RANGE:

The western portion of British Columbia southeast into western Montana and the western half of Idaho. Largely absent in Nevada and Utah, this species is found in Colorado, New Mexico, and Arizona to central Mexico, and extends along the Pacific Coastal areas of Baja California, California, Oregon, and Washington. In Idaho, it has been collected in eleven counties.

DESCRIPTION:

In Idaho, the upper fur is pale brown lacking the goldish sheen usually seen in little brown bats. The tail membrane often has hair dorsally and ventrally that extends to slightly beyond a line joining the knees. The ears are rounded, extend just past the muzzle, and are pale brown as contrasted to the darker ears of little brown myotis. The skull has a abrupt increase in height above the forehead, a condition also lacking in Myotis lucifugus. In spite of these differences, it is extremely easy to confuse Yuma myotis with little brown myotis, especially in limited light. Both species lack a keeled calcar, although an extremely small lobular piece of tissue is present along the calcar in many yuma myotis.

HABITAT:

Yuma myotis occur in a variety of western lowland habitats in areas of abundant water where it forages for insects just above the surface of slack water. It is an important riparian species and likely been eliminated along many streams in western states. Summer roosts include crevices in cliffs, old buildings, mines, caves, bridges, and abandoned cliff swallow nests. No large winter concentrations of this species have been studied in Idaho.

DIET:

Yuma myotis eat a variety of soft bodied small insects, especially moths and emergent aquatic insects including stoneflies and mayflies found near and over water.

ECOLOGY:

Little is known about the distribution and abundance of this species in Idaho and whether it migrates to areas outside of summer locations. It is probable that yuma myotis are highly susceptible to destruction of conditions favoring the production of tricopteran insects upon which they feed and nursery colonies may only occur in mines lacking human disturbance.

REPRODUCTION:

Mating likely takes place during the fall, and ovulation and implantation in spring. A single pup is produced in female-only maternity colonies that may occur in dome areas in mines with high humidity Pups are born in May to mid July, depending on weather conditions. The thermal conditions required to support nursery colonies in Hell's Canyon have been studied.

IMPORTANT STATE REFERENCE:

Betts, B.J. 1997. Microclimate in Hell's Canyon mines used by maternity colonies of Myotis yumanensis. Journal of Mammalogy 78:1240-1250.