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Although bats are often mistreated and misunderstood, these mammals are beneficial and important components of the ecosystem. They also eat many night-flying insects, including crop pests.
Despite the many benefits of bats, people should avoid contact with them and should not handle them. Bats can carry rabies. Dogs and cats can encounter bats, especially bats that are sick or injured, and should therefore be vaccinated against rabies. Even if bats are healthy, they should not be handled because they are fragile. Vampire bats do not live in Indiana.
The Indiana Bat (Myotis sodalis) is a medium-sized, dull gray bat. The length of its head and body ranges from 1.5 to 2 inches, and the animal weighs about 1/4 of an ounce. Most bats are very difficult to distinguish from their cousins unless examined closely. The size of the feet and the length of the toe hairs are characteristics used to differentiate the Indiana bat from other bats. Indiana bats live an average of five to 10 years, but some have reached 14 years of age.
The Indiana bat spends summer months living throughout the eastern United States. During winter, however, they cluster together and hibernate in only a few caves. The past 25 years, the population of Indiana bats has declined by about 50 percent. As a result, this bat has been classified as an endangered species by the United States government. Based on a 1985 census of hibernating bats, the Indiana bat population is estimated at about 244,000. About 23 percent of these bats hibernate in caves in Indiana. The Indiana bat dwells in caves only during the winter; however, there are few caves that provide the conditions necessary for hibernation. Stable, low temperatures are required to allow the bats to reduce their metabolic rate and conserve fat reserves. These bats hibernate in large, tight clusters which may contain thousands of individuals.
In spring, bats emerge from hibernation and migrate to their summer homes. Because they separate into smaller social units, little is known about summer habitat requirements. Females form maternity colonies of up to 100 bats during the summer. But only a few of these colonies have been found. The colonies discovered were located behind the loose bark of trees, usually near tree-lined streams and rivers.
Indiana bats give birth to only one young in midsummer. These young bats are capable of flight in a month. The remainder of the summer and fall is then spent accumulating fat reserves for hibernation.
In the fall, bats congregate in caves and begin a swarming period. During this time, the bats will fly in and out of their cave throughout the night. Mating occurs during swarming period, however; females store the sperm during hibernation and do not become pregnant until spring.
Indiana bats feed entirely on night flying insects, and a colony of bats can consume thousands of insects each night. A gray bat (an endangered species) will eat up to 3,000 insects per feeding. Bats locate these insects by emitting high-pitched sounds and waiting for the echo, which allows them to zoom in on the bug's location. The fat reserves accumulated by devouring these large quantities of insects during the summer and fall allow the bat to sustain itself during hibernation.
Bats are subject to natural hazards during hibernation, such as cave flooding, however; humans have been the major cause of declining bat populations. The clusters of hibernating bats are very susceptible to disturbance and vandalism. People touring caves can disturb bats and cause them to awaken. When a bat is aroused, it uses energy at a higher rate, which decreases the energy supply available for the rest of the winter. Vandals have knocked down and killed large clusters of bats, and although illegal, some people shoot bats for entertainment. Because bats feed on insects, the increased use of pesticides has undoubtedly resulted in the poisoning of some of these animals. In the past, the clearing of forests has caused a decline in the summer habitat of the Indiana bat. Modern forestry practices have been developed and implemented to minimize this impact.
The conservation of this species in Indiana is the responsibility of the Division of Fish and Wildlife’s Nongame and Endangered Wildlife Program. The program has funded studies to census hibernating bats and further investigate the summer habitat requirements of this species. It includes both mobile surveys and stationary monitoring locations.Because bats are misunderstood, perhaps the best conservation effort is to inform Hoosiers about these beneficial bug eaters. The nongame program has devoted much effort toward educating the public about bats and their benefits to man. An effort should be made to dispel those old myths and give bats the respect they deserve.