The habitat usage was investigated of the aquatic frog species Glandirana rugosa within the paddy fields of the Shonan Region, Honshu Island, Japan. Firstly, we determined that G. rugosa inhabits ...various types of cultivated paddy fields over a broad spatial scale. Out of the 12 environmental variables that we examined, such as water depth, waterbody type, and paddy field extension, frog abundance was positively depended on the presence of earth ditches that were constructed along paddy field margins. Secondly, we surveyed the habitat preference of G. rugosa among various wetland types at the local scale in a farmed valley. Controlling for the availability of different habitat types, frogs selected small streams and traditional earth ditches over other wetland habitats. Thirdly, we investigated frog abundance in relation to the 12 environmental variables along a small stream. More individuals were found in the open habitat situated upstream, compared to the closed habitat covered by high forest canopy situated downstream. Frogs were primarily found in the aquatic habitats with deeper water depths; such habitats tended to form under artificially created weirs. The results support the notion that traditionally managed paddy fields provide various types of wetland habitats that are beneficial for conserving G. rugosa.
