Monkey business: Wino chimps get drunk on alcoholic sap

There's nothing like a nice glass of wine after a hard day's work -- especially if you've spent most of your time picking the insects out of your partner's hairy back and swinging from tree to tree.

It seems that one way chimps in Bossou, south-eastern Guinea have learned to kick back is by drinking wine distilled by locals from the raffia palms who then carelessly leave it unguarded for the cheeky monkeys to swipe, according to a report published in the Royal Society's Open Science Journal.

The sap from the trunks of raffia palms when fermented turns into a light-alcoholic beverage known as palm wine.

Led by Dr Kimberley Hockings from Oxford Brookes University, the team observed the chimps drinking the wine -- which has an average ethanol presence of 3.1% -- over a 17-year period and noted that there were behavioural changes including a social aspect to the drinking.

The team noted: "All age and sex classes ingested palm sap, and there was no sex bias in the quantity of ethanol ingested during a feeding event. In addition, there does not appear to be a pattern in the amounts ingested by the same individual in different events. Some of the chimpanzees at Bossou consumed significant quantities of ethanol and displayed behavioural signs of inebriation."

Speaking to BBC News, Dr Hockings said: "Some individuals were estimated to have consumed about 85ml of alcohol -- the equivalent to 8.5 UK units [approximately equal to a bottle of wine]".

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

"On another occasion after drinking palm wine, one adult male chimpanzee seemed particularly restless. While other chimpanzees were making and settling into their night nests, he spent an additional hour moving from tree to tree in an agitated manner."