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Myotis occultus

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Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA CHORDATA MAMMALIA CHIROPTERA VESPERTILIONIDAE

Scientific Name: Myotis occultus
Species Authority: Hollister, 1909
Common Name(s):
English Arizona Myotis
Taxonomic Notes: The bats in the Myotis lucifugus-M. occultus-M. fortidens complex have long been of debatable taxonomic status. Myotis occultus was formerly included in M. lucifugus (Koopman 1993), but now it is regarded as a distinct species (Simmons 2005). Allozyme data suggested that the two are conspecific (Valdez et al. 1999), but mitochondrial DNA and morphological evidence suggest that M. occultus is a specifically distinct, monophyletic lineage (Piaggio et al. 2002).

Assessment Information [top]

Red List Category & Criteria: Least Concern ver 3.1
Year Published: 2008
Date Assessed: 2008-06-30
Assessor(s): Arroyo-Cabrales, J. & Álvarez-Castañeda, S.T.
Reviewer(s): Medellín, R. & Schipper, J.
Justification:
This species is listed as Least Concern in because of its wide distribution, occurrence in a number of protected areas, and because it is unlikely to be declining at nearly the rate required to qualify for listing in a threatened category.

Geographic Range [top]

Range Description: The range encompasses southeastern California, Arizona (Hoffmeister 1986, Arizona Game and Fish Department 2003), New Mexico (except perhaps extreme northeast; Frey 2004), southern Colorado, and perhaps southern Utah and western Texas (Piaggio et al. 2002; Valdez pers. comm.). In Arizona, this bat is distributed predominantly in the highlands and upper stream reaches (Piaggio et al. 2002). In New Mexico, it is known from low-elevation riparian areas in the Rio Grande Valley and montane highlands. In California, it occurs only along the Colorado River lowlands and in the adjacent desert mountain ranges. The range meets that of M. lucifugus in central Colorado; that species occupies the northern third of the state (Valdez pers. comm.). The only record from Texas is an unusual, perhaps intermediate specimen collected in the early 1900s near Fort Hancock in Hudspeth County (Piaggio et al. 2002; Valdez pers. comm.; Schmidly 2004).
Range limits in northcentral Mexico are uncertain; the species has been recorded from several localities in Chihuahua and a disjunct site near Texcoco in the Distrito Federal (Piaggio et al. 2002; Valdez pers. comm.). In Arizona, this bat is most common at elevations of 1,830-2,806 meters, but it also occurs much lower along rivers in desert regions (Arizona Game and Fish Department 2003).
Countries:
Native:
Mexico; United States
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: The total number of occurrences or subpopulations is unknown but is at least a few dozen. Total adult population size is unknown. Stager (1943) estimated that Myotis occultus made up about 40 percent of 2,000 bats in a mixed-species colony roosting under a bridge in May near Blythe, California. Hayward (1963) recorded an Arizona maternity colony that included 67 females in one year and 41 the next year.
Overall trend is unknown, but some subpopulations have apparently declined or been eliminated. One or two of the three or four known maternity colonies in Arizona have been eliminated, and another has been partially excluded from available buildings (AGFD 2003). Populations that were formerly common along the Colorado River in California and Arizona have apparently declined, perhaps drastically (K. Stager, P. Leitner pers. comm.).
Population Trend: Stable

Habitat and Ecology [top]

Habitat and Ecology: Habitats in Arizona include ponderosa pine and oak-pine woodland near water; this bat is also known from wooded riparian areas in desert areas (Hoffmeister 1986). In New Mexico, the species is usually associated with large bodies of water without respect to associated vegetation type; it is known from low elevation riparian areas in the Rio Grande Valley and montane highlands (Piaggio et al. 2002). Maternity colonies have been found in buildings (e.g., the attics of abandoned houses; Hoffmeister 1986; Chung-MacCoubrey 1999), in crevices between timbers of a highway bridge (Arizona Game and Fish Department 2003), and in snags. A few individuals have been found hibernating in mines in California and Sonora (Howell 1989).
Systems: Terrestrial

Threats [top]

Major Threat(s): Without citing specific examples, Schmidly (2004) reported that this species has declined as a result of pesticide use, control measures in nursery colonies, and disturbance at hibernation sites.

Conservation Actions [top]

Conservation Actions: In Mexico it is found in some protected areas.

Citation: Arroyo-Cabrales, J. & Álvarez-Castañeda, S.T. 2008. Myotis occultus. The IUCN Red List of Threatened Species. Version 2014.3. <www.iucnredlist.org>. Downloaded on 18 December 2014.
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