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Myotis sodalis Miller and Allen, 1928
Indiana Bat
Federal Protection: Listed Endangered
State Protection: Endangered
Global Rank: G2
State Rank: S1
Element Locations Tracked in Biotics: Yes
SWAP High Priority Species (SGCN): Yes
Element Occurrences (EOs) in Georgia: 5
Habitat Summary for element in Georgia: Limestone caves with pools; wooded areas near streams, upland forests, large snags in open areas including ridge tops
The dorsal hair of the Indiana bat is dark chestnut gray to pinkish gray, darker at the base, and lacks luster.The ears and wing membranes also have a flat coloration that does not contrast with the fur. The underfur is somewhat lighter colored with a pinkish cast. The hairs on the relatively small (9 mm, ⅜ inch) feet are short and inconspicuous. The calcar (a spur of cartilage arising from inner side of ankle and running along part of outer wing) is keeled. The total length is 41 - 49 mm (1⅝ - 1⅞ inches), the forearm length is 35 - 41 mm (1⅜ -1⅝ inches), the wingspread is 24 - 27 cm (9⅜ - 10⅝ inches), and the weight is about 5 - 8 grams (about ¼ ounce).
Little brown bat (Mysotis lucifugus) has glossy fur, a darker face, no keel on the calcar, and slightly larger feet with hairs extending over the claw (toe hairs are shorter than claws in Indiana). Southeastern bat (M. austroriparious) has larger feet with longer hair over the claws, no keel on the calcar, and woolly gray fur. Northern long-eared bat (M. septentrionalis) has longer ears and a long pointed tragus.
Indiana bats gather in large groups in suitable caves to hibernate, more than 85% of the population is in just nine caves in Indiana, Missouri, and Kentucky. These bats need winter caves with a stable temperature of 4 - 8°C (39 - 46°F) that contain standing water which maintains relative humidity above 74%. The bats usually cluster fairly near the entrance and awaken periodically throughout the winter. During the summer, Indiana bats roost in trees, usually under loose, exfoliating bark as found on shagbark hickories, dead hardwoods and pines, or in hollow trees. The roost sites are typically at a woodland edge or in a forest opening where the tree is warmed by the sun. The bats forage in the surrounding riparian, floodplain, and upland forest, and sometimes over open areas and water as well. Hibernation sites are cooler than those used by other Myotis.
Diet consists of flying insects, including moths, flies, mosquitoes, midges, beetles, bees, wasps, ants, caddis flies, and stoneflies.
In late March, females emerge from hibernacula and disperse to their summer ranges. From mid-April to mid-May, they begin to gather in maternity colonies numbering 25 - 100 under loose bark, in crevices, or in hollow trees. Each female gives birth to a single young in June or early July. The young are able to fly in about four weeks. Males emerge from hibernation a little behind the females. Some disperse and some remain near the hibernacula. Males roost singly or in small groups. They tend to forage in the canopy of the floodplain forests and wooded hillsides, whereas the females forage lower in riparian and floodplain forests. Migration to hibernacula begins in August. Upon arrival, the bats "swarm," a behavior in which great numbers of bats fly in and out of cave entrances throughout the night, with only a few bats actually roosting in the caves during the day. Swarming continues for several weeks and is related to mating activity. During this time, the bats also are building up fat reserves upon which they will depend during the winter. Breeding occurs mainly in early October; females store sperm throughout the winter, and fertilization occurs in the spring shortly after emergence. Some breeding activity also occurs in the spring. Almost all bats are in hibernation by late November. They hang from the cave roof in tight clusters with and in some sites densities of bats are about 3,200 bats per square meter. Individuals awaken and become active within the cave every 8 - 10 days, so they are a little less susceptible to disturbance during hibernation than are some other species. Bats of this species are known to live at least 20 years.
Guidelines for hibernacula surveys and summer mist-net surveys are given in the Indiana bat survey protocol made by the USFWS (https://www.fws.gov/midwest/endangered/mammals/inba/inbasummersurveyguidance.html). There are no known significant hibernacula (that is, with large numbers of bats) in Georgia for this species, but any survey of wintering bats should be conducted very carefully to avoid disturbance that could lead to awakening. Care should also be taken to avoid the spread of the invasive and causative fungus, Pseudogymnoascus destructans, of white-nose syndrome in caves. Refer to the National White-nose Syndrome Decontamination Protocol to avoid the spread (https://www.whitenosesyndrome.org/static-page/decontamination-information). If Indiana bats are encountered, the Georgia Department of Natural Resources and U.S. Fish and Wildlife Service should be notified immediately, and survey efforts at that site should be suspended pending further authorization.
