Myotis californicus
(California Myotis)

Order: Chiroptera
Order Description:
Family: Vespertilionidae
Family Description:

The upper fur is brownish chestnut and tends to have a yellowish cast. The cranium is not flattened, a condition found in western small-footed myotis with which this species may be confused. The ears are rounded at the margin and extend slightly beyond the muzzle. A brownish area exists across the face to the ears. The tragus Click word for definition is less than one-fourth of the length of the ear and is pointed. The calcar Click word for definition is keeled and the foot small.

The southeastern portion of Alaska and western half of British Columbia south through Idaho and Utah, along the western edge of Colorado, New Mexico, into central Mexico, west into Baja California and throughout the Pacific states of California, Oregon and Washington. In Idaho, this species has been collected in three counties.

From extreme southern Alaska and western Canada, south in lowlands through Montana, Utah, and California, and throughout desert Southwest. Winters in California, Nevada, Utah, Arizona, and Texas. Full extent of winter range is not known. In Idaho, species has only been observed near west-central border, but distribution is probably more widespread.

This bat has been found in western and panhandle counties in Idaho, in a variety of habitats from forest to desert conditions. It appears to be more common in areas with open areas of slack water. Summer roosts include crevices in rocky hillsides, rocky outcrops, buildings, trees with exfoliating bark, and cavities in snags.

Found from seacoasts to deserts, at elevations up to about 1800 m, in oak/juniper situations, canyons, riparian Click word for definitionwoodlands, desert scrub, and grasslands.

California myotis eat small insects including moths, beetles, and flies. The food taken may vary with the diet of similar-sized sympatric species if present, especially Western small-footed myotis. Insectivorous Click word for definition.

Periods of foraging activity may vary with temperature in this species and flight may occur during freezing conditions. Colonies appears to be small. Mine use may be limited, but the roosting requirements of this species needs further study.

Known to hibernate Click word for definitionin U.S. during winter, but winter activity has also been recorded. In southern California, occasional individuals have been found active on warm winter days. Active bats have been regularly caught in Nevada in fall and winter (frequently in temperatures below 43° F). Species hibernates in caves, mines, tunnels, or buildings. Forages with slow, erratic flight pattern approximately 1.5-3 m off ground. Often uses human-built structures for night roosts Click word for definition. Uses crevices of various kinds for summer day roosts.

Mating takes place during the fall, excepting California where it may occur during the spring. A single pup is born. Nursery colonies are small, the largest found in Canada consisted of 52 individuals. Very little is known about this species in Idaho.

Ovulation Click word for definitionand fertilization Click word for definitionare delayed until spring. Female gives birth to 1 young in late May to mid-June, depending on range (July in Canada). Nursery colonies are usually small (up to about 25 individuals).

Status: Unprotected nongame species
Global Rank: G5
State Rank: S1

Important State References:
Keller, B.L. 1987. Analysis of the bat species present in Idaho, with special attention to the spotted bat, Euderma maculatum. Dept. Biol. Sciences, Idaho St. Univ., Pocatello. 25pp.

Information written by Barry Keller,© 2000
Map image provided by
Stephen Burton,© 2000
Design by Ean Harker©1999, 2000.