U.S. Fish & Wildlife Service Gray Bat Oklahoma Ecological Service Field Office

GRAY BAT Myotis grisescens

Description The gray bat is a medium-sized bat with an overall length of about 3.5 inches and a wingspan of 10 - 11 inches. Weights range between approximately 7 - 16 grams. The gray bat can be distinguished from other species in the genus Myotis by the uniform color of its dorsal fur in which hair shafts are the same color from base to tip. The dorsal fur is gray, but often bleaches to reddish-brown by early summer. Additionally, the wing membrane attaches at the ankle of the foot instead of at the base of the toes as in other members of the genus Myotis.

Distribution Gray Bat. © Bat Conservation International The gray bat occurs in limestone karst areas (i.e., a landscape marked by caves, Within Oklahoma, maternity colonies are What Can You Do to Help sinkholes, springs and other features) known from caves in Adair, Cherokee, Do not enter gated caves/mines or caves/ of the southeastern and midwestern Delaware, and Ottawa counties. A single mines with a sign at the entrance which United States. In Oklahoma, it occurs offspring is born in late May or early indicates it is used by endangered bats. in the Ozark Highlands ecoregion in the June. Newborns typically become volant These gates and signs are in place to northeastern part of the state. within 21-33 days after birth. Gray protect bat colonies that are sensitive to bats feed on flying insects over bodies human disturbance. Disturbance during Life History of water including rivers, streams, and early summer before the young can fly Gray bats inhabit caves year-round. lakes. Mayflies, caddisflies, and stoneflies can result in thousands of flightless young They are known to migrate up to 300 make up the major part of their diet, but becoming dislodged and falling to their miles between summer and winter beetles and moths also are consumed. deaths. Every arousal during hibernation caves. Gray bats have such specific is energetically expensive. Fat reserves cave requirements that fewer than five Conservation required to sustain the bats are utilized to percent of caves are suitable. Winter The gray bat was federally-listed as some extent during each winter arousal. hibernation sites typically are deep endangered on April 28, 1976. The Too many arousals during hibernation vertical caves that trap large volumes of gray bat has declined primarily due to can exhaust a bat’s limited fat reserves cold air. Summer caves must be warm or human disturbance in caves. Habitat and result in mortality. have restricted rooms that can trap the loss and degradation and contamination body heat of clustered bats. Gray bats from pesticides also are considered a References mate in the fall when they begin to arrive cause of decline. Natural flooding and U. S. Fish and Wildlife Service. 1982. at hibernacula. During hibernation, the impoundment of waterways has resulted Gray Bat Recovery Plan. Minneapolis, species typically forms large clusters in temporary impacts to some caves and MN. 26pp. with some aggregations numbering in the the complete submersion and loss of hundreds of thousands of individuals. It other important cave sites. Conservation U. S. Fish and Wildlife Service. 2009. is estimated that 90 percent of the species efforts include protecting known gray Gray Bat 5-Year Review. Columbia, MO. range-wide population hibernates in only bat caves and wooded riparian corridors 33 pp. nine caves. No hibernating colonies are along streams near caves. Recovery known from Oklahoma. Adult females efforts also include educating the public For Further Information begin to emerge from hibernation in about the danger of disturbing bats and U.S. Fish and Wildlife Service late March, followed by juveniles and their ecological importance. Oklahoma adult males. Females become pregnant Ecological Services Field Office after emerging in the spring, and 9014 East 21st Street form maternity colonies in caves of Tulsa, OK 74129 a few hundred to many thousands of 918/581-7458 individuals. Gray bat summer colonies typically use several roosting caves located along a stream, river, or reservoir. August 2011