Carlsbad Caverns National Park was established to preserve Carlsbad Cavern and numerous other caves within a Permian-age fossil reef. The park contains 83 separate caves, including the nation's deepest limestone cave, and at 1,597 feet, the third longest. The so-called "Big Room" is large enough to hold 14 Astrodomes! The evening flight of Mexican free-tailed bats from the entrance of Carlsbad Cavern is one of the park's principal visitor attractions. Free-tailed bats are a colonial species that feed entirely on insects. The colony at Carlsbad is comprised primarily of females who give birth to their young from June through July before migrating south in October to winter in Mexico. (We were not able to see the bats since they had not yet returned from Mexico.)