Ears and membranes are a glossy dark brown. From Labrador to southern Alaska, the mountains of southern California, as well as from the Appalachians to Georgia and west into Arkansas. Stragglers can be found in New Mexico, Texas, Mississippi, and Alabama, and the coastal parts of the Carolinas. In the spring and summer females form maternity colonies of hundreds of individuals or more in attics, barns, and other retreats that are dark and hot during the daytime. In winter, these bats hibernate in caves and mines, frequently returning year after year to the same nursery colony and hibernation cave.
Colonies are far more common near lakes and rivers.
Rabies is seldom a problem with this species since it is not an effective biter due to its small teeth. Big brown bat, Eptesicus fuscus . Big brown bat, house bat, barn bat, dusky bat. Probably the largest bat commonly found in buildings except for the pallid bat. Most adults are copper-colored, but color may vary from light to dark brown.