flying squirrel

any of various nocturnal tree squirrels, as Glaucomys volans, of the eastern U.S., having folds of skin connecting the fore and hind legs, permitting long, gliding leaps.

[1605-15]

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Any member of two distinct groups of rodents that are able to make gliding leaps by means of parachute-like membranes connecting their forelegs and hind legs on each side.

North American and Eurasian flying squirrels, in the squirrel family (Sciuridae), are slender, long-limbed forest dwellers with soft fur and large eyes. They are 3–24 in. (8–60 cm) long, excluding the often-flattened tail, and feed on nuts, fruit, other plant material, and insects. They seldom descend to the ground. They can glide 200 ft (about 60 m) or more from one tree to another. The scaly-tailed flying squirrels of Africa (family Anomaluridae) have rows of scales on the underside of their tufted tail that help them climb and cling to trees. They are similar in appearance and feeding preferences to the sciurids and are about 4–16 in. (10–40 cm) long without the tail.

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▪ rodent

Introduction

 any of 43 species of gliding squirrels. Two species are North American, two live in northern Eurasia, and all others are found in the temperate (temperate forest) and tropical forests (tropical rainforest) of India and Asia. Although these rodents do not fly, glides of up to 450 metres (almost 1,500 feet) have been recorded for Oriental giant flying squirrels (Petaurista). Ample, loose skin and underlying muscle typically form a fur-covered membrane between each forelimb and hind limb; some species have smaller membranes between the head and wrists and between the hind limbs and tail. A cartilaginous (cartilage) rod that extends from the wrist supports the front part of each membrane alongside the body.

      Flying squirrels are long-limbed and slender and have large eyes; the long, bushy tail may be cylindrical or flattened. Their dense fur is soft and long and either silky or woolly in texture. A considerable range of body size exists among the 14 genera. Some giant flying squirrels of tropical India and southeastern Asia weigh 1 to 2.5 kg (2.2 to 5.5 pounds) and have a body length of about 30 to 60 cm (12 to 24 inches) and a tail 35 to 64 cm long. The smallest are the dwarf flying squirrels (Petaurillus) of northern Borneo and the Malay Peninsula; their bodies are just 7 to 9 cm long and their tails 6 to 10 cm. When seen in the tall trees of the tropical rainforest, the glides of these tiny rodents are easily mistaken for the flutter of large butterflies.

Natural history

      Unlike other squirrels, flying squirrels are nocturnal. They den in tree cavities, grottoes or rock crevices on cliffs, and cave ledges. Some also build globular nests high in trees where branches join the trunk. Nests are made of leaves, shredded bark, mosses, or lichens. Most species seldom leave the trees, but North American flying squirrels (Glaucomys) regularly descend to the ground to forage and bury nuts. Depending upon the species, diets can include seeds, fruit, leaves, flower buds, nuts, fungi, lichens, pollen, ferns, tree sap, insects, spiders, other invertebrates, small birds, eggs, snakes, and smaller mammals.

      From high in a tree, the squirrel leaps into the air and extends its limbs to stretch the membranes, transforming the body into a gliding platform that is controlled by manipulating the membranes and tail. The animal sails downward to an adjacent tree. Just before the glide ends, it pulls upward, landing deftly on all four feet. When not in use, the membranes are pulled close to the body.

Classification and evolution

      Flying squirrels constitute the subfamily Pteromyinae of the squirrel family (Sciuridae) within the order Rodentia (rodent). Some authorities regard flying squirrels as a family (Pteromyidae). A few species of anomalure are occasionally called scaly-tailed flying squirrels, but these rodents are classified in the family Anomaluridae. Some researchers have speculated that Pteromyinae is not a single group but members from two different clusters of tree squirrels or possibly nonsquirrel ancestors. Recent evidence derived from fossils and the anatomy of wrist and gliding membranes, however, indicates that all living flying squirrel species are closely related and likely evolved from a tree squirrel ancestor during the Oligocene Epoch (33.7 million to 23.8 million years ago).

Subfamily Pteromyinae (flying squirrels (squirrel))

 43 species in 15 genera. All but 4 species are found solely in Asia and India.

      Genus Petaurista (Oriental giant flying squirrels)

 10 species.

      Genus Hylopetes (pygmy flying squirrels)

 9 species.

      Genus Petinomys (small flying squirrels)

 7 species.

      Genus Glaucomys (North American flying squirrels)

 2 species.

      Genus Iomys (Horsfield's flying squirrels)

 2 species.

      Genus Aeromys (Sunda flying squirrels)

 2 species.

      Genus Petaurillus (dwarf flying squirrels)

 2 species.

      Genus Pteromys (Eurasian flying squirrels)

 2 species.

      Genus Aeretes (Chinese flying squirrel)

 1 species.

      Genus Belomys (hairy-footed flying squirrel)

 1 species.

      Genus Biswamoyopterus (Namdapha flying squirrel)

 1 species.

      Genus Eoglaucomys (Himalayan flying squirrel)

 1 species.

      Genus Eupetaurus (woolly flying squirrel)

 1 species.

      Genus Pteromyscus (smoky flying squirrel)

 1 species.

      Genus Trogopterus (Complex-toothed flying squirrel)

 1 species.

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