This species is known to occur throughout much of the midwestern and eastern U.S., but has been documented in Georgia from only two caves in Dade County in the northwestern part of the state and occasional winter records in other portions of NW GA. The Georgia records are from fall and winter collections; the nearest known maternity colonies are in southern Kentucky and northeastern Alabama. The species has been virtually eliminated from much of its former range.
Cave disturbance and alteration, including installation of poorly designed gates, along with vandalism and pesticides, have contributed to the decline of Indiana bats. Clearing of riparian forests has likely also been a factor. Significant natural factors include flooding of occupied caves, exposure to freezing temperatures during especially harsh winters, cave ceiling collapse, and destruction of tree roosts by severe weather. Although populations have increased in recent years, white-nose syndrome now poses an additional threat to this and other cave dwelling species. The disease triggers frequent arousal during hibernation, which depletes fat reserves and causes severe wing damage, dehydration, and starvation. Since the emergence of WNS, Indiana bats have experienced an annual population decline of roughly 10% throughout their range.
There are very few records of this species in Georgia, and no known occupied habitat.
Georgia has no known occupied habitat at this time. It is likely that small numbers of winter residents and transient individuals occur in the state. Protection of occupied caves, if any unprotected ones are found, is imperative. In other areas, proper gating of caves minimizes disturbance at roost sites. Forest management activities at summer roost sites should ensure that forested foraging habitat is available, that no roost trees are destroyed, and that a continuous supply of suitable roost trees are available. Since roosts are often in dead trees, each one is available for only a few years before it falls.
Baker, W. W. 1965. A contribution to the knowledge of the distribution and movements of bats in North Georgia. M.S. Thesis, University of Georgia, Athens.
Barbour, R. W., and W. H. Davis. 1969. Bats of America. University Press of Kentucky, Lexington. 286pp.
Dalton, V. M., and C. O. Handley, Jr. 1991. Social Myotis. Pages 569 - 570 in K. Terwilliger, (ed.). Virginia's endangered species. McDonald and Woodward Publ., Blacksburg.
Harvey, M. W., J. S. Altenbach, and T. L. Best. 1999. Bats of the United States. Arkansas Game and Fish Commission, Little Rock. 64 pp.
Humphrey, S. R., A. R. Richter, and J. B. Cope. 1977. Summer habitat and ecology of the endangered Indiana bat (Myotis sodalis). Journal of Mammalogy 58: 344-346.
Humphrey, S. R., A. R. Richter, and J. B. Cope. 1992. Indiana bat. Pages 54 - 62 in S. R. Humphrey and R. E. Ashton (eds.) Rare and Endangered Biota of Florida, Vol. 1, Mammals. University Press of Florida, Gainesville.
Jordan, J. R. 1986. Indiana Myotis, Myotis sodalis Miller and Allen. Pages 107-108 in R. H. Mount (ed.). Vertebrate animals of Alabama in need of special attention. Alabama Agricultural Experiment Station, Auburn University, Auburn.
Menzel, M. A., B. R. Chapman, W. M. Ford, J. M. Menzel, and J. Laerm. 2000. A review of the distribution and roosting ecology of bats in Georgia. Georgia Journal of Science 59: 143-178.
Trani, M. K., W. M. Ford, and B. R. Chapman. 2007. The land manager’s guide to mammals of the South. The Nature Conservancy, Durham, North Carolina. 566 pp.
U.S. Fish and Wildlife Service. 2007. Indiana bat (Myotis sodalis) draft recovery plan: first revision. U.S. Fish and Wildlife Service, Fort Snelling, Minnesota. 258 pp.
Whitaker, J. O., Jr., and W. J. Hamilton, Jr. 1998. Mammals of the eastern United States. Cornell University Press, Ithaca, New York. 583 pp.
Jim Ozier
J. Ozier, Aug. 2008: original account
K. Owers, Sept. 2009: updated status and ranks, added picture
K. Torrey, Nov. 2018: updated
S. Krueger, Jan. 2020: reviewed for final