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Founded 05-05-05

Researchers Find a New Location of Hibernating Bats on Grandfather

A recent exploration of a cave on Grandfather Mountain has delighted scientists with the discovery of 55 hibernating Virginia Big-Eared Bats. The bat, whose only North Carolina location is Avery County, is on the state and federal endangered species lists.

The Virginia Big-Eared Bat has previously only been documented at Cranberry Iron Mine and in Black Rock Cave on Grandfather Mountain. This new location, called Black Rock Mystery Hole, is also on Grandfather.

Bat counts are conducted in the winter, and research groups taking part in bat counts this year in Avery County have included the Nature Conservancy, US Fish and Wildlife Service, NC Wildlife Resources Commission and the Park Service.

The new site was discovered when a group of researchers went out with representatives of local caving group Flittermouse Grotto and found the 55 Big-Eared Bats in the Black Rock Mystery Hole rediscovered by the Flittermouse Grotto. Flittermouse Gotto originally discovered many caves on Grandfather Mountain more than 25 years ago and surveyed and mapped them. Today, group members still continue to help the Wildlife Resources Commission do surveys in caves.

“This is significant because it’s only the third known hibernating site in North Carolina,” said Scott Bosworth of the NC Wildlife Resources Commission. “Fifty-five bats is generally not a huge number, but when you think about how small the population size is to begin with, you understand that any addition is great.”

“We enter a cave and search through every nook and cranny for the bat,” Bosworth explained. After that, researchers use different ways to count the number of bats they find clustered tightly together for warmth.

“Sometimes it’s easier to count noses and sometimes it’s easier to count the forearm bones we see. It just depends on the tightness of the cluster,” added Bosworth.

The bats in Avery County will hibernate until the weather warms up and insects start hatching. The Virginia Big-Ears will not emerge until this food source becomes available.

A contributing factor to the Big-Eared Bat’s endangered status is its vulnerability. While hibernating, the bats can only tolerate minimal disturbances and need the cave to maintain a stable air temperature.

“Disturbances could be anything from humans nearby the cave having a loud conversation to raccoons going in and out of the cave,” said Bosworth.

While the bats wake up periodically in winter to find the best conditions, such as a cave with a better temperature, continued disturbances will cause the animals to leave and never return to the site. In the winter, this extra flying around causes the bat to burn its fat stores, and without food it could eventually die. To have the least impact, the scientists venturing into these caves to conduct counts limit their time and keep the cave temperature from significantly rising.

Another effort to protect the Big-Eared Bats has been the placement of gates to close off access to the caves. Both Cranberry Iron Mine and the Black Rock Cave at Grandfather Mountain have gates to protect the bats from possible disturbances.

Cranberry has five different gates and the last one was put in place in 2003. It is too early to tell if the effort there will be effective, but the gates at Grandfather Mountain have had promising results. The Black Rock Cave was gated in 1986 after approximately 20 Virginia Big-Eared Bats were first documented there in 1984. This most recent survey at the cave in February documented around 376 bats, making researchers believe that having the gates to combat disturbances seems to have helped.

While researchers are very happy with finding the endangered bats in a new location, they still have some questions.

“Since bats do move around from cave to cave some during hibernation, this could be happening here as well,” said Bosworth. Since there were weeks between the Black Rock Cave survey and the Black Rock Mystery Hole exploration, it is possible that during that time some bats relocated from the Cave to the Mystery Hole.

The researchers conduct the counts every two years and are looking forward to the results of future surveys.

“We couldn’t do these counts and explorations without the help of others and especially the Flittermouse Grotto,” said Bosworth. “Without their help and experience, none of this would have been possible.”