The Indiana bat is a medium-sized mouse-eared bat native to North America. It is similar in appearance to the more common Little brown bat but is distinguished by its feet size, toe hair length, pink lips, and a keel on the calcar. Indiana bats can have fur from black to chestnut with a light gray to cinnamon belly.
Indian bats are found in Southern and Midwestern United States. They live in hardwood and hardwood-pine forests and are also common in agricultural land, mainly in forests, crop fields, and grasslands.
Indian bats are social and nocturnal creatures. They perform seasonal migrations from winter hibernacula to summer roosts and may travel distances up to thousands of kilometers. During winter they hibernate in caves gathering in large, tight clusters that may contain thousands of individuals. Indiana bats begin to arrive at hibernacula from their summer roosting sites in late August, with most returning in September. Females enter hibernation shortly after arriving at hibernacula, but males remain active until late autumn to breed with females arriving late. Most Indiana bats hibernate from October through April, but many at the northern extent of their range hibernate from September to May. Spring migration can begin as early as late March, but most Indiana bats do not leave their winter hibernacula until late April to early May. Females emerge from hibernacula first, usually between late March and early May. Most males do not begin to emerge until mid-to-late April. Females arrive at summer locations beginning in mid-April and form summer nursery colonies of up to 100 adult females. Males typically roost alone or in small bachelor groups during the summer. Many males spend the summer near their winter hibernacula, while others migrate to other areas, similar to areas used by females. Indiana bats feed entirely on night-flying insects, and a colony of bats can consume millions of insects each night. In one day they may travel up to 1.6 miles (2.6 km) from their day roosts to their foraging sites.
Indiana bats are polygynous meaning that one male mates with multiple females. Breeding occurs in and around hibernacula in autumn. During this period, Indiana bats undergo a phenomenon known as swarming. During this activity, large numbers of bats fly in and out of caves from sunset to sunrise. Swarming mainly occurs from August to September and is thought to be an integral part of mating. Females delay fertilization until the end of hibernation, and gestation takes about 60 days. They typically give birth to a single pup in late May to early July. Pups are born altricial (helpless) and are weaned after 25 to 37 days; they are able to fly around the same time. The young become independent from their mothers when they are between 2 and 3 months old. Females can mate during their first fall, but some do not breed until their second year. Males become reproductively active during their second year of life.
Human disturbance and the degradation of habitat are the primary causes for the Indiana bat decline. The presence of people in caves can cause the bats to come out of hibernation, leading to a large increase in their energy use. By causing them to wake up and use greater amounts of energy stores, humans can cause high mortality in a cave population of hibernating Indiana bats. Other important threats to the species include direct and intentional killings by humans, mortality due to wind turbines, pesticide use, improper application of cave gates, climate change, and agricultural development.
According to the U.S. Fish and Wildlife Service resource, in 2005 the total population size of the Indian bat was estimated at about 457,000 individuals. Currently, this species is classified as Near Threatened (NT) on the IUCN Red List but its numbers today are stable.