Abstract
The structure of microhabitats used by Apodemus argenteus and A. speciosus, which are generally regarded as sympatric at the macrohabitat level, was analysed ; and habitat segregation patterns and interspecific competition between these two species were discussed. Transects of 50 Sherman live-traps set 10 m apart were laid in forests at four sites in northern Kyushu. After mark-and-release, variables reflecting the structure, diversity of vegetation and physical factors were examined in a quadrat of 10 m2 and a circle with the radius of 10 m both of which were centered on the trapping point. A discriminant function analysis by the stepwise method resulted in 66.6-100% of correct discrimination of microhabitats for the two species both at each site and at the four sites en bloc, indicating that A. argenteus selected microhabitats with characteristics of climax forests, and that A. speciosus did those with features of secondary forests. A principal component analysis on five selected variables revealed that the macrohabitat segregation between these two species was flexible. The more the two species approached each other, the more A. argenteus selected the microhabitat with complex strata of vegetation cover. The flexible horizontal and vertical microhabitat segregations would play a role in decreasing competition between these two species.
