Toxicity of Invasive Cane Toad Hatchlings to Predatory Native Anuran Tadpoles on Ishigaki Island, Japan

The cane toad, Rhinella marina, is invasive on several islands in Japan, including Ishigaki Island which lacks native bufonid species. Cane toads possess toxins in the aquatic and terrestrial life stages, and thus pose a risk to native predators, especially predators that have evolved in the absence of bufonids. We tested tadpoles of three anuran species native to Ishigaki Island (Fejervarya sakishimensis, Microhyla kuramotoi, Zhangixalus owstoni) for responses to cane toad hatchlings as potential prey. All three species showed high propensity to consume toad hatchlings. However, the species differed in sensitivity to hatchling toxins: consumption of toad hatchlings was always fatal to M. kuramotoi and Z. owstoni, whereas toxic effects on F. sakishimensis were variable (approximately 40% mortality) independent of tadpole size, developmental stage or the number of hatchlings consumed. Our results are the first to highlight the potential for toxic impacts of invasive cane toads on native anurans in Japan.