[pp.97-104]

‹Research Report›Status of Amphibians and Reptiles in the Oyama-Senmaida Terrace Paddy Field in the Southe

Satoshi OSAWA and Takehiko KATSUNO （Nihon University）

Abstract:
A terrace paddy field ecologically functions as a biotope for small animals in the rural landscape. We investigated the status of amphibians and reptiles in the Oyama-Senmaida terrace paddy field in the southern part of the Boso Peninsula in central Japan. We conducted a visual encounter survey, an egg-mass/sac survey for early spring-breeding amphibians, and an audio survey for frogs. We recorded 7 amphibian species and 5 reptilian species. Among the amphibians, the extensive breeding of Hynobius tokyoensis and Rana japonica was noticeable. Adults of R. japonica were most widely and commonly distributed during the daytime in early summer. The density of H. tokyoensis egg sacs in the terrace paddy fields on the hillside was higher than that in either the lowland paddy fields or in mountainous district. This may be due to greater length of edge between forest and nonforest environment (i.e., the paddy field) in the hillside terrace paddy fields, which has the possibility of influencing the inhabitation of H. tokyoensis. In reptiles, Takydromus tachydromoides was a dominant species, which was widely distributed in early summer. Therefore, the availability of sunny grassland on the earthen levee embankments of the hillside terrace paddy field may encourage the inhabitation of T. tachydromoides and R. japonica.

Key Word:
terrace paddy field, levee embankment, visual encounter survey, density of egg masses/sacs, rural landscape

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