The assumption that nonhuman consumption of ethanol is rare and accidental is challenged by ecologists in a review published in Trends in Ecology & Evolution. Ethanol is naturally present in nearly every ecosystem and is likely consumed regularly by fruit- and nectar-eating animals. The abundance of ethanol in the natural world has been underestimated, with most animals exposed to some level of ethanol when consuming sugary fruits.
The presence of ethanol became abundant around 100 million years ago when flowering plants began producing sugary nectar and fruits that yeast could ferment. Ethanol is present naturally in almost all ecosystems, with concentrations higher in lower-latitude and humid tropical environments compared to temperate regions. While most naturally fermented fruits only reach low alcohol concentrations, concentrations as high as 10.2% ABV have been found in over-ripe palm fruit in Panama.
Animals already possess genes that can metabolize ethanol, but evolution has fine-tuned this ability for mammals and birds that consume fruit and nectar. While it is not advantageous for animals to be inebriated due to the risks of predators, ethanol consumption could provide several benefits. Ethanol is a source of calories and the odorous compounds produced during fermentation could guide animals to food sources. Additionally, ethanol may have medicinal benefits, such as protecting eggs from parasites in fruit flies.
It is unclear whether animals intentionally consume ethanol for its effects, and more research is needed to understand its impact on animal physiology and evolution. Ethanol consumption could trigger the endorphin and dopamine system, leading to feelings of relaxation that could benefit social interactions. Further research is needed to determine if ethanol is producing a physiological response in the wild and to investigate the enzymes involved in alcohol metabolism.
The significance of ethanol consumption by wild animals remains an area of study with many unanswered questions. Future research will focus on the behavioral and social implications of ethanol consumption in primates, as well as a deeper examination of the enzymes involved in alcohol metabolism. This research was supported by various foundations and organizations, highlighting the importance of understanding the role of ethanol in wild animal diets and behaviors.