Abstract
Wild mice were trapped by snap-traps from 15 localities of Hokkaido which have various types of vegetations. Clethrionomys rufocanus bedfordiae (THOMAS) 277, C. rutilus mikado (THOMAS) 10, Apodemus argenteus TEMMINCK 224, and A. speciosus ainu THOMAS 51 were obtained. Three habitat factors, coverage, density of vegetation, and litter layer, were measured by the standard shown in Table 2 in the area of about 3m radius from a trap station at which a mouse was obtained. C. rufocanus bedfordiae is most common in the grass-field type of vegetation with large coverage, high density, and rich litter layer, and decreases in number toward the forest type of vegetation with low density and poor litter layer. C. rutilus mikado inhabits the forest and shrub types of vegetations with large coverage, high density, and rich litter layer, but is usually rare and sparse in Hokkaido. A. argenteus is a typical resident of the forest type of vegetation and rare or absent in grass field. This mouse does not prefer a particular grade of the coverage of shrub stratum or a particular depth of litter layer, but does prefer low density of vegetation. A. speciosus ainu is not so common in Hokkaido as the former species and does not appear to prefer a particular type of vegetation. The structure of the habitat, however, is somewhat similar to that of C. rufocanus bedfordiae.
