Nyctinomops macrotis

Big Free-tailed Bat

Family: Molossidae · Class: Mammalia · Order: Chiroptera

Conservation status: G5 S3

The Big Free-tailed Bat is a medium-sized bat with distinctive morphological features adapted for high-speed flight in open airspace. Adults measure 84 to 95 mm (3.3 to 3.7 inches) in total length, with a forearm length of 58 to 64 mm (2.3 to 2.5 inches). Body mass ranges from 20 to 35 grams (0.7 to 1.2 ounces). The species exhibits a brownish to reddish-brown dorsal pelage with slightly paler ventral coloration. The ears are large and joined at the base, extending forward over the rostrum when laid flat. The tail extends well beyond the interfemoral membrane, giving rise to the common name "free-tailed" bat. Wings are long and narrow, adapted for rapid flight speeds that can exceed 40 kilometers per hour (25 miles per hour). Historically, Big Free-tailed Bats ranged throughout much of the southwestern United States, including California, Arizona, New Mexico, Nevada, and Texas, extending south into Mexico and Central America. In California, the species occurs primarily in desert regions of the southeastern portion of the state, including the Mojave and Sonoran deserts. Records exist from Imperial, Riverside, San Bernardino, and Inyo counties. The species appears to have experienced range contraction in California, with fewer recent observations compared to historical records from the mid-20th century. Big Free-tailed Bats inhabit arid and semi-arid environments, typically at elevations ranging from sea level to 2,500 meters (8,200 feet). They roost in rock crevices, cliff faces, caves, and occasionally in human-made structures such as bridges and buildings. The species shows strong preference for vertical roosting sites that provide protection from weather and predators. Foraging occurs over open habitats including desert flats, washes, agricultural areas, and riparian corridors. This species is highly aerial, foraging primarily on flying insects captured during continuous flight. The diet consists predominantly of moths, beetles, flying ants, and other medium to large-sized insects. Big Free-tailed Bats are among the highest-flying North American bat species, often foraging 100 to 300 meters (330 to 980 feet) above ground level. Mating occurs in late winter, with females giving birth to a single pup in late spring or early summer after a gestation period of approximately 77 to 84 days. Maternity colonies can number several hundred individuals, while winter roosts are typically smaller. The Big Free-tailed Bat is not federally listed but carries a California state rank of S3, indicating the species is vulnerable to extirpation from the state. The global rank of G5 suggests the species is secure range-wide, but California represents the northwestern edge of its distribution. Primary threats include habitat loss from development, disturbance of roost sites, pesticide use that reduces insect prey, and climate change impacts on desert ecosystems. Wind energy development poses an emerging threat, as these bats fly at heights where turbine strikes may occur. Conservation efforts focus on protecting known roost sites and maintaining habitat connectivity in desert regions.

Data from The California Species Project — 14,000+ California species with verified data from CNPS, CDFW, USFWS, and more.