The Indiana bat (Myotis sodalis) is a medium-sized mouse-eared bat native to North America. It lives primarily in Southern and Midwestern U.S. states and is listed as an endangered species. The Indiana bat is grey, black, or chestnut in color and is 1.2–2.0 in long and weighs . 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 live in hardwood and hardwood-pine forests. It is common in old-growth forest and in agricultural land, mainly in forest, crop fields, and grasslands. As an insectivore, the bat eats both terrestrial and aquatic flying insects, such as moths, beetles, mosquitoes, and midges.
The Indiana bat is listed as an endangered species by the U.S. Fish and Wildlife Service. It has had serious population decline, estimated to be more than 50% over the past 10 years, based on direct observation and a decline on its extent of occurrence.
Description The length of the Indiana bat's head to the body is from 4.1 to 4.9 cm. The animal weighs about 8 g (.25 ounce). These bats are very difficult to distinguish from other species, especially the more common little brown bat (Myotis lucifugus), unless examined closely. The size of the feet, the length of the toe hairs, and the presence of a keel on the calcar are characteristics used to differentiate the Indiana bat from other bats. Indiana bats typically live 5 to 9 years, but some have reached 12 years of age. They can have fur from black to chestnut with a light gray to cinnamon belly. Unlike other common bats with brown hair and black lips, Indiana bats have brown hair and pink lips, which is helpful for identification.
Distribution Indiana bats spend the summer living throughout the eastern United States. During winter, however, they cluster together and hibernate in only a few caves. Since about 1975, their population has declined by about 50%. Based on a 1985 census of hibernating bats, the Indiana bat population is estimated around 244,000. About 23% of these bats hibernate in caves in Indiana. The Indiana bat lives in caves only in winter; but, there are few caves that provide the conditions necessary for hibernation. Stable, low temperatures are required to allow the bats to reduce their metabolic rates and conserve fat reserves. These bats hibernate in large, tight clusters which may contain thousands of individuals. Indiana bats feed entirely on night flying insects, and a colony of bats can consume millions of insects each night. The range of the Indiana bat overlaps with that of the more narrowly distributed Gray Bat (Myotis grisescens), also listed as endangered.
Endangered status The Indiana bat was listed as federally endangered under the Endangered Species Preservation Act, on 11 March 1967, due to the dramatic decline of populations throughout their range. Reasons for the bat's decline include disturbance of colonies by human beings, pesticide use and loss of summer habitat resulting from the clearing of forest cover. As of 1973, the Indiana bat has been listed as endangered under the Endangered Species Act (as amended), and additionally protected by the Federal Cave Resources Protection Act of 1988, to protect hibernacula on federal lands. In 2013, Bat Conservation International listed this species as one of the 35 species of its worldwide priority list of conservation.
Current threats Indiana bat populations in the northeastern United States are crashing with the rapid spread of white-nose syndrome, the most devastating wildlife disease in recent history. By the end of 2011, this unprecedented threat had killed 5.7 to 6.7 million bats in the United States since its discovery in 2007 based on photographs taken in 2006. Among these, at least 15,662 Indiana bats died from WNS in 2008 alone (3.3% of the 2007 range wide population), and an estimated 95% of Pennsylvania's entire cave bat population has died.
Although becoming less common, direct and intentional killings by humans have occurred. On 23 October 2007, Lonnie W. Skaggs of Olive Hill, Kentucky, and Kaleb Dee Carpenter, of Grayson, Kentucky, entered Laurel Cave in Carter Caves State Park, Kentucky, and killed 23 Indiana bats. Skaggs re-entered the cave three days later and killed another 82 endangered Indiana bats. An investigation began when Carter Caves State Park employees discovered at least 105 dead Indiana bats. The two men admitted to knowingly slaughtering an endangered species, using flashlights and rocks to knock hibernating bats off their roosts, and smashing their bodies with rocks. Bats that attempted to escape by flying away were knocked down from the air. The men stomped bats to death, bludgeoned them with flashlights, and crushed their bodies with rocks in several areas of the hibernaculum. BCI worked with the Kentucky Department of Fish & Wildlife Resources to establish a reward fund and provided the initial contribution. The reward quickly grew to $5,000 with support from the Southeastern Bat Diversity Network and Defenders of Wildlife and was widely reported, and the two men were caught following an anonymous tip. This incident was called a "senseless killing" by James Gale, Special Agent-in-Charge for the USFWS Southeast Region, and resulted in conviction. They pleaded guilty to violating the federal Endangered Species Act. U.S. Magistrate Judge Edward Atkins sentenced Skaggs to eight months in federal prison, and placed Carpenter on three years' probation. The case marks the first time nationwide that individuals were sentenced for killing endangered Indiana bats. BCI thanked members and donors for allowing them to help protect these bats and work toward a time when such killings finally cease.
