About 95% of entire known population hibernates in nine caves, over half in one cave. Roost sites are nearly exclusively restricted to caves throughout the year (Hall and Wilson 1966, Tuttle 1976), though only a few percent of available caves are suitable (Tuttle 1979). They are known to migrate up to 300 miles between summer and winter caves. Winter roosts are in deep vertical caves with domed halls. Large summer colonies utilize caves that trap warm air and provide restricted rooms or domed ceilings, maternity caves often have a stream flowing through them and are separate from the caves used in summer by males. Occasionally non-cave roost sites are used. There are occasional reports of mines (Sealander 1979, Brack et al. 1984, Harvey and McDaniel 1988) and buildings (Gunier and Elder 1971) being used as roost sites. Winter caves are deep and vertical and provide a large volume of air below the lowest entrance that acts as a cold air trap (Tuttle 1976). Cold air flows in and is trapped during successive winters, providing mean annual temperatures 6 °C or more below the above-ground mean annual temperature; winter cave temperatures range from 6 to 11°C (Tuttle 1976, 1979). In the summer, maternity colonies prefer caves that act as warm air traps or that provide restricted rooms or domed ceilings that are capable of trapping the combined body heat from thousands of clustered individuals (Wilson and Ruff 1999). Hibernation sites often have multiple entrances, good air flow, and temperatures of approximately 5-9 C, though 1-4 C may be preferred (Tuttle and Kennedy 2005).

Undisturbed summer colonies may contain up to 250,000 bats, and average 10,000 to 25,000 (Tuttle 1979). Summer caves are nearly always located within 1 km of a river or reservoir over which the bats forage (Tuttle 1979). Tuttle (1979) showed that forested areas along the banks of streams and lakes provide important protection for adults and young, which take shelter in forest areas near the entrance to cave roosts. These bats do most of their foraging over water, and are know to eat mayflies and other aquatic insects (Wilson and Ruff 1999), however, they do not feed in areas along rivers or reservoirs where the forest has been cleared (LaVal et al. 1977). Yearlings and adult males segregate into nomadic summer colonies that tend to roost in caves within a few kilometers of ones selected by adult females (Layne 1978, Wilson and Ruff 1999).

The Gray Bat (Myotis grisescens) occurs in the south-central and southeastern United States. Its range extends from southeastern Kansas and central Oklahoma east to western Virginia and western North Carolina, and from Missouri, Illinois, and Indiana south to southern Alabama and northwestern Florida (Decher and Choate 1995), occurs primarily in the cave region of Missouri, Arkansas, Kentucky, Tennessee, and Alabama (Wilson and Ruff 1999). Summer and winter ranges are essentially the same.

Cave protection efforts have led to recent population increases. By 1991, the range-wide population was stable and perhaps growing, apparently due to successful cave protection efforts. Since 1981, the maternity colony population in Oklahoma has increased from 56,000 to almost 150,000 (Hensley 2003). The recovery plan criteria for change from endangered status to threatened status is documentation of permanent protection of 90% of Priority 1 hibernacula and documentation of stable or increasing populations at 75% of Priority 1 maternity caves during a period of five years; recent studies indicate that these criteria have been met (Harvey and Currie 2002).

The Tennessee Valley Authority sponsored a recovery project that resulted in the protection of two critical maternity sites: the Hambrick and Nickajack caves in Tennessee. Blowing Wind Cave in northern Alabama, the most important summer cave known for gray bats, has been acquired by the U.S. Fish and Wildlife Service and a gate has been placed across the entrance. Fern Cave, the largest known gray bat hibernaculum, has also been purchased by the Fish and Wildlife Service and is being managed for protection of the bats. The U.S. Fish and Wildlife Service also has acquired and protects additional caves in Alabama. To protect habitat, The Nature Conservancy has established six voluntary protection agreements with private landowners for gray bat maternity sites. The National Park Service restricts human access to six Gray Bat maternity caves on its lands and monitors them for possible disturbance. The Indiana Bat and Gray Bat Comprehensive Plan contains a detailed list of caves that have been protected or are currently being managed.

Identify all caves used for different stages of the life history. Occupied caves should be protected from human disturbance. A buffer of undisturbed vegetation should be left around the entrances of caves inhabited by gray bats; wooded travel corridors between roosting and foraging sites should be protected; the use of herbicides and pesticides in areas adjacent to foraging and roost sites should be carefully controlled and monitored for unanticipated adverse effects (Alabama Forestry Commission).