Nyctinomops macrotisbig free-tailed bat

Geographic Range

The big free tailed bat has been found as far north as southwestern British Colombia and as far east as South Carolina. Nyctinomops macrotis ranges from southwestern North America, through northern and central Mexico, throughout South America. It has also been found on Cuba, Jamaica, and Hispanola.

(Parish, D.A., 1999; Nowak, 1999)


Nyctinomops macrotis mainly inhabits rugged and rocky terrain. They are a migratory species that travels seasonally from Mexico to the southwestern United States (Texas, Arizona, California, Nevada, Colorado) . They prefer rocky cliffs in weathered rock fissures and crevices. They have also been discovered roosting in buildings and in terrestrial plants including ponderosa pines, douglas firs, and desert shrubs.

A nursery colony in the Chisos mountains in Brewster County, Big Bend National Park has become quite famous.


(Nowak, 1999)

  • Range elevation
    0 to 1800 m
    0.00 to 5905.51 ft

Physical Description

Adult males of this species range in head-body length from 145-160 mm, females are smaller (120-139 mm, approx. avg. 132).

The coat of Nyctinomops macrotis is very velvety, glossy, seemingly almost greasy to the touch. The coat is bi-colored, dorsally dark red to dark brown and ventrally substantially lighter.

The wings are long and narrow, and the membrane of the wing is thin and leathery. The tail extends freely somewhere between 40 to 52 mm behind the small tail membrane. The face of Nyctinomops macrotis is black; the ears lay forward and are joined at their bases on top of the head; the muzzle is fairly thin; and the upper lip is very furrowed. The legs of Nyctinomops macrotis are short and very strong.

The dentition of Nyctinomops macrotis is: 1/2 1/1 1/2 3/3

(;; Nowak, 1999)
  • Sexual Dimorphism
  • male larger
  • Range mass
    22.0 to 30.0 g
    0.78 to 1.06 oz
  • Average mass
    24 g
    0.85 oz
  • Range length
    120 to 160 mm
    4.72 to 6.30 in
  • Range wingspan
    417 to 436 mm
    16.42 to 17.17 in
  • Average wingspan
    427 mm
    16.81 in


Once impregnated the females and males tend to part ways. Females separate themselves from the males, and each of the sexes form cave colonies amongst themselves

(; Parish, D.A. and Jones C., 1999;
Nowak, 1999; Klingel, J., 2000

The mating season for Nyctinomops macrotis lasts for only a few weeks in the mid to late winter. The female gives birth to a single young sometime in early to mid summer, in mid to late June..

Parish, D.A. and Jones C., 1999; Nowak, 1999; Klingel, J., 2000
  • Breeding season
    Late winter / early spring
  • Range number of offspring
    1 to 1
  • Range gestation period
    2 to 3 months
  • Average gestation period
    3 months
  • Range weaning age
    2 to 3 months
  • Average weaning age
    3 months
  • Range age at sexual or reproductive maturity (female)
    3 to 4 months
  • Average age at sexual or reproductive maturity (female)
    4 months
  • Range age at sexual or reproductive maturity (male)
    3 to 4 months
  • Average age at sexual or reproductive maturity (male)
    4 months

The care of the infant is the responsiblity of the females. After conception, the females rely partly on stored body fat and their colony to provide for the unborn infant. After birth, the lactating female provides for her offspring until it is able to function as an adult, which takes somewhere in the range of 2 to 3 months. The development of the offspring is quite rapid; a young bat is very close to full grown and able to fly by October, at an age of 3 to 4 months.

(; Parish, D.A. and Jones C., 1999;
Nowak, 1999; Klingel, J., 2000


Nyctinomops macrotis is strictly nocturnal. It only leaves the roost after sundown to forage for food. They are solitary hunters for the most part but have been known to hunt in small groups. They are particularly strong fliers and have a tendency to wander, which can put them into residential homes. This also may cause the extremes of their geological range. Nyctinomops macrotis tends not to be that aggressive, but do attempt to bite if cornered or handled.

(Parish, D.A. and Jones C., 1999;

Communication and Perception

Food Habits

The big free tailed bat feeds primarily on large moths, though it has been known to hunt ground dwelling insects including crickets, stinkbugs, and flying ants. They can be heard when hunting emitting a piercing chatter (audible to humans at a range over 20 kHz)


Parish, D.A. and Jones C., 1999; Best, T.L.,Harvey M.J., Altenbach J.S., and Sanchez-Brown, T.,

Economic Importance for Humans: Positive

Big free tailed bats probably help control populations of pest insects.

  • Positive Impacts
  • ecotourism
  • produces fertilizer
  • controls pest population

Economic Importance for Humans: Negative

Conservation Status

Nyctinomops macrotis is not endangered, but is not common either.

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 macrotis 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

The species Nyctinomops macrotis was recently transferred to the genus Nyctinomops from Tadarida.

In the civil war guano was collected and used as a base compound to make gunpowder by the Confederate army.

(; Nowak,1999)


James Lawrence (author), University of Michigan-Ann Arbor, Kate Teeter (editor), 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


living in the southern part of the New World. In other words, Central and South America.

World Map


young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

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.


an animal that mainly eats meat

causes or carries domestic animal disease

either directly causes, or indirectly transmits, a disease to a domestic animal


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


the nearshore aquatic habitats near a coast, or shoreline.


used loosely to describe any group of organisms living together or in close proximity to each other - for example nesting shorebirds that live in large colonies. More specifically refers to a group of organisms in which members act as specialized subunits (a continuous, modular society) - as in clonal organisms.

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.


humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.


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.

female parental care

parental care is carried out by females


union of egg and spermatozoan


forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.


An animal that eats mainly insects or spiders.

internal fertilization

fertilization takes place within the female's body


makes seasonal movements between breeding and wintering grounds


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.


active during the night

scrub forest

scrub forests develop in areas that experience dry seasons.


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


associates with others of its species; forms social groups.


living in residential areas on the outskirts of large cities or towns.


uses touch to communicate


that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).


Living on the ground.


the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.


reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.


"Big Free-tailed Bat" (On-line). Accessed October 6, 2001 at

1997. "Big Free-tailed Bat" (On-line). Accessed October 6, 2001 at

Best, T., M. Harvey, J. Altenbach, T. Sanchez-Brown. "Nyctinomops macrotis" (On-line). Accessed October 6, 2001 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

Harris, J., P. Brown, D. Alley, R. Duke. 1999. "Big Free-tailed Bat" (On-line). Accessed October 9, 2001 at

Klingel, J. 2000. "Biota Information System Of New Mexico BISON" (On-line). Accessed October 9, 2001 at

Klingel, J. 2000. "Biota Information System Of New Mexico BISON" (On-line). Accessed October 9, 2001 at

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

Nowak, 1999. "New World Free-tailed Bats". Pp. 471 in Walker's Mammals of the World vol. 1 Sixth Edition. Baltimore and London: The Johns Hopkins University Press.

Parish, D., C. Jones. 1999. "Nyctinomops Macotis". Pp. 130-131 in Smithsonian Book of North American Mammals. Smithsonian Institute.