Watch a chimp drink alcohol for science

Due to a local human village tapping in to raffia palm trees for their alcohol-rich sap, chimpanzees have found their own way to drink the drink in Bossou. This Guinea, West Africa environment sets the stage for a research paper which suggests that not only are African apes and humans both able to effectively metabolize ethanol, we're both voluntarily doing so now, too. This drinking of the contents of the raffia palm (Raphia hookeri, Arecaceae) by wild chimpanzees (Pan troglodytes verus) at Bossou in Guinea, West Africa, was observed from 1995 to 2012.

According to scientist and author Kimberley J. Hockings and crew, the alcoholic beverage derived from the sap of these trees has an average presence of ethanol of 3.1% alcohol by volume (ABV) and up to 6.9% ABV. That means it's between the average beer and most wines. Wines around the world have a typical ABV (alcohol by volume) of between 9% and 16%.

Local people are responsible for tapping the raffia palms – they're perfectly welcome to so so.

These chimps take the opportunity to take a taste using leaves as dippers and cups.

"An individual detaches leaves, and then folds or crumples them inside the mouth to produce a drinking tool, i.e. a leaf-fold, leaf-scoop or a leaf-sponge," says the research paper.

"The tool is immersed in the fluid, then retrieved and inserted into the mouth for compressive extraction between the tongue and palate."

While previous accounts of drunken monkeys (and chimpanzees, and gorillas) have occurred, these scientists suggest that all examples were in captivity – or due to local human involvement.

"An individual that ingested a small quantity of palm sap in one drinking event could ingest a greater quantity in other events," said the researchers, "and an individual that ingested a high quantity in one event was not averse to ingesting ethanol again shortly thereafter."

And what's the point of all this?

Why watch chimps drink alcohol in the wild, apart from the entertaining nature of a drunken primate?

The data this crew have collected suggests that ethanol "does not act as a deterrent" to feeding in this particular community of wild apes. Because of this, the idea that the last common ancestor of living African apes and modern humans "was not averse to ingesting foods containing ethanol" is reinforced.

More information can be found in the paper Tools to tipple: ethanol ingestion by wild chimpanzees using leaf-sponges by authors Kimberley J. Hockings, Nicola Bryson-Morrison, Susana Carvalho, Michiko Fujisawa, Tatyana Humle, William C. McGrew, Miho Nakamura, Gaku Ohashi, Yumi Yamanashi, Gen Yamakoshi, and Tetsuro Matsuzawa.

This paper is published in the journal Royal Society Open Science and can be found under code DOI: 10.1098/rsos.150150.