 Enews Signup
 Printer Friendly
 Send Page to Friend
|
Gray Bat
Myotis grisescens
Family: Vespertilionidae
Description: The largest member of its genus in the eastern United States, the gray bat weighs from 0.2 to 0.5 ounces (7 to 16 grams). Its forearm ranges from 1.6 to 1.8 inches (40 to 46 millimeters) in length. Gray bats have a uniform brownish-gray fur most of the year, but during the summer the fur turns a light rusty brown. The ears and wing membranes are gray to black. In contrast to other Myotis species, the gray bat's wing membrane connects to the foot at the ankle instead of at the base of the first toe.
| Status: |
Federally Listed Endangered (April 28, 1976) Global Rank: G3 State Rank: S1 |
Distribution: The gray bat's range is limited to karst regions of the southeastern United States. Major populations are found in Alabama, Arkansas, Kentucky, Missouri, and Tennessee. Smaller populations occur in Florida, Illinois, Indiana, and Oklahoma. In Arkansas, the gray bat is known from occurrences in 16 counties across the Salem and Springfield plateaus of the Ozark Mountains.
Habitat: The gray bat is one of many karst-dependent species in northern Arkansas. Karst habitats form in regions with limestone bedrock. Over thousands of years, water seeping into the ground dissolves limestone and forms sinkholes, underground streams, and caves. Gray bats reside in caves year round, with different caves occupied during summer and winter. Few gray bats have been found roosting outside of caves. During winter hibernation, gray bats occupy deep, vertical caves with large rooms that act as cold air traps. They choose hibernation sites where temperatures average 43-52°F (6-11°C). Gray bats hibernate in clusters of up to several thousand individuals.
During summer, adult female gray bats form maternity colonies of a few hundred to many thousands of individuals, often in large caves containing streams. Maternity colonies prefer caves that trap warm air (57-77°F; 14-25°C) or provide restricted rooms or domed ceilings capable of trapping the combined body heat from clustered individuals. Because of their highly specific habitat requirements, fewer than 5% of available caves are suitable for gray bat occupation. Summer caves, especially those occupied by maternity colonies, are rarely more than 2 miles (1.6 kilometers) from rivers or lakes. Each summer colony occupies a home range that often contains several roosting caves scattered along as much as 50 miles (80.5 kilometers) of river or lake shore.
Diet: Gray bats forage primarily over water along rivers or lake shores. Most foraging occurs within 15 feet of the surface. Mayflies are apparently a major item in the diet, but like many bat species, they often feed on other insects as well.
Reproduction: Upon arrival at their wintering caves in early fall, mature females enter estrus and are inseminated by sexually active males. The offspring, one per female, are born the following June when the colonies have migrated to their summer range. The period from birth to weaning covers about 2 months. During this time, the colonies are usually segregated into maternity caves, where the young are reared, and bachelor caves that house the adult males and yearlings of both sexes. By August, all of the juveniles are flying and there is a general mixing and dispersal of the colony over the summer range. Fall migration begins around the first of September and is generally complete by early November.
Conservation Status: Human disturbance and vandalism of cave habitat has been identified as the primary factor responsible for the gray bats' decline. Disturbance of a maternity colony may cause thousands of young to be dropped to the cave floor where they perish; excessive disturbance can also cause a colony to abandon a cave. Other factors that contributed to this species decline include pesticide poisoning, natural disasters such as flooding and cave-ins, and loss of caves due to inundation by man-made impoundments. Populations of the gray bat are now thought to be stable or even increasing due to cave protection efforts.
