The gray bat (Myotis grisescens) is a species of microbat endemic to North America. It once flourished in caves all over the southeastern United States, but due to human disturbance, gray bat populations declined severely during the early and mid portion of the 20th century. 95% of gray bats now hibernate in only 15 caves. M. grisescens has been listed as federally endangered by the U.S. Fish and Wildlife Service since 1976, and is protected under the Endangered Species Act. Gray bat populations were estimated at approximately 2 million bats around the time they were placed on the Endangered Species list. By the early 1980s populations of gray bats dropped to 1.6 million. With conservation efforts in place, in 2004, gray bat populations were estimated to have reached 3.4 million. Description M. grisescens are the largest members of their genus in the eastern United States. Of all U.S. mammals, gray bats are, perhaps, the most cave-dependent. Gray bats have uni-colored dark gray fur on their backs that may bleach to a russet or chestnut brown after the molting season (July or August). Unlike in other species of Myotis, where the wing membrane connects to the toe, in M. grisescens, the wing membrane connects to the ankle. Gray bats typically weigh between 7 and 16 grams. Gray bats can live up to 17 years, but only about 50% of gray bats survive to maturity. Sexual maturity occurs at about age 2. Although an adult gray bat's forearm measures only about 40–46 mm, Gray bats with forearm lengths of 39.5 mm (approx. 1.55 in) or less cannot fly. The flight speed of the gray bat, M. grisescens, has been calculated at 20.3 km/h (12.61 mph) during migration. While foraging, gray bats have been clocked at a flying rate of anywhere between 17 km/h and 39 km/h. Annual molting occurs between early June and early August, during which gray bats eat larger amounts of hair than at other times during the activity season. During grooming, gray bats also ingest ectoparasites such as chiggers that live in their fur. Gray bats are believed to groom extensively before beginning their nightly hunt. They then spend the nighttime hours hunting and digesting. Gray bats in the wild may reach ages of at least 13-14 years (based on recapture of banded individuals), although this is considered exceptional. Distribution Gray bats live in limestone karst areas in the