Mammal Species of the World
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Tadarida brasiliensis is a member of one of the widely distributed genera of bats in North and South America. Extensive studies on their range have yet to be completed, especially within South America; however they have been found throughout the much of the United States, Mexico, Central America, and southwestern South America, including Brazil, Chile, and Argentina. In the United States Tadarida brasiliensis is found from southern Oregon to Nevada and eastward to North Carolina and southwestern Virginia. In the last 50 to 100 years, Tadarida brasiliensis populations have declined, possibly due to a decrease in habitat, damage to roosts, and indirect consumption of pesticides.
Biogeographic Regions: nearctic (Native ); neotropical (Native )
occurs (regularly, as a native taxon) in multiple nations
Regularity: Regularly occurring
Type of Residency: Year-round
Global Range: (>2,500,000 square km (greater than 1,000,000 square miles)) Southern Oregon, northern Nebraska, and southern North Carolina (some records farther north) southward through most of Central America and Antilles (south to St. Lucia in Lesser Antilles; Tobago record probably an accidental, Jones 1989) to central Argentina, southern Brazil, and central Chile, excluding Amazonia (Wilkins 1989, Honacki et al. 1982).
With brown fur and large ears, Brazilian free-tailed bats are medium-sized, with distinctive short snouts and wrinkled upper lips. The free-tailed bats, which include the genera Tadarida, Eumops, and Nycintomops, are most easily recognized by their “free-tail,” which extends well beyond the uropatagium. They have powerful legs and can climb well. Their long, narrow, pointed wings make them well-suited for rapid, direct flight. Like other temperate bat species, Brazilian free-tailed bats take advantage of daily torpor to conserve energy and may hibernate.
Adults range in size from 79 to 98 mm in length, with a tail almost half the size (31 to 41 mm). Their body mass varies seasonally and depending on maturity, adults typically weigh 7 to 12 g. Ear length is 8 to 15 mm, forearm length ranges from 37 to 41 mm, and their hindfoot measures 6 to 9 mm. The dental formula is the same as other members of the genus Tadarida: Incisors= 1/3, canines= 1/1, premolars= 2/2, molars= 3/3, with a total of 32 teeth.
Range mass: 7 to 12 g.
Range length: 79 to 98 mm.
Average wingspan: 280 mm.
Range basal metabolic rate: 1.99 to 7.31 cm3.O2/g/hr.
Other Physical Features: endothermic ; heterothermic ; bilateral symmetry
Sexual Dimorphism: sexes alike
Length: 11 cm
Weight: 14 grams
Size in North America
Average: 95 mm
Range: 85-109 mm
Range: 10-15 g
Brazilian free-tailed bats use a variety of different roost sites, including caves and man-made structures, such as bridges and attics. Caves with large rooms and high ceilings are the primary roosting habitats, although roosts also occur in hollow trees. Roosts are used for nesting, breeding, and interaction between individuals.
Habitat Regions: temperate ; terrestrial
Terrestrial Biomes: chaparral ; forest
Other Habitat Features: urban ; suburban ; caves
Habitat and Ecology
Comments: Roosts primarily in buildings (generally old ones) in southeastern U.S. (sometimes in hollow trees), U.S. West Coast, and Jamaica; in caves in southwestern U.S.; in both buildings and caves in Puerto Rico. May use rock crevice, bridge, sign, or cliff swallow nest as roost during migration. Generally roosts high (at least 3 m) above ground to allow free fall required to attain flight. Large maternity colonies inhabit buildings and caves (rarely used in Florida); also uses culverts and bridges. Tends to return to natal cave to breed (Caire et al. 1989).
Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.
Locally Migrant: Yes. At least some populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).
Locally Migrant: Yes. At least some populations of this species make annual migrations of over 200 km.
In the eastern U.S. (to eastern Texas) and U.S. West Coast: hibernates but does not migrate. Antillean subspecies ANTILLARUM does not migrate (Jones 1989). Texas and Great Plains through southwestern U.S.: most migrate to Mexico or to southwestern U.S., usually toward end of October, return in March. (See Wilkins 1989 for more detail.) Individuals from southern Great Plains migrate, beginning in late August, to winter range from southern edge of Edwards Plateau in Texas south nearly to latitude of Mexico City (Caire et al. 1989).
