There are nine species of bats that can be found in NJ, six of which stay here year round. Caves are their natural habitat but are become increasingly disturbed by human contact, leaving them unsuitable for them to hibernate in. Abandoned mines and tunnels are rarely entered by people because of their relative lack of safety, and are now their preferred place to remain during the winter.
The Hibernia Mine in Rockaway Township, Morris County was first used by bats in the 1930s. Thrillseekers and explorers persisted in entering the mine, leading to attempts to seal the mine. Doing so would seal it off from the bats as well, making this an unsuitable solution.
Enter the Bat Gate
In 1994, the Endangered and Nongame Species Program was able to install a bat gate, which is a specialized gate that keeps people out but lets bats freely enter and exit. The mine is now part of the Wildcat Ridge Wildlife Mangement Area, and an estimated 30,000 bats call the mine home. During the months of July & August the bats can be seen at dusk leaving the mine by the thousands. Bat watching has become so popular that watch stands were installed to give people a comfortable place to view from.
There is a geocache here.