Big Brown Bat (Eptesicus fuscus)

Big Brown Bat (Eptesicus fuscus)

Appearance

The Big Brown Bat is a relatively large bat that ranges from 98-131 mm in length and typically weighs between 12 g and 22 g. They have a large, broad head, broad nose and long, lax fur. Its fur colour varies from pale to dark brown. Its flight membranes and ears are black. The ears just reach the nose when pushed forward; the tragus is short and blunt. The calcar has a prominent keel. The skull is robust, with thick, heavy jaws, a flattened brain-case and large teeth.

Natural History

The Big Brown bat is known to have a strong affinity for buildings and it is often referred to as a house bat or barn bat. In British Columbia, maternity colonies have been found in the attics of houses, cabins and barns. Maternity colonies of Big Brown Bats as large as 700 individuals have been reported, but those associated with buildings in British Columbia are small, comprising no more than 50. This species emerges around dusk to feed. It is regarded as a generalist that hunts in a variety of situations: over water, over forest canopies, along roads, in clearings, and in urban areas, often around street lights that attract insects. The Big Brown Bat makes several feeding flights during the night, each 30 to 60 minutes in duration. Between flights it usually roosts near the feeding area.

Habitat: The Big Brown Bat inhabits a variety of habitats in the province, including arid grassland and interior and coastal forests. It ranges in elevation from sea level to 1070 metres.

Range: The Big Brown Bat has a vast range that extends from northern South America to southern Canada. In British Columbia, it is found on Vancouver Island, the coastal mainland north to the Bella Coola River Valley and the interior where its northern limits are unknown. Northernmost localities in the province are from the Prince George and the Peace River region, but because there is a record from the interior of Alaska the range may extend into extreme northern British Columbia.

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