Family: Vespertilionidae, Vespertilionid Bats view all from this family
Description A medium-size bat. Nearly black, with silvery-tipped hairs on back, giving frosted appearance. Interfemoral membrane lightly furred above. Short, rounded, naked ears. L 3 5/8–4 1/4" (92–108 mm); T 1 1/2–1 3/4" (37–45 mm); HF 3/8" (9–10 mm); FA 1 1/2–1 3/4" (37–44 mm); Wt 1/4–1/2 oz (9–15 g).
Warning Bats are susceptible to rabies, a serious viral disease that results in death if untreated. Rabid bats rarely attack humans or other animals, but bats found lying on the ground may be rabid. Never touch or pick up any bat. Stay away from any animal that seems to be acting strangely and report it to animal-control officers. If you are bitten by a possibly rabid animal, you must immediately consult a doctor for a series of injections; there is no cure once symptoms emerge.
Similar Species Much paler-colored overall, the solitary tree bats (genus Lasiurus) have whitish-tipped fur and much more fur on upper part of interfemoral membrane.
Breeding Mates in fall; implantation delayed until spring. Usually 2 young born in early summer, probably in hollows or crevices in trees. Although this is thought to be a solitary bat, females apparently may form maternity colonies.
Habitat Both deciduous and coniferous forests. In summer, roosts in protected spots such as under bark or in dead trees, woodpecker holes, or bird nests. In winter, hibernates in trees, crevices, buildings, and other protected places.
Range Across southern half of Canada and southward through most of U.S. In summer, found in much of w U.S., but in East only in n U.S. and Canada.
Discussion Generally regarded as a solitary, tree-roosting species, the Silver-haired Bat is usually found roosting under a slab of bark or in some other protected spot, although there are a few records of it roosting among foliage. It emerges in early evening, flying very slowly to feed on a variety of insects, especially moths, caddis flies, and flies. Generally migrating south for the winter, it possesses a well-developed homing instinct; one bat traveled 107 miles (172 km) to its home roost. Over major parts of its range it is present only during the spring and fall migrations. In winter, it hibernates from the latitude of middle Indiana and southward. In southern Illinois, it occasionally hibernates in silica mines but rarely enters caves. There is no reliable evidence as to whether females giving birth are solitary or colonial.
