A community of chimps in West Africa is partial to the occasional alcoholic beverage. There are “behavioral signs of inebriation (intoxication, excitement),” note researchers, according to The Guardian.
In Bossou in southeast Guinea, villagers tap into the trunks of raffia palms to drain off the sap into plastic containers fitted to the trees. These sugary fluid ferments, result in a lightly alcoholic “palm wine” that is collected and consumed. But when the humans are away, the local chimps will occasionally come in for a tipple, using leaves to scoop up tasters of the beverage.
“When I first observed the behavior it immediately sparked my interest,” says Kimberley Hockings, a behavioral ecologist at Oxford Brookes University in the UK. But as she’d only seen the chimps sampling the palm wine on a few occasions, she approached others who’ve worked on this community over the past 20 years and got them to dig into their notebooks for similar records. The result is a collaborative paper published today in the Royal Society’s open-access journal Open Science based on 51 wine-drinking events.
With an average ethanol content of three percent, the palm wine is of similar strength to a weak beer. “When the sap is fresh, it’s quite sweet and tastes very pleasant,” says Hockings. But it ferments very quickly. “After 24 hours it turns very acidic and vinegary and from my perspective is undrinkable,” she says. The strongest sample collected by the researchers came in at almost 7 percent alcohol by volume, which would presumably pack quite a punch for an animal that’s half the size of a human.
Hockings and her colleagues estimate that the leafy receptacles probably convey between 10 and 50 ml at a time and the chimps make a dip every 6 or 7 seconds. So in a swift session of about minute, a chimp would consume around 100 ml of palm wine or 3 ml of ethanol. But the longest recorded binge lasted more than 30 minutes, during which time the chimp might have taken on as much as 3 liters of wine and 90 ml of ethanol. Even by the most excessive of human standards, this is a serious bender.
Combing through the supplemental data, I notice that it was this same chimp – a male known affectionately as FF – that was responsible for approximately one-third of the 51 drinking events. I asked Hockings if he might have a drink problem, but she is careful not to cast aspersions. “I don’t think it’s an addiction, as he drinks it rarely,” she says. “But, anecdotally, he always drinks palm wine when it is available and is often the first to climb the raffia.”
In the discussion to the paper, Hockings and her colleagues touch on what everyone will be wondering. “Some of the chimpanzees at Bossou consumed significant quantities of ethanol and displayed behavioral signs of inebriation,” they write. When I read this, I pictured a whole load of debauched chimps, slurring their pant-hoots and tumbling out of trees, but Hockings’ stories are disappointingly sober. On one occasion, she saw several chimps conclude a drinking session by having a rest. On another, an adult male was not his usual self after a drink. “Whilst other chimpanzees were making and settling into their night nests, he spent an additional hour moving from tree to tree in an agitated manner,” she says.
All of this is more than just a description of a few wayward animals. The occasional boozing of Bossou chimps supports molecular evidence that the ability to metabolize alcohol appeared in the common ancestor of humans and chimps about 10 million years ago.
So chimps have a grasp of cooking and can drink quite considerable quantities of alcohol. “What chimp-based surprise will I be writing about next week, I wonder?”