Nickajack Cave formerly served as a refuge for Native Americans and a hideout for river pirates who preyed on travelers on the Tennessee River. During the Civil War, the cave was mined by both the Union and Confederate armies for saltpeter, an important ingredient used to make gunpowder. After the war, the entrance of the cave's cool interior was ideal for recreational use and was even equipped with a dance floor.
Nickajack Cave was partially flooded in 1967 when Nickajack Dam was constructed by the Tennessee Valley Authority. Today, it provides sanctuary for endangered gray bats and is managed jointly by TVA and Tennessee Wildlife Resources Agency solely for their protection.
Biologically, Nickajack Cave is one of the most important caves in the Tennessee Valley, serving as a maternity roost for the gray bat. Pregnant females arrive in spring to give birth to a single pup. Pockets in the cave ceiling trap warm air, which provides just the right temperature for developing baby bats.
Gray bats feed on insects over the reservoirs, consuming thousands of emerging adult aquatic insects, moths, and beetles each night. In one year, this colony may consume 274,000 pounds of insects. Cliff swallows, the birds you see emerging from the cave, feed on the same insects during the day. They build jug-like mud nests in the twilight zone on the ceiling of Nickajack Cave. The bats and birds share the same habitat and food source, but on different schedules.
Human disturbance is one of the most significant reasons for decline of this species. The Tennessee Valley Authority fenced Nickajack Cave in 1981 to protect the bats, and in 1992 Tennessee Wildlife Resources Agency designated Nickajack as Tennessee's first non-game wildlife refuge.
Why is the cave closed? TVA closed the cave to protect this significant colony of gray bats. Recently, TVA has joined other agencies in supporting the closure of all caves on publicly managed lands in an effort to reduce the spread of white-nose syndrome, a devastating disease impacting cave-dwelling bats. White-nose syndrome, or WNS, is named for a white fungus that appears on the faces, ears, and wings of hibernating bats. Scientists are trying to determine the cause of WNS and its impact to bat populations. Once a colony is infected, WNS spreads rapidly and has killed at least 95 percent of bats at some sites in just two years. Other monitored bat colonies affected by WNS are experiencing similar levels of fatalities. This devastating disease has quickly spread from one cave in New York (2006) to caves throughout much of the eastern U. S. and Canada. There have been no reported human illnesses attributed to WNS and there is currently no evidence to suggest that WNS is harmful to humans or other organisms. Biologists are concerned that WNS could devastate populations of endangered Indiana and gray bats, and reduce numbers of common bat species to dangerously low population levels. Bats play a key role in keeping insects such as agricultural pests, mosquitoes, and forest pests under control. Between April and October, they usually eat their body weight in bugs per night.