Arizona Myotis: Myotis Occultus

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Image of Arizona Myotis

Arizona Myotis Description

The Arizona myotis (Myotis occultus) is a tiny brown bat found in a number of states in the United States, including Arizona, New Mexico, California, Colorado, Utah, and Texas, as well as parts of northern Mexico. In general, it prefers living near large bodies of water, such as rivers and lakes, and around 1,800-2,200 meters at high altitudes, although it can also be found in lowland regions.

The Arizona myotis is considered to be common, but in some areas its numbers may be declining. Some scientists believe pesticides can lead to population loss. In recent years, several known roosting sites have become inactive, potentially due in part to human disturbance.

Learn More: Bat Families In The U.S.

Behavior Of The Arizona Myotis

The Arizona myotis is a night bat that usually emerges at dusk from its roosts. Two hours after dark and another before dawn, as the bats are feeding and flying before returning to their roosts to sleep, there is a high activity peak.

Every day outside of the hibernating season, Arizona myotis may enter torpor. In general, these bats begin hibernation between September and November, and between March and May, hibernation will end. However, in order to build up fat reserves for hibernation, young people stay active later in the fall. These bats may remain entirely inactive for 90 consecutive days during hibernation. Arizona myotis are known to conduct both local and long-distance migrations for hibernacula.

This bat species has separate roosts for the day, night, hibernation, and motherhood periods. The majority of day roosts consist of buildings, trees, and under rocks/wood. Night roosts are very similar to daytime roosts, though they are usually in more confined spaces.

Although specific measurements have not been recorded, night roosts are generally warmer than others due to the number of bats in them. In similar locations as day and night roosts, women have maternity roosts, though they also have to roost in places with an appropriate temperature to save energy.

There have been reported aggregations of Myotis occultus of up to 300,000 individuals. Maternity roosts have been reported to have up to 800 females at one time. Hibernation roosts, though above freezing, are commonly in caves or mines with temperatures fairly cold.

Arizona myotis can detect prey at very short distances and capture several prey in rapid succession. This species returns to the same feeding area, and feeding usually occurs over water such as lakes, streams, and ponds. ¹

Arizona Myotis Habitat

This species is found primarily in areas dominated by creosote bush, palo verde, brittlebush, and cactus in the southwest’s lower elevations.

Range Of The Arizona Myotis

The Arizona myotis range covers:

Southeast California
Arizona
New Mexico
Southern Colorado
Southern Utah
Western Texas
Northern/Central Mexico

This bat is predominantly distributed in the highlands and upper streams of Arizona at elevations of 1,830-2,806 meters, but it also occurs much lower in desert regions along rivers. ²

Arizona Myotis Diet

Cave myotis species are insectivores that feed on a broad range of insects during the night. This bat will leave the roosting cave at night and search familiar feeding sites for prey.

This bat utilizes echolocation to find its prey. This hunting method provides the bat with information on the shape and size of its prey. It also allows the bat to avoid obstacles during flight. ³

Sources:

Jenkins, S. 2017. “Myotis occultus” (On-line), Animal Diversity Web. Accessed January 06, 2021 at https://animaldiversity.org/accounts/Myotis_occultus/

https://explorer.natureserve.org/Taxon/ELEMENT_GLOBAL.2.638468/Myotis_occultus

https://www.desertmuseum.org/kids/bats/cave_myotis.php