Brazilian Free-Tailed Bat: Tadarida Brasiliensis

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Illustration of the Brazilian Free-Tailed Bat body

The Brazilian free-tailed bat is a medium-sized bat species that is commonly found in warm climates. It can be found roosting in cave rock crevices or even in the attics of man-made structures. This species will migrate roosts in order to find a stable source of food. The majority of the bat’s diet is made up of moths and other flying insects. Brazillian free-tailed bats use echolocation to hunt down their prey.

Learn More: How Do Bats Communicate?

Characteristics Of The Brazilian Free-Tailed Bat

Tadarida brasiliensis (Brazilian free-tailed bat) is known as a small bat with its distal half freely extending beyond the tail membrane. There is no keel for its calcar (which helps support the uropatagium). Long hair stretches out from your feet. On its leading-edge, the bat’s rounded ears have bumps (papillae). There are vertical wrinkles on the upper lip, and the pelage is dense and short.

The bat’s coat varies from dark brown to grayish brown to very pale, the dark color resulting from the ammonia accumulation in the roosts. The Brazilian Free-tailed Bat can be distinguished by its tail, which projects well beyond the uropatagium’s posterior border, from all other bat species. ¹

Brazilian Free-Tailed Bat Size

The average exterior measurements of Tadarida Brasiliensis:

Total Length: 90-108 mm
Average Weight: 8-14 g
Ear length: 13-19 mm
Tail Length: 30-40 mm
Foot Length: 8-12 mm

Habitat Of The Brazilian Free-Tailed Bat

A range of particular roosting sites is used by Brazilian free-tailed bats, including caves and human-made structures, such as bridges and attics. The primary roosting habitats are caves with large rooms and high ceilings, although roosts also exist in hollow trees. For nesting, breeding, and interaction between people, roosts are used.

Brazilian Free-Tailed Bat Range

This species appears in the Southern & Northern United States, Mexico, Caribbean Islands, and Brazil. The subspecies is Tadarida brasiliensis cynocephala, which also occurs in the southeastern United States, including Florida.

Brazilian free-tailed bats have a population in the upper thousands in areas such as Bracken Cave (San Antonio, Texas) and Carlsbad Caverns National Park (New Mexico). They are also known to live with similar bats of their subspecies. ²

Diet Of The Brazilian Free-Tailed Bat

Free-tail bats eat vast quantities of moths and other insects. It is known that some roosts contain millions of bats. A single colony of Brazillian free-tailed bats can eat an estimated 250 tons of insects every night. ³

Brazilian Free-Tailed Bat Behavior

After sunset, Brazilian free-tailed bats start foraging and feed throughout the night. To get to a foraging area, they may fly over 50 kilometers. Their flight is straight and rapid. Among bats, this species has the highest flight altitude ever recorded, at over 3300 meters. Also capable of long-distance flight, Brazilian free-tailed bats can forage over large areas and migrate seasonally.

Observations at a Colorado mine showed that Brazilian free-tailed bats were most active in the late morning and afternoon during June through September through feeding and searching for roost sites. Weather can influence their activity; warm weather stimulates more significant activity, and there is less activity in cold weather. Brazilian free-tailed bats call, squeak, and move around during their waking hours. Brazillian free-tailed bats live in large colonies and seem to be social animals. ⁴

Reproduction Cycle Of The Brazilian Free-Tailed Bat

Each female only gives birth to one child per year. Bats are born fur-free and unable to fly. They are placed together in continuous colonies on particular areas of the roost ceilings and are not taken along on their mother’s nocturnal feeding flights. Remarkably, female bats can recognize and locate their own young among the swarms of millions of bats and their offspring when they return from their nightly activities.

The majority of babies have fur within one month of birth, are almost full-grown, and can fly outside the cave to find their own food. In a very short period of time, the caves become too crowded because the baby bats grow up so quickly. The adult bats leave the caves for the fledglings to cope with the congestion and move completely away from their mates. ⁵

Brazilian Free-Tailed Bat Communication

By using echolocation, which is a way of judging distance through listening to echoes, Brazilian free-tailed bats navigate and find prey. They send out calls with constant frequency while flying.

Their calls change frequency to between 40 and 75 kHz when they pick up on food or another object. Their regular frequency is 49 to 70 kHz, but it can drop to 25 to 40 kHz when objects cross their flight path.

Using echolocation, chemical signals, sight, and hearing, Brazilian free-tailed bats recognize one another. Female bats also locate their young via scent and sound frequencies. ⁶

Brazilian Free-Tailed Bat Species Threats

As it is a known carrier of rabies, this bat has received considerable attention. Brazilian free-tailed bat specimens are submitted more often than any other species to the Texas Department of State Health Services (DSHS).

A study conducted by DSHS from 1994 to 1998, 258 (18 percent) out of 1,455 specimens (Brazilian Free-Tailed Bat) tested positive for the rabies virus. Though this number of rabies carrying bats is minuscule compared to the bat population as a whole, caution should be exercised when encountering these bats. ⁷

Sources:

“Kansas Mammal Atlas: Brazilian Free-Tailed Bat.” Fort Hays State University, Sternberg Museum of Natural History, webapps.fhsu.edu/ksmammal/account.aspx?o=32&t=184. Accessed 12 Jan. 2021.
NPS. “Brazilian Free-Tailed Bat – Everglades National Park (U.S. National Park Service).” National Park Service, U.S. Department Of The Interior, 17 Oct. 2017, www.nps.gov/ever/learn/nature/brazilianfreetailedbat.htm.
“Mexican Free-Tailed Bat Fact Sheet.” Arizona-Sonora Desert Musem, www.desertmuseum.org/kids/bats/mexican_free_tailed_bat.php. Accessed 12 Jan. 2021.
Sosnicki, J. 2012. “Tadarida brasiliensis” (On-line), Animal Diversity Web. Accessed January 12, 2021 at https://animaldiversity.org/accounts/Tadarida_brasiliensis/
“Brazilian Free-Tailed Bat (Tadarida Brasiliensis).” Texas Parks And Wildlife, Texas Parks and Wildlife Department, tpwd.texas.gov/huntwild/wild/species/brazilfreetailbat. Accessed 12 Jan. 2021.
Schmidly, David, and Robert Bradley. “A Species Account of the Brazilian Free-Tailed Bat (Tadarida Brasiliensis) | Mammals of Texas | Natural Science Research Laboratory | TTU.” University Of Texas, Texas Tech University Natural Science Laboratory, www.depts.ttu.edu/nsrl/mammals-of-texas-online-edition/Accounts_Chiroptera/Tadarida_brasiliensis.php. Accessed 12 Jan. 2021.
Sosnicki, J. 2012. “Tadarida brasiliensis” (On-line), Animal Diversity Web. Accessed January 12, 2021 at http://www.biokids.umich.edu/accounts/Tadarida_brasiliensis/