Gabon: Fatal attacks by chimpanzees on gorillas observed for the first time

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Chimpanzee in Uganda (archive image)

Photo: Yannick Tylle / Getty Images

The dispute was widely audible.

"At first we only heard the screams of the chimpanzees and thought we were observing a typical encounter between neighboring chimpanzee communities," says Lara Southern, a doctoral student at the University of Osnabrück.

"But then we heard chest drumming, an impressive behavior that is characteristic of gorillas, and found that the chimpanzees had encountered a group of five gorillas."

Southern describes a scene that took place in the Loango National Park in Gabon in 2019, where chimpanzees and gorillas coexist. Together with Simone Pika and Tobias Deschner from the Max Planck Institute for Evolutionary Anthropology in Leipzig, she reports in the specialist magazine "Scientific Reports" on a total of two clashes between the great ape species with an outcome that has never been described: both times a group of chimpanzees attacked Gorillas together and killed one cub each.

It is well known that chimpanzees can sometimes be extremely brutal with other animals.

In rare cases, they even attack members of their own group.

For example, a case from Senegal is documented in which chimpanzees killed a former leader and even desecrated his body.

Encounters between chimpanzees and gorillas have so far not been known to be problematic.

Southern and her colleagues now report in detail how the fatal encounter between the chimpanzee and gorilla groups in Gabon developed: The chimpanzees initially formed a coalition and attacked the gorillas.

In both cases they were clearly in the majority: In both attacks, their groups consisted of 27 members each, who attacked five and seven gorillas respectively.

The silverback and the females of the gorilla groups defended themselves and their children during the attacks.

Although the gorillas managed to escape, the chimpanzees snatched a total of two children from their mothers and killed them.

A total of two young animals thus died.

Food may be scarce

"Interactions between chimpanzees and gorillas have so far been considered relaxed," says co-author Simone Pika: "We regularly observed both species peacefully in forage trees and our colleagues from the Congo even witnessed games between chimpanzees and gorillas." Fatal encounters between neither of the great ape species has yet been documented.

The researchers have several possible explanations for the observed aggressions.

They say: Kills between different species can be interpreted either as hunting behavior or as competition for food.

It is possible that the coexistence of chimpanzees, gorillas and forest elephants in Loango National Park has increased competition for food.

Perhaps there is also a decline in the productivity of the rainforest, as has been observed in other national parks in Gabon.

Climate change, for example, is responsible for this.

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