Some primates prefer nectar with a bigger alcohol kick

Some primates have a taste for the good stuff. Groups of chimpanzees sometimes indulge in alcoholic palm sap, and some primates, including humans, produce a form of the enzyme responsible for breaking down alcohol that gets them more bang for their buck in alcohol digestion. Higher alcohol content translates to higher calories, so researchers at Dartmouth University wanted to see if certain nectar-guzzling primates display a preference for boozier brew.

The team focused on slow lorises (Nycticebus coucang), which drink fermented palm nectar, and aye-ayes (Daubentonia madagascariensis), which primarily eat beetle larvae but occasionally consume nectar from traveler trees (Ravenala madagascariensis). At Duke’s Lemur Center in North Carolina, researchers served up sugary concoctions of varied alcohol levels to two aye-ayes and one slow loris. In 30 trials, the aye-ayes consistently went for the more fermented options, and in five trials, the slow loris exhibited a similar preference, the team reports July 20 in Royal Society Open Science.

The results come with caveats. While aye-ayes do have the alcohol-processing enzyme, slow lorises haven’t been tested for it. Low numbers of primates and trials in this study and a lack of data on traveler tree nectar fermentation also make it hard to say whether the preference for boozier nectar reflects a larger trend in these species and other primates. However, the results add to evidence that the ability to digest fermented foods influenced primate evolution.