Dispersal of Brown Frogs Rana japonica and R. ornativentris in the Forests of the Tama Hills.

Abstract

For the conservation of forest frogs, it is important to conserve not only water sites for breeding but also forests for living in the non-breeding season. Therefore, the two species of brown frogs (Rana japonica and R. ornativentris) common to Japan were surveyed for their dispersal capability and the range of activity in the non-breeding season. The survey was conducted 16 times in forests on undeveloped land (about 28 ha) of the Tama Hills by the capture-and-mark method. The migrating distances were calculated from the sites of capture and spawning. As a result, 90% of the individuals were within the range of 200 to 270m (R. japonica) and 330 to 390m (R. ornativentris). The maximum distance was about 500m and both species were found capable of migrating at least 500m. The migrating distances of recaptured individuals indicated that both species have specific summer habitat. Yearlings especially of both species grow rapidly between summer and fall in the fprests. R. ornativentris was only rarely captured at the edge of the forest. The study demonstrated that the forest is the main habitat and main dispersion route for R. ornativentris in the non-breeding season. We discuss the conservation of both species from the viewpoint of landscape ecology.