Alcohol consumption is widespread in the animal world

Despite stories of “drunken wasps” and “beer-drinking beetles”, alcohol consumption among the non-human animal world was not thought to be particularly common, deliberate or sought for physiological benefit. Now ecologists are challenging this theory, saying it is much more common and strategic than scientists thought.

A team of international ecologists substantiated the fact that ethanol is a naturally occurring compound in almost every ecosystem on the planet and is often consumed by animals that feed on fruit and nectar.

“We’re moving away from this anthropocentric view that ethanol is just something that people use,” says behaviorist and senior study author Kimberly Hawkings of the University of Exeter. “It’s much more abundant in nature than we previously thought, and most animals that eat sugary fruit will be exposed to some amount of ethanol.”

Alcohol, of course, has its origins in the ancient history of mankind – with rice beer 9000 years ago, for proof of beer consumed in China 5000 years in the past. But despite anecdotal reports of non-human animals appearing intoxicated after eating ripe fruit or sweet substances, very little research has been done on its actual prevalence in the wider realm of life.

In the study, researchers cite cases of animal intoxication, in particular: “Elephants (Loxodonta africana), baboons (Papio ursinus), and other wild animals apparently “get drunk” on marula (Sclerocarya birrea) fruit in Botswana and moose (Alces alces), found stuck in a tree in Sweden, was reportedly drunk on fermented apples. In none of these cases was ethanol measured in fruit, nor was ethanol (or its metabolites) confirmed in animals. However, mammals accept alcoholic beverages from humans. For example, wild green monkeys (Chlorocebus aethiops) brought to the Caribbean in the 1600s accept alcoholic fruit cocktails from tourists on St. Kitts.”

Ethanol, the key alcohol compound produced when yeast ferments the sugars in fruits, grains, and vegetables, has been readily available for about 100 million years. Around this time, the evolution of flowering plants to produce sweet nectar and fruit enabled the natural production of ethanol and consumption by animals living on specific diets.

While the amount of ethanol in naturally fermented products averages only about 1-2% alcohol by volume (ABV), some ripe fruits in tropical regions, for example, are very ripe, the researchers add. Astrocarium standlianum palm fruit in Panama – reached an ABV level of 10.3%. However, this is not indicative of all tropical areas, as the fruit in Singapore has been found to contain between 0.006% and 0.61% ABV.

For context, a regular can of beer, hard seltzer, or hard cider is around 5% ABV.

Although animals are genetically capable of processing and breaking down ethanol before yeast fermentation begins, researchers believe there may have been some evolutionary switches that caused certain species to seek out fruits and nectar with higher sugar concentrations.

“On the cognitive side, it has been suggested that ethanol may trigger the endorphin and dopamine system, leading to a feeling of relaxation that may have social benefits,” says behavioral ecologist and first author Anna Bowland of the University of Exeter. . “To test this, we really need to know if ethanol causes a physiological response in nature.”

More research is needed to determine whether ethanol consumption affects the species more strongly than previously thought, or whether the overripe fermentable fruits are other factors, such as their strong odor that allows animals to find them more easily, or the higher levels of sugar means that they are a beneficial source of energy. After all, the non-animal kingdom is a fine-tuned energy and cost machine, and more sugar means more fuel for humans.

“It’s not ecologically beneficial to be drunk when you’re climbing trees or surrounded by predators at night — that’s a recipe for your genes not being passed on,” says molecular ecologist and senior author Matthew Kerrigan of the College of Central Florida. “It’s the opposite of people who want to be high but don’t really want the calories – from a non-human perspective, animals want the calories but not the high.”

However, there may still be more to the way animals use alcohol for their biological benefit. Fruit flies deliberately lay their eggs in foods rich in ethanol, which is thought to protect against parasites. The larvae of these flies (Drosophila melanogaster) will also increase ethanol consumption when targeted by parasitic wasps.

Previous research has looked at alcohol consumption and behavior in the animal world – for example, whether hummingbirds get drunk while eating beneficial social changes in buzz flies and how zebrafish are getting bolder when “drunk”.

The researchers are calling for more research on ethanol use in nature, as anecdotes about “drunk” animals suggest we may not fully understand what’s behind species looking for potentially intoxicating food. The team will now investigate how the primates’ ethanol consumption – and the enzymes responsible for breaking down the alcohol in their diet – relates to their social interactions and behaviour.

“A broad eco-evolutionary view of alcohol use suggests that ethanol is neither uncommon nor simply avoided,” the researchers concluded. “It can be toxic, but also protective against ‘competing’ organisms, and metabolic adaptation to ethanol can expand the resources that provide the animal with calories. This forces us to reconsider the ecological role of ethanol and the evolutionary impact on nature.

The study was published in the journal Trends in ecology and evolution.

Source: University of Exeter