Tadarida brasiliensis

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.

Large range (southern North America to South America); very large population; many roost sites but bulk of known population uses only a couple dozen sites; trend poorly known due to questionably reliable historical data; vulnerable to disturbance to roosts; mortality from turbines at wind energy facilities may be an increasingly significant threat.

Range extends from Oregon, Nevada, Utah, Colorado, Nebraska, Arkansas, Mississippi, Alabama, and North Carolina (some records farther north) southward through most of Mexico, Central America, and the Antilles to central Argentina, southern Brazil, and central Chile, excluding Amazonia (Wilkins 1989; Simmons, in Wilson and Reeder 2005). Elevational range extends to at least 3,000 meters in some mountain ranges in the Western United states.

The number of distinct occurrences has not been determined using standardized critertia. This species is represented by a very large number of roosts, though the bulk of the known population occurs in about 20 caves in the southwestern United States.

The species' tendency to roost in large numbers in relatively few locations makes it vulnerable to human disturbance and habitat destruction. Human disturbance and vandalism of key roosting sites in caves are likely the single most serious causes of decline (Texas Parks and Wildlife). Human rabies deaths attributed to this species have led to eradication efforts in some areas. In Mexico, efforts to eliminate vampire bats have led to indiscriminate killing of bats and destruction of roosting sites. Alteration of caves in conjunction with commercialization, guano mining, vandalism, and other human activities has contributed to declines in some locations.

These bats may accumulate heavy loads of potentially lethal pesticides, and broadcast applications of pesticides may result in reductions in bat food resources. Lethal effects of DDT-derived compounds may have played a major role in the reported major population decline observed at Carlsbad Caverns between the 1930s and 1950s (Clark 2001). However, subsequent data cast doubt on the degree (if any) to which the population has declined (Hristov et al. 2010) and thus call into question the importance of pesticides as a major threat.

This species is vulnerable to significant mortality from turbines at wind energy facilities (Arnett et al. 2008). Arnett and Baerwald (2013) estimated that wind turbines killed roughly 21,300-44,100 individuals in the United States and Canada during the period 2000-2011. High rates of mortality can occur during the reproductive period when females are pregnant or lactating, thus compounding the impact (Piorkowski and O’Connell 2010). As wind energy development continues to expand in the southwestern United States and Mexico, further information is needed to better understand the impact of wind turbines on T. brasiliensis, and how best to avoid or minimize this threat (Kunz et al. 2007).

Drought may depress insect populations and bat food supply, but the extent to which this is a significant threat is uncertain.