Bats of Colorado > Silver-haired bat (Lasionycteris noctivagans)
A medium-sized bat with black hair tipped in silver or yellow; the silver-haired bat is one of Colorado's most distinctive and attractive mammals. Wingspan ranges from 270 to 310 mm. Average measurements of 10 males from northwestern Colorado were: total length, 104 mm; forearm, 39 mm; and weight, 12 g.
This is a northern species that occurs throughout Alaska, Canada and all of the contiguous United States except Florida. In Colorado it is found statewide but is more common in the forested mountains at elevations up to 10,000 feet.
The silver-haired bat is usually solitary, but it is occasionally found in pairs. It roosts in silver haired battrees, under bark, under rocks and infrequently in open soft-walled caves or mines. Silver-haired bats also roost in open buildings, such as sheds or garages. It is seldom found in closed structures, such as the attics of houses. This bat occasionally has been found hibernating in mines in Colorado but probably usually migrates elsewhere to spend the colder months. Field data indicate the silver-haired bat is most abundant during late spring and early fall when both sexes are found in the state. Predators include skunks, owls and probably snakes.
Little is known of the reproductive habits of this species. Two young are produced in early summer. Mating probably occurs in autumn with the female storing sperm during the winter. Ovulation occurs in April or May. Gestation is 50-60 days. There is some evidence that the sexes are segregated during summer. Silver-haired bats occasionally form fairly large nursery colonies of 200 or more females and their young.
Like all Colorado bats, the silver-haired bat is an insect-feeder, preferring moths, flies, beetles and wasps. The silver-haired bat is a slow flyer, often seen foraging near the ground. It commonly flies around ponds and woodland streams.
The slow flight of this bat is unusual. The animals are hooked occasionally by anglers fly-fishing. Because silver-haired bats roost in tree hollows and behind loose bark, clear-cutting and removal of standing dead trees may affect their distribution and abundance.
