Nyctinomops femorosaccus (Pocketed Free-tailed Bat)

Weight: 10-14 grams

Wingspan: 34-35 centimeters


Southwestern United States to southcentral Mexico.

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Ecology and Behavior:

The common and scientific names refer to a shallow fold of skin on the underside of the interfemoral membrane near the knee, which forms a pocket-like structure. It occurs in the arid lowlands of the desert Southwest, and primarily roosts in crevices in rugged cliffs, slopes, and tall rocky outcrops. Colonies are small, usually less than 100 individuals. In day roosts, these bats squeak or chatter much of the time, and usually will leave the roost well after dark. When first taking flight, they produce shrill, sharp, high-pitched chattering calls, which may continue while the bats are in flight. As with other free-tailed bats, the flight is swift and lacks the fluttering characteristic of many vespertilionid bats. At stock ponds and other water sources, they fly swiftly about the pool, making distinctly audible whistling and fluttering sounds with their wings. In drinking, these bats will hit the water hard while in flight and scoop up a mouthful of water.

Food Habits:

Moths are common prey, but other foods include beetles, flying ants, flies, leafhoppers, crickets, stinkbugs, lacewings, and grasshoppers.

Reproduction and Longevity:

One baby is born in late June or July.

Status of Populations:

Uncommon in the United States.

Text, in its original form, provided by T. L. Best, M. J. Harvey, and J. S. Altenbach. Printed spectrographs provided by M. J. O'Farrell. Distribution maps, call descriptions, and AnaMusic sound clips produced by W. L. Gannon. Accounts assembled by T. C. Sanchez-Brown.