Stories dating back centuries tell humorous and often cautionary tales involving animal intoxication occurring after they consume fermented fruits. While many of these stories have long been considered myths, now an international team of researchers proposes that ethanol—commonly found in ripe, fermented fruits—is likely a regular part of the diets of fruit and nectar-consuming animals. Their findings were published in the journal Trends in Ecology and Evolution.
The team, led by behavioral ecologist Kimberley Hockings of the University of Exeter, argues that we must broaden our understanding of alcohol beyond the human context.
“We’re moving away from this anthropocentric view that ethanol is just something that humans use,” Hockings said in a recent statement. “It’s much more abundant in the natural world than we previously thought, and most animals that eat sugary fruits are going to be exposed to some level of ethanol.”
How Nature Makes Alcohol
Ethanol became widely available approximately 100 million years ago when flowering plants developed sugary nectars and fruits. Naturally occurring yeasts ferment these sugars, creating ethanol. Today, it’s found across ecosystems, with higher concentrations observed in tropical regions. In some cases, naturally, fermented fruits can reach alcohol concentrations as high as 10.2% alcohol by volume (ABV), like certain overripe palm fruits found in Panama.
Interestingly, animals already possessed genes that could metabolize ethanol before yeasts evolved to produce it. Over time, animals like primates and treeshrews have adapted these genes, enabling them to process ethanol efficiently. From an evolutionary perspective, this adaptation makes sense: inebriation would be dangerous for animals living in trees or avoiding predators.
“It is not advantageous to be inebriated as you’re climbing around in the trees or surrounded by predators at night,” Matthew Carrigan, a molecular ecologist at the College of Central Florida, said.
This means that for these animals, alcohol provides a source of calories rather than the buzz humans seek.
Why Animals Consume Alcohol
While researchers are still trying to determine if animals purposefully seek out alcohol, some experts have uncovered some potential benefits that may encourage its consumption. For one, ethanol-rich fruits can provide valuable calories. Fermentation also produces distinct odorous compounds that may help animals locate ripe fruits, although it’s unclear if they can detect ethanol specifically.
Ethanol might also offer medicinal advantages. In one example, fruit flies lay their eggs in ethanol-rich environments to protect against parasites. Additionally, fruit fly larvae increase their ethanol intake when parasitized by wasps, suggesting that ethanol may help reduce parasite load.
On the social side, researchers are considering how ethanol might affect animal interactions.
“Ethanol can trigger the endorphin and dopamine system, which leads to feelings of relaxation that could have benefits in terms of sociality,” says Anna Bowland, a behavioral ecologist and first author of the study.
However, it remains unclear if wild animals experience the same physiological response to ethanol as humans.
Which Animals Are Known for Consuming Alcohol?
Certain animals are more inclined to consume alcohol due to natural availability in their habitats, occasional human interactions, or physiological tolerance levels. Elephants, for example, occasionally binge on fermented fruits or locally brewed alcohol, sometimes leading to dramatic encounters.
Primates, such as monkeys, have also been documented enjoying alcoholic beverages, especially in areas frequented by humans. Shrews and bats are particularly interesting as they regularly consume fermented nectar in the wild without apparent intoxication. At the same time, other animals like bears, moose, and squirrels can show clear signs of inebriation when consuming overripe, fermented fruits.
While these interactions can range from humorous to dangerous, researchers continue to study a wide range of animals and their interactions with alcoholic sources to understand the animals’ motivations further.
Still More Questions
The ecological significance of ethanol consumption in animals remains an open investigation. Hockings and her team are especially interested in how ethanol affects animal behavior and social dynamics in the wild. Their future research aims to explore these effects more deeply, focusing on primates to understand better the evolution of alcohol metabolism and its role in animal societies.
Kenna Hughes-Castleberry is the Science Communicator at JILA (a world-leading physics research institute) and a science writer at The Debrief. Follow and connect with her on X or contact her via email at kenna@thedebrief.org