Like the Brazilian free-tailed bat, these animals have a tail that extends well beyond the uropatagium. This bat is much larger than the Brazilian free-tailed bat, and its ears join at the midline of the forehead. Color varies from pale brown to black. Wingspan is approximately 425 mm. Average measurements are: total length, 140 mm; length of ear, 25 mm; length of forearm, 60 mm.
The big free- tailed bat occurs mainly in southern California, Arizona, New Mexico, Texas and Mexico. Long thought to be an accidental wanderer in Colorado, recent data show the presence of breeding colonies in Colorado. Indeed, audible echolocation calls and recordings provide evidence of widespread occurrence across Colorado.
This bat frequents rocky or canyon country where it roosts in crevices. This migratory species is a swift, powerful flier, and occasional individuals wander as far north as Canada. Little is known of mortality and longevity.
Breeding probably occurs in midwinter while the species is in warmer latitudes. A single young is born in mid-June to early July. Females form small nursery colonies, and the young do not leave the nursery until they are almost full grown.