The pen-tailed treeshrew (Ptilocercus lowii) is a treeshrew native to southern Thailand, the Malay Peninsula, Borneo, and some Indonesian islands.
It is the only species in the genus Ptilocercus. All other treeshrew species are grouped in the family Tupaiidae. It is considered the closest relative of extant primates.
Pen-tailed treeshrews are the only known wild mammals that consume alcohol every night. According to a study of treeshrews in Malaysia, they spend several hours per night consuming the equivalent of 10 to 12 glasses of wine with an alcohol content up to 3.8% drinking naturally fermented nectar of the bertam palm. This nectar contains one of the highest alcohol concentrations of all natural foods. Pen-tailed treeshrews frequently consume large amounts of this nectar while showing no signs of intoxication. Measurements of a biomarker of ethanol breakdown suggest that they may be metabolizing it by a pathway that is not used as heavily by humans. Their ability to ingest high amounts of alcohol is hypothesized to have been an evolutionary adaptation in the phylogenic tree. However, how pen-tailed treeshrews benefit from this alcohol ingestion or what consequences of consistent high blood alcohol content might factor into their physiology is unclear.
The Ptilocercidae are a family within the order Scandentia. Numerous morphological and genetic differences support the classification of the Ptilocercidae as a separate family from the rest of the treeshrews which diverged around 63 million years ago. Interestingly, treeshrews were considered a close relative of primates, but recent genetic data have concluded that the Dermoptera, not the Ptilocercidae are the appropriate out-group for study of primates.
Pen-tailed treeshrew Wikipedia