The Ngogo chimpanzee community in Uganda’s Kibale National Park engaged in the first documented civil war among wild nonhuman primates that occurred without human interference. According to an academic study published by Science in April 2026, at least 28 chimpanzees have died since 2018 from six years of lethal raids by the Western faction against the Central faction, marking an unprecedented intragroup confrontation.
Lead author and UT Austin primatologist Aaron Sandel identifies the Ngogo conflict as a definitive civil war. This conclusion stems from three decades of continuous research initiated in 1995. Recalling the early violence in 2015, University of Michigan’s John Mitani described the outbreaks as a chaotic scene of screams and chases.
Leadership crisis and the Jackson fracture
For decades, this community of 200 individuals maintained a unified territory and social alliances. The polarization began in 2015 when a new alpha male, Jackson, ousted the established leader. This hierarchical instability immediately spiked aggression between the males of the two emerging factions.
In 2017, a lethal outbreak of human metapneumovirus — likely introduced by researchers or tourists — ravaged the community, claiming the lives of 25 chimpanzees. This tragedy did more than reduce their numbers; it wiped out the vital mediators who held the groups together, shattering the community’s last hope for unity. By 2018, the rupture was absolute: The Western faction retreated toward the park’s edge, leaving the Central faction alone in the forest’s original heart.
Infanticide tactics and collective violence
The Western faction’s raids have systematically targeted the rival faction’s infants since 2021. Attackers carried out 24 raids against the Central group. These attacks resulted in the deaths of seven adult males and 17 infants between 2018 and 2024. The aggressors employed collective violence through groups of 10 individuals. They held down and beat their victims to death.
Overpopulation and food competition triggered the initial split. When the individuals who served as social bridges disappeared, the group lost its final ties of cohesion. This structural collapse fundamentally changed how the chimpanzees perceived one another, turning former relatives into hostile enemies.
The Uganda Wildlife Authority (UWA) has been protecting the Kibale ecosystem uninterruptedly for three decades. Following the 2017 epidemic, researchers imposed a mandatory seven-day quarantine for any human entering the forest. These sanitary measures are reducing the viral load among the chimpanzees. Meanwhile, scientists maintain the policy of not intervening in the attacks.
Historical precedent in Gombe National Park
Between 1974 and 1978, Jane Goodall documented the Gombe Four-Year War in Tanzania, the only recorded civil war among chimpanzees. The conflict began when a single community split into the Kasakela and Kahama factions. Over four years, the Kasakela group systematically exterminated every male in the separatist Kahama group, highlighting the lethal potential of primate social fractures.
Several critics argued that the war occurred because Goodall provided bananas to the chimpanzees, and the artificial food supply created unnatural competition that altered their behavior. The main difference with Ngogo lies in the absence of human interference through food provision, confirming the natural character of the aggression. Experts warned of new attacks during the early months of 2026, suggesting that the Central faction faces imminent disappearance.