v1-Hoary Bat (Lasiurus cinereus)

Hoary Bat (Lasiurus cinereus)

Appearance

The Hoary Bat is the largest bat in British Columbia with a total length between 125-144 mm and a weight between 20-38 g. They are distinctive because of their striking hoary colour which it takes its name from. The long, soft fur on its back is a mix of dark brown and grey hairs that are tinged with white. There are small patches of yellow or white on its shoulders and wrists. Yellow fur also appears on the throat, around the ears and on the underside of the wing membranes. The wing membranes are dark brown with paler areas on the forearm and fingers. The ears are round and short with a short, broad tragus. The dorsal surface of the tail membrane is densely furred; the hind foot is relatively small with a heavy covering of fur on the upper surface. The calcar has a narrow keel.

Natural History

Because of its tendency to roost in the branches of coniferous and deciduous trees, the Hoary Bat is often referred to as a tree bat. Specific details on tree roosts in British Columbia are not available as only a few individuals have been found roosting in the province it seems to select sites that will conceal it from predators and yet also provide an open flight path for easy access to and from the roost. In Oregon the Hoary Bat prefers old Douglas-fir forests, presumably because of its tree-roosting habits. Although its usual day roosts are in the branches of trees, the Hoary Bat has been found roosting in tree cavities in British Columbia. The Hoary Bat rarely roosts in caves or buildings. In summer, males are solitary and females roost with their young. Female Hoary Bats do not congregate in maternity colonies. Because their tree roosts are more exposed than the maternity roosts of other bats, females will stay with their undeveloped young for longer periods to keep them warm. Family groups will use the same roost for more than a month. Hoary Bats emerge about 30 minutes after sunset to feed and continue to forage throughout the night. The Hoary Bat is often attracted to insect concentrations at lights outside buildings; permanent outdoor lights may even be responsible for its presence at some locations in the province. In well-lit areas where insect prey is concentrated, a Hoary Bat will establish a feeding area and chase away other bats. Loud chirping calls audible to the human ear are often emitted during these chases. Besides their role in communication, these calls may also provide some echolocation information.

 

Range: The Hoary Bat has the broadest distribution of any North American bat ranging from South America to northern Canada. It has managed to colonize a number of isolated islands including the Hawaiian Islands. In British Columbia, it is found on Vancouver Island, the coastal mainland north to Garibaldi Provincial Park, and the southern interior north to the Williams Lake region. In some regions of North America the sexes appear to occupy separate summer ranges. Based on the few available records the sexes appear to overlap extensively in British Columbia.

Habitat: The Hoary Bat is associated with a variety of forested and grassland habitats in the province. It ranges in elevation from sea level to 1250 metres.

 

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