Brazilian free-tailed bats (Tadarida brasiliensis) emerging from an artificial bat cave costructed of reinforced steel rods and gunite on the Selah Ranch in Texas. The structure occupies 3,000 square feet but provides roughly 8,000 square feet of roughened roosting surface. It typically is estimated to house 300,000 to 500,000 bats. Conservation, Bat Houses & Emergences