Field Guide to Mammals
of Southern California
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Western Small-Footed Myotis (Myotis ciliolabrum)
The western small-footed myotis occurs from southern British Columbia, Alberta, and Saskatchewan to the southwestern United States (Harvey and others 1999). In California, this species is found mostly at middle and higher elevations, but may also be found at low elevations in some deserts (Philpott 1997).
Until recently, western and eastern forms of small-footed myotis were considered a single species, Myotis leibii, but morphological and biochemical data indicate that the western populations are a separate species, M. ciliolabrum (Nagorsen 1990). Only one subspecies, M. c. melanorhinus, occurs in California.
Western small-footed myotis occurs in a variety of vegetation types, including desert scrub, grasslands, oak and pinyon-juniper woodlands, and pine forests (Philpott 1997). This species is associated with cliffs, talus fields, and prairies with clay buttes and steep riverbanks (Harvey and others 1999). They have been found roosting in crevices and cavities of cliffs or rocks, caves, mine shafts, burrows, among rocks, under bark, in tree cavities, beneath rocks on the ground, bridges, culverts and buildings (New Mexico Game and Fish 2002, Philpott 1997). Caves and mines are used for hibernacula (Harvey and others 1999), and maternity colonies have been found in buildings and tree cavities (Arizona Game and Fish Department 1999). They have been observed on the sides of buildings and chimney structures on the San Bernardino National Forest (Stamer pers. comm.)
Mating occurs in the fall (Arizona Game and Fish Department 1999) and potentially after hibernation (Idaho State University Website). One young is born per female between May and June. Twins have also been noted (Harvey and others 1999). Females form small maternity colonies typically consisting of fewer than 30 individuals, although maternity colonies with greater than 50 individuals have been recorded (Philpott 1997). Some females care for their pups alone while others form small groups. The western small-footed myotis rears its young in cliff-face crevices, erosion cavities, and beneath rocks on the ground (Bat Conservation International 2000).
Western small-footed myotis emerge shortly after sunset (Harvey and others 1999). Nightly activity peaks occur at 10–11 p.m. and 1–2 a.m. (Harvey and others 1999). The species hibernates during the winter, and is a year-round resident in California (Philpott 1997).
Diet and Foraging
The diet of western small-footed myotis consists of small moths, flies, ants, and beetles (Philpott 1997). The flight of this bat is slow and erratic and it forages at heights of 3–10 feet (1–3 meters) along cliffs and rocky slopes (Harvey and others 1999). Foraging occurs in open areas (Philpott 1997), and may occur over water if not in association with California myotis (M. californicus) (Harvey and others 1999).
No information is available on territorial behavior or home range patterns in western small-footed myotis.
No information is available on predator-prey relations of western small-footed myotis, but bats in general are often subject to predation by falcons (Mumford 1980).
Arizona Game and Fish Department. 1999. Arizona wildlife views (special edition). Phoenix, AZ: Arizona Game and Fish Department.
Bat Conservation International. 2002. Bat Conservation International web site, species descriptions. [Homepage of Bat Conservation International, Inc.], [Online]. Available: http://www.batcon.org/.
Harvey, M.J.; Altenbach, J.S.; Best, T.L. 1999. Bats of the United States. Arkansas Game and Fish Commission.
Federal Register. 1994. Endangered and threatened wildlife and plants; Animal candidate review for listing as endangered or threatened species, proposed rule. Department of the Interior. Tuesday, November 15, 1994. 50 CFR Part 17.
Idaho State University Website. Key to the bats of Idaho and Utah. Western small-footed Myotis. [Online]. Available: http://imnh.isu.edu/Bat-page/cilliolabrum.htm.
Mumford, R.E. 1980. Two cases of hawk predation on bats. Bat Research News 21, 2, 11.
Nagorsen, D. 1990. The mammals of British Columbia. A taxonomic catalogue. Memoir No. 4. Royal British Columbia Museum in cooperation with the Wildlife Branch, Ministry of Environment.
New Mexico Game and Fish. 2000. Biota Information System of New Mexico BISON Version 1/2000. Western Red Bat. [Online]. Available: http://www.fw.vt.edu/fishex/nmex_main/species/050085. htm.
Philpott, W. 1997. Summaries of the life histories of California bat species. Unpublished document. USDA Forest Service, Sierra National Forest, Pineridge Ranger Station.
Stephenson, J.R.; Calcarone, G.M. 1999. Southern California mountains and foothills assessment: Habitat and species conservation issues. General Technical Report GTR-PSW-175. Albany, CA: Pacific Southwest Research Station, Forest Service, U.S. Department of Agriculture.
Western Bat Working Group. 1998. Western bat species: Regional priority matrix. Developed at Western Bat Working Group Workshop, Reno, Nevada, February 9–13, 1998.
Zeiner, D.C.; Laudenslayer, W.F., Jr.; Mayer, K.E.; White, M., eds. 1990. California's wildlife. Volume III: Mammals. California Statewide Wildlife Habitat Relationships System. Sacramento, CA: California Department of Fish and Game.
Information gathered from California DFG - California Interagency Wildlife Task Group