There are anecdotes of wild animals behaving as if they were ‘drunk’ after eating fermented fruits. For example, in South Africa, villagers talk about elephants going ‘trunks’ through their streets, fighting each other and causing destruction after drinking the intoxicating juice of marula trees. Until now, it has been assumed that these stories are rare or accidental, but a team of researchers believes that animal ‘drunkenness’ may be much more common than is believed, since, since ethanol is naturally present in almost In all ecosystems, it is likely that most species that feed on fruits and nectar consume it regularly.
“We’re 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 fruits are going to be exposed to some level of ethanol.” Their conclusions appear this Wednesday in the magazine ‘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 in lower latitude and humid tropical environments compared to temperate regions. Most of the time, 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 that could break down ethanol before yeast started producing it, but there is evidence that evolution honed this ability in mammals and birds that consume fruit and nectar. In particular, primates and tree shrews have adapted to metabolize ethanol efficiently.
«From an ecological perspective, it is not advantageous to be drunk while climbing trees or surrounded by predators at night; “That’s 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
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 several benefits to wild animals. First, it is a source of calories, and the odorous compounds produced during fermentation could guide animals to food sources, although researchers say it is unlikely that animals would be able to detect ethanol on its own. Ethanol may also have medicinal benefits: fruit flies intentionally lay their eggs in ethanol-containing substances, which protects their eggs from parasites, and fruit fly larvae increase their ethanol intake when parasitized. by wasps.
“From a cognitive point of view, the idea has been proposed that ethanol can activate the endorphin and dopamine system, generating feelings of relaxation that could have benefits in terms of sociability,” says 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 their future research, the team plans to investigate the social and behavioral implications of ethanol consumption in primates and further examine the enzymes involved in alcohol metabolism.
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