Wild Chimpanzees Wage 'Civil War' in Uganda's Kibale Forest

What Sandel witnessed was the opening act of what researchers now call the first documented "civil war" among wild chimpanzees, a seven-year conflict that would claim at least 24 lives and rewrite our understanding of primate violence. The violence that erupted among the Ngogo chimpanzees represents something unprecedented in the animal kingdom. While chimpanzees have long been known to wage lethal campaigns against outsiders, witnessing a unified group turn on itself mirrors the darkest aspects of human conflict. "Cases where neighbours are killing neighbours is more troubling and, in a way, it gets closer to the human condition," Sandel told The Guardian. "How do we have this seeming contradiction within us where we are able to cooperate, but then also very quickly turn on one another?" By 2018, two distinct factions had crystallized — the western chimps and the central chimps. What followed was systematic violence on a scale rarely seen in nature. The western group launched 24 coordinated attacks over seven years, employing what can only be described as military tactics: flanking maneuvers, strategic retreats, and coordinated assaults. The sophistication of these attacks sets them apart from typical chimpanzee aggression. Rather than spontaneous violence, the western chimps demonstrated planning and coordination that researchers found disturbingly familiar. "These shifting group identities and dynamics that we see in human civil war rarely have a parallel in other animals, but they do have a parallel in the case of chimpanzees," Sandel noted. The morning Sandel first observed the strange behavior in 2015, the group's alpha male had earlier grunted in submission to another chimpanzee — a dramatic shift in the established hierarchy. But the roots of division ran deeper. The deaths of several key older individuals in preceding years had weakened the social fabric that held the massive group together. "Their abrupt death likely weakened connections among the neighbourhoods, which then made the group vulnerable to this polarisation that happened when the alpha change occurred," Sandel explained to The Guardian. The strategic nature of the conflict becomes clear when viewed through the lens of evolutionary fitness. Brian Wood, an evolutionary anthropologist at UCLA who has studied the Ngogo chimpanzees, explained the brutal calculus: "You can increase your Darwinian fitness by increasing your own survival, increasing your reproduction or by decreasing the survival and reproduction of your competitors." This is exactly what the western chimps accomplished. Their systematic campaign devastated the central group, which according to gizmodo, now faces the lowest survival rates ever documented among wild chimpanzees. The violence wasn't random — it was purposeful elimination of reproductive competition. Sylvain Lemoine, a biological anthropologist at Cambridge University, emphasized the profound implications: "Here we have the first thoroughly reported case of what can be qualified as civil warfare in the species. It shows that, even in absence of cultural group markers, social ties and network connectivity are the cement of group cohesion." The Ngogo conflict offers a sobering window into the evolutionary origins of organized violence. The chimpanzees demonstrated capacity for strategic thinking, coalition building, and sustained aggression that researchers once thought unique to humans. They formed alliances, planned attacks, and systematically eliminated rivals — all without language, tools, or cultural institutions. For conservation efforts, the study raises alarming questions. Any human activity that disrupts social cohesion — whether through habitat destruction, climate change, or disease — could trigger more frequent civil conflicts among chimpanzee communities already struggling to survive. The fragility of these groups and the scale of the Ngogo violence point to the risk of losing even more of our closest genetic relatives.