The Indiana Bat - Myotis sodalis
By Stephanie Obley, SCWF Volunteer
The tiny Indiana bat was first identified as endangered nearly 36 years ago, one of the first species under the Endangered Species Preservation Act passed in 1966. It is one of 6 out of the 45 continental U.S. bat species currently listed as federally endangered.
The Indiana bat’s scientific name, Myotis sodalis, means “mouse-ear companion” due to its tiny mouse-like ears and its social nature, with thousands of bats hibernating together each year. This is true to such an extent that 85% of the remaining known species population (approximately 350,000) hibernates in just 7 caves in Missouri, Indiana and Kentucky. During winter hibernation, there can be as many as 300 bats per square foot.
The first Indiana bat was described scientifically in 1928 in Indiana. It is known to occur over much of the eastern U.S. and is listed as endangered in 23 states. The range stretches roughly from western Oklahoma to the Great Lakes states and from Vermont south to northern Florida. A mammal, the Indiana bat is part of the family Vespertilionidae.
With a weight of about 3/10 of an ounce (or about 3 pennies), the Indiana bat measures only a few inches long and has a wing span of 9 to 11 inches. It resembles the brown bat, although its fur is more of a grayish chestnut and the basal portions of its back hairs have a dull lead color. The fur on its underparts is pinkish to cinnamon, and its hind feet are smaller and more delicate.
The Indiana bat is listed as endangered in South Carolina by both the federal and state government, although it is unclear if and to what extent the species occurs here. Maternity roosts have been found in western North Carolina, and a team from USDA Forest Service Southern Research Station's Threatened and Endangered Species Unit in Clemson, SC, is looking for similar sites in South Carolina. None have been found to date.
According to the U.S. Army Corps of Engineers’ web site on Endangered and Threatened species of the Upper Savannah River Basin, the Indiana bat is suspected to migrate to parts of South Carolina during the summer months, although no record has been made of the species here. According to Bat Conservation International’s web site, one sighting was reported in 1993. Some range maps show the Indiana bat occurring in just the western edge of South Carolina.
The Indiana bat uses limestone caves for winter hibernation, preferring caves with a temperature averaging 37 to 43 degrees Fahrenheit, and relative humidity averaging 87 percent. Mating occurs in the early part of October prior to hibernation. In late March, the hibernating colonies disperse to upland, riparian and flood plain habitats throughout their range, possibly including South Carolina, where females congregate in small groups in maternity roosts. These roosts are typically found under loose bark and in the hollows of trees, and occasionally under bridges and in old buildings. Females give birth to 1 young in June or July. Like many bat species, Indiana bats eat large quantities of insects daily.
The Indiana bat’s population has declined by about 60 percent since the 1960s and continues to decline. The U.S. Fish and Wildlife Service estimated the total population at 550,000 in 1983 and the April 9, 1999, Federal Register put the total at 353,000 bats. The major threats to the Indiana bat include commercialization of roosting caves, alteration of cave temperatures, destruction by vandals, and intrusion by spelunkers. A single visit by people to a cave in winter can rouse hibernating bats, leading to a raise in the bats‘ metabolism levels which consumes energy needed to sustain hibernation. Such interruptions can be fatal. Because Indiana bats tend to return to the same caves each year, destruction of winter caves is particularly deadly.
The bats' summer habitat and maternity roosts are affected by human development, logging, tree removal and dam construction. Their slow reproductive rate of one offspring born per female bat per year, makes recovery difficult.
The original federal Indiana bat recovery plan was approved in 1976, and revised in 1983. The major goals include preserving critical winter habitat by securing primary caves and mines and restricting entry to those locations; initiating an education program; and monitoring population levels and habitat. So far, conservation efforts have involved controlling access to critical habitats by installing gates across cave entrances. The National Speological Society and the American Society of Mammologists are also taking measures to promote conservation.
To help the endangered Indiana bat, there are several things a person can do. The first is to dispel myths about bats. For example, very few bats carry rabies. They do not get tangled in people’s hair. They are not rodents, and none of the U.S. species are vampire bats.
Backyards can also be turned into inviting habitats for bats. For the Indiana bat, dead trees and snags can be left in place for summer roosting. They favor oak and hickory, but also will use cottonwood, elm and other trees with loose, sloughing bark. People should avoid going near any caves in which bats hibernate or any area known to be a maternity roost. If you believe you’ve spotted an Indiana bat, report it to the state Department of Natural Resources or the U.S. Fish and Wildlife Service.
Information for this article was obtained from the following Web sites:
Nature Serve Explorer
U.S. Fish and Wildlife Service
USDA Forest Service
U.S. Army Corps of Engineers
National Wildlife Federation
Bat Conservation International Inc.