Myotis yumanensisYuma myotis

Geographic Range

Myotis yumanensis is found in western North America, ranging from British Columbia to Central Mexico and eastward to Colorado (Whitaker, 1996) and as far east as Oklahoma (Barbour and Davis, 1969).


Myotis yumanensis is found in a variety of habitats, ranging from juniper and riparian woodlands to desert regions near open water (Nowak, 1991). One is almost guaranteed to find this species wherever there are rivers, streams, ponds, lakes, etc. In fact, M. yumanensis is more closely associated with water than any other North American species of bat (Barbour, 1969). When not near water over which to forage, these animals can be found in the thousands roosting in caves, attics, buildings, mines, underneath bridges, and other similar structures. Little is known about the migration of this species. However, it has been recorded in Texas as well as in its normal range during the winter season (Allen, 1994).

Physical Description

Myotis yumanensis is a small species of Myotis, with a body length of 84 to 99 mm and a tail length from 32 to 45 mm. Their forearms are 33 to 37 mm long and the overall wingspan is about 235 mm (Barbour, 1969). The skull is shortened (usually less than 14 mm) and does not have a sagittal crest. Teeth include somewhat small and separated incisors with dilambdodont molars. Other distinguishing features include an unkeeled calcar and no nose leaf (Nowak, 1991).

Myotis yumanensis has short fur shaded tan or brown on top, with whitish or buffy underparts (Whitaker, 1996). Yuma myotis resemble M. lucifugus but the latter is larger and has shinier fur. (Barbour and Davis, 1969; Nowak, 1991; Whitaker, 1996)

  • Sexual Dimorphism
  • sexes alike
  • Range mass
    5 to 7 g
    0.18 to 0.25 oz
  • Range length
    84 to 99 mm
    3.31 to 3.90 in
  • Average wingspan
    235 mm
    9.25 in
  • Average basal metabolic rate
    0.047 W


Ovulation and fertilization occur only in the spring (Nowak, 1991). Sperm are held in the reproductive tract of females over the winter. Females give birth to only one young and usually do so between May and June (Allen, 1994). During birth, they sit upright and catch the newborn with the uropatagium (Creech, 1996). Females aggregate (in caves, abandoned buildings, or anywhere else that has a high and stable temperature of 86 to 131 F) in maternity roosts sometime around April (Whitaker, 1996). Males are usually absent from these maternity colonies and remain solitary as the young are being reared. During this time, almost all of the females in the population have a newborn (Barbour and Davis, 1969). (Allen, 1994; Barbour and Davis, 1969; Nowak, 1991; Whitaker, 1996)

  • Breeding interval
    Breeding occurs annually in these bats.
  • Breeding season
    Breeding occurs in the fall, but ovulation and fertilization do not occur until the following spring.
  • Range number of offspring
    1 to 1
  • Average number of offspring
  • Average age at sexual or reproductive maturity (female)
    1 years
  • Average age at sexual or reproductive maturity (male)
    1 years
  • Parental Investment
  • altricial
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female


  • Average lifespan
    Status: captivity
    8.8 years


Like most bats, M. yumanensis is nocturnal. Not long after sunset these bats become active and start to call; however they do not emerge until dark (Barbour and Davis, 1969). Once they have emerged from their roosts, they fly very low over surfaces of water to feed, and after feeding for several minutes they begin to drink. These bats usually disappear 2 hours after dark, suggesting remarkable efficiency in hunting. They are suprisingly inconsistent and fluttering in their flight (Allen, 1994). When roosting, they hang on a vertical surface by their thumbs and toes with their wings tucked alongside their bodies (Nowak, 1991). (Allen, 1994; Barbour and Davis, 1969; Nowak, 1991)

Communication and Perception

Food Habits

Myotis yumanensis is a very efficient insectivorous feeder that begins foraging at dusk and usually finishes two hours after sunset (Barbour and Davis, 1969). These bats usually feed over water, and their prey primarily consists of moths, midges, caddisflies, craneflies, beetles and other various small insects (Whitaker, 1996). Like most bats, they locate insects in flight by emitting ultrasonic sounds (echolocation). Then they either catch the insects in their mouths or use their tail membranes as a pouch in which to snare larger prey.

  • Animal Foods
  • insects

Economic Importance for Humans: Positive

All insectivorous species of bats are seen as a safe and sensible means of pest control on agricultural crops. A Yuma myotis can consume up to half of its weight every night feeding on moths, beetles, flies, etc. (Nowak, 1991).

  • Positive Impacts
  • controls pest population

Economic Importance for Humans: Negative

All bats, including Yuma myotis, have been known to carry diseases such as rabies, as well as mites, and fleas (Creech, 1996). This becomes problematic to humans mainly if they handle wild bats without prior knowledge of their health status.

Conservation Status

This species of Myotis is commonly observed. There has been a slight decline in the number of these bats due to destruction of suitable roosting sites.

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 yumanensis 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

There are five subspecies of M. yumanensis in the United States: M. y. yumanensis (found in the southwestern desert), M. y. phasma ( found in Utah and Colorado), M. y. sociabilis (found in California and Canada), M. y. oxalis (found in the San Joaquin Valley), and M. y. saturatus ( found along the Northwestern Coast) (Barbour, 1969).


Nancy Shefferly (editor), Animal Diversity Web.

Kelly Sims (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


uses sound to communicate


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 disease in humans

an animal which directly causes disease in humans. For example, diseases caused by infection of filarial nematodes (elephantiasis and river blindness).

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


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.


The process by which an animal locates itself with respect to other animals and objects by emitting sound waves and sensing the pattern of the reflected sound waves.


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.


union of egg and spermatozoan


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


having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.


the state that some animals enter during winter in which normal physiological processes are significantly reduced, thus lowering the animal's energy requirements. The act or condition of passing winter in a torpid or resting state, typically involving the abandonment of homoiothermy in mammals.


An animal that eats mainly insects or spiders.


offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).


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


the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.


Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).

seasonal breeding

breeding is confined to a particular season


remains in the same area


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


associates with others of its species; forms social groups.


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


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.

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.


uses sound above the range of human hearing for either navigation or communication or both


uses sight to communicate


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


Allen, H. 1994. "The Mammals of Texas - Online Edition" (On-line). Accessed November 22, 1999 at

Barbour, R., W. Davis. 1969. Bats of America. Lexington, Kentucky: The University Press of Kentucy.

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

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

Nowak, R. 1991. Walker's Mammals of the World: Fifth Edition. Baltimore and London: The Johns Hopkins University Press.

Whitaker, J. 1996. National Audubon Society Field Guide to North American Mammals. New York: Alfred A. Knopf, Inc..