Sandel and colleagues published a study in Science documenting what may be the first observed 'civil war' among wild chimpanzees, with Uganda's Ngogo group — socially cohesive from at least 1995 — splitting into western and central factions by 2018.
- The western chimps launched 24 sustained, coordinated attacks on the central group over seven years, killing at least 7 adult males and 17 infants, with primatologist Sandel first noticing the group's unraveling on a June day in 2015.
- Researchers tied the rupture to a 2015 alpha-male change, the deaths of key older individuals that had weakened social bonds, and a 2017 disease outbreak that likely expedited the split.
- Sylvain Lemoine of the University of Cambridge called it 'the first thoroughly reported case of what can be qualified as civil warfare in the species,' noting that even without cultural group markers, social ties can be 'fragilised' when they rely on few key individuals.
- Brian Wood of UCLA framed the conflict through Darwinian fitness — the western chimps boosted their own survival and reproduction by devastating the central group, which now has the lowest survivorship ever documented in a wild chimpanzee community.
- A similar rupture may have occurred in the 1970s within Jane Goodall's Gombe chimpanzee group in Tanzania, though behavioral understanding at the time was too limited to recognize in-group violence.
- Based on genetic evidence, such chimp 'civil wars' likely only occur every 500 years, but human disruptions like deforestation, climate change, and disease could make these fractures more common — a concern given chimpanzees are threatened with extinction.
Why it matters: The documented attacks, drawing on 30+ years of continuous observation, give scientists the first thoroughly detailed case of within-group lethal violence in wild chimps, deepening the evolutionary parallel to human civil conflict. For conservation, the finding that ruptures appear to be rare but can be triggered by deaths of socially central individuals and disease means that human-driven pressures (deforestation, climate stress, outbreaks) could accelerate splits in already vulnerable populations.
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