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Scott Wilson

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Stanislaus River Report


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Stanislaus River Basin and Calaveras River Water Use Program
Threatened and Endangered Species Report - March 1995
Bay Delta and Special Water Projects Division, CA Dept of Fish and Game

Small-footed Myotis

Myotis ciliolabrum
Category 2 candidate for listing by the U.S. Fish and Wildlife Service as Threatened or Endangered

Life History

The small-footed myotis is described as having buff to golden brown fur above, usually with glossy tips and buff to white below. The face and ears are black. When the ear is laid forward it barely extends beyond the muzzle. The calcar is long and keeled and the forehead is gradually sloped between the rostrum and braincase. M.ciliolabrum resembles Myotis californicus which has a steep slope to the forehead, and the ears extend beyond the muzzle when laid forward (Hall 1981). Body measurements are: total length, 75 to 88 mm; foot, 7 to 9 mm (Ingles 1965); ear, 12.2 to 15 mm; forearm, 29.6 to 36 mm; greatest length of skull, 13.1 to 14.7 mm (Hall 1981).

This myotis is found from southwestern Canada, south to Mexico and distributed over the United States except along the north pacific coast, the south eastern states, and the center strip of the U.S.. Four subspecies of M. ciliolabrum occur in the United States with only one species, M.ciliolabrum melanorhinus, occurring in California (Hall 1981).

M. ciliolabrum is a common bat of arid uplands in the Upper sonoran and Transition life zones of California. It occurs along the southern half of the California coast and the west and east sides of the Sierra Nevada to about 8,900 feet (2700 meters). They seem to prefer open stands in forests, woodlands and brushy habitats.

The small-footed myotis feeds on a variety of small flying insects including moths, flies, and beetles while flying over water and among trees. It requires more water than most other bats and can be found drinking shortly after night emergence. The small-footed bat can be found roosting in caves, buildings, crevices and sometimes under bark and bridges, preferring more humid areas. Females form small maternity colonies and bear a single young or twins from May through June. Young are usually able to fly by mid August (Zeiner 1990).

Emergence is shortly after sunset and activity peaks 30 minutes afterward and again 2 to 3 hours after sunset. They roost mainly in caves, buildings, mines and crevices and may make small movements to hibernating sites. This bat has a very high tolerance of cold and hibernates from November to March (Zeiner 1990).

Findings and Conclusions

Reasons of decline for this species include loss of suitable roosting sites habitat, including destruction and disturbance, and pesticide use.

The Stanislaus River flows through the range of the small-footed myotis. Our surveys occured during the colder part of the year and did not resulted in the capture of any animals. Small-footed myotis should occur along the majority of the Stansislaus River and should be surveyed for at other times of the year.

The project should have minimal impacts on the Small-footed myotis as long as foraging areas and roosting sites are not destroyed. Further surveys for foraging and roosting areas should be carried out and sites identified.