Almost all human cultures know and use alcoholic beverages from fermented plant parts, as Kimberley Hockings of Oxford Brookes University in Oxford and her colleagues report. Even our ancestors drank such brews to intoxicate themselves for cultic purposes or to celebrate successes. Some species of monkeys have also been observed feeding on fermented fruits or even deliberately drinking alcoholic beverages. The Plumploris native to Southeast Asia drink the fermented nectar of a palm species, green monkeys on the Caribbean island of St.Kitts have learned to steal their cocktails from tourists. However, whether our closest relatives, the chimpanzees, drink alcohol in the wild when they happen to be available to them, has remained unclear. Observations by Hockings and their colleagues in Guinea now indicate that apes are not averse to the intoxicating drink.
In the village of Bossou in Guinea, the inhabitants use the juice of raffia palm trees (Raphia hookeri) to make an alcoholic drink. For this they collect the palm juice dripping from root injuries in 30 to 50
Liters of plastic containers covering them with leaves. Twice a day, the already fermented juice is collected, until then the containers are left unguarded in the forest. As observations have shown, this source of sweet, alcoholic juice has not escaped even the chimpanzees of the area. Again and again, the researchers caught the monkeys as they approached the containers and tapped juice with a sophisticated method. On average, this happened about three times a year, as the scientists report.
Leaf sponge as a remedy
To get to the palm juice, the chimpanzees first pushed aside the cover sheets of the containers. Then they made themselves a tool: they took some of the leaves in the mouth and chewed them until a spongy mass emerged. "These absorbent tools then pushed them into the small opening of the container and dipped it into the palm juice, " the researchers report. Then the chimpanzees retrieved the soaked sponge and licked it out with his mouth. If several chimpanzees were at the juice containers, they alternated either or the later arriving
formed a snake and waited patiently until it was their turn. The drink was quite effective: "Some of the chimpanzees ingested significant amounts of alcohol and showed clear signs of drunkenness, " said Hockings and her colleagues. No wonder, the juice contains at least three percent ethanol, as measurements showed.
"This is the first empirical evidence that apes in the wild repeated and targeted alcohol consumption, " the researchers state. That this happens only accidentally, as with fermented fruits, is very unlikely in this case. Because the chimpanzees not only use a tool to get to the fermented palm juice, they also search the containers repeatedly. The typical - and distinct - alcohol taste of the juice seems to disturb our next relatives little. However, whether they drink the juice because of the alcohol, or rather because it also tastes sweet, must now be investigated in experiments. display
- Kimberley Hockings (Oxford Brookes University, Oxford) et al., Royal Society Open Science, doi: 10.1098 / rsos.1501