The bertam palm's flower buds house yeast communities that ferment the nectar where it sits. Measurements found a maximum alcohol content of about 3.8 per cent, comparable with a beer and among the highest recorded in any natural food, though the average across buds was well under one per cent. The flowers are visited nightly by several small mammals, including the pen-tailed treeshrew.
What makes the case notable is what does not happen. Treeshrews studied in Malaysia regularly took doses that would intoxicate a person, without observable drunkenness. Their hair carried high concentrations of ethyl glucuronide, a by-product formed when the body attaches alcohol to sugar rather than oxidising it, indicating chronic intake handled along a route humans use only as a minor pathway.
The headline version of the story, that the animals drink heavily every night for pleasure, overstates it. The relationship looks mutualistic: the mammals get a reliable energy source and the palm gets pollinated. How the treeshrews benefit, and what a consistently high alcohol intake does to them, remains unclear, and the original study covered few individuals.