Myotis auriculus
southwestern myotis

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)

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. (Arizona Game and Fish Department, 1994; Barbour and Davis, 1969; Cook, 1986; Morrel, 1999)

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. (Arizona Game and Fish Department, 1994; Gannon, 1999)

Life span is at least 3 years. (Harvey, Best, and Altenbach, 2000)

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. (Arizona Game and Fish Department, 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. (Arizona Game and Fish Department, 1994)

Home Range

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

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)

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. (Harvey, Best, and Altenbach, 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)

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

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)

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

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

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

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)