Entrance to Hubbard's Cave
Entrance to Hubbard's Cave Entrance to Hubbard's Cave © Byron Jorjorian

Places We Protect

Hubbard's Cave


Among rolling hills, hidden beneath an oak-hickory forest canopy, lies a gaping hole in the ground.

Among the rolling hills of Warren County and discreetly hidden beneath the canopy of an oak-hickory forest lies a gaping hole in the ground 75 feet in diameter. This pit-like opening, formed by the collapse of a limestone shell, is commonly known as Hubbard’s Cave, The Nature Conservancy’s foremost cave preserve. The cave contains three separate forks, each opening at the main entrance and leading to distinctively contoured passages of varying lengths and dimensions. The west fork (the longest of the three), for example, reveals rooms reaching 50 feet in height and is decorated with magnificent gypsum formations. The south fork is the location of one of the most important bat hibernation sites in the world.

The cave was discovered in 1810 by Joseph Heberlein and subsequently named after him. The cave’s name was gradually corrupted to the more pronounceable Hubbard’s Cave and has been a site of great activity since its discovery. During the Civil War, Hubbard’s Cave was used as a nitrate mine and gunpowder was ground on the still-existing dirt mound assembled by the miners. Remnants such as ladders, bridges and troughs can be found intact in certain areas of the cave, and etched-in names date as early as 1809.


Warren County

What to See

Hubbard’s Cave contains the ideal environment for thousands of bats that travel across the southeastern United States to spend their winter months in hibernation. It is reported that there is no other cave in North America with a higher diversity of bats, and its total winter population (once recorded at 4,000,000) is one of the largest known anywhere in the world.

Although Hubbard’s Cave houses a total of seven bat species in the winter months, two species in particular are of special interest. The cave contains one of the largest hibernating colonies of the federally endangered gray bat (Myotis grisescens) in Tennessee. Since the Conservancy bought the cave in 1984 and gated it, the cave's gray bat population has grown from 50,000 to 500,000. The federally endangered Indiana bat (Myotis sodalis) also has a significant hibernating colony at Hubbard’s Cave that roosts together with the gray bat population.

Why the Conservancy Selected This Site

The Nature Conservancy purchased Hubbard's Cave in 1984 to protect its bat population, particularly its endangered gray bats. The cave (and the surrounding 50 acres) had a long history of human visitation. The Nature Conservancy and partner organizations have restricted access to this cave, determining it was best for the bats and other cave life.

What the Conservancy Has Done/Is Doing

Hubbard’s Cave is the site of one of the world's most massive bat gates, which protects the south fork entrance. In May 2006, the Conservancy replaced its original 1985 gate with a new, state-of-the-art cave gate. Since the Conservancy's protection of this site began, the gray bat population has increased tenfold. The Conservancy has also installed gates to protect the western (1998) and northern entrances (1999). In addition to protecting the bats that use the cave for hibernation, the gates also protect the cave from looters. The gate at the west entrance protects Civil War saltpeter mining artifacts.

If you see bats roosting in clusters outside the gate, please do not disturb them.

Our Partnership with the National Speleological Society

The Nature Conservancy works closely with local members of the National Speleological Society to achieve our cave conservation, research and management goals. This long-standing and valuable partnership was formalized in 1992 through a Memorandum of Understanding.