Eptesicus fuscus Photo Chris Burney ©
This medium-sized bat has long, glossy, chestnut-brown fur and broad blackish wings. It roosts in attics, hollow trees, outbuildings, culverts and under bridges. When roosting in caves this bat often chooses a spot near the entrance, sometimes in partial sunlight. Compared with other bats, the big brown bat is a well-studied species, and quite a lot is known about its habits. Banding studies have shown that most of these bats live their lives within about 10 miles (16 km) of their birthplace. They typically begin hunting about 20 minutes after sunset, and spend about 90 minutes a night foraging. The feed mainly on beetles, but also eat caddis flies, moths, and mayflies.
They weigh about 14-25 gm (0.5 to 0.9 oz) and consume 50-100% of their body weight in insects each night, depending on whether or not they are lactating. Nursing females must eat their own body weight in insects to produce enough milk for the young.
Big brown bats are seen foraging near lakes, city parks, and the edges of forests and fields.
ID tip. These bats are relatively slow, straight fliers.
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