The pen-tailed treeshrew is the only nocturnal species of shrews. Treeshrews are small mammals native to Southeast Asia. Though called “treeshrews” they are not being true shrews. They live – as the name indicates – in forests on the Malay Peninsula, Sumatra and parts of Borneo as well as some smaller offshore islands. Pen-tailed treeshrews are excellent climbers. During the day they rest curled up in self-made nests made of leaves and twigs. Treeshrews are omnivores: their diet consists of insects, small vertebrates such as geckos, and fermented fruits.

According to a study published in 2008, pen-tailed treeshrews consume the fermented nectar of Berry Palm (Eugeissona tristis) fruits, commonly called bertram or wild Bornean sago. The nectar of the betram palm can have an alcohol content of up to 3.8 percent, one of the highest known alcohol concentrations in natural food which is similar to drinking a beer. The palm is pollinated by mammals  such as squirrels, and pen-tailed treeshrews. Despite constant daily alcohol consumption, pen-tailed treeshrews show no signs of drunkenness, and have adapted to chronic alcohol consumption. The little mammals can obviously break down alcohol very efficiently, and the daily alcohol consumption is proven to make an integral part of their diet. According to the researchers, the alcohol consumption could also have positive psychological effects on the animals. There are other known animals consuming alcohol but none of them consumes as much and as continuously as the small pen-trailed treeshrew which makes it the world’s true party animal.