Lasionycteris noctivigans - Silver Haired Bat
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.
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).
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).
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.
Altenbach, S.J., T.L. Best, and M.J. Harvey. 1999. Bats of the United States. Arkansas Game and Fish Commission: 28.
Birney, E.C. and K.J. Jones Jr. 1998. Handbook of Mammals of the Northern-Central States:118-119. University of Minnesota Press-Minneapolis.
Hamilton Jr., W.J., and J.O. Whitaker. 1998. Mammals of the Eastern United States:107. Comstock Publishing Associates with the Advising of Cornell University Press Ithaca and London.
Hazard, E.B. 1982. Mammals of Minnesota:36-37. University of Minnesota- Minneapolis.
Jung, T.S. et al. 1999. Habitat selection by forest bats in relation to mixed-wood stand types and structure in central Ontario. Journal of Wildlife Management 63(4): 1309-1319.
Kurta, A. 1995. Mammals of the Great Lakes Region: 80-82. The University of Michigan Press.
Newmann, R. 1996. Lasionycteris noctivagans. <http://animaldiversity.ummz.umich.edu>.
Reference written by Lindsay Opelt, Biol 378: Edited by Chris Yahnke. Page last updated 4-23-04.