Western Long-eared Myotis (Myotis evotis)

Western Long-eared Myotis (Myotis evotis)

Appearance

The Western Long-eared Myotis is a large Myotis species measuring between 74-103 mm in total and weighing between 4.2-8.6 g. Their ears are long, extending 5 mm or more beyond the nose when pushed forward. Its dorsal fur colour is extremely variable, ranging from yellowish brown to dark brown or nearly black. Blackish brown shoulder patches are usually evident but they can be indistinct on dark individuals. The outer edge of the tail membrane has a fringe of tiny hairs that can be seen with a hand lens. The ears and flight membranes are nearly black and usually contrast sharply with the paler fur. The tragus is long and slender with a small lobe at its base. The calcar lacks a distinct keel. The skull has a relatively broad interorbital area and a gradually sloping forehead. The skull of the Western Long-eared Myotis has a longer toothrow than that of Keen’s Long-eared Myotis and the Northern Long-eared Myotis: the distance from the last upper premolar to the last upper molar is greater than 4.2 mm.

Natural History

In summer the Western Long-eared Myotis uses buildings or under the bark of trees as day roosts; there are also a few records of this species roosting in caves, sink holes and fissures in cliffs. Maternity colonies, usually located in buildings, are generally small (5 to 30 individuals) and may contain a few adult males. Caves and mines are used as temporary night roosts.There are no winter records for the province; in fact, this bat’s winter biology is poorly documented throughout its range. In the western United States, a few individuals have been found hibernating in caves and mines and there is a December record from coastal Oregon of an individual that was found in a garage. Western Long-eared Myotis typically emerge 10 to 40 minutes after dark to feed. It is quite flexible in its feeding behaviour, eating airborne insects as well as gleaning insects from vegetation or off the ground.It is known to prey mainly on moths, as well as beetles, flies and spiders. Its quiet, short-duration, high-pitched echolocation calls are an adaptation for hunting in habitats with heavy vegetation. Furthermore, these calls are not readily detected by most moths. When closing in for an attack, the Western Long-eared Myotis often stops calling and listens for sounds produced by its prey. Moths may be especially vulnerable to predation by the Western Long-eared Myotis because their fluttering is audible.

 Range:  This is a western bat that ranges from Baja California through the western United States to Saskatchewan, Alberta and British Columbia, where it occupies the entire mainland as far north as the Bella Coola Valley on the coast and the Prince George region in the interior. It also inhabits Vancouver Island but appears to be absent from the Queen Charlotte Islands.

Habitat: This species is found in a wide range of habitats in the province, from arid grasslands and ponderosa pine forests to humid coastal and montane forests. In British Columbia it ranges in elevation from sea level on the coast to 1220 m in the Cascades (Manning Provincial Park) and Rocky Mountains (Kootenay National Park). This is one of the few bats found consistently at high elevations in western Canada. In the Kananaskis region of the Alberta Rockies, summer populations consisting of both sexes live at 1350 to 2050 m.

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