Foraging habitat is very broad. May range as far as 80 km from cave to feed (Caire et al. 1989). Bats that roost in Carlsbad Cavern, New Mexico, forage up to at least 56 km from the cavern (Best and Geluso 2003).
Brazilian free-tailed bats are aerial insectivores that use echolocation to find and consume their prey. Their diet varies based on geographical range, but mainly includes moths (Lepidoptera), beetles (Coleoptera), dragonflies (Odonata),flies (Diptera), true bugs (Hemiptera), and wasps, bees, and ants (Hymenoptera). Diet is influenced by the abundance of prey, weather conditions, metabolic demands, and lunar illumination, which can alter food availability. Brazilian free-tailed bats prey on flying insects while they are, themselves, in flight.
Animal Foods: insects
Primary Diet: carnivore (Insectivore )
Comments: Opportunistic; diet includes moths, flying ants, beetles, bugs, and other insects; often preys on densely swarming insects. May fly considerable distances to favorite feeding areas.
Brazilian free-tailed bats are also known as guano bats. Excrement (guano) in roosts can build-up and result in tons of guano. Guano can be harvested as fertilizer and can pose a health risk in spreading diseases that are transmitted through the air (e.g., histoplasmosis). During the summer, disease transmission risk worsens, with higher temperatures and movement from within the caves generating dust clouds. Higher temperatures are also ideal for parasites and pathogens.
Brazilian free-tailed bats play host to both ecto- and endoparasites. Individuals that are part of a colony are at higher risk for being parasitized than individuals in smaller roosts. Mite, tick, chigger, flea, and beetle infections are common among Brazilian free-tailed bats, and may act as vectors for other diseases. For example, the chigger Microtrombicula merrihewi affects the nasal passages of Brazilian free-tailed bats, while other parasites affect the blood stream and digestive system. Brazilian free-tailed bats, like other mammals, are also hosts for the rabies virus and at least five other known viruses, such as the Rio Bravo virus, St. Louis encephalitis virus, Eastern equine encephalitis, Western equine encephalitis, and Japanese B encephalitis.
During the summer months, these bats significantly affect local insect populations, which makes maintaining them important to agriculture and human health by eating agricultural pests and disease vectors. More studies are needed on associations with other bat species. In Texas, Myotis velifer are most commonly seen in roosts with T. brasiliensis. Although segregated, individuals can be seen within the other’s colony especially if the roost is crowded. The flight paths of M. velifer and T. brasiliensis differ, which helps avoid competition between the two species while exiting the roost. Roosts of Brazilian free-tailed bats are used by deer mice (Peromyscus species) and squirrels.
- chiggers (Microtrombicula merrihewi)
- ticks (Ixodoidea)
- chiggers (Trombiculidae)
- fleas (Siphonaptera)
- beetles (Coleoptera)
Predators of Brazilian free-tailed bats include a number of raptors, such as red-tailed hawks (Buteo jamaicensis), American kestrels (Falco sparverius), great horned owls (Bubo virginianus), barn owls (Tyto alba), and Mississippi kites (Ictinia mississippiensis). Virginia opossums (Didelphis virginiana), striped skunks (Mephitis mephitis), and raccoons (Procyon lotor are among the mammalian roost predators. Snakes also prey on these bats in roosts, including eastern coachwhips (Masticophis flagellum) and eastern coral snakes (Micrurus fulviusprey). However, predation on Tadarida brasiliensis is rare; the number of bats lost due to predation is very low compared to their total population of around 100 million individuals.
- red-tailed hawks (Buteo jamaicensis)
- American kestrels (Falco sparverius)
- great horned owls (Bubo virginianus)
- barn owls (Tyto alba)
- Mississippi kites (Ictinia mississippiensis)
- Virginia opossums (Didelphis virginiana)
- striped skunks (Mephitis mephitis)
- raccoons (Procyon lotor)
- eastern coachwhips (Masticophis flagellum)
- eastern coral snakes (Micrurus fulviusprey)
Anti-predator Adaptations: cryptic
Number of Occurrences
Note: For many non-migratory species, occurrences are roughly equivalent to populations.
Estimated Number of Occurrences: 21 - 80
Comments: Bulk of total abundance is confined to about 20 caves in the southwestern U.S. Rest are small in size, though numerous. All large colonies probably known.
