Successional change of small mammal fauna on Kahoku-gata [Japan] reclaimed land with agricultural development

Small mammals were trapped each year from 1976 to 1984 no Kahoku-gata reclaimed land in Ishikawa Prefecture. This area, which had been covered with grassland, was gradually transformed to cultivated fields. Before cultivation started, 3 species of rodents and 1 species of insectivore were trapped. Microtus montebelli, Rattus norvegicus and Mus molossinus were abundant. After cultivation, Apodemus speciosus was added to this fauna. Microtus and Mus were as dominant as before. Three dominant species were found in all sampling plots of this area. Their level of abundance was roughly equal to that in each plot before cultivation began, but R. norvegicus was usually found near a water source. After the start of cultivation, these homogeneous patterns of distribution changed. Microtus decreased in the cultivated areas and the level of abundance in the Mus population differed. A remarkable change was found in the Rattus population in this area : this species increased from 1977 to 1979 and then rapidly disappeared. Such a pattern of fluctuation is supposed to be characteristic of a reclaimed land ecosystem.