We know lots of animal and insect species like to booze it up every now and again. Butterflies like a little tipple, and Youtube is full of birds that get a little loose after eating fermented berries, and when wasted, slur their songs. One time, a drunk moose even got caught in a tree while stealing fermented apples in Sweden.
Even primates like to hit the happy juice. A 2014 study shows that humans and African great apes have a genetic mutation that allows them to digest alcohol more quickly. It’s a trait we share with the aye-aye, a type of nocturnal lemur only found on Madagascar that looks like Mickey Mouse on an acid trip. In a recent study, researchers looked at whether this unusual primate and a much cuter prosimian primate native to south Asia called the slow loris, actually sought out alcohol, rather than accidentally coming across it.
According to a press release, the aye-aye primarily uses its long bony fingers to extract grub from trees. But in the rainy season, the primate slurps up 20 percent of its calories from the flowers of the traveler tree, some of which may be fermented. According to Conor Gearin at New Scientist, the slow loris spends much of its time drinking bertam palm nectar, which is also often fermented.
To test the animals’ preference for the hard stuff, researchers at Dartmouth College studied two captive aye-ayes, Morticia and Merlin, and one slow loris named Dharma. Once a day for 15 days, the aye-ayes were allowed access to containers containing a sucrose solution between 0 and .5 percent alcohol, similar to naturally fermented nectar. Water was also offered as a control. The aye-ayes in the study preferred the alcohol, and in fact, the higher the concentration, the more they liked it.
“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,” Dartmouth evolutionary biologist, Nathaniel Dominy, author of the study which appears in the journal Royal Society Open Science, tells Gearin.
Dharma, the slow loris, was only tested five times, so there was less information to go off of, but in the study Dharma also greatly preferred the cups with the higher concentrations of alcohol, says the press release. In either case, the alcohol did not appear to have negative effects on the animals or get them wasted.
The findings fit with ideas put forth by evolutionary psychologist Robert Dudley in his 2014 book, The Drunken Monkey: Why We Drink and Abuse Alcohol. In it, he says that a preference for alcohol is an evolutionary adaptation, and argues that the smell of fermenting fruit allowed the early ancestors of apes and humans to find fruit sources hidden in trees. The enzymes which allow apes and humans to process alcohol more efficiently probably evolved when our ancestors began spending more time on the ground, where overripe and fermented fruit is more prevalent.
Though the researchers have yet to tackle the enzymes of the aye-aye, their drive to drink could reflect a similar evolutionary path.