10,000 to >1,000,000 individuals
Comments: Estimated 120-150 million. See Arita (1993) for information on population size in Mexico.
Roosts in tightly packed groups. Winter congregations typically much smaller than summer colonies. Sexes generally segregate during summer; males may form small (but sometimes up to 100,000) at higher elevations, whereas females usually form nursery colonies in warmer areas of the species' northern range (Freeman and Wunder 1988). Typically feeds within 50-mile radius of day roost, but up to 150 miles away (Whitaker 1980).
Life History and Behavior
Brazilian free-tailed bats use echolocation as their primary mode of perception for navigation and detecting prey. They emit brief constant frequency calls as they travel, unless food or another object is detected, then they transfer to modulated frequency calls between 75 and 40 kHz. Their normal frequency ranges from 49 to 70 kHz, but can drop to 25 to 40 kHz when objects cross their flight path. Mate and intra-specific recognition is determined through the use of echolocation and through chemical, visual, and audible vocalizations. Females do not roost with their offspring, they must find their young through scent and sound recognition.
Communication Channels: visual ; tactile ; acoustic ; chemical
Perception Channels: visual ; tactile ; echolocation ; chemical
Comments: On overcast days, often found feeding in early evening. In predominantly male colony in Colorado: began to leave mine shaft at about 2300 h; a few began returning by 2300, continuing until 0430; none returned after 0515 (Freeman and Wunder 1988); in some areas some groups do not return to cave until after daylight (Caire et al. 1989); in other areas may forage for a few hours, return to cave roost for a few hours, then go out on another foraging trip, returning after dawn. Typically hibernates in the eastern U.S. and on U.S. West Coast.
Dental studies determined that the longest-living individual was over eight years old. Most adults have a survival rate of 70 to 80% each year, with the rate decreasing with age. Males and females have roughly equal lifespan and mortality rates. The longest reported life in captivity was 12 years old, so it is expected that they can live longer than 12 years in captivity.
Status: wild: 8 years.
Status: captivity: 12 years.
Status: wild: 8.0 years.
Lifespan, longevity, and ageing
Male Brazilian free-tailed bat behavior and scent-marking changes throughout the year based on the breeding season. Females gather in large numbers at maternity roosts in caves, while smaller groups can be found in tree, bridges, buildings, and other man-made structures. Males vocalize and mark territories in order to attract potential mates. Male and female free-tailed bats call to each other, singling out a mate. Once found, they move away from the group. Males aggressively mate with the female, restricting her movement by grabbing her neck, jaw, or ear. He moves onto her back, biting her neck to keep her in place. The female and male call to each other during mating. Some free-tailed bats mate multiple times, moving from mate to mate.
Mating System: polygynandrous (promiscuous)
Brazilian free-tailed bat males mature at about two years, while females mature at nine months. They are monestrous, with females having one annual estrous cycle lasting roughly five weeks during ovulation, which occurs in the spring. Male sexual activity coincides with spring female receptivity, suitable timing for mating interactions to occur. Females usually give birth to a single offspring after an 11 to 12 week gestation period. Births occur upside down and last roughly 90 seconds. It takes an additional 10 to 15 minutes for the newborn to find a nipple for feeding. The sex-ratio is typically 1:1 in pups.
Breeding interval: Breeding occurs once yearly.
Breeding season: Ovaluation lasts roughly 5 weeks in females and occurs in spring, when breeding occurs.
Average number of offspring: 1.
Range gestation period: 11 to 12 weeks.
Range time to independence: 4 to 7 weeks.
Average age at sexual or reproductive maturity (female): 9 months.
Average age at sexual or reproductive maturity (male): 2 years.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; viviparous
Average birth mass: 2.8 g.
Average number of offspring: 1.
Average age at sexual or reproductive maturity (male)
Sex: male: 547 days.
Average age at sexual or reproductive maturity (female)
Sex: female: 273 days.
Because mothers do not roost with their offspring, but rather leave them with a larger cluster of pups (a creche), she has to identify her own young through a series of calls and odors produced by the pup. Loughry and McCracken (1991) found that the scent of mothers is imprinted during early stages of development; however, pups will try latching onto any female that passes in the cluster to get fed. The young are nursed daily. They reach adult size, are weaned, and are independent in 4 to 7 weeks after birth. Brazilian free-tailed bat females have the highest milk fat content of any bat, over 28% fat, which allows their pups to grow relatively quickly.
