Nyctinomops femorosaccuspocketed free-tailed bat

Geographic Range

Nyctinomops femorosacca, the Pocketed Free-tailed Bat, is a member of the Molossidae. It inhabits the southwestern United States and northwestern Mexico. The bat has been seen in southern Arizona, southern California, southeastern New Mexico, western Texas, and into Mexico to the state of Michoacan. ( )


This species inhabits semiarid desertlands. Their roosts can be found in caves, tunnels, mines, and rock crevices. They have also been found hanging under the roof tiles of buildings. They are usually found in large colonies. (Vaughn, Ryan, Czaplewski, 1999)

Physical Description

The Pocketed Free-tailed Bat has a large broad head with grooved lips. The face has many stiff hairs with spoonlike tips. A tragus is present and the ears are thick and leathery. These ears are joined in the middle of the forehead. The length of the bat on average is approximately 112mm. The feet are 10mm, the tail is 46mm, the ears 23mm, and the forearms are 46mm. The nasals are located on the nasal protuberance and no nose leaf is present (Grzimek, 1990). The wings are long and narrow. The tail extends well beyond the edge of the uropatagium. The fur is short. A fold of skin stretches from the inner side of the femur to the middle of the tibia. Ths fold produces a pocket on the underside of the interfemoral membrane, which gives the animal its common name, the Pocketed Free-tailed Bat. The dental formula is 1/2, 1/1, 2/2, 3/3=30, with the incisors placed close together. ( )

  • Range mass
    10 to 14 g
    0.35 to 0.49 oz


Females bear a single embryo. Young are born to the female in late June to early July. The gestation period is about 70 to 90 days. When young are born, they weigh 3-4 grams, or about 22% of the adult weight. (Grzimek, 1990) Data on the reproduction of this species is scarce.

  • Key Reproductive Features
  • gonochoric/gonochoristic/dioecious (sexes separate)
  • sexual


These bats leave their roost late in the evening or early night to forage. They are very swift and have powerful flight. Krutzsch recorded the following observations on a colony of 50-60 Pocketed Free-tailed Bats: a daytime roost was located in the crevice of the face of a cliff in San Diego, CA. The first bats left at approximately 6:15 p.m., and others followed in twos and threes for another half and hour. They dropped from 1 to 1.5 meters before taking wing. The flight was rapid, with complete wing beats. When first taking flight, they uttered a high pitched, chattering call, which was repeated while in flight. They also called a lot while in the roost. (

Communication and Perception

Food Habits

This species of bat is strictly insectivorous. Peak activity for feeding occurs at two different times, at the beginning of the night, and again at the end. Like many bats, the Pocketed Free-tailed Bat uses echolocation to detect the presence of its prey. (Grzimek, 1990). They catch their food in mid-flight. They typically eat moths, crickets, flying ants, stinkbugs, froghoppers, and lacewings. (httm://

Economic Importance for Humans: Positive

They are insectivorous and play a part in controlling many of the pesky insects that destroy plants and crops.

Conservation Status

The status of the Pocketed Free-tailed Bat is not known. They are undoubtedly being threatened by the habitat modification and pesticide dispersal by humans. (Grzimek, 1990) There are no conservation projects underway specifically for Nyctinomops femorosacca.

Temperate North American bats are now threatened by a fungal disease called “white-nose syndrome.” This disease has devastated eastern North American bat populations at hibernation sites since 2007. The fungus, Geomyces destructans, grows best in cold, humid conditions that are typical of many bat hibernacula. The fungus grows on, and in some cases invades, the bodies of hibernating bats and seems to result in disturbance from hibernation, causing a debilitating loss of important metabolic resources and mass deaths. Mortality rates at some hibernation sites have been as high as 90%. While there are currently no reports of Nyctinomops femorosaccus mortalities as a result of white-nose syndrome, the disease continues to expand its range in North America. (Cryan, 2010; National Park Service, Wildlife Health Center, 2010)

Other Comments

Males of this species have chest and throat glands. The echolocation signals are short and are emitted through the mouth. Their enemies include humans, diurnal and nocturnal birds of prey, and parasites. (Grimek, 1990). There is limited information on this particular species of bat.


Eric Lancaster (author), University of Michigan-Ann Arbor, Phil Myers (editor), Museum of Zoology, University of Michigan-Ann Arbor.



living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.


Found in coastal areas between 30 and 40 degrees latitude, in areas with a Mediterranean climate. Vegetation is dominated by stands of dense, spiny shrubs with tough (hard or waxy) evergreen leaves. May be maintained by periodic fire. In South America it includes the scrub ecotone between forest and paramo.


uses smells or other chemicals to communicate

desert or dunes

in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.


animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.


having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.


reproduction that includes combining the genetic contribution of two individuals, a male and a female


uses touch to communicate


"The Mammals of Texas, The Pocketed Free-tailed Bat" (On-line). Accessed December 9, 1999 at

Cryan, P. 2010. "White-nose syndrome threatens the survival of hibernating bats in North America" (On-line). U.S. Geological Survey, Fort Collins Science Center. Accessed September 16, 2010 at

Grzimek, B. 1990. Grzimek's Encyclopedia of Mammals. McGraw-Hill Publishing Co..

Macdonald, D. 1984. The Encyclopedia of Mammals. New York, N.Y.: Facts on File, Inc..

National Park Service, Wildlife Health Center, 2010. "White-nose syndrome" (On-line). National Park Service, Wildlife Health. Accessed September 16, 2010 at

Vaughan, T., J. Ryan, N. Czaplewski. June 1999. Mammalogy. Philadelphia, PA: Saunders College Publishing.