Microhabitat Separation among Sympatric Microtines, Clethrionomys californicus, Microtus oregoni and M. richardsoni

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Abstract
This study examined microhabitat distribution of Microtus oregoni, M. richardsoni, and Clethrionomys californicus, sympatric microtine rodents that are similar in morphology and life history patterns. Populations were sampled in riparian and upland habitats within old-growth and mature forest stands in the western Cascade Range of Oregon [USA]. As indicated by discriminant function analysis, relative to availability C. californicus occurred in microhabitats with a high percent cover of western hemlock and lichen, low percent cover of deciduous trees and high total length of decayed logs. Microtus oregoni occurred in microhabitats high in percent cover of deciduous herbs, evergreen herbs and deciduous shrubs. Microhabitats where M. richardsoni occurred had a high percent of exposed soil, high total length of recently fallen logs and low percent cover of Douglas fir. The results of combining the three microtine species in one discriminant procedure, indicated that microhabitat separation among the species was significant and was a function of canopy cover of deciduous trees, percent cover of lichen and distance from streamside.