Lasionycteris noctivagans
Silver Haired Bat
Description:
The pelage on the silver haired bat is dark brownish black with the ends of much
of the ventral side covered in silver. This type of coloring is found in both sexes while
very prominent in young. The silver tips are absent on the face and throat. The fur on
the upper body extends to the interfemoral membrane for ½ its length. The dental
formula is I 2/3 C1/1 P 2/3 M3/3 = 36 (Hazard, 1982). This is a moderate sized bat
between the Big Brown Bat and the Little Brown Bat with the weight anywhere between
8-12 grams (Kurta, 1995). The ears on Lasionycteris noctivigans are rounded and
hairless.
Distribution:
The Silver Haired Bat is found only in North America and throughout the entire
state of Wisconsin between April and November thereafter migrating further south for
hibernation (Altenbach, 1999).
Reproduction:
This species mates in autumn with delayed fertilization until spring and a June
birth is typical after and 50-60 day gestation period. Litter size is usually two. This
species may or may not form maternity colonies of up to a dozen or so females (Kurta,
1995). At parturition, the female roosts with the head up and captures the young with the
patagium. The birthing process is usually 20 minutes with about 20 minutes between the
births of the two offspring ( Kurta, 1995). The young are born hairless with eyes closed
and ears folded over with most of its 22 deciduous teeth (Kurta, 1995). Individuals
weight about 2 grams and can generally forage for themselves after 36 days (Kurta, 1995).
Ecology and Behavior:
The silver haired bat migrates during a two-week period in May in Illinois and
spends April in Kentucky and Tennessee. The autumn migration generally takes a longer
period of time. It has been suggested that males may stay behind in the wintering range
year round with the females migrating north in April-May to birth. They are found in
wooded or semi wooded areas sheltering themselves in the holes of trees. Recent studies
have suggested that old-growth forests may be important habitat for some species of bats
(Jung et al., 1999).They have been found in cliff crevices, caves, and mines. They fly
low along wooded watercourses in the early evening and are often spotted before the sun
goes down to lessen competition for prey species with the larger bats (Hamilton, 1998).
They generally only have two predators which are the great horned owl and the striped
skunk (Birney, 1998). They usually live up to 12 years which is shorter than the colonial
species such as the big and small brown bats (Hazard, 1982).
Remarks:
The incidence of rabies surrounding these bats is very low, but the silver haired
bat has recently been implicated in the deaths of several humans although it has not been
proven that these humans had any contact with the bats.
Literature Cited:
Altenbach, Scott J. Best, Troy L., Harvey, Michael J. Bats of the United States.
Arkansas Game and Fish Commission. 1999. pp 28.
Birney, Elmer C., Jones, Knox J Jr. Handbook of Mammals of the Northern-Central
States. University of Minnesota Press. Minneapolis. 1998. pp 118-119.
Hamilton, William J. Jr., Whitaker, John O. Mammals of the Eastern United States.
Comstock Publishing Associates with the Advising of Cornell University Press
Ithaca and London. 1998. Cornell University NY. pp 107.
Hazard, Evan B. Mammals of Minnesota. University of Minnesota. Minneapolis. 1982.
pp. 36 and 37.
Jung, T.S. et al. Habitat selection by forest bats in relation to mixed-wood stand types
and structure in central Ontario. Journal of Wildlife Management. October 1999.
63(4): 1309-1319.
Kurta, Allen. Mammals of the Great Lakes Region. The University of Michigan Press.
1995. pp. 80-82.
Newmann, Robert. 1996. Lasionycteris noctivagans.
http://animaldiversity.ummz.umich.edu.
Reference written by Lindsay Opelt, Biol 378: Edited by Chris Yahnke. Page last updated