Frog assemblage patterns in a small-scaled traditional rice paddy (yatsuda) area in Japan

Abstract In Japan, small traditionally managed rice paddies in small valleys ( yatsuda ) are rarely subject to land consolidation and have the potential to retain well-connected wetland habitats. In this study, we investigated frog assemblages in various lentic habitats including cultivated and fallow rice paddies, irrigation ponds, and biotopes in a yatsuda area in Saitama, Japan. Monitoring was conducted weekly for 44 weeks, and then, multivariate analysis was applied to assess frog assemblages. The structure and phenology of frog assemblages were similar among habitat types, indicating the importance of permanently retained lentic habitat in maintaining frog assemblages regardless of habitat type or management history. The forest green tree frog ( Zhangixalus arboreus ) characterized frog assemblages in forested irrigation ponds, suggesting that a combination of open spaces, i.e., rice paddies, and shady spaces i.e., irrigation ponds, enhances the species diversity of frogs in yatsuda areas. This study highlights the importance of permanent lentic environments in small traditional rice paddies and connected surrounding area for conserving amphibians in an era of depopulation and rice paddy abandonment in Japan.