Minnesota Profile - Big Brown Bat (Eptesicus fuscus)

Description

The big brown bat’s scientific name, Eptesicus fuscus, is Latin for dark house-flier. It is the more common of the two bat species sometimes found in houses and barns. An adult is about 5 inches from nose to tail and has a wingspan of about 10 inches. It has glossy copper or chocolate-brown fur and black membranes on its face, ears, wings, and tail. Long, slender finger bones are encased in leathery skin to make up its wings. This bat belongs to an order of mammals called Chiroptera, from the Greek for hand-wing.

Range and habitat

Big browns range throughout temperate North America into South America and many Caribbean islands. At home in city and country, they are among Minnesota’s hardiest bats.

Diet and echolocation

They feed at night on flying insects, especially beetles. Nursing females ingest their body weight in insects each night. Bats locate prey by emitting high-frequency sound and listening for echoes bouncing off objects in front of them. The big brown’s call is beyond human hearing.

Reproduction

Big browns mate in fall. In spring females form maternity colonies in attics, barns, and hollow trees. They give birth to one or two pups in early summer. Within a month, pups can fly and forage with their mothers.

Hibernation

They hibernate in caves, sewers, mines, and buildings. They are the last of Minnesota’s cave bats to enter hibernation—usually forced in by a November storm—and among the first to leave in spring. Hibernating bats do not eat and must survive on fat reserves. They can lose more than 25 percent of their body weight over winter.

Place in the ecosystem

Bats eat insects, including agricultural pests. During summer a colony of 150 bats can consume 38,000 cucumber beetles, 16,000 June bugs, 19,000 stink bugs, and 50,000 leafhoppers. People can minimize conflict with big browns by closing up holes to keep them out of buildings and putting up bat houses. To learn more, contact the DNR Information Center, see page 79.

Where to look

Watch the twilight sky for a bat the size of a sparrow fluttering above the forest canopy, cruising down a tree-lined road, or swooping under streetlights.

Gerda Nordquist, mammalogist and animal survey coordinator

DNR Minnesota County Biological Survey