Parental Investment: altricial ; female parental care ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female)
Breeds late February-March or early April in North America. None of 8 females collected in late December in Jamaica was pregnant (Goodwin 1970). Gestation lasts 2.5-3.5 months. Births mainly June-July in North America (early to mid-June in Texas). Litter size: 1 (females occasionally carry 2 embryos). Despite the huge numbers of young that may be present in a colony, females recognize and nurse their own offspring. Young nurse for about 45 days, first fly at 6-7 weeks. Females may become pregnant as yearlings; males become sexually mature at 18-22 months. Maternity colonies initially consist of almost only of pregnant females. Some colonies include more than 1 million individuals (20 million adult females give birth in Bracken Cave near San Antonio, Texas); 10,000s in eastern North America. If a nursery falls below about 20,000 females, usually it is abandoned (Caire et al. 1989).
Evolution and Systematics
The flanks of Brazilian free-tailed bats aid thermoregulation due to a unique arrangement of arteries and veins creating thermal windows.
"The Brazilian free-tailed bat (Tadarida brasiliensis) experiences challenging thermal conditions while roosting in hot caves, flying during warm daylight conditions, and foraging at cool high altitudes. Using thermal infrared cameras, we identified hot spots along the flanks of free-ranging Brazilian free-tailed bats, ventral to the extended wings. These hot spots are absent in syntopic cave myotis (Myotis velifer), a species that forages over relatively short distances, and does not engage in long-distance migration. We hypothesized that the hot spots, or 'radiators,' on Brazilian free-tailed bats may be adaptations for migration, particularly in this long-distance, high-flying species. We examined the vasculature of radiators on Brazilian free-tailed bats with transillumination to characterize the unique arrangements of arteries and veins that are positioned perpendicular to the body in the proximal region of the wing. We hypothesized that these radiators aid in maintaining heat balance by flushing the uninsulated thermal window with warm blood, thereby dissipating heat while bats are flying under warm conditions, but shunting blood away and conserving heat when they are flying in cooler air at high altitudes. We also examined fluid-preserved specimens representing 122 species from 15 of 18 chiropteran families and radiators appeared present only in species in the family Molossidae, including both sedentary and migratory species and subspecies. Thus, the radiator appears to be a unique trait that may facilitate energy balance and water balance during sustained dispersal, foraging, and long-distance migration." (Reichard et al. 2010:358)
Learn more about this functional adaptation.
Molecular Biology and Genetics
Barcode data: Tadarida brasiliensis
Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.
See the BOLD taxonomy browser for more complete information about this specimen and other sequences.
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Download FASTA File
Statistics of barcoding coverage: Tadarida brasiliensis
Public Records: 6
Specimens with Barcodes: 33
Species With Barcodes: 1
Populations of Tadarida brasiliensis have declined over the last century. Some suggest this decline has been caused by disturbance and destruction of roost sites and indirect poisoning by pesticides. Tadarida brasiliensis is labeled as “near threatened” by the International Union for Conservation of Nature, with a Species Action Plan created.
US Federal List: no special status
CITES: no special status
IUCN Red List of Threatened Species: least concern
IUCN Red List Assessment
Red List Category
Red List Criteria
- 1996Lower Risk/near threatened(Baillie and Groombridge 1996)
National NatureServe Conservation Status
Rounded National Status Rank: N5 - Secure
NatureServe Conservation Status
Rounded Global Status Rank: G5 - Secure
Reasons: Large range (southern North America to South America); suitable sites for large colonies are extremely limited; threats include pesticides and disturbance to major roosts.
Degree of Threat: B : Moderately threatened throughout its range, communities provide natural resources that when exploited alter the composition and structure of the community over the long-term, but are apparently recoverable
Comments: Threatened by disturbance, pesticides, and habitat destruction in tropics.
Biological Research Needs: A relatively well-studied species. Needs some resolution of subspecies.
Global Protection: Few (1-3) occurrences appropriately protected and managed
Comments: Carlsbad Caverns N.P., New Mexico.
