Rediscovery of otters on the Tsushima Islands, Japan by trail cameras

Otters are thought to be extinct in Japan, although they were widely distributed there until the early 20th century. Records of otters on Tsushima Islands, located between Kyushu and the Korean Peninsula, were found only in two sources from about 1735 and 1809, and there has been no evidence of their existence since the middle of 19th century until now. We set infrared trail cameras to monitor the Tsushima leopard cat on the northern island of Tsushima. Otter(s) were recorded by these cameras four times, on February 6 and July 16, 2017 in the Tanohama area and on October 1 and 3, 2017 in the Sago area of the island. This is the first record of an otter in Japan since the last record was made in Kochi Prefecture in 1979. The otters recorded on the islands could not be identified to species level based on the footage feed from the trail cameras. Based on historical information about otters in Tsushima and the surrounding areas, the origin of the otters is thought to have been natural dispersal from the Korean Peninsula, the nearest habitat of the Eurasian otter.