Lasionycteris noctivagans
(Silver-haired Bat)

Order: Chiroptera
Order Description: Bats
Family Description:

The dorsal fur is longish and usually blackish or dark brownish with silver-tipped hairs. The tragus is short and blunt, the ear cupped and broadly rounded. The calcar Click word for definitionis not keeled.

Occurs throughout U.S. and most of southern Canada. Small populations may also be found in northern Mexico and southern Alaska. Apparently, most individuals overwinter in southern part of range. Males seem to stay farther south in spring and summer than do females. Idaho distribution is not well known.

This bat is found in a wide range of elevations in trees containing natural or bird-excavated cavities or under exfoliating bark. In northern Idaho, hibernating single individuals have been found in mine adits. In southern Idaho, lava-tube caves may be used as day roosts during fall north-south migrations. Logging, especially snag destruction, likely impacts the distribution of silver-haired bats. In Idaho, maternity colonies consist of small populations of females that change locations during pup rearing. The degree of yearly Site fidelity Click word for definitionis unknown.

Beetles, moths and a wide variety of small insects found along water courses, impoundments, and ponds are consumed.

This species has been studied in southern Idaho forest. Large numbers are rarely caught at any single netting site. The silver-haired bat may be an especially good indicator of the number of snags and green trees needed to support breeding and recruitment. In Idaho, over 50 percent of bats submitted that test positive for rabies Click word for definitionare silver-haired bats. Thus, this bat should never be handled, especially if found on the ground during daylight hours.

Hibernates Click word for definition(rarely in caves). Species is relatively cold tolerant; may be active at low air temperatures (roosting migrants in Manitoba study became torpid at air temperatures below 20° C). Forages over small water bodies, forest canopy, and (in more open habitats) low over ground and shrub vegetation. Leaves roost Click word for definitionand begins to forage relatively late. Major activity peaks 3 hr after sunset and 7-8 hr after sunset, but this varies with latitude. Usually roosts singly, but will occasionally form groups of 3-6. Summer roosts and nursery sites are in tree foliage, cavities, under loose bark, or sometimes in buildings (in Manitoba study, migrants typically roosted in narrow crevices in tree trunks). Densities are probably low. May congregate in large numbers and migrate several hundred miles.

It appears likely that this species has evolved a sex specific population structure in some areas as males and females appear to be broadly geographically separated in some states. Maternity colony sites may contain several dozen individuals in Idaho. Females give birth to twins in late June after 50-60 days of gestation Click word for definition.

Status: Unprotected nongame species
Global Rank: G5
State Rank: S5

Important State References:
Bohn, K. M. 1999. Day roost selection by silver-haired bats (Lasionycteris noctivagans) and the effects of a selective timber harvest on bat populations in Caribou National Forest. M.S. Thesis, Department of Biology, Idaho State University, Pocatello. 89 pp.+ appendix.

Keller, B.L. 1987. Analysis of the bat species present in Idaho, with special attention to the spotted bat, Euderma maculatum. Dept. Biol. Sciences, Idaho St. Univ., Pocatello. 25pp.

Information written by Barry Keller ,© 2000
Map image provided by
Stephen Burton,© 2000
Design by Ean Harker©1999, 2000.