AGAINST THE desert sunset at Carlsbad Caverns National Park, the flight of the Mexican free-tailed bats (Tadarida brasiliensis) is a highlight for many visitors. Many see bats for the first time at this famous site. The park has done much to help change misperceptions about these animals; as many as a thousand people in a single summer night listen to park naturalists lecture about the bats. See story on page 4.