Even apes need a break once in a while. A 17-year study of chimpanzees in Guinea observed the animals drinking fermented palm sap, with some of the chimps exhibiting "visible signs of inebriation" after overconsumption. "Some individuals were estimated to have consumed about 85ml of alcohol," the approximate equal of a bottle of wine, the research leader tells BBC News. The team found that the naturally fermented sap produced by raffia palm trees contains about 3% alcohol by volume. And those "visible signs of inebriation"? They included "falling asleep shortly after drinking," or as humans might call it, "passing out."
The study, published this week in Royal Society Open Science, shows "evidence of ... long-term and recurrent" drinking, and marks the first time researchers have recorded and measured wild apes voluntarily consuming alcohol. Though scientists knew apes and humans could both metabolize ethanol, only humans had been documented as drinking the stuff voluntarily. As for chimps' drinking apparatus of choice, the team notes they often used "leafy tools," using torn-off leaves to dip into and soak up fluid and transfer it into the mouth. (This recent study found chimps are like humans in another fascinating way.)