Someone have a word with the chimps? Observations of the apes in the wild show them imbibing the alcoholic equivalent of a half pint of beer a day through the vast amount of fermented fruit in their diet.
Researchers arrived at the first estimates of wild chimp daily alcohol intake after measuring ethanol levels in fallen fruit that the apes gather from the forest floor in Kibale national park in Uganda and in Taï national park in Ivory Coast.
While individual fruits contained less than 0.5% alcohol, the chimps’ daily intake swelled as they devoured the ripe fruit pulp. The apes were particularly fond of figs, which contained some of the highest levels of alcohol the team recorded.
Aleksey Maro, a graduate student at the University of California, Berkeley, said at both African sites, males and females consumed about 14g of pure ethanol per day through fermented fruit. That is equivalent to one standard US drink or half a pint of 5% ABV lager.
“The chimps are eating 5 to 10% of their body weight a day in ripe fruit, so even low concentrations yield a high daily total, a substantial dosage of alcohol,” said Prof Robert Dudley, also at UC Berkeley.
Dudley believes the chimps’ consumption of alcohol in the wild supports his “drunken monkey” hypothesis, which posits that the human penchant for drink has roots in our primate ancestors’ need for energy-rich, ripe, fermented fruit. The human attraction to alcohol probably arose from this “dietary heritage”, Maro said. Details are published in Science Advances.
The observations are not the first to capture chimpanzees’ booze habits. In 2015, researchers said a troop in south-eastern Guinea were the first known to indulge in regular, habitual drinking. Some of the apes started at 7am before knocking it on the head before bedtime. In footage this year, chimps appeared to bond over fermented African breadfruit.
Chimps are not the only ones. A review of evidence published last year found alcohol consumption to be commonplace in the animal kingdom. And looks can be deceiving: slow lorises, known for being wide-eyed fur balls, will down the strongest alcoholic drinks they can get their hands on.
Although chimps devour impressive quantities of fermented fruit, working through about 4.5kg a day, they show no obvious signs of inebriation. According to Maro, to feel the full effects of alcohol, the apes would need to eat enough fruit to make them bloated.
As for humans, the NHS recommends people have no more than 14 units a week, where a unit is 8g of pure alcohol, to keep health risks to a minimum. But studies show there is no healthy level of alcohol consumption.