Researchers say it is the first time lethal chimpanzee attacks on gorillas have been recorded (Picture: Loango Chimpanzee Project/Lara M. Southern)

Chimpanzees have been seen ganging up and killing gorillas for the first time ever in the wild as climate change and diminished food supplies threaten their habitat.

Researchers working in the Loango National Park in the west African country of Gabon, witnessed two lethal encounters between the two great ape species in what are considered to be a scientific first.

The team, who published their findings in the journal Nature, said gorillas and chimpanzees usually have a peaceful coexistence – but recently, they have witnessed violent encounters.

Chimpanzees formed ‘coalitions’ to attack the gorillas, said researchers, before killing their infants when they tried to flee.

They suggest the fatal attacks could be due to increased food competition amid dimished fruit supplies – with other Gabon national parks experiencing a ‘fruit famine’ – exacerbated by the effects of climate change.

The researchers, from Osnabrück University and the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, have been observing around 45 chimpanzees in the park since 2014.

They said the relationship between the two great ape species had previously been considered ‘relatively relaxed’.

Researchers film rare instance of chimpanzees attacking gorillas

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Cognitive biologist Simone Pika said: ‘We have regularly observed both species interacting peacefully in foraging trees. 

‘Our colleagues from Congo even witnessed playful interactions between the two great ape species.’

But in 2019, the team witnessed the chimps’ first violent attack on the gorillas – something that has never been documented, says the report.

The two encounters, which typically lasted for around an hour, saw the chimpanzees form ‘coalitions’, attack the outnumbered gorillas, and kill their infants when they got separated.

Describing the first attack, lead report author Lara M. Southern, said: ‘At first, we only noticed screams of chimpanzees and thought we were observing a typical encounter between individuals of neighboring chimpanzee communities.

Two adult males of the Rekambo community in Gabon checking the area (Picture: LCP/Lara M. Southern)
Footage captured the lethal attacks between the two great ape species (Picture: LCP/Lara M. Southern)

‘But then, we heard chest beats, a display characteristic for gorillas, and realized that the chimpanzees had encountered a group of five gorillas.’

Around 18 chimps surrounded five gorillas – a silverback, three females and an infant – in a thicket, before the male charged at a female chimp and knocked her into the air.

At least 10 chimpanzees surrounded the silverback and ‘repeatedly jumped down on and hit him whilst screaming and barking’, read the report.

When the gorilla infant became separated from the fleeing adults, it was beaten and killed by the chimps.

The second lethal encounter happened after a group of 27 chimps attacked around seven gorillas, including infants, in the trees.

After the silverback fled, several chimps tried to pull the infant gorilla from its mother’s arms. It was killed after they were separated.

Researchers said they are only just beginning to understand the effects of food competition between the species and need to investigate further.

Tobias Deschner, primatologist at the Max Planck Institute for Evolutionary Anthropology, said: ‘It could be that sharing of food resources by chimpanzees, gorillas and forest elephants in the Loango National Park results in increased competition and sometimes even in lethal interactions between the two great ape species.’

The team added that the the increased competition may ‘may also be caused by the more recent phenomenon of climate change and a collapse in fruit availability as observed in other tropical forests in Gabon’.

Mr Deschner said: ‘Our observations provide the first evidence that the presence of chimpanzees can have a lethal impact on gorillas. We now want to investigate the factors triggering these surprisingly aggressive interactions.’

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