(Lasionycteris noctivagans Leconte)
From: Saunders, D. A. 1988. Adirondack Mammals. State University of New York, College of Environmental Science and Forestry. 216pp
The scientific name of this species means “hairy wandering night bat,” an appropriate description. The common name refers to the color of the long, soft fur which is dark brown to black, and except for the throat, head, and neck, tipped with silvery-white. Among Adirondack bats, only the hoary bat (Lasiurus cinereus) resembles this species. However, the hoary bat is much larger with frosted yellowish brown fur, and has yellowish to tan throat. Silver-haired bats weigh 8-11 kg (0.3-0.4 oz.). Their total length is 92-115 mm (3.6-4.5 in). The wingspread is 27-31 cm (10.6-12.2 in).
Range and Habitat: This North American bat occurs from southeastern Alaska across the southern half of Canada, throughout the U.S. (except for parts of the southern fringes of the southern states), and into northeastern Mexico. Silver-haired bats reside in coniferous and mixed forests near water. Summer roosts include foliage, hollows, and loose bark of trees, and abandoned woodpecker cavities and birds’ nests. Hollow trees, mines, caves, rock crevices, and buildings serve as winter roosts.
Little is known about the relative abundance, distribution, and habits of silver-haired bats. Casual observations by biologists familiar with the Adirondack Park’s bats do not support Merriam’s unsubstantiated claim that, “this is our commonest bat, far outnumbering all the other species together,” (p. 188). Perhaps because of disturbances such as deforestation, this species has declined since Merriam’s time. Today, the silver-haired bat is uncommon to rare throughout the Northeast.
Food and Feeding Behavior: Silver-haired bats may begin foraging before sunset, returning to their roosts during the night, and then leaving to feed again before sunrise. Competition with other large species such as big brown and hoary bats, may modify foraging schedules. Moths, beetles, and the emerging adults of aquatic insects are the primary prey of the silver-haired bats which catch these insects over water, and within and over forests.
Activity and Movement: The flight of the silver-haired bat is slow, erratic, and punctuated with short glides. On a straight course, it may attain a speed of 18 km per hour (10.9 mph). These summer residents migrate into the southern parts of the range in autumn, returning in late April and May.
Reproduction: The breeding habits of this species are not well known. Adults mate in autumn and females store sperm from these matings until spring when fertilization occurs. The gestation period is 50-60 days. Females bear one litter per year of two young (occasionally one) in July. At birth the young are wrinkled, pink, hairless, and weigh about 2 g (0.07 oz.). A few hours after birth the young become darkly pigmented. They are capable of flying at 3-4 weeks, and at least some begin breeding at the end of their first summer. Longevity is unknown.
Predators: Few documented instances of predation on the silver-haired bat exist. Great-horned owls and striped skunks are known predators.
Social Behavior: The lack of reports of large colonies of silver-haired bats, rather than the sightings of individuals of this secretive species, suggests it is solitary or roosts in small colonies throughout the year. Too little is known about social encounters to describe the social system and the means by which individuals communicate. Merriam and other naturalists have noted the near absence of males among Adirondack specimens as well as those obtained from many parts of the northern range of this species. Possibly, males remain at lower latitudes.
Barbour, R. W. and W.H. Davis. 1969. Bats of America. University Press of Kentucky, Lexington, 286pp.
Kunz, T.H. 1982. Lasionycteris noctivagans. Mammalian Species, 172:1-5.