Bat Gate at Tesla Mine Complex On January 16, 2008, an 8'x8' bat gate was fitted into the opening (adit) of a mid-20th century sand mine located at the Tesla Mine Complex. The gate was installed to protect the public safety, preserve the historic value of the mine, and provide habitat and ease of access to the various bat species who may live in the mine and surrounding areas. Two of these important species include the pallid bat and Townsend's big-eared bat.