Humans and other apes have the ability to metabolize alcohol quickly, minimizing damage to the body. This has allowed many primate species to incorporate alcohol into their diets, often sourced from fermented fruits. Researchers found that two prosimian primates, the aye-aye and the slow loris, can detect alcohol levels and actively seek out substances with higher alcohol content. The findings were just published in the journal Royal Society Open Science.
Aye-ayes are nocturnal lemurs with long, bony fingers used for finding and grabbing grubs out of tree trunks. Oddly, they have the same alcohol gene mutation as humans, allowing for rapid digestion of alcoholic substances. The mutation makes sense in primates that regularly consume fruit but the aye-aye is largely an insectivore. The research team came up with a possible explanation. During the wet season, aye-ayes consume large amounts of nectar from plants called traveler’s trees. The researchers speculated that the nectar is fermented, explaining the need for efficient alcohol metabolism in the lemur. The slow loris also has the mutation and is already known to consume fermented nectar. The research team decided to conduct feeding trials for both primate species to learn their preferences.
The team designed multiple-choice feeding experiments using synthetic nectar drinks that varied in alcohol content. The order of the containers was randomized and the experimenters were unaware of this order to avoid any observational biases. The researchers found that the aye-ayes preferred higher alcohol concentrations. The aye-ayes continued to poke at the containers that had originally contained higher alcohol levels, even after the containers had been emptied for a long time. The slow loris showed similar reactions but because the team could only use one loris in the study, they couldn’t derive any statistically significant results.
The findings suggest that aye-ayes and other prosimian primates have the alcohol gene mutation for a reason. The ability to efficiently metabolize alcohol allows them to take advantage of a sugary food source in their environment, fermented nectar. Past research has linked alcohol consumption to important evolutionary events in human history, including the domestication of cereals such as wheat and barley. A tendency to seek out and consume alcohol may have helped the evolution of humans and other primates.
Samuel R. Gochman et al. Alcohol discrimination and preferences in two species of nectar-feeding primate. Royal Society Open Science (2016).