What do they look like?

The body of Indiana bats is about the same size as a mouse, ranging in length from 73 to 100 mm and weighing 6 to 11 grams. The fur on the back varies from black to light brown, but the overall color is dull gray. Belly fur has a pinkish-white tint to it. Females' forearms are, on average, larger than the males'. These bats are similar in appearance to little brown bats, but differ in having fur that is dull, rather than glossy, as in little brown bats.

Where in the world do they live?

Indiana bats are found in the cavernous limestone areas of the midwestern, southern, and eastern United States. This range extends from the Ozarks of Oklahoma in the west, north to southern Wisconsin, as far east as Vermont, and as far south as northern Florida. During their winter hibernation, they are found throughout the Ohio Valley but are not found in southern Michigan, northern Indiana, and south of Tennessee. These bats have recently been reported hibernating in two caves in Ohio: one in Lawrence County, and another in Preble County, which had more than 10,000 hibernating bats.

What kind of habitat do they need?

In winters, Indiana bats live in caves and mines that are appropriate for hibernation, with a cool, stable temperature. It is not clear where males are found and roost during the summer. Females and their young roost mainly under the loose bark of large trees.

How do they reproduce?

In the fall, Indiana bats swarm around their hibernation sites, and this activity accompanies mating. Females enter into hibernation soon after they reach the cave, but the males wait so that they can mate with the incoming females.

Indiana bats mate in the fall, but females do not become pregnant until after they have left the hibernation site the next spring. The young bats are born in late June or early July, after a pregnancy of about 60 days. One young is born per year and the bats become independent from their mothers after 25 to 37 days. Cold temperatures may affect the rate of development of the young bat.

Like all female mammals, Indiana bats provide their young with milk. The young become independent after about 25 days.

How long do they live?

Indiana bats live to be 14 years old in the wild.

How do they behave?

In the early fall, Indiana bats swarm and mate at the hibernation sites. Bats enter the warmer parts of the cave and remain alert. For a while, they leave the cave at night to feed and build up body fat. During hibernation, they gather on a flat surface, either a ceiling or a wall. The groups are smaller in the warmer parts of the cave. These bats are known as "cluster bats" because they form large, thick groups during hibernation. As winter goes on, Indiana bats move to cooler parts of the cave. Those living in the warmer parts of the cave may wake up during hibernation and leave the roost before the winter ends. Normally, they leave the hibernation sites from April to June. In the summer, males and females live apart from each other, with the females forming nursery colonies in hollow trees or under bark. Indiana bats leave their roosts about a half an hour after sunset to feed. They prefer to look for food near the tops of trees in thick forests.

Home Range

In the summer, female Indiana bats have home ranges of about 52 hectares (128 acres). This range expands to 94 hectares (232 hectares) after the young are born.

How do they communicate with each other?

Indiana bats use echolocation to find their way around. They use their vision to help them find their way over long distances. These bats have excellent hearing, and no doubt communicate with each other using sound.

What do they eat?

The diet of Indiana bats is made up of small insects with soft bodies, but may also include moths and beetles. At the end of the summer, the bats change from eating insects with soft bodies to insects with hard bodies.

What eats them and how do they avoid being eaten?

Indiana bats rarely have to fear predators. Their biggest threat is habitat destruction by humans.

What roles do they have in the ecosystem?

Indiana bats eat large numbers of insects, so they are an important part of the food web in their ecosystem.

Do they cause problems?

Like all bats, Indiana bats may carry diseases such as rabies and histoplasmosis.

How do they interact with us?

Where large numbers are found, these bats help control populations of harmful insects.

Are they endangered?

Indiana bats are listed as endangered. While fairly large numbers of these bats remain, they only live in a very small number of caves during the winter and are therefore especially at risk from disturbance at those sites. The decrease in numbers over the past few decades is a result of natural disasters, human interference, and changing climate in the hibernation caves. The range of the Indiana bat has decreased as well. Humans are working at increasing the population by protecting the existing roost sites and restoring habitats in the previous range.

Some more information...

The hibernation caves of Indiana bats are popular tourist attractions. This is nice for humans, but the winter disturbance may not be good for the bats.

Contributors

Allison Poor (editor), University of Michigan: February, 2005.

Toni Lynn Newell (author), University of Michigan: June, 1999.

References

Baker, R.H. 1983. Michigan Mammals. Michigan State University Press. United States of America.

Thomson, C.E. (25 May 1982) "Myotis sodalis." Mammalian Species. The American Society of Mammalogists, 163.

Kurta, A. 1995. Mammals of the Great Lakes Region. Ann Arbor: The University of Michigan Press.

Ravenswood Media, Inc., 2005. "Cave Biota . . . an evolving "webumentary"" (On-line). Accessed July 05, 2005 at http://www.cavebiota.com/.

U.S. Fish and Wildlife Service, D. 1991. "Indiana Bat" (On-line). U.S. Fish and Wildlife Service, Division of Endangered Species: Species Accounts. Accessed August 23, 2003 at http://endangered.fws.gov/i/a/saa08.html.