Additional threat to Hynobius salamander eggs: Predation by loaches (Misgurnus sp.) in agricultural wetlands

Anthropogenic modifications of the environment have clear negative impacts on species. These effects may reach a higher magnitude in highly altered habitats, for example in wetlands transformed into rice paddies. This is the case for the amphibian species of the genus Hynobius in the Republic of Korea, which originally breed in slow streams and valleys. However, a comparatively high proportion of the natural breeding sites used by the species in the lowlands has been transformed into rice paddies. Here, we assessed whether anthropogenic modification of wetlands leads to an additional threat to breeding Hynobius spp. in the form of increased vulnerability of their egg clutches to loach predators (Misgurnus species) in such modified habitats. We conducted weekly occurrence surveys at 27 randomly selected sites in the Republic of Korea and recorded the following information: Type of site (natural versus agricultural), air temperature, water conductivity, moon phase and predation by Misgurnus sp. Our results reveal, for the first time, cases of predation of Hynobius spp. eggs by Misgurnus loaches. We also show that the risk of predation was higher in agricultural sites in comparison to natural sites. In conclusion, we demonstrate the increased predation risk of Hynobius spp. eggs by Misgurnus sp. at anthropogenically disturbed sites, and thus a new type of threat to Hynobius populations. This new type of threat may, however, be due to expansion of the breeding habitats following human disruptions to landscapes. We therefore call for the development of mitigating measures to wetland modifications.