Silver-haired bat (Lasionycteris noctivagans)

GenusLasionycteris (1)
SizeHead-body length: 5.5 - 6.5 cm (2)
Tail length: 3.5 - 5 cm (2) (3)
Wingspan: 27.9 - 31 cm (4)
Forearm length: 3.7 - 4.4 cm (2)
Weight6 - 14 g (2)

Classified as Least Concern (LC) on the IUCN Red List (1).

The only species in its genus (2) (3), the silver-haired bat is easily recognised by its dark black to blackish-brown fur, with silvery-white tipped hairs which give the overall ‘frosted’ appearance for which this bat is named (2) (3) (4) (5). This frosting is most conspicuous on the back, being reduced or absent on the face, head and throat. The underparts of the body are paler and also have less pronounced frosting (2) (4). The silver-haired bat has relatively short, rounded, naked ears (2) (3) (4), with a broad, blunt tragus (3) (4), and a tail membrane that is furred on the upper surface for about half of its length (2) (3) (4) (5). The wing and tail membranes are dark brown to black (3) (5). Male and female silver-haired bats are similar in appearance (4), while juveniles usually have more conspicuously white-tipped hairs than adults (3) (4). Older individuals may lack the white tips to the hairs, or may appear slightly yellowish (3).

The silver-haired bat occurs across North America, from Alaska and southern Canada, through most of the United States, south to Tamaulipas in northeast Mexico (1) (2) (3) (4) (5). It has also been recorded in Bermuda and on the Caicos Islands in the Bahamas (1) (2) (5).

This species is typically found in temperate woodland and montane coniferous forest, close to streams, ponds or rivers (1) (2) (3) (4) (5). During the spring and summer, the silver-haired bat roosts in tree hollows, behind loose bark, in birds’ nests, and sometimes in buildings or caves (1) (2) (4) (5). In winter, this bat may hibernate inside hollow trees, under loose bark, in rock crevices, caves or mines, or inside buildings (1) (3) (4).

The silver-haired bat feeds on insects (1) (2) (4), commonly taking flies, beetles, flying ants, termites and moths, although it is an opportunistic hunter that will also eat a wide range of other insect prey (1) (3) (5). It is believed to be one of the slowest flying bats in North America, but is highly manoeuvrable, and typically pursues prey over short distances (1) (2) (3) (4). Foraging commonly takes place along streams and ponds or in small clearings (4), although this species has also been reported to consume insect larvae on trees and even to forage on the ground (1).

Although often regarded as a solitary species, the silver-haired bat may form small ‘maternity colonies’ in spring, and has been reported to come together in groups of both sexes for the autumn migration (1) (2) (4), which takes place from August to October (2) (4). Courtship and mating also occur in the autumn, and most of the bats travel south to hibernate for the winter months (1) (2) (3) (4) (5), although some individuals are also known to hibernate in more northerly locations (1) (5). Female silver-haired bats are believed to migrate further than males (3), and it is possible that some males remain in the winter range throughout the year, with females moving north in April and May to give birth (2) (4) (5).

After mating, the female silver-haired bat is believed to store sperm over winter, delaying fertilisation until the spring. Two young (sometimes one) are normally born between June and July, after a gestation period of 50 to 60 days (1) (2) (3) (4) (5). The female roosts with the head facing upwards during the birth and bends the tail membrane forward to catch the young as it is born (1). The young are weaned after around 36 days and start to fly at about 3 weeks (2) (5). The silver-haired bat may reach sexual maturity after 5 months, and individuals have been recorded living for up to 12 years (2).

The silver-haired bat is a widespread and relatively abundant species and is not currently considered at risk of extinction (1). However, as it inhabits woodlands and often roosts in trees, there are fears that deforestation and modern forestry management practices may pose a threat (1) (3) (6). In addition, there is concern about the potential impact of wind turbines on its populations, given that it is one of the bat species most frequently found killed at these developments in North America, although the exact cause of the deaths remains unclear (7) (8). Although generally having little association with humans, the silver-haired bat is also the bat species most frequently associated with incidents of human rabies within its range, despite a lack of evidence that a bite or close contact with the bats were involved in these cases (2) (4) (6).

This distinctive bat is found in a number of protected areas across its range, and in Mexico it is listed as subject to special protection under national legislation (1). However, surprisingly little is known about many aspects of its behaviour and population dynamics (4). The silver-haired bat may therefore benefit from further research, including into the impact of forestry management practices and wind turbine developments on its populations (6) (7) (8).

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  1. IUCN Red List (July, 2010)
  2. Nowak, R.M. (1991) Walker’s Mammals of the World. The Johns Hopkins University Press, Baltimore and London.
  3. Kunz, T.H. (1982) Lasionycteris noctivagans. Mammalian Species, 172: 1-5. Available at:
  4. Whitaker Jr, J.O. and Hamilton Jr, W.J. (1998) Mammals of the Eastern United States. Cornell University Press, Ithaca.
  5. Schmidly, D.J. (1994) The Mammals of Texas. Revised Edition. University of Texas Press, Austin.
  6. Hutson, A.M., Mickleburgh, S.P. and Racey, P.A. (2001) Microchiropteran Bats: Global Status Survey and Conservation Action Plan. IUCN/SSC Chiroptera Specialist Group, IUCN, Gland, Switzerland and Cambridge, UK. Available at:
  7. Cryan, P.M. and Barclay, R.M.R. (2009) Causes of bat fatalities at wind turbines: hypotheses and predictions. Journal of Mammalogy, 90(6): 1330-1340.
  8. Kunz, T.H., Arnett, E.B., Erickson, W.P., Hoar, A.R., Johnson, G.D., Larkin, R.P., Strickland, M.D., Thresher, R.W. and Tuttle, M.D. (2007) Ecological impacts of wind energy development on bats: questions, research needs, and hypotheses. Frontiers in Ecology and the Environment, 5(6): 315-324.