Environmental Factors Influencing the Relative Abundance of Brown Frogs in Urban Area Ecological Parks

Abstract

To clarify the environmental factors that affect the abundance of two brown frogs, Rana japonica and R. ornativentris. We recorded the number of egg masses in seven parks of the middle-and south-Tama hill and north Miura hill, eastern Japan, and analyzed the landuse around the parks. The average number of egg masses of R. japonica were between 13 and 2250 at seven parks from 1999 to 2001, and 15 and 165 for R. ornativentris. The relative abundance of R. japonica was affected by the area of poorly drained paddy fields (rs=1.00), which is superfluously wet. On the other hand, the relative abundance of R. ornativentris, was not affected by the area of cultivated paddy fields, but was affected by the area of uncultivated ones (rs=0.94). Thus the area and management of landcover used for breeding was a regulation factors for abundance of two brown frog species. In contrast, there were no relationships between any of land covers used for non-breeding season and the abundance of the frogs.