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t <br />which the nacaw vole was encountered. It was t3te most azuntiwit species <br />captured in riparian (3.8 individuals /100 trap nights) and second most <br />abundant species over all habitat types (0.3 individuals /100 trap nights). <br />The sex ratio of meadow voles was 0.33 males and 0.67 females. <br />The house rouse was captured only in the riparian habitat. House mice <br />commonly inhabit houses and outbuildings; however, they also inhabit grain <br />fields and fence rows (Lechleitner 1969). In colder months, the house <br />mouse may migrate into dwellings. A refuse dump located adjacent to the <br />riparian habitat type probably supports a large population of house mice. <br />The total relative abundance of the house mouse over all habitat types was <br />0.4 individuals /100 trap nights and the sex ratio was 0.50 males and 0.50 <br />females: The house mouse by virtue that all observations occurred in riparian <br />habitat, showed an affinity for this type. <br />Western harvest mice are most cften found in dense grassy or weedy areas, and <br />often in riparian situations (Lechleitner 1969). Food sources of this <br />rricrotine include seeds, green portions, of plants,and insects. Only one <br />western harvest mouse was captured in the study area. This individual (male) <br />was captured in the riparian habitat type. The total relative abundance <br />of this species over all types was 0.2 individuals /100 trap nights. <br />Other Nnrnals. Small and medium-sized mammal species not captured in live <br />traps but whose presence on the Nucla mine site has been substantiated during <br />other field activities include the following species: desert cottontail <br />(Sylvilagus audutonii) , muskrat (Ondatra zibethicus) , and Gunnison's prairie <br />dog (f cp)nnisoni) . <br />The desert cottontail appears to be very comron in the study area. Five cotton- <br />tails were observed during the 1979 -1980 field season. The habitat of the <br />desert cottontail includes a variety of ecological situations (e.g.,,desert, <br />grassland, shrubland, and riparian). Cottontails were observed on the study <br />area in the upland sagebrush, riparian and grassland pasture habitat types. <br />One muskrat was observed in the riparian type during April, 1979. Muskrats <br />are aquatic mammals, living in streams, laces, ponds and swamps (techleitner <br />-30- <br />JUN 1 1 1980 <br />