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Myotis auriculussouthwestern myotis

By Kristen Puzach

Geographic Range

Myotis auriculus is found throughout Mexico from Veracruz, Distrito Federal, and Jalisco, northward into New Mexico and Arizona. In the United States, the range of the species is restricted to southwestern New Mexico and southeastern Arizona. The winter range of these animals is unknown. It is thought that migration may result in selection of different habitats during different seasons. (Barbour and Davis, 1969)

Habitat

These bats usually found in arid woodlands and desert scrub. They can be found in a variety of habitat types, from mesquite and chaparral forest to oak forests and pinon-juniper habitats. M. auriculis is also found in sycamore, rabbitbrush, cottonwood, oak savanna, oak woodland, and coniferous forest. It seems to reach its greatest abundance in areas of extensive rocky cliffs where some water is available. No day roosts are known but night roosts include buildings, mines, and caves. These bats are usually found at an elevation of 366 to 2,227 m. ("Myotis auriculus", 1994; Barbour and Davis, 1969; Cook, 1986; Morrel, 1999)

  • Range elevation
    366 to 2,227 m
    1200.79 to ft

Physical Description

Myotis auriculus is also known as the southwestern bat. The species has brownish fur that is not glossy. It also has long, brownish ears (20 to 22 mm.) and a narrow pointed tragus. The bat has a calcar without a keel and a wingspan of about 270 mm. Myotis auriculus also has a distinct sagittal crest and an inflated skull. These bats weigh between 5 and 8 g. Myotis auriculus is easily identified from Myotis evotis and Myotis thysanodes with which they are sympatric in Arizona, because their flight membranes are brown, and lack a fringe of hairs on the posterior margin of the interfemoral membrane. ("Myotis auriculus", 1994; Gannon, 1999)

  • Range mass
    5 to 8 g
    0.18 to 0.28 oz
  • Average wingspan
    270 mm
    10.63 in

Reproduction

The mating system of this little-studied animal has not been reported.

What is known wih certainty about reproduction in M. auriculus is limited. Usually a single young is born measuring from 12 to 18 mm. Young are usually born in June or early July, although birthing season is later in the southern portion of the species' range. (Best, et al., 2000)

Beyond that, we must speculate on the reproductive biology of M. auriculus. Like other long-eared bats in the genus Myotis, it is likely that this species mates in the autumn when the bats enter their hibernaculum. In their close relatives, ovulation and fertilization do not occur until the following spring, and it is likely that M. auriculus is similar. ("Myotis auriculus", 1994)

  • Breeding interval
    These animals breed once annually.
  • Breeding season
    Although not known with certainty, it is very probably that these bats breed in the autumn.
  • Range number of offspring
    1 to 1

Parental investment for this species has not been described. However, in most of the genus, females care for their young in maternity roosts. Females provide the young with milk, grooming, and protection until weaning. The role played by the father int he parental care of this species is unknown.

  • Parental Investment
  • no parental involvement
  • altricial
  • pre-fertilization
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female
  • pre-independence
    • provisioning
      • female
    • protecting
      • female

Lifespan/Longevity

Life span is at least 3 years. (Best, et al., 2000)

  • Typical lifespan
    Status: wild
    3 (low) years
  • Average lifespan
    Status: wild
    3 years

Behavior

Myotis auriculus is most active from 1.5 to 2.0 hours after sunset, but also shows other peaks of activity throughout the night. Flight speed is about 13 kilometers per hour (8 miles per hour). Males appear to spend more time in marginal upland habitat, whereas reproductive females concentrate their activities along streams. Individuals, both males and pregnant females, have been found roosting in woodpecker holes, rotten ends of sycamore branches, and in a variety of other small tree cavities. Seasonal migration my result in this species opting for different habitat during different seasons, but little is know on the topic. ("Myotis auriculus", 1994; Tuttle, 1996)

Bats of the genus Myotis typically spend winter in a hibernaculum. However, the hibernation patterns, locations of hibernacula, and related topics are unknown in this little studied species. ("Myotis auriculus", 1994)

Home Range

The size of the home range of these animals has not been reported.