Needs: Protect largest colonies. Protect tropical winter areas.
Relevance to Humans and Ecosystems
There is no known negative economic importance. However, histoplasmosis is a potential health concern in caves with large guano accumulations and, like other bats, Brazilian free-tailed bats can carry and transmit rabies.
Negative Impacts: injures humans (carries human disease); causes or carries domestic animal disease
Brazilian free-tailed bats eat large numbers of insects nightly, some of which are agricultural pests or disease vectors. Their positive economic impact on agriculture is substantial. However, agricultural pests are often exposed to pesticides through agricultural applications, which can indirectly lead to population decline. In addition, the large amount of guano produced in Brazilian free-tailed bat colonies are used for fertilizer and as a component in gunpowder.
Positive Impacts: produces fertilizer; controls pest population
Comments: Large colonies produce voluminous guano in roost caves; guano has been (and still is) mined for use as a fertilizer in some areas.
Mexican free-tailed bat
The Mexican free-tailed bat (Tadarida brasiliensis), also known as the Brazilian free-tailed bat and Austonian bridge bat, is a medium-sized bat that is native to the Americas and is widely regarded as one of the most abundant mammals in North America.
However, its proclivity towards roosting in large numbers in relatively few roosts makes it especially vulnerable to human disturbance and habitat destruction, and declining numbers at some roosts such as in the western state of Utah have been documented. In the western coastal state of California, the bat is considered a species of special concern as a result of declining populations. The species' winter migratory habits and destination points are still relatively unknown.
Mexican free-tailed bats are about 9 cm (3.5 in) in length, and they weigh about 12.3 g (0.43 oz). Their tails make up almost half their lengths. Their ears are wide and set apart to help them find prey with echolocation. They are also fairly close behind the snout and eyes. Their fur color varies from dark brown to gray. Their muzzles are condensed, with wrinkled upper lips. The tail of these bats stretches further than the uropatagium, hence they are named "free-tailed" bats. The wings are elongated and narrow with pointed tips, making them well-equipped for quick, straight flight patterns.
Range and ecology
The Mexican free-tailed bat is one of the most widespread mammals in the Western Hemisphere. It ranges from the southern half of the continental United States through most of Mexico, and through most of Central America into South America. The range of the Mexican free-tailed bat in South America is less understood where it lives in the eastern Brazilian highlands and coast, the northeastern Andes and the coast of Peru and northern Chile. It is absent in much of the Amazon rainforest. The bat is also found in the Caribbean, and is 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; research indicates the bats from this colony congregate in huge numbers at altitudes between 180 and 1,000 m (590 and 3,300 ft), and even as high as 3,000 m (9,800 ft).
Mexican free-tailed bats roost primarily in caves. However, they will 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, on the other hand, 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.
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 though western edge of the Sierra Madre Oriental into Jalisco, Sinaloa and Sonora. Some bats that summer in Kansas, Oklahoma, eastern New Mexico and Texas will migrate southward to southern 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.
In Austin, Texas, a colony of Mexican free-tailed bats summers (they winter in Mexico) under the Congress Avenue Bridge ten blocks south of the Texas State Capitol. It is the largest urban colony in North America, with an estimated 1,500,000 bats. Each night they eat 10,000 to 30,000 lb (4,500 to 13,600 kg) of insects. Each year they attract 100,000 tourists who come to watch them. In Houston, Texas, a colony is living under the Waugh Street Bridge over Buffalo Bayou. It is the home to 250,000 bats and also attracts viewers. The Mexican free-tailed bat is the official "flying mammal" of the state of Texas.
Bats ranging eastward from East Texas do not migrate, but local shifts in roost usage often occur seasonally. Also, a regional population that ranges from Oregon to California, has a year-round residence.
Mexican free-tailed bats are primarily insectivores. They hunt their prey using echolocation. The bats eat moths, beetles, dragonflies, flies, true bugs, wasps, and ants. Bats usually catch flying prey in flight. Large numbers of Mexican free-tailed bats fly hundreds of meters above the ground in Texas to feed on migrating insects. The consumption of insects by these bats can be quite significant.
