抄録
We investigated the density of Rana japonica on the grassland of levee in the rice terrace called “Oyama-Senmaida” in Boso Hills. The number of individuals on the grassland of levee was counted once at each month from April to October, 2005. For juveniles, the seasonal change was clarified that they stay temporary in levee after metamorphosis, and afterwards disperse all together. For adults, it was 1.6-1.9 times density in slope compared with levee top in irrigation period. It is thought that the habitat of Rana japonica has been formed by maintaining semi-natural grassland according to the cultivation management.
