The world has long fought against binge drinking, with more and more countries promoting moderate alcohol consumption or complete abstinence because of its great economic and health benefits. Meanwhile, more and more observations point to the presence of alcohol in wild fruits, nectars, juices. It is possible that it is much more prevalent in wildlife than is known. An international team of scientists in a new review summarised all the available evidence and concluded that ethanol has probably been an evolutionary factor for many species.
In nature, animals are thought to consume alcohol on exceptionally rare occasions. For example, wild monkeys in Guinea have been spotted independently addicted to palm wine. And hummingbirds constantly drink large doses of fermented flower nectar and do not die thanks to a high metabolic rate.
The authors of the review, published in the journal Trends in Ecology & Evolution, believe that ethanol is much more readily available in the wild than is commonly believed. And since it is, it’s likely that many species whose diets are based on fruits and nectars consume it regularly.
‘We’ve moved away from the anthropocentric view that alcohol is an exclusively human beverage. It is found many places in the animal kingdom and many species that eat sweet fruits are used to a certain strength of nectars,’ said ecologist and lead author of the paper Kimberley Hawkings from the University of Exeter (UK).
Ethanol appeared in nature about a hundred million years ago, when flowering plants began producing sweet nectar and fruit. These products are easily fermented. Now alcohol is found in almost all ecosystems. In low latitudes and arid tropics, it is available year round in higher concentrations compared to regions in temperate climates. On average, fermented fruit contains one to two per cent of its volume, and palm fruit in Panama can contain as much as 10.2 per cent of its volume.
It seems that animal bodies learnt to break down ethanol long before yeast fungi began to produce it. It is likely that in mammals and birds that eat nectar and fruit, this ability is genetically hardwired. Primates and tupayas, squirrel-like arboreal animals from the tropics of Southeast Asia, metabolise ethanol most successfully.
‘From an ecological perspective, being drunk is disadvantageous if you climb trees or are surrounded by predators at night. Your genes are less likely to be inherited. Humans seek intoxication, although they do not view alcohol as a source of calories. Animals, on the other hand, seek caloric food but not intoxication,’ explained molecular ecologist Matthew Carrigan of the College of Central Florida (USA), a participant in the study.
It is still unclear whether wild animals are deliberately ‘taking alcohol’. According to the authors of the review, alcohol carries several benefits. Firstly, it is a source of calories. It is unlikely that animals and birds can smell alcohol, they are more likely to go for the odour spread by the fermentation process.
Second, ethanol can also serve as a medicine. For example, fruit flies lay their eggs on alcohol-containing substrate to protect themselves from parasites. Their larvae increase their intake if attacked by wasps.
Third, according to scientists, alcoholic dope may also be beneficial. Perhaps ethanol activates the brain’s endrophin and dopamine systems, leading to feelings of relaxation. And that’s socially beneficial. But to test this, we need to find out whether wild animals actually get drunk.
There are too many questions in this topic, the researchers admitted. The next step they intend to investigate the behavioural and social consequences of ethanol consumption in primates and experiment with the enzymes involved in its metabolism.
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