2024-10-30 04:00:00
There are anecdotes of wild animals acting as if they were ‘drunk’ after eating fermented fruit. For example, in South Africa, villagers talk about elephants walking “trunk-like” through their streets, fighting each other and causing destruction after drinking the intoxicating juice of marula trees. Until now it had been assumed that these stories were rare or random, but a team of researchers believes that animal “drunkenness” may be much more common than previously believed, as ethanol is naturally present in almost all ecosystems , most species that feed on fruit and nectar are likely to consume it regularly.
“We are moving away from this anthropocentric view that ethanol is simply something that humans use,” says behavioral ecologist and lead author Kimberley Hockings of the University of Exeter. “It’s much more abundant in the natural world than we previously thought, and most animals that eat sugary fruit will be exposed to some level of ethanol.” Their findings will appear this Wednesday in the journal “Trends in ecology and evolution”.
Ethanol first became abundant about 100 million years ago, when flowering plants began producing sugary nectar and fruits that yeast could ferment. It is now naturally present in almost all ecosystems, although concentrations are higher and production occurs year-round at lower latitudes and in humid tropical environments than in temperate regions. In most cases, naturally fermented fruits only reach between 1% and 2% alcohol by volume (ABV), but concentrations of up to 10.2% have been found in overripe palm fruits in Panama.
Animals already had genes capable of breaking down ethanol before yeast started producing it, but there is evidence that evolution has honed this ability in mammals and birds that consume fruit and nectar. In particular, primates and shrews have adapted to metabolize ethanol efficiently.
«From an ecological point of view it is not advantageous to be drunk while climbing trees or surrounded by predators at night; “This is a recipe for not passing on genes,” says molecular ecologist and lead author Matthew Carrigan of the College of Central Florida. “It’s the opposite of humans, who want to get drunk but don’t really want the calories; From the non-human perspective, animals want the calories, but not the intoxication.
A capuchin monkey eating fruit
Julia Casorso
It is unclear whether animals intentionally consume ethanol for the sheer pleasure of consuming it, and more research is needed to understand its impact on animal physiology and evolution. However, researchers say ethanol consumption could bring numerous benefits to wild animals. For one, it is a source of calories, and odorous compounds produced during fermentation could guide animals to food sources, although researchers say animals are unlikely to be able to detect ethanol on their own. Ethanol may also have medicinal benefits: Fruit flies intentionally lay their eggs in substances containing ethanol, which protects their eggs from parasites, and fruit fly larvae increase their intake of ethanol when parasitized by wasps.
“From a cognitive point of view, the idea has been put forward that ethanol can activate the endorphin and dopamine system, generating sensations of relaxation that could have benefits in terms of sociability,” explains the behavioral ecologist and first author Anna Bowland, of the University of Exeter. “To test this, we would really need to know whether ethanol produces a physiological response in nature.”
According to the authors, there are many unanswered questions about the importance of ethanol consumption for wild animals. In future research, the team plans to study the social and behavioral implications of ethanol consumption in primates and further examine the enzymes involved in alcohol metabolism.
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