How many times have you seen videos of “drunk animals” on social media? Elephants staggering after eating fermented fruit, monkeys looking like they’ve had too much to drink, birds flying in a crazy way. Yet, the reality is much more complex and fascinating than these viral anecdotes.
In recent years, scientific research has revealed that ethanol consumption among animals is surprisingly widespread (from bees to chimpanzees) but not for the reasons you might imagine. The “drunk” animals we see in videos are probably more a figment of our imagination than a real phenomenon. Evolution, in fact, has equipped many species with extraordinary alcohol-metabolizing systems which allow them to feed on fermented fruit without staggering like us humans after a few too many drinks.
We're not the only ones toasting
For decades, many believed that alcohol consumption was unique to humans, a peculiarity of our species linked to our ability to deliberately produce fermented beverages. This belief is rapidly collapsing under the weight of scientific evidence.
The reality is that Many animals regularly consume naturally occurring ethanol, and these are by no means isolated cases or anomalous behaviors.
The list of species that ingest alcohol in the wild continues to grow with each new research. vinegar flies, long associated with alcohol because of their tendency to breed on fermented fruits, are just the tip of the iceberg. Insects like bees and butterflies, birds like Hummingbirds and Waxwings, mammals such as the feather-tailed tupai and pygmy lorises, and even non-human primates, including chimpanzee (one of our closest evolutionary relatives), have all been documented consuming substances containing ethanol.
Nature is an open-air bar
Ethanol is surprisingly common in the natural environment. Contrary to popular perception that associates it mainly with man-made beverages, it is found naturally in many fruits, nectars and saps. The process is as simple as it is inevitable: when yeasts, including Saccharomyces cerevisiae (the famous brewer's yeast), colonize fruits rich in sugars, ferment these sugars producing ethanol.
This natural fermentation process transforms forests and jungles into open-air bars. Studies conducted in various parts of the world (from Panama to Costa Rica, from Singapore to Israel to Finland) have documented the presence of ethanol in wild fruits. Although the concentration of ethanol in these fruits is generally lower than that of man-made alcoholic beverages, some overripe fruits, such as those of the black palm (Astrocaryum standleyanum), can contain ethanol levels comparable to those of a standard beer (around 5%).
This ubiquity of ethanol in nature explains why so many different species ingest it regularly. It's not that these animals are trying to get drunk; they're simply eating what's available in their natural environment, which often includes fruits in various stages of fermentation.
So, are drunk animals a myth or reality?
Despite numerous stories of elephants staggering after eating fermented fruit or monkeys appearing to be intoxicated, scientists are skeptical about the reality of “drunk animals” in the wild. Anecdotes abound, but None of these cases have been scientifically validated. And there's a good evolutionary reason for this skepticism.
From the standpoint of natural selection, getting drunk would be extremely disadvantageous. An intoxicated animal would be more vulnerable to predators, less able to find food or shelter, and generally less able to survive in the wild. Imagine a primate who, in a drunken stupor, loses his balance while moving through the branches of a tree: the consequences could be fatal.
Rather than tolerate these negative effects, evolution has favored adaptations that allow animals to metabolize ethanol efficiently, thus avoiding intoxication. These adaptations allow them to consume fermented fruits (which are often riper and richer in nutrients) without suffering the effects of drunkenness.
The Superheroes of Alcohol Metabolism
The metabolic process of ethanol in animals is surprisingly similar to that of humans. Ethanol is first oxidized into acetaldehyde (a toxic intermediate) by the enzyme alcohol dehydrogenase, and then acetaldehyde is converted to acetate (less toxic) by aldehyde dehydrogenase. However, the efficiency with which different species metabolize ethanol varies greatly.
Some species have developed particularly advanced metabolic capabilities. Chimpanzee, gorillas and bonobos, just like humans, share a mutation that makes them particularly efficient at metabolizing ethanol. Interestingly, the only large Asian primate, the orangutan, which is highly arboreal (tree-dwelling), does not exhibit this mutation. This may be because orangutans feed primarily on fruit directly from trees, where fermentation is less likely than from fallen fruit on the ground.
I am fascinated by how these metabolic differences reflect the different feeding strategies and environments in which these species have evolved. The adaptations for metabolizing ethanol are not uniform, but are closely linked to the specific evolutionary pressures that each species has faced throughout its evolutionary history.
More Than Just a Hangover: The Benefits of Ethanol
If animals don't consume ethanol to get drunk, why do they do it? The answer may lie in the many benefits that ethanol can offer, beyond its psychoactive effects.
Ethanol has antimicrobial properties, which may help neutralize potentially harmful pathogens in food. Vinegar flies, for example, are known to use ethanol as a self-medication against parasites. Although research on other animals is limited, it is possible that other species also use ethanol for medicinal purposes. Considering that many animals, from chimpanzees to orangutans, have been observed using plants to self-medicate, the use of ethanol in this way may be more widespread than currently known.
Furthermore, ethanol itself is a source of calories., and its presence often indicates a high content of sugar and nutrients in food. Ambrosia beetles, for example, use the odor of ethanol as an indicator to find suitable host trees to colonize, since ethanol promotes the growth of the fungi they feed on.
Many of us are well aware of the cognitive impact of ethanol, including feelings of relaxation. While ethanol may play a significant role in promoting sociability in humans, this effect has not yet been studied in a natural setting in other species. Could other animals experience similar effects? The question remains open and intriguing.
The celebration in nature: from “drunk” animals still much to discover
Despite advances in understanding ethanol consumption by wild animals, many questions remain unanswered. Many hypotheses remain untested, and little is known about whether animals actively seek out ethanol and fermented foods.
What is clear is that the ethanol drinking “fest” is much larger than previously thought, and we humans are just one of many species participating. The main difference may be that we are consciously seeking intoxication, while other animals are simply reaping the nutritional and medicinal benefits of ethanol without suffering the negative side effects.
I like to think that while we humans continue to worry about the consequences of drinking too much, our animal cousins solved this problem long ago, evolving metabolic systems that allow them to enjoy the benefits of ethanol without having to deal with the inconvenience of a hangover the next day.
The next time you see a viral video of a “drunk animal,” you might want to reconsider what you’re actually looking at. Rather than an intoxicated animal, you might be looking at a skilled ethanol metabolizer simply enjoying a nutritious meal, completely sober despite the high alcohol content of his food.