Communication and Perception

Although communication patterns have not been reported, we can assume that this species resembles other members of its genus. Myotis auriculus probably uses some combination of tactile communication (which is especially important in the roosts, where they are in close proximity with conspecifics), and vocalizations in the audible spectrum. Although visual signals may be used, bats are not known for their keen eyesight, and other signals may be more important. Scent cues are probably important, especially in identifying young in the maternity roost. Myotis auriculus can perceive ultrasonic signals, and uses these to locate food. However, there is no evidence that such signals are used in communication in this species. (Chung-MacCoubrey, 1995)

Food Habits

Southwestern bats are insectivorous. Their primary food is moths with wingspans ranging between 3 and 4 cm. Males eat significantly more of these than do females. This bat is known to glean its prey with from buildings and tree trunks. These bats may briefly land on the substrate to pick the insect off the surface. Like most microchiropterans, southwestern bats find their insect prey through echolocation. (Best, et al., 2000)

Water is also very important to insectivorous bats because of the high proportion of protein in their diet, and because of their high rates of evaporative water loss. These bats are usually found in close proximity to some source of water. (Chung-MacCoubrey, 1995)

  • Animal Foods
  • insects

Predation

It is unknown what predators this bat may be faced with.

Ecosystem Roles

Due to their high-energy requirements and subsequently incredible appetites, insectivorous bats may have a substantial impact on insect populations, insect activity, and a variety of insect-related ecological processes such as herbivory, pollination and disease transmission. (Chung-MacCoubrey, 1995)

Economic Importance for Humans: Positive

Myotis auriculus consumes massive quantites of insects nightly. This species therefore assists humans by controlling populations of pesky moths. (Chung-MacCoubrey, 1995)

  • Positive Impacts
  • controls pest population

Economic Importance for Humans: Negative

Bats are a common known carrier or rabies, but southwesten bats are not particularly know for carrying rabies.

Conservation Status

Populations appear to be stable and no conservation efforts are underway. (Best, et al., 2000)

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 auriculus 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

This species was thought to be a subspecies of M. evotis until 1969, when it was found that this bat occurred with M. evotis in New Mexico. Researchers concluded that the two could not be conspecific. (Barbour and Davis, 1969)

Contributors

Nancy Shefferly (editor), Animal Diversity Web.

Kristen Puzach (author), University of Wisconsin-Stevens Point, Chris Yahnke (editor, instructor), University of Wisconsin-Stevens Point.

Glossary

Nearctic

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

Neotropical

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

World Map

acoustic

uses sound to communicate

altricial

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.

carnivore

an animal that mainly eats meat

causes or carries domestic animal disease

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

chaparral

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.

chemical

uses smells or other chemicals to communicate

colonial

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.

crepuscular

active at dawn and dusk

delayed fertilization

a substantial delay (longer than the minimum time required for sperm to travel to the egg) takes place between copulation and fertilization, used to describe female sperm storage.

echolocation

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.

endothermic

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.

fertilization

union of egg and spermatozoan

forest

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

hibernation

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.

insectivore

An animal that eats mainly insects or spiders.

iteroparous

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).

migratory

makes seasonal movements between breeding and wintering grounds

motile

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.

scrub forest

scrub forests develop in areas that experience dry seasons.

seasonal breeding

breeding is confined to a particular season

sexual

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

sperm-storing

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.

tactile

uses touch to communicate

temperate

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).

tropical

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

ultrasound

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

visual

uses sight to communicate

viviparous

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

References

Arizona Game and Fish Department. Myotis auriculus. AMACC01080. Phoenix, AZ: Arizona Game and Fish Department Heritage Data Management System. 1994.

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

Best, T., M. Harvey, J. Altenbach. 2000. "Myotis auriculus" (On-line). Batcall: Accoustic library and species accounts. Accessed October 01, 2002 at http://talpa.unm.edu/batcall/accounts/accountsbase/myoaur.html.

Chung-MacCoubrey, A. 1995. Bat species composition and roost use in pinyon-juniper woodlands of New Mexico. Bats and Forests Symposium, 23/1996: 19-21.

Cook, J. 1986. The Mammals of the Animas Mountains and Adjacent Areas, Hidalgo County, New Mexico. Occasional Papers the Museum of Southwestern Biology, 4: 45.

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 http://www.fort.usgs.gov/WNS/.

Gannon, W. 1999. Syntopy between two species of long eared bats (Myotis evotis and Myotis auriculus). Southwestern-Naturalist, 43: 394-396.

Morrel, T. 1999. Bats captured in two ponderosa pine habitats in north central Arizona. Southwestern-Naturalist, 44: 501-509.

National Park Service, Wildlife Health Center, 2010. "White-nose syndrome" (On-line). National Park Service, Wildlife Health. Accessed September 16, 2010 at http://www.nature.nps.gov/biology/wildlifehealth/White_Nose_Syndrome.cfm.

Tuttle, M. 1996. Responses from Bat Conservation International (BCI) to USFS Region 3. Report to USFS Region 3.

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