"Aye-ayes are essentially primate woodpeckers," Dartmouth's Nathaniel J. Dominy, who oversaw the new research, said in a statement. The strange-looking Madagascar natives use their alien-like fingers to tug grubs out of trees, which doesn't give them much call to metabolize ethanol. But Dominy and his colleagues suspect that a local plant called the traveler's tree — the nectar of which becomes a significant food source for the aye-aye during some seasons — might be naturally fermented. Slow lorises are already known to consume alcoholic nectars.
Unfortunately, the study published this week in Royal Society Open Science doesn't examine aye-aye nectar itself. But by showing that the genetic adaptation to digest alcohol extends to a desire to consume it, the study suggests that the animals can or do have some kind of alcoholic delicacy on their dinner menu.
In a small experiment led by Dominy's student Samuel Gochman, the researchers presented three animals — two aye-ayes and a slow loris — with a multiple-choice feeding test. They prepared ersatz nectar with varying concentrations of alcohol, then arranged them (along with some tap water as a control) randomly in accessible containers. Once a day for several days, the animals were led to the array of drink choices one by one and allowed to pick their preference.
Not only did the primates avoid tap water when given alcoholic nectar as an alternative, but the animals also consistently sought out the most alcoholic brews available. In fact, the animals kept returning to pots of booze they'd already emptied, seemingly eager to drink more.
“Aye-ayes used their fingers to compulsively probe the cups long after the contents were emptied, suggesting that they were extremely eager to collect all residual traces,” Dominy told New Scientist.
But they didn't get drunk, likely thanks to the genetic mutation they share with humans and the intelligence they don't.
Because the study only followed three individual animals for a few days of experiments, more research is needed to follow up on the results. In fact, the single slow loris studied didn't provide enough data for statistically significant analysis. But Gochman and Dominy say their initial observations are promising, and that further investigation could help support one popular theory of human evolution: the idea that our ancestors developed a tolerance for alcohol when we started walking upright, allowing us to live off fermenting fruit picked up off the ground instead of plucked from trees.
"This project has definitely fueled my interest in human evolution," Gochman said in a statement. "Our results support the idea that fermented foods were important in the diets of our ancestors."