Lethal attacks by groups of chimpanzees on gorillas in the wild have been documented for the first time. Experts say that this proves that the closest relatives of humans can also possess a danger to those species that are a little further genetically removed.
Before that encounter, the great apes were generally relaxed around each other in Loango National Park in Gabon. This unusual observation between the chimpanzees and gorillas could yield insights into early human evolution.
The observation is documented in the paper titled "Lethal coalitionary attacks of chimpanzees (Pan troglodytes troglodytes) on gorillas (Gorilla gorilla gorilla) in the wild," which was published in Scientific Reports.
Chimpanzees vs. Gorillas
Researchers from Osnabruck University and the Max Planck Institute for Evolutionary Anthropology in Leipzig have been studying the behavior of around 45 chimpanzees in Loango National Park with a special group focus on the relationships within and between chimpanzee troops.
"Interactions between chimpanzees and gorillas have so far been considered as relatively relaxed," says Professor Simone Pika said in a news release. "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 recalled that the first attack happened. They noticed screams of chimpanzees and heard chest beats, which is a display characteristic of gorillas. They realized that the chimpanzees had encountered a group of gorillas in a fight.
Sky News reported that the first encounter lasted for 52 minutes and the party of 27 chimpanzees formed a group to attack a group of gorillas. The second encounter lasted for 72 minutes, involving 27 chimpanzees that attacked a group of seven gorillas.
In the paper, they wrote that the first event happened after a territorial patrol in which males made a deep incursion into the neighboring territory of a group of chimpanzees. The second encounter happened at the start of a suspected territorial boundary patrol.
Unfortunately, both first and second encounters resulted in one dead baby gorilla each and seven injured chimpanzees in the first encounter. The team found that the dead baby gorilla in the second encounter was almost entirely consumed by one adult chimpanzee female.
The team noted that the aggressors of both encounters were male chimpanzees.
Why Did Chimpanzees Attack the Gorillas?
The team investigated what caused the lethal attacks from the chimpanzees. They pointed out that these encounters happened during the seasons when the diet of the two great ape species overlap heavily. Although during other times of the year, both chimpanzees and gorillas were friendly with each other.
The authors suspect that the feud between the two species is no coincidence, IFL Science reported. Fruit trees in Gabon have been producing lesser fruit in recent years due to climate change. The team thinks that the likely reason for the encounter could be competition for food sources rather than direct predation as observed on the dead infant gorillas, although the second one might have been eaten.
Pika said that their team is still in the early stage of understanding the competition on interactions between chips and gorillas in Loango. The observations had opened new doors for exploration and discovery on human's closest living relatives. Perhaps, studying further about these lethal attacks could give insights into the early human evolution.