Invasive species have a significant negative impact on the environment where they have been introduced, and amphibians are among some of worse invasive species. All known amphibian introductions are linked to human activities, generally in relation with pest control or food provisioning.
This is the case of all amphibians on Ulleung Island, Republic of Korea, which were originally and mistakenly thought to be “reintroduced” after extirpation, or introduced for unrealised purposes such as food provisioning and pest-control. We conducted call and visual encounter surveys in all valleys of Ulleung Island, Republic of Korea, in April and May 2021 to detect the presence of amphibian species. The call surveys and subsequent call analyses revealed the presence of two geographically independent populations of Pelophylax nigromaculatus, and encounter surveys resulted in the sampling of Rana tadpoles identified as Rana huanrenensis with molecular tools. These results highlight the presence of these two species at low density on this island, but do not provide data on the impact of their presence.