Landscape Structure and Breeding Site Conditions Shape the Urban Distribution of the Two Frog Species, <i>Dryophytes japonica</i> and <i>Rhacophorus schlegelii</i>

Urbanization poses significant threats to amphibians through habitat loss, fragmentation, and degradation of breeding sites. This study investigated the distribution of two frog species, <i>Dryophytes japonica</i> and <i>Rhacophorus schlegelii</i>, which have relatively similar ecological traits in paddy fields in high-populated, i.e., heavily urbanized areas of Tokyo and Kanagawa, Japan, focusing on landscape- and microhabitat factors simultaneously. Calling surveys were conducted at approximately 100 sites over 2 years (2022-2023) during the breeding season to identify key environmental variables influencing species occurrence. As a landscape factor, both species were positively associated with surrounding forest, suggesting the importance of landscape connectivity between forest as habitats and paddy fields as breeding sites. As a microhabitat factor, water retention in the paddies was a significant factor for both species. Notably, <i>R. schlegelii</i> depended on microhabitat features, in specific soil channels, whereas <i>D. japonica</i> did not. These findings suggest that while both species benefit from nearby forests in urbanized areas, only <i>R. schlegelii</i> is vulnerable to concreting that disrupts soil channels as breeding sites. The study underscores the need for conservation strategies that address both landscape- and microhabitat requirements to support amphibians in urbanizing agricultural regions. Importantly, species with similar ecological niches may respond differently to urban stressors, requiring species-specific management strategies.