We normally consider alcohol to be a completely human vice, but that may not be the case. If wine, beer and spirits are certainly an invention of our species, ethanol – the substance responsible for the euphoria that accompanies excessive alcohol consumption – is quite widespread in nature. And it is therefore plausible to imagine that it is consumed regularly by many animal species. This is supported by an article just published in the journal Trends in Ecology & Evolution, which takes stock of the knowledge available regarding the relationship between animals and alcohol.
A story 100 million years old
Just like the grapes from which we make wine, or the barley from which we make beer, almost every fruit with sufficient sugar content ferments naturally when it reaches maturity and begins to decompose. And for animals that eat fruit, coming into contact with the product of this alcoholic fermentation is quite easy. Indeed, it can even be convenient, given that alcohol – as anyone who has tried to follow a weight loss diet knows – is extremely rich in calories.
Ethanol has been present in nature for approximately 100 million years. That is, since when plants with flowers began producing sugary nectar to attract pollinators, and fruits with which to sow their seeds. An invention that has proven to be extremely effective on an evolutionary level, so much so that today nectar and fruits are present in practically every ecosystem on Earth. The quantity of alcohol formed from the natural fermentation of fruit depends on various factors, including the temperature and the sugar content of the fruit: on average we are talking about an alcohol volume of between one and two percent, but Palm trees have been found, particularly in Panama, with fruit that could contain 10 percent alcohol by volume, more or less that of a double malt beer.
Calories, but at what cost?
As we were saying, for the animals that feed on this fruit, ethanol is a precious contribution in terms of extra calories. Which, however, also exposes you to the risk of becoming intoxicated, with all the dangers involved. However, various research has shown that many fruit-eating animals, particularly primates, have developed genes that allow them to degrade ethanol, and therefore reduce its harmful effects.
“From an ecological perspective, it is not very advantageous to be drunk while climbing a tree, or when surrounded by predators at night, in fact, it is perfect to ensure that you do not pass your genes on to the next generation,” explains ecologist Matthew Carrigan molecular scientist at the College of Central Florida and a co-author of the paper. “For animals, it’s the opposite of what happens to humans, who would like to get drunk without taking in extra calories: from their non-human perspective, animals want the calories without getting intoxicated.”
Many questions are still open
Among the benefits of ethanol, the authors of the article list the possibility that fermented fruits are an energetic and easy-to-detect food source, thanks to the strong odor produced by fermentation. It may also have beneficial medicinal properties, such as those exploited by fruit flies, which lay their eggs in alcohol-containing substrates if possible, to keep them safe from predators. And it’s even possible that animals use naturally occurring alcohol just like we do: to socialize.
“It has been proposed that ethanol may activate the endorphin and dopamine system, which could have relaxing effects and provide social benefits,” explains Anna Bowland, a behavioral ecologist at the University of Exeter. “To test this hypothesis, we should study the physiological effects of ethanol in nature.” In fact, there are still many unanswered questions. For their part, the authors of the article want to further research, studying the behavioral and social implications of alcohol consumption by primates.