RANGE:

From Alaska throughout southern Canada to Nova Scotia, southward along the Atlantic coast to Georgia and across Texas to mid-California, especially in forested areas, along wooded watercourses and in desert areas where trees have been planted adjacent to human habitations. This species has a very broad distribution. Records exist for 14 counties in Idaho.

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 is not keeled.

HABITAT:

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 is unknown.

DIET:

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

ECOLOGY:

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 are silver-haired bats. Thus, this bat should never be handled, especially if found on the ground during daylight hours.

REPRODUCTION:

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.

IMPORTANT STATE REFERENCE:

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.