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yesterday

Wild Chimpanzees Consume About One Drink’s Worth of Alcohol Each Day, Study Shows

Field tests at two African sites measured low fruit ethanol levels that accumulate over heavy daily intake.

Two male chimpanzees eating the plum-like fruit of the evergreen Parinari excelsa tree at Taï National Park in the Ivory Coast in 2021.
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A chimpanzee is seen in the trees of Kibale National Park in Uganda. 

Overview

  • Peer-reviewed research in Science Advances directly measured ethanol in fruits eaten by wild chimpanzees at Ngogo, Uganda, and Taï, Ivory Coast.
  • Across 21 fruit species, average ethanol content was about 0.26–0.32% by weight, yielding roughly 14 grams of ethanol per day from an estimated 4.5 kilograms of fruit.
  • Researchers said that intake equals one U.S. standard drink per day, or nearly two human-equivalent drinks after adjusting for chimpanzees’ lower body mass.
  • No outward intoxication was observed because feeding occurs throughout the day, though commonly eaten fruits such as Ficus mucuso and Parinari excelsa had among the highest alcohol levels.
  • The findings support the ‘drunken monkey’ hypothesis, with urine metabolite analyses underway to test internal exposure and possible selection for higher-ethanol fruits.