Additionally, Mexican free-tailed bats are also efficient pollinators. Their pollination of sugarcane as well as their consumption of insects that damage sugar cane may be among the reasons why Bacardi rum features the Mexican free-tailed bat as its icon. Bacardi Ltd. themselves attribute the use of the bat in the logo to, "... Don Facundo’s wife, Amalia, who suggested using a bat for the company logo. It was an insightful choice, because according to Cuban and Spanish lore, bats symbolize good health, good fortune and family unity."
Health and mortality
One individual bat was recorded to have lived eight years, based on dentition. Predators of the bat include large birds such as red-tailed hawk, American kestrels, great horned owls, barn owls, and Mississippi kites. Mammal predators include Virginia opossums, striped skunks, and raccoons. Snakes such as eastern coachwhips and eastern coral snakes may also prey on them, but at a lesser extent. Certain types of beetles prey on neonate and juvenile bats that have fallen to the ground. This species seems to have a low incidence of rabies, at least in the United States. They do, however, contain certain pesticides.
Mexican free-tailed bats are nocturnal foragers and begin feeding after dusk. They travel 50 km in a quick, direct flight pattern to feed. This species flies the highest among bats, at altitudes around 3300 m. Bats appears to be most active in late morning and afternoon between June and September. Free-tailed bats are more active in warm weather.
Mexican free-tailed bats use echolocation for navigation and detecting prey. Traveling calls are of a brief but constant frequency. However, they switch modulated frequency calls between 40 and 75 kHz if they detect something. Typically, the frequency range of their echolocation is between 49 and 70 kHz, but can be between 25 and 40 kHz if something crosses their path while in flight.
On 6 November 2014, Aaron Corcoran, a biologist at Wake Forest University, North Carolina, reported online in Science that he and his team had detected Mexican free-tailed bats emitting ultrasonic vocalizations which had the effect of jamming the echolocation calls of a rival bat species hunting moths. The ‘jamming’ call led to an increased chance of the rival missing its prey, which the Mexican free-tailed bat was then able to eat itself. Earlier researchers had discovered some 15 types of social calls made by Mexican free-tailed bats and reported that they could adjust their calls to avoid interfering with others in range of their calls.
Mating and reproduction
During the breeding season, females aggregate into maternity roosts. The size of these roosts depends on the environment, with caves having the larger roosts. Mating can occur in an aggressive or passive form. In the aggressive form, the male controls the female's movements, keeping her away from the other bats in the roost. He also tends to vocalize when mating. During passive copulation, the males simply flies to a female in her roost and quietly mounts her with no resistance. This species is a promiscuous breeder and both sexes copulate with multiple partners. Females become sexually mature at about 9 months, while males take even longer, at two years. Females enter estrus once a year, which typically lasts five weeks in the spring. The gestation period of the bat 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. The mother imprints her scent on the young early on. However, young try to steal a suckle from any female that passes through the cluster. A mother will nurse her young daily, and by 4–7 weeks old they are full grown, fully weaned, and independent.
Though abundant and widespread, some local populations have prompted protection and conservation efforts. For instance, during the spring and summer, one of the largest Mexican free-tailed bat populations inhabits Cueva de la Boca, a cave near Monterrey, Mexico. In 2006, the Mexican environmental conservation NGO, Pronatura Noreste, purchased the property. Because of a reduction of more than 95% of the original 20 million bat population, as a result of vandalism, pollution, and uncontrolled tourism, the organization decided to buy the property to place it under conservation. Other species of high ecological value that inhabit the cavern are also being protected.
- Bat bomb, an experimental incendiary weapon that used Mexican free-tailed bats as a dispersal mechanism
- Barquez, R., Diaz, M., Gonzalez, E., Rodriguez, A., Incháustegui, S. & Arroyo-Cabrales, J. (2008). Tadarida brasiliensis. In: IUCN 2008. IUCN Red List of Threatened Species. Retrieved 4 March 2009.
- "Tadarida brasiliensis". Integrated Taxonomic Information System. Retrieved 23 March 2006.
- "Carlsbad Caverns National Park – Bats' Wintering Sites (U.S. National Park Service)".
- "Freetail Brewing Company webpage - "Where'd We Get That Silly Name?"".
- Wilkins, K. (1989). "Tadarida brasiliensis". Mammalian Species , 331: 1-10.
