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Silver Haired Bat

Lasionycteris noctivagans
Silver-haired Bat

Identification: Small to medium sized bat; back dark brown with a strong wash of silver; slightly lighter belly with less obvious silver wash; short ears equal in length and width.
Measurements and weights: Total length ranges from 95-115cm, weight ranges from 6-14 grams
Taxonomic comments: No subspecies recognized.
Status: Global rank is G5 and state rank is S1.
Habitat: Old Growth forest, especially along streams and rivers. 
Range: Throughout most of the continental United States, southern Canada, southeastern Alaska, northeastern Mexico, and Bermuda.

Food habits: insectivorous, primarily flies, beetles, moths; hunts in early evening or late afternoon along streams or along forest edges.  Two foraging periods each night, first period is 3-4 hours after sunset and the second one is 6-8 hours after sunset. The Silver-haired bat uses tail and wing membranes as nets to catch and trap food1.

Life expectancy: Not more than 12 years.

Reproduction: Individuals reach sexual maturity at 1 year of age.  Mating begins at the end of September and 1-2 young are born in June or July.  May reproduce in large groups of up to 12 females; young begin to forage with mothers at 3 weeks of age.

Migration behavior: During the winter (October-April/May) residents of cold climates migrate to warmer regions.  Bats that reside in warmer regions (i.e., Louisiana) are typically permanent residents and do not migrate.  In some places L. noctivagans will hibernate in caves and occasionally trees or buildings during the winter.  Individuals are solitary but this species forms groups to migrate.

Reason for decline:  Historically rare in Louisiana.  Populations may be threatened by the destruction of old growth forest - the habitat that this species is dependent upon for breeding and roosting.

Interesting facts: Although most bats typically roost head-down, pregnant females of Lasionycteris noctivagans roost head-up.  By adopting this sleeping posture the tail membrane can be used as a basket to catch her newborn babies1.

Known distribution in Louisiana:

Dates of documented observations are: 1958, 1974, and 1997

References

Hall, E. Raymond, K. R. Kelson. 1959. The mammals of North America. Volume I. The Ronald Press Company. New York, New York.

Lowery, George H. Jr. 1974. The mammals of Louisiana and its adjacent waters. Kingsport Press Inc. Kingsport, Tennessee.

NatureServe Explorer: An online encyclopedia of life [web application]. 2001. Version 1.6. Arlington Virgina, USA: NatureServe. Available: http://www.natureserve.org/explorer. (Accessed: December 6, 2002).

Nowak, Ronald. M. 1991. Walker’s mammals of the world 5th edition, Volume I. The Johns Hopkins University Press. Baltimore, Maryland.

Naumann, R. 1996. Lasionycteris noctivagans: Sliver-haired bat. Animal Diversity Web, University of Michigan, http://animaldiversity.ummz.umich.edu/accounts/lasionycteris/l._noctivagans. (Accessed: December 15, 2002/

1 This information is reprinted with permission from Bat Conservation International, Inc. (BCI). For more information about bats, BAT Magazine, or membership in BCI, please visit the BCI web site at www.batcon.org or write or call: bat Conservation International, Inc., P.O. Box 162603, Austin, Texas, 78716, 512.327.9721.  For a donation in any amount, you will receive bat house plans and information about bats.  Basic membership, which includes a one-year subscription to BAT magazine, is only $30.00.