The pen-tailed tree shrew of Malaysia subsists mainly on the fermented nectar of bertam palm tree flowers, which contains approximately 3.8% alcohol. Although the rat-sized mammals spend approximately two hours each night drinking the alcoholic nectar, they do not display any signs of drunkenness.National Geographic: Boozing Mammal Drinks "Beer" Every Night... (July 29, 2008)
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"Over a period of 12 hours they will drink the equivalent to nine small glasses of wine, or four and half pints of beer. That would make you or me legally intoxicated. Indeed, on average, if humans were to drink this amount they would be inebriated every third night."—German researcher, Frank WiensThe Independent: Shrew with a taste for the amber nectar (July 29, 2008)