Chimpanzee ‘Civil War’ in Uganda After Group Split, Scientists Unsure Why

A long-term study of wild chimpanzees in Uganda has found a rare and serious conflict inside one large group. The violence started after the group split into two rival sides in Kibale National Park.

The study was published in Science and is based on many years of observation of the Ngogo chimpanzee community, which once had around 200 members.

A Group Splits Into Two

The Ngogo chimpanzees, part of the species Pan troglodytes, lived together for many years. They often formed small sub-groups but still shared the same area peacefully.

Over time, stronger cliques started forming, especially among adult males. Around 2015, the large group slowly split into two separate factions. By 2018, most cooperation had ended, and the two sides rarely interacted peacefully.

Violence Increases

After the split, the situation became dangerous. Researchers recorded:

• Attacks between the two groups
• Killings of adult males
• Infanticide starting in 2021

Some chimpanzees also disappeared, so the real number of deaths may be higher. Violent clashes have continued even after the study period, with reports up to 2025 and 2026.

Possible Reasons

Scientists say there is no single reason for this conflict, but several factors may have played a role:

• The large size of the group
• Competition for food and territory
• Changes in leadership
• Disease outbreaks

In 2017, a respiratory disease killed several chimpanzees. This event, along with leadership changes, may have weakened the group’s unity.

Why It Is Called “Civil War”

Lead researcher Aaron Sandel said the term “civil war” is used carefully. Chimpanzees do not have politics like humans, but this conflict shows what happens when a close social group breaks apart.

Similar behavior was seen in studies by Jane Goodall, but such long and deadly conflict is very rare.

What This Study Shows

Experts say this study helps us understand how animal groups can change quickly under stress. It also shows that even intelligent animals can experience serious internal conflict.

However, scientists warn that this should not be directly compared to human wars. Other related species, like bonobos, are known to be more peaceful.