Wildlife acting like drunken humans after eating fermented fruit is generally considered anecdotally rare and not well documented in the academic literature. However, a group of ecologists are challenging the assumption that animals don’t eat ethanol-laden fruits and nectars so often. They argue that since ethanol-laden fruits are present in almost every ecosystem on the planet, these fruits are likely consumed on a more regular basis by animals that eat nectar and fruit. The argument is elaborated in a article published October 30 in the journal Cell Press Trends in ecology and evolution.
“We’re moving away from this anthropocentric view that ethanol is just something people use,” said Kimberley Hockings, co-author of the study and a behavioral ecologist at the University of Exeter in Britain. said in a statement. “It’s much more common in the natural world than we previously thought, and most animals that eat sugary fruits will be exposed to some level of ethanol.”
[Related: Different kinds of alcohol might make you feel different emotions.]
What is ethanol?
With fruit, Ethanol is a naturally occurring substance–the result of the fermentation of fruit sugars by yeast. The first became abundant about 100 million years agowhen flowering plants began to produce the sugary nectar that yeast could ferment. Ethanol is now present in virtually any ecosystembut its concentrations are higher and occur year-round in tropical areas at lower latitudes and in humid tropical areas.
Usual, naturally fermented fruit only reaching 1 to 2 percent alcohol by volume (ABV). However, concentrations as high as 10.2 percent alcohol have been found in overripe palm fruits in Panama. By comparison, most alcoholic drinks that people consume range from 3 percent ABV (a light beer) to 50 percent ABV (spirits).
While animals the genes needed to break down ethanol Before yeasts started producing it, there is evidence that evolution refined the ability of mammals and birds to eat fruit and nectar. Primates and small mammals Treeshews have adapted to metabolize ethanol extremely efficiently. Spider monkeys feed on fermented fruits of yellow mombin, which have a fruit ethanol content between one and 2.5 percent. Wild chimpanzees Fermented palm has also been observed to be ingested repeatedly. Elephants, baboons and other wildlife too apparently getting “drunk” on marula fruit in Botswana. However, in these cases, ethanol was not measured in the fruit and ethanol was not confirmed in the animals.
“From an ecological perspective, it’s not beneficial to be drunk while climbing around in trees or surrounded by predators at night — that’s a recipe for not passing on your genes,” study co-author and College of Central Florida molecular ecologist Matthew Carrigan said in a statement. “It’s the opposite of humans wanting to get drunk but not really wanting the calories – from a non-human perspective, the animals want the calories but not the drunkenness.”
Potential benefits
In the new paperthe team analyzed the available scientific literature to understand the prevalence and role of ethanol in the natural world and what its evolutionary benefits might be for animals.
They found that it is still unclear whether animals consciously consume ethanol and that more research is needed to understand how this affects animal physiology and evolution.
However, they did note that ethanol consumption can bring several advantages for wild animals. It is a source of calories and the odors produced during fermentation can guide animals to food sources. The team does not believe that animals can detect the ethanol in the fruit itself based on the smell alone.
[Related: Why fruit bats can eat tons of sugar without getting diabetes.]
Ethanol may also have some medicinal benefits. For example, fruit flies deliberately lay their eggs in them substances that contain ethanol. This protects the eggs from parasites. The fruit fly larvae also increase their ethanol intake when they are parasitized by wasps.
“On the cognitive side, ideas have been put forward that ethanol may activate the endorphin and dopamine systems, leading to feelings of relaxation that may have benefits in terms of sociality,” study co-author and behavioral ecologist Anna Bowland of the University of Exeter. said in a statement. “To test that, we really need to know whether ethanol causes a physiological response in the wild.”
According to the teamThere are still several unanswered questions about the significance of ethanol consumption for wildlife. In future research, they plan to investigate the behavioral and social implications of ethanol consumption in primates and take a closer look at the enzymes involved in alcohol metabolism.