tree shrew, small, arboreal mammal of the family Tupaiidae, found in S Asia. The 17 known species of tree shrews are classified as the order Tupaioidea or Scandentia. Tree shrews superficially resemble squirrels, and are commonly brown, gray, or olive in color. They have large eyes, good vision, and can use their clawed forepaws effectively for holding food. Tree shrews are territorial, omnivorous, and extremely active; they dart about constantly in the trees screaming and fighting with one another. The common tree shrew, Tupais glis, looks like a squirrel with an elongated, shrewlike snout. Its body is about 8 in. (20 cm) long, and it has a bushy tail about 6 in. (15 cm) long. It is found from India to Malaysia. The pen-tailed tree shrew, Ptilocercus lowi, of Sumatra, Borneo, and the Malay Peninsula is the most distinctive tree shrew; it is a mouse-sized nocturnal animal, dark gray above and yellow below, with a naked, black tail bearing two fringes of white hair at the tip. Tree shrews bear some anatomical resemblance to both the true shrew, which is an insectivore, and to the lemur, which is a primate. Tree shrews are now seen as a possible model for early primate behavior. They are classified in the phylum Chordata, subphylum Vertebrata, class Mammalia, order Scandentia, family Tupaiidae.
See R. D. Martin, Primate Origins and Evolution (1990).