Data Sheet

Pronunciation: my-oh-tis gri-sess-sens

Approximately 95% of the entire known population of gray myotis hibernate in just nine caves each winter. In these few caves, dense concentrations of bats are extremely vulnerable to human disturbance. Fewer than five percent of available caves are suitable for gray myotis occupancy at any time. Exceptionally cold and warm caves are necessary for hibernation and for rearing young.

Loss of these critically important caves, through human disturbance and vandalism, combined with the adverse effects of the pollution of waterways from which the bats feed, resulted in an alarming 80% decline of gray myotis in less than two decades. In 1976, this bat was one of the first to be listed as Endangered by the U.S. Fish and Wildlife Service. Since the listing, several critical hibernation and maternity caves have been gated, leading to stable and growing populations in many areas.