Just as people drink alcohol to bond, wild chimpanzees have been captured on camera sharing naturally fermented fruit containing alcohol in the wild for the first time.
Researchers from Exeter University noted on the 22nd that "a group of wild chimpanzees in Cantanhez National Park, Guinea-Bissau, was filmed sharing naturally fermented fruit 10 times" in the international journal Current Biology.
Over the years, instances of intoxicated animals have often been introduced. There have been recorded moments of animals stumbling or experiencing hangovers after consuming alcohol that naturally occurs from fermented fruits or honey. In the past, such behavior was considered a mere coincidence of ingesting alcohol.
The Exeter University researchers believed that chimpanzees intentionally hold gatherings to drink. In an analysis published in the same journal last October, it was suggested that various animals are repeatedly exposed to alcohol through fermented fruits or honey, and some intentionally seek it out. It was also found that primates that frequently consume sugar, such as spider monkeys or tree shrews, have evolved alcohol-degrading genes.
Long-term cases of alcohol consumption by chimpanzees have also been reported. From 1995, for 17 years, a village in West Africa, Guinea, observed chimpanzees repeatedly drinking alcohol created from fermented palm sap a total of 51 times. The chimpanzees even exhibited tool-use behavior by chewing leaves and placing them in containers of sap. The alcohol concentration of this palm sap ranged from 3.1% to 6.9%, reaching beer levels.
The recent observations of chimpanzees also support this interpretation. The fruit that the chimpanzees shared was African breadfruit, which naturally fermented and contained alcohol. The alcohol concentration in the fruit was up to 0.61%, significantly lower than beer. However, considering that 60% to 85% of a chimpanzee's diet consists of fruit, they might consume alcohol frequently.
The researchers analyzed that the sharing of fermented fruit among chimpanzees, who typically do not share food, has special significance. Anna Bowland, a researcher at Exeter University's Center for Ecology and Conservation, explained, "When humans drink alcohol, neurotransmitters such as dopamine and endorphins that induce feelings of happiness and relaxation are released in the brain," adding, "For this reason, drinking plays an important role in fostering social bonds." He stated, "Chimpanzees may also experience a similar effect."
Kimberley Hockings, a professor at Exeter University and the corresponding author of the paper, said, "We need to find out if chimpanzees intentionally seek out fruits containing alcohol and how they metabolize alcohol, but this behavior could be an early form of 'party culture,'" suggesting that this culture may have originated from a common ancestor of humans and chimpanzees.
This behavior is sometimes explained by the 'Drunken Monkey Hypothesis.' In 2004, Professor Robert Dudley from the University of California, Berkeley, claimed that "ancestors of humans and monkeys may have used the scent of alcohol from ripe fruits as a cue to find energy-efficient fruits."
Alcohol was, in itself, a favorable signal for survival, and individuals that adapted survived, leading to the evolution of alcohol degradation abilities. In fact, genetic analyses published by researchers from Santa Fe College indicate that alcohol-degrading enzymes (ADH4) rapidly evolved in the ancestors of humans around 10 million years ago.
However, not all animals enjoy alcohol. Some studies suggest that animals may exhibit behavior to regulate 'drinking over the limit.' In experiments where pigs were fed alcohol, the hierarchy among pigs broke down due to intoxication, leading higher-ranking pigs to avoid alcohol. Among the chimpanzees that enjoyed palm alcohol, only one individual who wandered alone while other chimpanzees slept showed excessive drinking. This demonstrates that while alcohol can be a social tool, excessive consumption can lead to social disapproval among animals.
References
Current Biology (2025), https://www.cell.com/current-biology/fulltext/S0960-9822(25)00281-7
Trends in Ecology & Evolution (2024), DOI: https://doi.org/10.1016/j.tree.2024.09.005
Royal Society Open Science (2015), DOI:
https://doi.org/10.1098/rsos.150150
PNAS (2014), DOI: