Gray Bat in North Carolina

Status: Endangered

The following description is taken from Harvey, Michael J., BATS OF THE EASTERN UNITED STATES, Arkansas Game & Fish Commission, USFWS, Center for the Management, Utilization, and Protection of Water Resources - Tennessee Technological University, February, 1992:

The range of the endangered gray bat is concentrated in the cave regions of Arkansas, Missouri, Kentucky, Tennessee, and Alabama, with occasional colonies and individuals found in adjacent states. The species' present total population is estimated to number over 1,500,000; however, about 95 percent hibernate in only eight caves--two in Tennessee, three in Missouri, and one each in Kentucky, Alabama, and Arkansas. Although gray bat numbers are still relatively high, their total population has decreased significantly during recent years.

Gray hats are cave residents year-round, although different caves are usually occupied in summer and winter. Few have been found roosting outside caves. They hibernate primarily in deep vertical caves with large rooms acting as cold air traps. Gray bats hibernate in clusters of up to several thousand individuals, about 170 bats per square foot. They choose hibernation sites where temperatures average 42 to 52 degrees F.

During summer, 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, because of their configuration, trap warm air (usually 58 to 77 degrees F) 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 five percent of available caves are suitable for gray bat occupation. Male gray bats, along with non-reproductive females, form summer bachelor colonies.

Gray bats occupy a wider variety of caves during spring and autumn transient periods. During all seasons, males and yearling females seem less restricted to specific cave and roost types. Summer caves, especially those occupied by maternity colonies, are rarely more than two miles, and usually less than one mile, from rivers or lakes. Each summer colony occupies a home range that often contains several roosting caves scattered along as much as 50 miles of river or lake shore.
 
Mating occurs in September and October when gray bats arrive at hibernation caves. Females enter hibernation immediately after mating.  Males remain active several weeks, replenishing fat supplies depleted during breeding activities. Juveniles and adult males enter hibernation several weeks later than adult females. Adult females emerge from hibernation in late March or early April, followed by juveniles and adult males.

Females store sperm through the winter and become pregnant soon after emerging from hibernation. A single young is born in late May or early June.  Growth rates of young vary with temperatures at maternity roosts;  young in warmer roost situations grow more rapidly. Most young begin flying within 20 to 25 days after birth.

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 most species, they often feed on other insects as well.  Longevity data indicate life spans of at least 14 to 15 years.

Estimating gray bat population declines is possible because of the presence of guano deposits and ceiling stain left in caves by roosting bats. Estimates based on guano and ceiling stain have indicated an 89 percent decline in Kentucky, a 72 to 81 percent decline in Missouri, a 61 percent decline in Arkansas, and a 76 percent decline in Tennessee and Alabama.
Species Distribution from known occurrences. Species may occur in similar habitats in other counties.Green counties indicate observed within 20 years. Red counties indicate observed more than 20 years. Yellow counties indicate an obscure data reference to the species in the county.ago.

Species Location Map based on information provided by the North Carolina Natural Heritage Program.
For additional information regarding this Web page, contact Robert Currie, in Asheville, NC, at robert_currie@fws.gov

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