Kentucky Bat Working Group

Gray Bat (Myotis grisescens)

Status: Endangered

Description: The gray bat, 3 - 4 inches in length, is the largest species of Myotis found in the eastern United States. Its fur is gray, sometimes russet in summer. It is the only Myotis with the wing membrane attached to the ankle (instead of at the base of the toe), and the only bat in its range with dorsal (back) hair that is uniform in color from base to tip.

Range: The core range of the gray bat encompasses the cave regions of Alabama, northern Arkansas, Kentucky, Missouri, and Tennessee. Populations also occur in portions of Florida, Georgia, Kansas, Indiana, Illinois, Oklahoma, Mississippi, Virginia, and possibly North Carolina.

Distribution of Gray Bats in Kentucky:  

Habitat: Gray bats are restricted to caves or cave-like habitats. Few caves meet their specific roost requirements. This results in about 95% of the populations hibernating in only 8 or 9 caves. For hibernation, the roost site must have an average temperature of 42 to 52 degrees F. Most of the caves used by gray bats for hibernation have deep vertical passages with large rooms that function as cold air traps. Summer caves must be warm, between 57 and 77 degrees F, or have small rooms or domes that can trap the body heat of roosting bats. Summer caves are normally located close to rivers or lakes where the bats feed. Gray bats have been known to fly as far as 12 miles from their colony to feed.

Life history: Gray bats roost, breed, rear young and hibernate in caves year round. They migrate between summer and winter caves and will use transient or stopover caves along the way. Mating occurs as bats return to winter caves in September and October. By November, most gray bats are hibernating. Adult females begin to emerge in late March, followed by juveniles and adult males. Females store sperm over winter and become pregnant the following spring. A few hundred to many thousands of pregnant females congregate to form maternity colonies. Males and nonreproductive females gather in smaller groups to form what are known as bachelor colonies. A single pup is born in late May or early June. Young begin to fly 20 to 25 days after birth. Gray bats feed primarily on flying insects over rivers and lakes. Aquatic insects, particularly mayflies, make up most of their diet.

Causes of decline: Because gray bats are found in caves year round, they are very vulnerable to human disturbance. This has contributed greatly to their decline. As with any cave bat, alterations of caves and cave entrances (e.g., commercialization and improper gating) have negatively affected their populations. Gray bats have also been killed during natural flooding and flooding caused by manmade impoundments. The overuse of pesticides has also contributed to their decline. Pollution and siltation of streams causing a reduction in aquatic insects may also affect gray bat populations.

Related links:

Arkansas Game and Fish Commission - Gray Bat

Endangered Gray Bat Benefits from Protection

Georgia's Protected Critters - Gray Bat

Gray Bat - Alabama

Gray Bat in North Carolina

U.S. Fish & Wildlife Service - Gray bat

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