Chimpanzees drink the equivalent of two cocktails daily from fermented fruit

In a significant discovery, scientists from the University of California Berkeley and other institutions conducted a study revealing that wild chimpanzees in Uganda and Côte d'Ivoire consume fruit with natural alcohol content, amounting to roughly two typical cocktails per day. The study was meticulously carried out over three seasons and involved significant challenges including limited electricity and humidity, which threatened the researchers' instrumentation. By focusing on figs from Uganda's canopy and plum-like fruits found on the forest floor in Côte d'Ivoire, the researchers aimed to measure the ethanol levels in the fruits that chimpanzees commonly consume. The findings indicated that the fruit carried an average alcohol content of approximately 0.3% by weight. Given that chimpanzees can eat up to 10 pounds of these fruits daily and typically weigh around 90 pounds, this culminates in the consumption of about 14 grams of ethanol each day. This parallels the alcohol intake of humans who might consume two cocktails. However, it's crucial to note that the researchers stated that to actually get intoxicated, chimpanzees would have to consume an excessive amount of fruit, leading to noticeably bloated bellies, which they do not typically experience. The study sheds light on the theory proposed by Robert Dudley, a senior author of the paper and a professor of integrative biology at UC Berkeley. Dudley had previously suggested a 'drunken monkey' hypothesis, positing that the attraction to alcohol might stem from ancestral fruit-eating habits of primates. He emphasized that since their diets have historically centered around ripe fruits, it makes sense that primates have evolved a tolerance and even a preference for alcohol, recognizing its presence as an aperitif that can enhance their feeding behavior. The research also links chimps' affinity for alcohol to the broader narrative of humans' relationship with alcoholic beverages, suggesting that this attraction may be an inherited trait from our primate ancestors. Additionally, the study highlights similar behaviors in other animals, noting that spider monkeys, slow lorises, and even elephants have been observed indulging in naturally fermented fruits or nectar. The distinction of this research lies in its provision of the first direct chemical measurements of ethanol found in fruits that wild chimpanzees eat regularly, connecting this data to their daily fruit intake and contributing to our understanding of animal behavior regarding alcohol consumption.