The Indiana bat hibernates in mines and caves, but males and females roost in crevices and under the bark of trees during the warmer months of the year. Female Indiana bats form maternity colonies, giving birth and raising their young in these tree roosts.
This species was federally-listed as endangered prior to the start of white-nose syndrome and subsequently suffered population declines of 71% from 2007-2015. Many of the general areas where maternity and bachelor colonies are known to occur are in areas that are subject to increasing development.
The maximum total count increased from approximately 13,000 to 41,000 Indiana bats from 2001-2006. This increase in numbers was largely the result of discovery of new hibernacula and improved methods of counting overwintering bats but may also have reflected an increase in the overall size of the population. Winter hibernacula surveys from 2007-2015 documented population declines of 71%.
The long-term trends are unknown but is likely greater than a 70% reduction in population numbers since historic times; despite an apparent increase, or at least stable period, from 2001-2006.
Indiana bats had suffered significant past declines and were listed as endangered in 1967 (USFWS 2014). Past disturbances to winter hibernacula were thought to have resulted in decline since they hibernate in limited locations and are suceptible to disturbance. Currently, the largest threat to Indiana bats in New York is white-nose syndrome (WNS) which was first discovered among bats in a cave in Schoharie County, New York in 2006. White-nose syndrome is caused by a fungus Pseudogymnoascus destructans (previously Geomyces destructans) that is often visible on the bats' muzzle and wings (Blehert et al. 2009). The fungus may invade hair follicles and cause lesions under the skin (Blehert et al. 2009). Bats wake from hibernation to groom and consequently burn fat reserves that are needed to survive the winter and they become emaciated (Blehert et al. 2009). Extensive damage to their wing membranes and dehydration may also be contributing factors to mortality (U.S. Fish and Wildlife Service 2013).
Tree cutting can impact this species when felled trees contain colonies or roosting individuals. There are very few colonies left in New York so loss of summer roosts containing bats is even more devestating to dwindling populations. Habitat loss from development is also a threat which can limit suitable habitat.
Bats may be particularly sensitive to environmental toxins including those found in herbicides and pesticides. Although no studies have targeted Indiana bats in New York directly, elevated levels of persistent organic pollutants including especially PCBs, DDT, Chlordanes, and PBDEs have been found in a similar species, the little brown bat, in the Hudson River Valley in New York (Kannan et al. 2010). The levels found in the bats were only 1 to 3 times less than lethal concentrations reported from previous studies (Kannan et al. 2010). Lesser toxin levels may be expected in Indiana bats since little brown bats typically consume a greater percentage of prey with an aquatic life stage. Bats are highly susceptible to DDT residue and this chemical was widely used as a pesticide to control bat infestations in houses in the 1940s (USGS 2013). It was widely used as an agricultural pesticide in the 1950s and 60s until its agricultural use was banned in 1972. Since DDT is highly persistent (soil half-life is 2-15 years, aquatic half-life is about 150 years) (NPIC 1999), it can pose a threat to bats when there is exposure to trace residues in the environment (USGS 2013). Extensive applications of insecticides and some bio control methods, such as Btk, could also pose an indirect risk to Indiana bats by reducing availability of prey.
If proper precautions are not used, cavers and researchers entering hibernacula may cause disturbance that rouses bat colonies or transport the fungus that causes WNS on their clothing (NatureServe 2013). Other potential threats may include climate change, commercial cave development, flooding and hibernacula collapse; habitat loss and fragmentation from development, hydraulic fracturing, and construction of new wind facilities; and direct mortality from wind facilities (U.S. Fish and Wildlife Service 2013).
Continue to monitor populations at hibernacula every other year as recommended by the United States Fish and Wildlife Service. Forest cover in agricultural landscapes, including small, isolated patches, should be conserved for foraging and roosting bats and maternity colonies (Kniowski and Gehrt 2014, Womack et al. 2013). Snags should be left standing when possible during forest management activities (Timpone et al. 2010).
Additional research is needed to locate new maternity and bachelor colonies and to determine habitat use surrounding these areas.
Indiana bats hibernate in caves and mines during the winter. These bats show a strong preference for woodland and wooded riparian habitat over cropland (Kniowski and Gehrt 2014). Predominately female Indiana bats radio-tracked from hibernacula in Jefferson, Essex, and Ulster Counties were found to move between approximately 12 and 40 miles to roost location on their foraging grounds. The roosts consisted of living, dying, and dead trees in both rural and suburban landscapes.
