FAMILY: VespertilionidaeGENUS: Eptesicus

SPECIES: fuscus

PRONUNCIATION: eo-tess-a-cus-fuss-cuss


Fur is a uniform brown above, and lighter below. The hair has a blackish base but is brown-tipped. The uropatagium and patagium are naked and blackish in color.


Insects. They appear to prefer beetles. A colony of 150 big brown bats can eat enough cucumber beetles each summer to protect local farmers from up to 33 million or more rootworms each year.



This is one of the most widespread bats in the U.S. occurring throughout the lower 48 states, and the bat with which people are most likely to encounter. The Big Brown Bat is found in virtually all habitats including mountains, deserts, evergreen and deciduous forests, even big city parks.

While hibernating, the body temperature of the Big Brown may register only slightly above freezing, enabling this species to be in attics or more exposed parts of caves of mines – for that reason, most Big Browns now live year round in buildings or other man-made structures.

Those that choose to live more on the ‘wild side’ hibernate in deep rock crevices, caves, mines and other underground structures. During the summer roost sites include the traditional hollow tree, as well as attics, barns, bridges (and other man-made structures). Colonies of a few to several hundred females gather to form maternity colonies.


big brown

Big brown bats in this area produce twins annually. The big brown bat is a hardy species and is active both in late fall and early spring, as well as on some warm days in winter. These animals are easily attracted to well-places and properly constructed bat houses.