Animals regularly consume alcohol in the wild, new study finds

Recent research has revealed that many animals naturally consume alcohol, challenging the notion that humans are unique in drinking behavior. A study published in Trends in Ecology & Evolution has found that animals have been consuming ethanol for hundreds of years, challenging the assumption that such consumption is uncommon and accidental.

The research team, led by behavioral ecologist Kimberley Hockings from the University of Exeter, analyzed available scientific literature to understand ethanol prevalence and its role in the natural world. They argued that since ethanol is naturally present in almost all ecosystems, most animals that eat fruits and nectar likely consume it habitually. "We are moving away from this anthropocentric view that ethanol is simply something that humans use," said Hockings, a behavioral ecologist and lead author from the University of Exeter.

Ethanol is a naturally occurring substance in fruit, resulting from the fermentation of fruit sugars by yeast, and is present in almost every environment, with higher concentrations in humid tropical regions. Naturally fermented fruits usually reach only 1% to 2% alcohol by volume (ABV), but concentrations as high as 10.2% ABV have been observed. For example, palm fruits in Panama have been found to exceed 10% ABV, similar to wine. By comparison, most alcoholic drinks that humans consume range from 3% ABV (a light beer) to 50% ABV (distilled spirits).

"Most fruit-eating and nectar-sipping animals likely consume ethanol, which may be a regular part of their diet," according to the researchers. Many animals have adapted to efficiently metabolize ethanol. Animals that eat alcoholic fruit often have genes that help them break down ethanol without getting drunk, a trait they have harbored for millions of years. Primates, birds, and small mammals called treeshrews have adapted to efficiently metabolize ethanol, particularly those that enjoy fruit and nectar.

Matthew Carrigan, a molecular ecologist and coauthor from the College of Central Florida, said, "From an ecological perspective, it is not advantageous to be inebriated as you're climbing around in the trees or surrounded by predators at night—that's a recipe for not having your genes passed on." He added, "It's the opposite of humans, who want to get drunk but actually don't want the calories; from the non-human perspective, animals want the calories but not the intoxication."

There are many anecdotes of wild animals behaving as if they were "drunk" after eating fermented fruits, including elephants and baboons in Botswana consuming marula fruit, as well as primates like capuchin monkeys and chimpanzees eating alcoholic fruit. In 1974, the film "The Funny World of Animals" from South Africa showed various species, including elephants and baboons, reaching for the partially fermented fruits of the Marula tree and moving unsteadily, although experts question whether this behavior is due to enjoyment of the fallen fruit.

Observations of staggering hedgehogs, climbing-impaired squirrels, or uncoordinated chimpanzees have been reported. However, biologists estimate that elephants would need to eat more than 400 times the extreme amounts of marula fruit consumed to be visibly intoxicated. Wild chimpanzees in southeastern Guinea have been observed repeatedly ingesting the alcoholic sap of raffia palms. Spider monkeys on Barro Colorado Island, Panama, are partial to ethanol-laden yellow mombin fruit, which contains between 1% and 2.5% alcohol.

Fruit flies intentionally lay their eggs in substances that contain ethanol, which protects their eggs from parasites. Fruit fly larvae increase their intake of ethanol when they are parasitized by wasps, which makes their internal environment less hospitable to invaders. This behavior of increased ethanol consumption in fruit fly larvae is an example of self-medicating in the wild. Ethanol could have medicinal benefits for animals, as seen in insects like fruit flies. Researchers say that ethanol consumption could bring several benefits to wild animals, including being a source of calories and potential medicinal benefits.

The aromatic compounds produced during fermentation could guide animals toward food sources. "The odorous compounds may lead them to sweet food that provides many calories," the researchers noted. However, it is unclear whether animals intentionally consume ethanol for its own sake or for the mere pleasure of consuming it, and whether they intentionally seek out overripe fruits to experience the effects of alcohol needs to be researched more closely.

"From a cognitive standpoint, the idea has been proposed that ethanol may activate the endorphin and dopamine system, generating feelings of relaxation that could have benefits in terms of sociability," said Anna Bowland, a behavioral ecologist and first author from the University of Exeter. She added, "To test that, we'd really need to know if ethanol is producing a physiological response in the wild."

Researchers emphasized that they don't know if animals seek out intoxication. The idea that animals avoid getting drunk is a hypothesis, not a well-founded conclusion. There are still several unanswered questions about the significance of ethanol consumption to wild animals, including whether they intentionally seek out overripe fruits to experience the effects of alcohol. More research is needed to understand the impact of ethanol consumption on animal physiology and evolution, including its behavioral and social implications, as well as its effects on social lives, family dynamics, and evolutionary adaptations.

In future research, Kimberley Hockings' team plans to investigate the behavioral and social implications of ethanol consumption in primates. The team also plans to examine more closely the enzymes involved in alcohol metabolism. "One of our next steps is to test whether animals in the wild prefer ethanol-containing food or eat it only when ethanol levels are too low to detect or unfermented fruit is hard to find," said Matthew Carrigan.

The findings of this research have been published in Trends in Ecology & Evolution.

Sources: Popular Science, La Razón, La Voz, Der Standard, The Hill, The Guardian, WION, Telegraaf

This article was written in collaboration with generative AI company Alchemiq