Bat Species on Endangered List Seems to Be Making Comeback
By MORGAN SIMMONS, simmonsm@knews.com
A survey of two caves in Middle Tennessee has turned up evidence that a species of bat once headed toward extinction may be on the rebound.
The caves — one located on the Highland Rim, the other on the Cumberland Plateau — serve as important hibernating sites for the gray bat, a Southeastern species that has been on the federal endangered list for decades.
This winter, researchers counted substantially more hibernating gray bats in each cave than in 2002, when the caves were surveyed last. The first cave had 144,558 gray bats, a 58.7 percent increase over 2002.
The second cave, known as Hubbard’s Cave, showed an even more remarkable increase, going from 156,000 hibernating gray bats in 2002 to 519,570 this winter.
The Nature Conservancy owns both caves. Heather Garland, cave program manager for the conservancy’s Tennessee chapter, said the bats in Hubbard’s Cave have responded to a 25-by-30-foot steel gate built in 1985 near the entrance to the cave that permits the bats to come and go but limits public access when the bats are hibernating.
"When the problem is human visitation at the wrong time of the year, a cave gate can make a tremendous difference," Garland said.
The Nature Conservancy is among a number of public and private conservation groups currently working with the U.S. Fish and Wildlife Service to determine if the gray bat population is healthy enough to be removed from the endangered species list.
A leading figure in that study is Merlin Tuttle, president and founder of Bat Conservation International. Tuttle began his research career at Hubbard’s Cave in the early 1960s, when only a few thousand gray bats could be found hibernating near the mouth of the cave and the floor often was littered with bats that people had stoned to death.
One winter day, Tuttle discovered a way around a huge pile of rock and rubble that previously had formed a dead-end to the cave passage. Hearing squeaking noises, he followed the sound to a low room where every square inch of roof was covered with hibernating gray bats. At the time, it ranked as one of the important discoveries of hibernating bats in America.
"There were at least 250,000 of them," Tuttle said. "A lot of the ones I had banded at locations all over the Southeast were there."
In the late 1970s disaster struck when raccoons found their way around the rubble pile in Hubbard’s Cave and began feasting on the gray bats, which were hibernating only a few feet off the ground. At one point, the number of gray bats in Hubbard’s Cave dropped to below 80,000.
In 1982 Tuttle formed Bat Conservation International and made the recovery of the gray bat a top priority. He said a key part of the mission was — and remains today — educating the public and working with private landowners.
"Bats used to rank between cockroaches and rattlesnakes in popularity," he said. "That situation is improving, but it’s a slow process."
During the recent survey of Hubbard’s Cave, researchers were happy to discover that most of the bats had moved from the back of the cave, where they were vulnerable to predators, to the front of the cave, where the higher roof puts them out of reach of raccoons.
"If we can assure the long-term protection of key sites like Hubbard’s Cave, we may be close to de-listing this species," Tuttle said. "This is almost unheard of in endangered species listing in America."
Morgan Simmons may be reached at 865-342-6321.
BATS: BY THE NUMBERS
8,500 Number of known caves in Tennessee, more than any other state
15 Number of bat species found in Tennessee
2 Number of species in Tennessee that are endangered — the gray bat and the Indiana bat
DID YOU KNOW?
Seventy percent of all bats in the world eat insects. Thanks to their high metabolism, some bats are capable of devouring 2,000 mosquito-sized insects per night.
Some bats feed on crop-damaging insects and are much friendlier to the environment than pesticides.
Bats are the only members of the mammal family that can fly.
While most people think of bats as living in caves, in the summer, they actually live beneath tree bark and man-made structures such as barns and bridges.
With more than 1,100 species of bats worldwide, bats account for almost 25 percent of all mammal species.