Using 3473 trap-nights, collection of small mammals was carried out on the lowland habitats in the districts of Kyoto, Chugoku, and northern Shikoku. Traps were set within the runway of voles, mice and moles. When Microtus montebelli was not collected, Apodemus speciosus entered into the traps on the habitats of river banks, abandoned paddy fields, footpaths between paddy fields and vegetable fields. Furthermore, A. speciosus was restricted to slopes in the presence of M. montebelli, while in

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... e area where M. montebelli was absent A. speciosus was well represented on the flat area as well. These findings are discussed with other reports. It is suggested that the density of M. montebelli affected the habitat of A. speciosus in lowland habitats.