The researchers used video cameras to observe a troop of 26 wild chimps living in Bossou, Guinea, between 1995 and 2012. The villagers living around Bossou routinely tap into the raffia palm tree and collect its sap, which ferments in plastic buckets before being drunk. The villagers collect the fermented palm wine, which has an alcohol content as high as 6.9%, in the early morning and late afternoon. While villagers were away, the chimps approached the buckets, fashioned drinking cups from folded leaves—a toolmaking skill widely observed among wild chimps—and proceeded to consume the beverage themselves. As the team reports online today in Royal Society Open Science, over 17 years it observed 20 “drinking sessions” involving 13 of the chimps, who lapped up the sap at an average rate of about nine leaf dips per minute. On the low end of the scale, that’s roughly equivalent to one liter of beer per session. The 13 chimps included males, females, and young chimps, although not babies. The other 13 animals were never observed drinking during the entire period.
Friday, June 12, 2015
Chimps and Palm Wine
The latest in the quest for the evolutionary origins of human behavior: