A hibernation colony of endangered Virginia big-eared bats (Plecotus townsendii virginianus) has grown from 17 to 139 bats according to a December 1988 survey. Since construction of a protective gate in 1986, the population has doubled each year.
The colony was first discovered in western North Carolina in the early 1980's and at the time was thought to be a new colony of Eastern big-eared bats (P. rafinesquii). But a few years later, at the North Carolina State Museum of Natural History, Mary K. Clark, curator of mammals and a member of BCI, discovered a misidentified P. rafinesquii in the museum's collection and determined it to be P. t. virginianus instead. What puzzled her was that the specimen had been collected in western North Carolina, a state where the species had never been seen. She called another BCI member, Bob Currie, a wildlife biologist with the Endangered Species Office of the U.S. Fish and Wildlife Service. Bob remembered the earlier, unconfirmed discovery of an Eastern big-eared bat colony in North Carolina and together, he and Mary Kay made arrangements to visit the cave in January of 1985. What they found instead were 33 hibernating Virginia big-eared bats, the first confirmed discovery outside of West Virginia, Virginia and Kentucky.
The USFWS moved quickly to protect the colony and install a gate to prevent human intrusion while the bats were present. The Service obtained a cooperative agreement with Grandfather Mountain, Inc., who owns the cave, and with funding from the National Park Service and the help of local volunteers, a gate was completed in late summer of 1986. That winter, a survey counted 62 bats in hibernation, double from the previous count two winters earlier before the gate was installed. Such population growth is significant in a species known only to number 10,000 bats.