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NATURAL HISTORY

INDIANA BAT } Myotis sodalis
FAMILY: Vespertilionidae

DESCRIPTION: The Indiana bat is a medium-sized bat reaching a length of about 41 to 49 millimeters. It has grayish-chestnut and lead-colored fur with pinkish to cinnamon-colored underparts.

HABITAT: During the winter, Indiana bats reside in underground hibernacula, mostly caves but also cave-like locations including abandoned mines. Even small changes in the temperature, barometric pressure, and humidity of a hibernaculum can make it unsuitable for bats. In the spring, fall, and summer, bats typically roost under the exfoliating bark of trees, or sometimes in trees’ vertical crevices. Most trees occupied by female Indiana bats in the summer are dead or nearly dead.

RANGE: The Indiana bat is known to occur in Alabama, Arkansas, Connecticut, Georgia, Illinois, Indiana, Iowa, Kentucky, Maryland, Michigan, Mississippi, Missouri, New Jersey, New York, North Carolina, Ohio, Oklahoma, Pennsylvania, Tennessee, Vermont, Virginia, and West Virginia.  

MIGRATION: Indiana bats hibernate in caves and mines in the winter and migrate over varying distances to summer habitat in a variety of habitat types — most often forests, but also wetlands, parklands, and agricultural areas. Reproductive females may migrate great distances to form maternity colonies. Hibernation typically lasts from October through April. 

BREEDING: Indiana bats converge at hibernacula during a “swarming” period in preparation for mating during the late summer and fall. Adult females store sperm throughout the winter, delaying fertilization until their emergence from hibernation in the spring. Females usually give birth to one offspring in June or early July while in their maternity roosts. Poor physical condition at the end of winter may prevent a female from being able to successfully bear young.

LIFE CYCLE: Indiana bats live to be about 14 years old in the wild.

FEEDING: Indiana bats are nocturnal insectivores, eating flying insects (and very occasionally spiders) during the nighttime hours.

THREATS: Indiana bats are threatened by loss and fragmentation of summer habitat due to logging, road building, development, and other human impacts; alteration of hibernacula; pesticides; and human disturbance. Bats in the Northeast are also severely and increasingly threatened by the deadly white-nose syndrome. 

POPULATION TREND: By 1967, remaining Indiana bat populations represented a small portion of historical numbers. Since the 1950s, many hibernating populations have decreased in size, and by 1985, more than 85 percent of the known rangewide population hibernated in just eight caves and one mine. From 1965 to 2001, the rangewide population estimate dropped by approximately 57 percent. From 2003 to 2005, overall numbers may have increased, but it’s likely that by today white-nose syndrome has nearly wiped out the species in New York and Vermont, and possibly throughout the Northeast.

Photo by Adam Mann, Environmental Solutions and Innovations