Seventeen Indiana bat hibernacula are known to be extant. These hibernacula occur in the following counties: Albany (2), Essex (2), Jefferson (2), Onondaga (1), Orange (1), Putnam (1), Ulster (7), and Warren (1). One of the Ulster County sites is among the 10 largest hibernacula for the species in the country. Maternity colonies have been identified through radio-telemetry studies and mist-net captures in Cayuga, Columbia, Dutchess, Essex, Jefferson, Onondaga, Orange, Oswego, Seneca, and Ulster counties. Bachelor colonies have also been identified through radio-telemetry studies and mist-net captures in Albany, Cayuga, Dutchess, Jefferson, Onondaga, Orange, and Ulster counties.
The range of the Indiana bat includes much of the eastern half of the United States, from Vermont south to Massachusetts, Connecticut, and northern New Jersey, southwest to northwestern Florida and eastern Oklahoma, and north to southwestern Wisconsin. The largest hibernating populations are found in Indiana, Missouri, and Kentucky with other large hibernation sites in Arkansas, Illinois, New York, Ohio, Tennessee, Virginia, and West Virginia (USFWS 1999).
The Indiana bat is a small bat, approximately 2 inches (51 mm) in length and weighing approximately 0.2 to 0.3 ounces (6-9 grams) (Harvey et al. 1999; NYSDEC 2006). The pelage is very fine and fluffy and is dark gray to grayish-brown in color and the nose is pinkish in color (NYSDEC 2006). The feet have few hairs that do not extend beyond the tips of the toes. Indiana bats have a keeled calcar, which is a cartilaginous projection from the foot which helps support the membrane between the foot and the tail (NYSDEC 2006).
When in hand, the gray-brown pelage, pinkish nose, toe hairs that don't extend beyond the tips of the toes, and keeled calcar are used in combination to distinguish Indiana bats from little brown bats. Hibernating Indiana bats are distinguished from other bats by their tight clusters, grayish-brown pelage and pinkish noses.
Most Indiana bats migrate seasonally between traditional winter and summer roost sites. Hibernation sites include both natural caves and mines. Caves and mines chosen for hibernation have been reported to have stable temperatures below 10 degrees Celsius (50 degrees Fahrenheit) and preferably from 4-8 degrees Celsisus (39 - 46 degress Fahrenheit). Relative humidities are fairly high at hibernation sites, usually above 74 % (Hall 1962; Humphrey 1978). Depending on local weather conditions, Indiana bats hibernate from October through April (Hall 1962). Summer foraging habitat consists of wooded or semi-wooded areas and may be along streams. Indiana bats have strong fidelity to summer colony areas, roosts, and foraging habitat (USFWS 1999), and radio-telemetry studies in New York have shown this to be true for maternity roost locations. Maternity colonies are generally in hollow trees or under loose bark of living or dead trees that are often exposed to direct sunlight. Although the majority of maternity sites reported have been in riparian areas, recent studies in New York and elsewhere indicate that upland habitats are used more than previously thought (Humphrey et al. 1977; Garner and Gardner 1992).
Indiana bats feed entirely on flying insects and the food items reflects the environments in which they forage. Prey items may include moths (Lepidoptera), caddisflies and flies (Diptera), mosquitos and midges, bees, wasps, and flying ants (Hymenoptera), beetles (Coleoptera), leafhoppers and treehoppers (Homoptera), stoneflies (Plecoptera), and lacewings (Neuroptera) (NatureServe 2006).
Females begin hibernation soon after mating, whereas males often remain active through mid-October to November (Cope and Humphrey 1977). Most individuals are in hibernation by late November although some are still active until December (Barbour and Davis 1969). Activity is resumed generally in April, with few bats still in the hibernation caves by mid-May. In Michigan, bats were present at tree roosts as late as 10 September (Kurta et al. 1993). Primarily nocturnal.
The time of year you would expect to find Indiana Bat present, active, and reproducing in New York.
Myotis sodalis Miller and Allen, 1928
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Information for this guide was last updated on: June 24, 2020
Please cite this page as:
New York Natural Heritage Program. 2021. Online Conservation Guide for Myotis sodalis. Available from: https://guides.nynhp.org/indiana-bat/. Accessed March 2, 2021.