Myotis thysanodesfringed myotis

Geographic Range

The fringed myotis is found across the western United States. It has been found as far east as the Trans-Pecos region of Texas during summer months, as far north as British Columbia and as far south as Mexico.

(Davis and Schmidly 1994, Nowack 1994)


This is a highly migratory species that roosts in caves, mine tunnels, rock crevices and old buildings. Their winter habitat is largely unknown.

(Davis and Schmidly 1994)

Physical Description

Myotis thysanodes is one of the larger species of the Myotis genus and has a total body length of 85mm, tail length of 37mm, foot length of 9mm and ear length of 16.5mm. Its name comes from the fringe of short hairs that line the interfemoral membrane. This species has a full pelage of light brown on its back and off -white underparts. It has a dental formula of I 2/3, Ca 1/1, Pm 3/3 and M 3/3.

(Schmidly 1991, Davis and Schmidly 1994)

  • Range mass
    5 to 9 g
    0.18 to 0.32 oz
  • Average mass
    6 g
    0.21 oz


After a gestation period of 50 - 60 days, a single young is born in late June or early July. Young bats are not entirely precocial, but are able to fly in about 16 days.

(Schmidly 1991)

  • Range number of offspring
    1 to 1
  • Average number of offspring
  • Range gestation period
    50 to 60 days
  • Average weaning age
    21 days



In the southern United States, this species usually arrives around mid-May to begin nursery colonies which may contain hundreds of individuals. Female "nurse bats" remain at the roost to care for the young while other adults are out foraging. Males and females usually do not associate with one another during summer months and males are not normally found within the maternity roosts. The colonies have usually dispersed by the end of October.

(Davis and Schmidly 1994, Schmidly 1991)

Communication and Perception

Food Habits

Myotis thysanodes feeds mainly on beetles and other insects and appear in the late evening. Observations indicate that this species uses its ability for highly maneuverable flight to forage close to the vegetative canopy. It has been suggested that the fringe of hairs along the uropatagium is used to trap small insects.

(Davis and Schmidly 1994, Glass and Gannon 1994)

Economic Importance for Humans: Positive

Bats act as an essential past control by eating hundreds of pounds of insects each night that they forage. They are of great interest to farmers for this role in preventing crop destruction by the insects without the use of harmful chemicals and pesticides.

(Schmidly 1991)

Conservation Status

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 Myotis thysanodes 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)


Sara Vingiello (author), Southwestern University, Stephanie Fabritius (editor), Southwestern University.



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.


uses smells or other chemicals to communicate


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.

seasonal breeding

breeding is confined to a particular season


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


mature spermatozoa are stored by females following copulation. Male sperm storage also occurs, as sperm are retained in the male epididymes (in mammals) for a period that can, in some cases, extend over several weeks or more, but here we use the term to refer only to sperm storage by females.


uses touch to communicate

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.


A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.


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


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

Glass, P., W. Gannon. 1994. Description of M. uropataginalis, with additional comments from the micropsy study of the uropatagium of the fringed myotis. Canadian Journal of Zoology, 72: 1752-1753.

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

Schmidly, D. 1991. Bats of Texas. College Station: Texas A&M University Press.

Schmidly, D., W. Davis. 1994. The Mammals of Texas. Austin: University of Texas Press.