Abstract
Stable isotopes provide knowledge of dynamic relationships within ecosystems. However, research on the trophic niche of domestic anurans—which serve as biological indicator of ecosystem health—using stable isotope analysis is limited. Therefore, we analyzed stable isotope values in the bone collagen of three anuran species—Bombina orientalis, Rana uenoi, and R. huanrenensis—representative of the domestic forest ecosystem to determine the trophic levels, niche partitioning, overlap, and shifts with growth within populations. Our findings indicate that B. orientalis occupied a relatively higher trophic level, while no significant difference was observed between the two Rana species. R. uenoi and R. huanrenensis, which share similar ecological characteristics and life cycles, tended to utilize a wide range of overlapping resources. Large Rana individuals occupied higher trophic levels and broader trophic niches than small individuals, indicating size-based niche partitioning within populations. B. orientalis showed a high trophic niche overlap between males and females, indicating resource sharing, although males were found to utilize a wide range of resources. Ultimately, the three anuran species might function as higher-order consumers as their size increases and two Rana species would increasingly consume terrestrial prey resources as they grow, while B. orientalis would consume more aquatic-origin prey resources.