RANGE:

Broadly distributed from British Columbia east across southern Canada to Maine southward along the Atlantic coast to Florida and west to Baja California. This species extends south through Central America into Columbia. In Idaho, it has been collected in 15 counties but likely occurs everywhere in the state.

DESCRIPTION:

The dorsal fur, often oily, is a dark brown to cinnamon brown. The typically bare ears are broad with rounded margins that, if extended forward, do not reach significantly beyond the tip of the broad nose. The tragus, which is slightly curved forward, is less than one-half the length of the ear. The calcar is keeled. The tail, enclosed in the tail membrane, usually extends several millimeters beyond the posterior margin of the membrane. Young of the year are usually darker and have duller fur than adults.

HABITAT:

A common species in urban areas, the big brown bat often roosts in homes, especially behind shutters, in cool attics, and under eaves. In other buildings it may occur between enclosed walls. In forested areas, hollow spaces in snags or living trees are occupied. It is a common species near the entrances of caves and mines but usually does not cluster with other individuals in these colder locations. It appears to hibernate for a shorter period of time than members of the genus Myotis.

DIET:

An predator on beetles, this species is important as a result of its consumption of cucumber beetles which are agricultural pests. A variety of other insects are consumed, especially along water courses and in forests. Food items may include up to ten orders of insects.

ECOLOGY:

Big-brown bats may select temporary roosting sites during bouts of foraging on warm, dry nights, although foraging usually occurs near their permanent roosts. Seasonal movements to hibernal areas are largely restricted to nearby sites. Females demonstrate strong fidelity to nursery sites which are often used by a larger number of individuals as contrasted to hibernal sites. Bats taken from roosting areas and released elsewhere can return to the area of collection, in one study, return occurred over a distance of 450 miles.

REPRODUCTION:

Reproduction begins in the fall upon break-up of maternity roosts and may extend over winter and spring. Maternity colonies appear to be located in warm conditions and may move to alternate roosts by females that carrying their young in flight. Implantation occurs from April to May and birth about 60 days later. In the west, a single pup is born in late May or early June.

IMPORTANT STATE REFERENCE:

Keller, B.L. 1987. Analysis of the bat species present in Idaho with special attention to the spotted bat, Euderma maculatum. Department of Biological Sciences, Idaho State University, Pocatello. 25pp.

IMPORTANT GENERAL REFERENCE:

Kurta, A. and R. H. Baker. 1990. Eptesicus fuscus. American Society of Mammalogists, Mammalian Species, 356:1-10.