In the depths of Uganda’s Kibale National Park, an extraordinary and unsettling drama is unfolding.

Deep in the ancient forests of Ngogo, the world’s largest known wild chimpanzee community — once a thriving “empire” of nearly 200 individuals — has torn itself apart.

What began as subtle social tensions in 2015 has escalated into a permanent fission and years of brutal, sustained coalitionary violence between former companions.

Researchers are calling it the first clearly documented case of lethal inter-group conflict following a group fission in a completely unprovisioned wild chimpanzee population.

The landmark study, published April 9, 2026, in Science by primatologist Aaron A. Sandel (University of Texas at Austin) and long-term collaborators including John Mitani, draws on three decades of continuous observations (1995–2025), 24 years of detailed social-network data, 10 years of GPS ranging records, and meticulous demographic tracking.

It reveals a chilling three-phase breakdown:

1. Sudden polarization — On June 24, 2015, a party from the “Western” cluster confronted the “Central” cluster. Grooming, mating, and friendly associations across the two groups plummeted almost overnight.
2. Spatial and social separation — By 2017–2018, the factions stopped sharing core areas and behaving as one community. Long-standing social bonds that had endured for decades simply dissolved.
3. Lethal raids — Starting in 2018, the Western group began launching repeated, coordinated attacks on the Central group. Between 2018 and 2024, researchers documented or strongly inferred at least 24 killings: at least 7 adult males and 17 infants. Many more individuals “disappeared,” suggesting the true death toll is higher. Attacks were often coalitionary — groups overwhelming lone victims — and frequently included infanticide, with infants torn from their mothers. The violence continues into 2026, with the Western faction steadily expanding its dominance.

This is only the second such event ever recorded in wild chimpanzees.

The first was the famous 1970s Gombe “Four-Year War” studied by Jane Goodall — but that involved a population that had been artificially provisioned with food. At Ngogo, the chimps were never fed by humans; the split and the killing were entirely natural.

The exact trigger remains unknown — a point the authors stress. The Ngogo forest is exceptionally rich in fruit and resources, so simple scarcity does not explain it.

Possible contributing factors include:

• The community’s unusually large size, which may have strained the social fabric of a fission-fusion species.
• The deaths of key “bridge” males who had maintained connections between subgroups.
• Leadership changes and intense male-male competition.
• A 2017 respiratory disease outbreak that killed roughly 25 individuals and may have destabilized social networks.

Crucially, there was no single “ideological” divide or external enemy. Chimps who had hunted together, groomed one another, patrolled borders side-by-side, and even mated for years suddenly redefined each other as outsiders once new group identities hardened. Former allies became lethal enemies based purely on which faction they joined.

Chimpanzees share approximately 98.7% of our DNA and display many of the same complex social behaviors: coalition-building, territorial patrols, and lethal inter-group aggression. What makes the Ngogo case so unsettling is that the violence turned inward — directed at former members of the same community rather than neighboring strangers.

Lead author Aaron Sandel cautions against directly labeling it a “civil war,” noting the term carries distinctly human political baggage. Yet the rapid polarization, the erasure of prior relationships, and the sustained coalitionary killing provide a rare, unfiltered window into how large, successful social groups can fracture. Such permanent fissions followed by lethal aggression are estimated to occur only about once every 500 years in any given chimpanzee community.

The Ngogo chimps became global celebrities through the Netflix documentary series Chimp Empire. Their real-life unraveling — from a unified, thriving society to rival factions waging deadly raids — offers no simple moral or easy explanation. It simply shows that even among our closest living relatives, large-scale cooperation is fragile. When group identity overrides individual bonds, yesterday’s friends can become today’s targets with shocking speed and brutality.

Ongoing research at Ngogo continues to track the conflict’s evolution. The drama unfolding in the depths of Kibale National Park is more than a primate soap opera.

It is a raw, unscripted glimpse into the evolutionary roots of tribalism, coalitionary violence, and the conditions under which unity can dissolve into lethal division — lessons that resonate far beyond the forests of Uganda.