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gray bat

gray bat (Myotis grisescens) [state and federally endangered]
Photo © Michael Durham

Features and Behaviors

The gray bat is large with long forearms. Its back has gray hair while the belly fur is gray-brown. Each wing is attached to the ankle.

The gray bat may be found in Illinois near the Ohio River in the summer and along the southern one-half of the Mississippi River and in west central Illinois in winter. It lives in a cave or mine in the summer while in winter, it hibernates in a cave. The gray bat eats insects. It looks for insects among trees and over water bodies. Females form maternity colonies in summer in caves or mines. It is possible that there is only one maternity colony in Illinois. Males and females hibernate together in the winter. Although there is little information available, it is believed that the southern Illinois gray bats move to Kentucky for the winter. Other gray bats winter in caves in Adams, Madison and Pike counties. Adult females leave the wintering site before any of the other gray bats and begin to establish the maternity colony. Young are born in late May and June. One young is born per female. The young bat can fly about four weeks after birth. The maternity colony begins to break up in July. Movement back to the winter colony begins in August. Mating occurs in the fall. Females do not bear young until their second year.

Illinois Range


​Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Chiroptera
Family: Vespertilionidae

Illinois Status: state and federally endangered

The endangered status of the gray bat in Illinois is due to human disturbance and vandalization of caves and from the bats ingesting insecticides from their prey. The gray bat is also on the federal endangered species list for the United States.