Brazilian free-tailed bat
The Mexican free-tailed bat (Tadarida brasiliensis) is a medium-sized bat native to the Americas and is regarded as one of the most abundant mammals in North America. It has been claimed to have the fastest horizontal speed (as opposed to stoop diving speed) of any animal, reaching top ground speeds over 100 mph (161 km/h).
The tails of these bats are almost half their total length and stretch beyond the uropatagium, giving them the name "free-tailed" bats. Their ears are wide, rounded, and large compared to their heads, nearly meeting at the front of the face, but distinctly not joined at the midline and projecting anterodorsally from just before the muzzle to the back of the head. They use their large ears to help them find prey using echolocation. The Mexican free-tailed bat is distinguished among North American Tadarida bats in possessing deep wrinkles on the upper lip and in having a Z-shaped upper third molar, which is used for grinding insects. These individuals possess canines which are larger in males than in females. The wings are elongated and narrow with pointed tips, making them well-equipped for quick, straight flight patterns. Their fur color ranges from dark brown to gray. The Mexican free-tailed bat's large feet have distinct long, white bristles.
Mexican free-tailed bat range from the southern half of the continental United States through most of Mexico, and through most of Central America into South America. They are also found in the Caribbean and are native to all of the Greater Antilles and 11 of the Lesser Antilles. 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. Before buildings, free-tailed bats in the Southeastern United States probably roosted in the hollows of trees such as red mangroves, black mangroves, white mangroves, and cypress.
Mexican free-tailed bats are social animals that live in large colonies. They are nocturnal foragers and begin feeding after dusk using echolocation for navigation and detecting prey. Their traveling calls are of a brief but constant frequency. These bats will fly 50 km (31 mi) in one night to reach foraging areas and they usually catch flying prey in flight. In warm weather free-tailed bats become more active and between June and September, they can be spotted in the late morning and afternoon. Mexican free-tailed bats are highly migratory and during winter most populations move to Mexico and Central America. Some bat populations do not migrate, but are residents and may make seasonal changes in roost sites.
Mexican free-tailed bats are carnivores (insectivores). They eat moths, beetles, dragonflies, flies, true bugs, wasps, and ants.
Mexican free-tailed bats are polygynandrous (promiscuous) breeders and both sexes mate with multiple partners. The mating season occurs once a year and typically lasts five weeks in the spring. During this time females aggregate into maternity roosts. The gestation period lasts 11-12 weeks, with only one young being born. A number of pups are left in "creches", while their mothers roost elsewhere. The female uses vocalizations and scent to identify her pup. She will nurse her young daily, and by 4-7 weeks old, the pup will be full-grown, fully weaned, and independent. Females become reproductively mature at about 9 months of age, while males are ready to breed when they are 2 years old.
Though abundant and widespread, some local populations of the Mexican free-tailed bat are threatened by habitat destruction, human disturbance, mining in caves, pollution, and poisoning by pesticides.
According to IUCN, the Mexican free-tailed bat is locally common and widespread throughout its range but no overall population estimate is available. Currently, this species is classified as Least Concern (LC) on the IUCN Red List and its numbers today are stable.