- Baker, R. J., Genoways, H. H. 1978. Zoogeography of Antillean bats. In. Zoogeography in the Caribbean, ed. F. B. Gill pp. 53-97. Philadelphia: Acad
- Glass BP (1982) Seasonal movements of Mexican free- tail bats Tadarida brasiliensis mextcana banded in the Great Plains. Southwestern Nat., 27:127-133.
- "Bat Conservation International page on the Congress Avenue Bridge Bat Colony".
- "Texas State Symbols, Texas State Library and Archives Commission".
- McWilliams, L. 2005. Variation in diet of the Mexican free-tailed bat (Tadarida brasiliensis mexicana). Journal of Mammalogy, 86/3: 599-605.
- Gary F. McCracken, Erin H. Gillam, John K. Westbrook, Ya-Fu Lee, Michael L. Jensen and Ben B. Balsley (2008) "Brazilian free-tailed bats (Tadarida brasiliensis: Molossidae, Chiroptera) at high altitude: links to migratory insect populations", Integrative and Comparative Biology 48(1):107-118.
-  Do Bats Control Mosquitoes?
-  Animal Fact Sheet: Mexican Free-Tailed Bat, Desert Museum
-  Bacardi Ltd. Official Web Site - The Early Years
- Gannon, M., A. Kurta, A. Rodriquez-Duran, M. Willig. 2005. Bats of Puerto Rico. Jamaica: The University of the West Indies Press.
- Williams, T., L. Ireland, J. Williams. 1973. High altitude flights of the free-tailed bat, Tadarida brasiliensis, observed with radar. Journal of Mammalogy, 54/4: 807-821.
- Svoboda, P., J. Choate. 1987. Natural history of the Brazilian free-tailed bat in the San Luis Valley of Colorado. Journal of Mammalogy, 68/2: 224-234.
- Allen, L., A. Turmelle, M. Mendonca, K. Navara, T. Kunz, G. McCracken. 2009. Roosting ecology and variation in adaptive and innate immune system function in the Brazilian free-tailed bat (Tadarida brasiliensis). Journal of Comparative Physiology, 179: 315–323.
- Gillam, E., G. McCracken. 2007. Variability in the echolocation of Tadarida brasiliensis: effects. Animal Behavior, 74: 277-286.
- Morell, Virginia (6 November 2014). "Holy blocked bat signal! Bats jam each other's calls". new.sciencemag.org. Retrieved 8 November 2014.
- Hogenboom, Melissa (7 November 2014). "Bats sabotage rivals' senses with sound in food race". BBC News. Retrieved 8 November 2014.
- Keeley, A., B. Keeley. 2004. The Mating System of Tadarida brasiliensis (Chiroptera: Molossidae) in a Large Highway Bridge Colony. Journal of Mammalogy, 85/1: 113-1.
- Loughry, W., G. McCracken. 1991. Factors influencing female-pup scent recognition in Mexican free-tailed bats. Journal of Mammalogy, 72/3: 624-626.
- Kunz, T., S. Robson. 1995. Postnatal growth and development in the Mexican free-tailed bat (Tadarida brasiliensis mexicana): birth size, growth rates, and age estimation. Journal of Mammalogy, 76/3: 769-783.
Names and Taxonomy
Comments: The specific relationships of Antillean populations of Tadarida remain obscure; it has been suggested that Caribbean populations represent a distinct species or that they are related to T. b. cynocephala (of the southeastern U.S.) but not to other populations of the brasiliensis complex (Jones 1989). Two of the nine subspecies (T. b. mexicana and T. b. cynocephala) occur in the U.S. Though morphological data suggest intergradation (Schmidly 1977), these two subspecies differ widely in behavior (migratory vs. nonmigratory) and roost preference, and gene flow between them has been reported to be minimal and unidirectional at most (Owen et al. 1990). However, McCracken and Gassel (1997) found high genetic similarity and evidence of gene flow between these nominal subspecies, such as typically seen between geographic populations of the same subspecies.
The generic name Rhizomops was proposed in 1984 for Tadarida brasiliensis (and presumably all subspecies), but this was rejected by Owen et al. (1990) because the genus was based entirely on plesiomorphic characters.
McCracken et al. (1994) examined allozyme data from several maternity and winter colonies within the range of subspecies mexicana and determined that populations are not structured genetically into distinct geographic units.