Smithsonian National Museum of Natural History, North American Mammals
Search the Archive

  Chiroptera · Molossidae · Nyctinomops macrotis
   Smithsonian Institution
   Copyright Notice
   Privacy Notice
Nyctinomops macrotis

Big Free-tailed Bat

Order: Chiroptera
Family: Molossidae

sound   Click to play (0:11, 952 kb)
Credit: New Mexico Bat Call Library, W. L. Gannon
Image of Nyctinomops macrotis
Click to enlarge. (69 kb)

Conservation Status: Least Concern.

The big free-tailed bat has long, narrow, tapering wings. The length and shape of the wings give it speed and enable it to fly long distances, but its flight is not as maneuverable as that of bats with shorter, broader wings. These bats live in rugged habitats in the Southwest in the summer and migrate to Mexico in the winter. When they are foraging, they emit echolocation calls that sound like clicks to human ears. Most bats use calls that are beyond the range of human hearing. The bats forage, mostly for large moths, in total darkness, not leaving their day roosts until well after sunset. Their tails extend well beyond the tail membrane (uropatagium), the membrane that stretches between the hind legs.

Sexual Dimorphism:
Males are slightly larger than females.

Range: 145-160 mm males; 120-139 mm females

Range: 22-30 g


Gray, J.E., 1840.  Descriptions of some mammals discovered in Cuba by W.S. MacLeay, p. 5.  Annals and Magazine of Natural History, 4:1-7.


Mammal Species of the World

Mammalian Species, American Society of Mammalogists' species account

Distribution of Nyctinomops macrotis

Image of Nyctinomops macrotis
Click to enlarge. (85kb)