Family: Sciuridae, Squirrels view all from this family
Description A small squirrel. Very soft fur, rich brown above, white below; abdominal hairs usually gray at base. Loose fold of skin between forelegs and hindlegs. Tail has characteristic flattened appearance; dark brown above and white below. Large black eyes. L 10 3/8"–14 1/2" (263–368 mm); T 4 1/2–7 1/8" (115–180 mm); HF 1 1/2–1 3/4" (38–45 mm); Wt 2 3/8-5 oz (70–140 g).
Endangered Status Two Appalachian Mountain subspecies of the Northern Flying Squirrel are on the U.S. Endangered Species List. The Carolina Northern Flying Squirrel is classified as endangered in North Carolina and Tennessee, and the Virginia Northern Flying Squirrel is classified as endangered in Virginia and West Virginia. The Northern Flying Squirrel is a creature of the cool boreal forests of Alaska, Canada, and the far northern U.S. The two endangered subspecies are the most southerly of these squirrels, and were probably stranded in these now slightly warmer regions after the last ice age. As the climate warmed over the millenia and the habitat changed, their populations probably naturally declined. Nowadays the last of the Appalachian Mountain flying squirrels live in restricted, isolated habitats that are vulnerable to human disturbance as logging activity and ski areas and other recreational developments encroach upon them. Additionally, the more aggressive Southern Flying Squirrel tends to outcompete the Northern when the two overlap.
Similar Species Southern Flying Squirrel is generally smaller and grayer, with abdominal fur white at base.
Breeding Mates in late winter; 1 litter per year of 2–5 young born in spring after gestation of 40 days. Newborns weigh 1/8–1/4 oz (4–6 g), and are weaned at 55 to 60 days.
Habitat Coniferous and mixed forests; may occur in hardwoods where old or dead trees have numerous woodpecker-type nesting holes.
Range Eastern Alaska, s Yukon, and s Northwest Territories, and southern tier of Canadian provinces east to Labrador; south in w U.S. through California, Idaho, Montana, Utah, and n Wyoming; in e U.S. to Minnesota, Wisconsin, Michigan, New England, and New York, and through Appalachians.
Discussion The Northern Flying Squirrel, unlike its southern counterpart, which sometimes enters torpor, is active throughout the year. This animal is quite common, foraging on the ground a great deal, but because it is nocturnal it is seldom seen except when the old, hollow trees in which it lives are cut down. Flying squirrels glide from tree to tree by spreading their legs and stretching their flight skin, which acts as a sail. They pull upright at the last instant to land gently, using the tail as a rudder. The Northern Flying Squirrel feeds primarily on lichens and subterranean fungi, such as Endogone and its relatives. In feeding, it dispenses fungal spores and the nitrogen-fixing bacteria that help trees obtain nutrients and water. (This offers a compelling argument against clear-cutting, which breaks up this natural andnecessary association for the germination and proper growth of the forest.) This species also eats various nuts, seeds, and insects, probably storing much food for winter use. The Northern Flying Squirrel makes a nest of shredded bark in tree hollows, sometimes capping an abandoned bird’s nest to provide temporary shelter or, in summer, using a leaf nest. The young are often born in a hollow stump or limb, or sometimes in a bark nest in a conifer crotch. There is apparently only one litter per year, in contrast to the Southern Flying Squirrel, which sometimes has two. The Northern Flying Squirrel’s chirping, bird-like notes are similar to those of night-flying warblers. The best way to locate this species is to look for and tap on dead vertical tree stubs with woodpecker holes. If these gregarious animals are present, they will peek out immediately and will scamper or glide away if tapping is continued. Although the Southern Flying Squirrel is more aggressive and sometimes displaces the Northern, when the two species occur together the Southern selects hardwoods and the Northern conifers. Owls are the Northern Flying Squirrel’s main predators.
