Silver-haired Bat (Lasionycteris noctivagans)

Silver-haired Bat (Lasionycteris noctivagans)

Appearance

The Silver-haired Bat measures from 90-117 mm in length and weighs between 6-12 g. It has a distinctive appearance with fur that is dark brown or black with scattered silver-white-tipped hairs giving it a lightly-frosted appearance. IOn the underside, the frosted hairs are concentrated in the belly. The ear is short and round with a short, blunt tragus. The ear and wing membranes are black. The dorsal surface of the tail membrane is lightly furred. The calcar lacks a keel. The skull has a blunt rostrum and is flat in profile.

Natural History

This species is generally regarded as a tree bat, although there is limited information on its summer roosting habits. Individuals have been found under the bark of trees and in crevices in tree trunks, abandoned woodpecker holes and bird nests. Trees appear to be the most important hibernation sites in the province: Silver-haired Bats have been found hibernating under the bark of Western Red-cedars in Vancouver; one was discovered in a Douglas-fir snag near Kamloops. Typically the Silver-haired Bat roosts alone or in small groups of two to six. Even when roosting in groups, individuals are rarely found in close contact. Most Canadian populations of the Silver-haired Bat are thought to be migratory overwintering in the United States however it can be found in British Columbia in all seasons. Changes in seasonal occurrence suggest that its range shifts northward in spring and southward in winter. This species emerges about 30 minutes after sunset to hunt in clearings around tree-top level and over water. There are two well-defined peaks in activity: the first between 10 pm and midnight, and the second an hour before dawn. Night-time activity is sharply curtailed when temperatures are below 8°C.

Range: The Silver-haired bat ranges widely in North America from northernmost Mexico to southern Canada and southeastern Alaska. In British Columbia it inhabits several coastal islands including Vancouver Island and the Queen Charlotte Islands, the coastal mainland north to Rivers Inlet, and the interior as far north as the Peace River and Spatsizi Plateau. In some parts of North America, males and breeding females appear to occupy separate summer ranges. This may not be the case in British Columbia because male and female distributions overlap extensively in all seasons.

Habitat:  In British Columbia, the Silver-haired Bat is associated with forest and grassland habitats and ranges in elevation from sea level to 1220 metres.

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