California Myotis (Myotis californicus)

Protection Status Notes
Little is known about population trends. The species is not state or federally protected.
Myotis californicus is a small bat with dark brown to black ears and wing membranes, a distinctly keeled calcar, and pelage that varies from dark brown to pale reddish‑yellow to blond. It differs from M. ciliolabrum, which is sympatric and similar in appearance, by having a more globose skull, narrower rostrum, overall more delicate appearance, and no black mask. These two species are often difficult to distinguish in the field.
Life History
M. californicus mates during autumn, perhaps in the spring in California. In spring or early summer, females form maternity colonies where they give birth to one pup per year. Individuals are known to be active periodically in the winter, even at temperatures below freezing. California myotis have been known to live up to 15 years.

During summer, M. californicus roost alone or in small groups in caves, mines, rocky hillsides, under tree bark, and in buildings. Recent studies in Canada have documented maternity colonies of up to 52 individuals roosting under sloughing bark, and in cracks and hollows of large diameter, intermediate stage snags (preferably ponderosa pine). In winter, solitary individuals and small groups have been found in caves, mines, and buildings.

California myotis are acrobatic fliers and use small waterholes to obtain needed moisture; the kidneys are adapted for arid environments. Individuals are most active soon after sunset and periodically rest at night roosts. They typically feed on moths and flies, but have been known to eat other insects.
This species occurs in a wide variety of habitats. While typical of deserts and interior basins in the western U.S., it also occurs in forested and mountainous regions.
M. californicus ranges across much of western North America from southeastern Alaska and southwestern British Columbia, through most of the United States west of the Rocky Mountains, and south to Baja California and much of mainland Mexico, and into Guatemala.

This western species known in Texas from the Trans-Pecos region is one of the few species that winters in Texas.
Threats and Reasons for Decline
M. californicus may be affected by closure of abandoned mines without adequate surveys and by recreational caving. The species may be affected by some timber harvest practices, particularly the removal of large diameter snags. Like all bats it also could be subject to contaminant poisoning.
Ongoing Recovery
Conservation and management recommendations are similar to the previously discussed long-legged myotis. Known colonies in buildings, trees, and cliff crevices should be protected from disturbance. Bat-friendly gates can prevent human disturbance of hibernation sites in caves and mines.
More information is needed on roosting and foraging requirements. The use and acceptance of bat gates needs to be studied.
For more information

Refer to the online version of The Mammals of Texas for additional details on the California Myotis.