June 10, 2015 7:06 AM EDT

A 17-year-long study of chimps by the Royal Society Open Science has recorded chimpanzees from the Republic of Guinea using leaves to drink fermented plant sap, reported the BBC.

The chimps made absorbent sponges with chewed leaves and then dipped them into the sap of the raffia palm trees. They often consumed so much ethanol that they showed “visible signs of inebriation.”

“Some individuals were estimated to have consumed about 85ml of alcohol,” said the leader of the research team, Dr Kimberley Hockings from Oxford Brookes University and the Centre for Research in Anthropology in Portugal. An amount which equates to a bottle of wine.

“[They] displayed behavioural signs of inebriation, including falling asleep shortly after drinking.”

This is the first time researchers have recorded any wild ape’s voluntary alcohol consumption.

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