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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

Long-eared Myotis

Myotis evotis

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


Life History

This bat can be distinguished by its large ears, extending about 7 mm past the muzzle, a long pointed tragus, gradually sloping forehead, black wing membranes and ears, and light to dark brown fur. Body measurements are: total length, 75 to 97 mm; foot, 7 to 10 mm (Ingles 1965); ear length, 18 to 22.4 mm; forearm length, 35.5 to 41; greatest length of skull, 15 to 16.4 (Hall 1981).

Myotis evotis is distributed from British Columbia, south to Baja California and east to North Dakota, and then southward through South Dakota, Nebraska, and New Mexico; excluding the southern deserts of Arizona and California. Two subspecies exist in North America ( M.e. evotis, M.e. pacificus) and both are found in California (Hall 1981).

The long-eared myotis is found throughout California except in the hot central valley and the dry hot deserts of southern and southeastern California. This bat can be found in brush, woodland and forests habitats up to 9,000 feet (2700 meters), possible preferring coniferous woodlands and forests, yet is uncommon in most of its range (Zeiner 1990).

M. evotis feeds on many different arthropods and eats more beetles than other myotis. It feeds over water, among trees and shrubs within four feet (12 meters) of the ground and catches insects while in flight, feeding from the ground, or gleaning from foliage. This bat is capable of hovering and feeds on the edges of habitat or over water. Emerges late in the evening to forage.

The long-eared myotis can be found roosting in buildings, rock crevices, under bark and in snags and may use caves as night roosts. Usually roosts singly or in small groups of 12-30 animals, including maternity colonies. Mating likely occurs in the fall with usually one young born in May to June. The young are able to fly by early August. Winter habits of the long-eared myotis are poorly known, but they may make short movements to hibernating sites.

Findings and Conclusions

The destruction of suitable roosting sites and maternity colonies is probably the main reason for decline. Pesticide use, eradication from buildings and destruction of foraging habitat could also play a critical role.

The upper portion of the Stanislaus River is in the range of the long-eared myotis. Our surveys occurred during the colder part of the year and did not resulted in the capture of any animals. The long-eared myotis is expected to occur along the Stanislaus River.

The project should have minimal impacts on the long-eared 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.