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.

shrew, common name for the small, insectivorous mammals of the family Soricidae, related to the moles. Shrews include the smallest mammals; the smallest shrews are under 2 in. (5.1 cm) long, excluding the tail, and the largest are about 6 in. (15 cm) long. Light-boned and fragile, shrews have mouselike bodies and long, pointed snouts with tiny, sharp teeth. They are terrestrial and nocturnal, mostly living under vegetation; some occupy the burrows of other small animals. Their musky odor, produced by a pair of glands on their flanks, deters some of their potential predators. Extremely active and nervous, they have a higher metabolic rate than any other animal. The heart of the masked shrew, Sorex cinereus, beats 800 times a minute, considerably faster than that of the hummingbird. Shrews must eat incessantly in order to stay alive; most will starve to death if deprived of food for half a day. They eat anything available, but prefer small animals; they are economically important as destroyers of insects and slugs that harm crops. Shrews are easily startled and will jump, faint, or drop dead at a sudden noise. They are vicious fighters, killing and eating larger animals, such as mice, as well as other shrews. A belief that the shrew's bite is poisonous was dismissed for years as a folk tale, but has since been substantiated: the saliva of at least one species of shrew is lethal to mice and can cause considerable pain to humans. Shrews live about 15 months and reproduce rapidly, bearing up to four litters a year, with up to eight young in a litter. Shrews are found in Europe, Asia, North and Central America, and N South America. There are over 100 species, all rather similar, classified in about 20 genera. The subfamily of red-toothed shrews, with orange- or red-tipped teeth, includes both Old and New World species; the white-toothed shrews are confined to the Old World. The common shrews of the Northern Hemisphere belong to the red-toothed genus Sorex, with many species in North America and a few in Europe and Asia. The water shrew of Canada and N United States, Sorex palustris, is adapted to aquatic living and can actually walk on the surface of water for a short distance. There are other aquatic shrews, of several genera, in Europe and Asia. The giant water shrew of Africa is not a true shrew but an insectivore related to the tenrec. The elephant, or jumping, shrews of Africa are insectivores of the family Macroscelididae; they resemble miniature kangaroos with trunks. The Oriental tree shrew is an insectivorelike primate. True shrews are classified in the phylum Chordata, subphylum Vertebrata, class Mammalia, order Insectivora, family Soricidae.

Any of more than 300 species of small insectivores constituting the family Soricidae. About 40percnt of these species live in Africa, but shrews are also found throughout the Northern Hemisphere. Shrews are absent from Australia and most of South America. They have tiny eyes and ears, a movable snout, and long, hook-tipped incisors. Typically 2 to 3 in. (6 to 8 cm) long, with a shorter tail, many shrews weigh only about 0.5 oz (14 g). Some are considered the smallest mammals, weighing only a few grams, with bodies less than 2 in. long. Most species live in ground litter, but some live in burrows or trees and a few are semiaquatic. Because they are so small, shrews have the highest metabolic rates of any mammals (with pulses as high as 800 beats per minute). They spend most of their time searching for food, as they can survive only a few hours without eating. Their normal prey is invertebrates such as worms, though some will eat other small animals as well. Some species have toxic saliva (painful to humans). Raptors and snakes eat shrews, but mammals avoid them. Tree shrews (family Tupaiidae) belong to a separate mammalian order (Scandentia) unrelated to true shrews.

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