Additionally, Indiana bat mortality due to wind turbines has been confirmed, even resulting in a December 2009 injunction against a West Virginia wind farm. As of 2013, only five Indiana bat mortalities have been documented; two females at Fowler Ridge in Indiana in September 2009 and 2010, one female at the North Allegheny Wind Energy Facility, Pennsylvania, in September 2011,Good, R. E., W. Erickson, A. Merrill, S. Simon, K. Murray, K. Bay, and C. Fritchman. (2011). Bat monitoring studies at the fowler ridge wind energy facility in Benton County, Indiana. WEST, Incorporated one male at the Laurel Mountain Wind Power facility, West Virginia in July 2012, and one female at the Blue Creek Wind Farm, Ohio in October 2012. Fatality rates of up to 63.9 bats per turbine, per year have been estimated.Fiedler, J. K., H. Henry, R.D. Tankersley, and C.P. Nicholson. (2007). Results of bat and bird mortality at the expanded buffalo mountain wind farm, 2005. Final report prepared for Tennessee Valley Authority. Mortality is caused both by direct impact with rotors and by barotrauma.Cryan, P.M. and R.M.R. Barclay. 2009. Causes of Bat Fatalities at Wind Turbines; Hypotheses and Predictions. 90 (6):1330–1340.
Other anthropogenic effects have contributed to the loss of Indiana bat populations, including pesticide use, human disturbance of hibernacula, improper application of cave gates, climate change, and agricultural development. As a result, the Indiana bat experienced a nationwide 57% population decline from 1960 to 2001.
Plant communities Common dominant trees used by Indiana bats throughout their range include oaks (Quercus spp.), hickories (Carya spp.), ashes (Fraxinus spp.), elms (Ulmus spp.), eastern cottonwoods (Populus deltoides), locusts (Robinia spp.), and maples (Acer spp.). The understory may include hawthorns (Crataegus spp.), dogwoods (Cornus spp.), fragrant sumac (Rhus aromatica), giant ragweed (Ambrosia trifida), sedges (Carex spp.), Virginia creeper (Parthenocissus quinquefolia), wood nettle (Laportea canadensis), goldenrod (Solidago spp.), poison ivy (Toxicodendron radicans), and wild grape (Vitis spp.).
Indiana bats were found in a variety of plant associations in a southern Iowa study. Riparian areas were dominated by eastern cottonwood, hackberry (Celtis occidentalis), and silver maple (Acer saccharinum). In the forested floodplains, the dominant plants included black walnut (Juglans nigra), silver maple, American elm (Ulmus americana), and eastern cottonwood. In undisturbed upland forest, the most common plants were black oak (Quercus velutina), bur oak (Q. macrocarpa), shagbark hickory (Carya ovata), and bitternut hickory (C. cordiformis). Black walnut, American basswood, American elm, and bur oak dominated other upland Indiana bat sites.
Indiana bats use at least 29 tree species during the summer. The greatest numbers of tree species are found in the central portion of Indiana bats' range (primarily Missouri, southern Illinois, southern Indiana, and Kentucky), but this is likely because the majority of research conducted on the species has occurred in this region. Roost trees from these central states, which are mainly in the oak-hickory cover type, include silver maple, red maple (Acer rubrum), sugar maple (A. saccharum), white oak (Q. alba), red oak (Q. rubra), pin oak (Q. palustris), scarlet oak (Q. coccinea), post oak (Q. stellata), shingle oak (Q. imbricaria), eastern cottonwood, shagbark hickory, bitternut hickory, mockernut hickory (C. alba), pignut hickory (C. glabra), American elm, slippery elm (Ulmus rubra), honey locust (Gleditsia triacanthos), sourwood (Oxydendrum arboreum), green ash (Fraxinus pennsylvanica), white ash (F. americana), Virginia pine (Pinus virginiana), American sycamore (Platanus occidentalis), and sassafras (Sassafras albidum).Garner, James D.; Gardner, James E. (1992). Determination of summer distribution and habitat utilization of the Indiana bat (Myotis sodalis) in Illinois. Illinois Department of Conservation, Illinois Natural History Survey. Final Report: Project E-3Gumbert, Mark W.; O'Keefe, Joy M.; MacGregor, John R. "Roost fidelity in Kentucky", pp. 143–152 in KurtaKiser, James D.; Elliott, Charles L. (1996). Foraging habitat, food habits, and roost tree characteristics of the Indiana bat (Myotis sodalis) during autumn in Jackson County, Kentucky. Frankfort, KY: Kentucky Department of Fish and Wildlife ResourcesMacGregor, John R.; Kiser, James D.; Gumbert, Mark W.; Reed, Timothy O. (1999). Autumn roosting habitat of male Indiana bats (Myotis sodalis) in a managed forest setting in Kentucky. In: Stringer, Jeffrey W.; Loftis, David L., eds. "Proceedings, 12th central hardwood forest conference; 1999 February 28 – March 2"; Lexington, KY. Gen. Tech. Rep. SRS-24. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southern Research Station.: 169–170
In southern Michigan and northern Indiana, which are mainly in the oak-hickory and elm-ash-cottonwood cover types, trees used as roosts include green, white, and black ash (Fraxinus nigra), silver maple, shagbark hickory, and American elm. And finally, in the southern areas of the Indiana bat's range (primarily Tennessee, Arkansas, and northern Alabama), which include the oak-hickory and oak-pine cover types, Indiana bats use shagbark hickory, white oak, red oak, pitch pine (P. rigida), shortleaf pine (P. echinata), loblolly pine (P. taeda), sweet birch (Betula lenta), and eastern hemlock (Tsuga canadensis).
Major life events
Indiana bats begin to arrive at hibernacula (caves and mines in which they spend the winter) 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. Occasionally, Indiana bats are found hibernating singly, but almost all are found hibernating in dense clusters of 3,230 to 5,215 bats/m2.