gray. The Mexican free-tailed bat's large feet have distinct long, white bristles.https://upload.wikimedia.org/wikipedia/commons/b/b9/Mexican_free-tailed_bat_%288006850693%29.jpg The dental formula of Tadarida brasiliensis is . Range and ecology The Mexican free-tailed bat ranges from the southern half of the continental United States through most of Mexico, and through most of Central America into South America. Their range in South America is less understood where they live in the eastern Brazilian highlands and coast, the northeastern Andes, the coast of Peru and northern Chile, and the center of Argentina. They are absent in much of the Amazon rainforest. They are also found in the Caribbean, and are native to all of the Greater Antilles and 11 of the Lesser Antilles. The largest known colony is found at Bracken Cave, north of San Antonio, Texas, with nearly 20 million bats; the bats from this colony congregate in huge numbers at altitudes between , and even as high as . Habitat Mexican free-tailed bats roost primarily in caves. However, they also roost in buildings of any type as long as they have access to openings and dark recesses in ceilings or walls. The bats can make roosting sites of buildings regardless of "age, height, architecture, construction materials, occupancy by humans and compass orientation". Caves, though, need to have enough wall and ceiling space to fit millions of bats. Before buildings, free-tailed bats in the Southeastern United States probably roosted in the hollows of trees such as red mangrove, black mangrove, white mangrove, and cypress. However, most bats in Florida seem to prefer buildings and other man-made structures over natural roosts. Caves in Florida tend to be occupied mostly by the southeastern myotis. Caves in Florida tend to have pools of water on the floor and the free-tailed bats do not need as much relative humidity as the southeastern myotis. Migration Mexican free-tailed bats in southeastern Nevada, southwestern Utah, western Arizona, and southeastern California come together to migrate southwest to southern California and Baja California. Bats in southeastern Utah, southwestern Colorado, western New Mexico, and eastern Arizona travel through the western edge of the Sierra Madre Oriental into Jalisco, Sinaloa, and Sonora. Some bats that summer in Kansas, Oklahoma, eastern New Mexico, and Texas migrate southward to South Texas and Mexico. Some bat populations in other areas of North America do not migrate, but are residents and may make seasonal changes in roost sites. While this migration is extremely