The river otter found on the island of Tsushima in southwestern Japan is unlikely to be a Japanese river otter, an endemic species that has been declared extinct, a researcher said Thursday.
The Environment Ministry conducted research across Tsushima between Aug. 28 and Sept. 2 after a video image captured a wild river otter on the island in Nagasaki Prefecture in February, marking the first discovery of the creature in the country in 38 years.
The survey found that at least one Eurasian otter, a species similar to the type that live in South Korea and the Russian province of Sakhalin, inhabits the island, the ministry said.
The possibility that the otter in Tsushima was a Japanese river otter is “very low,” as they are distantly related genealogically, Hiroshi Sasaki, professor at Chikushi Jogakuen University, who participated in the research, told a press conference.
Tsushima is located about halfway between the Japanese mainland and the Korean Peninsula. The Japanese river otter, whose scientific name is Lutra nippon, was categorized as extinct on Japan’s red list in 2012.
The research found four Eurasian otter droppings and a river otter footprint. Among the droppings, three were determined to be those of a male, while the sex of the remaining one was unidentified.
Further analysis is necessary to confirm whether two or more otters inhabit Tsushima, the ministry said.
According to the survey results, the DNA sequence detected in the droppings is distantly related to that from the extinct otters that were captured in Kochi Prefecture and Kanagawa Prefecture in the past.
In addition, the ministry suggested that there is a slight chance that otters have been living on Tsushima since before the Edo Period, which ended in 1867.
The Tsushima otter was probably brought to the island by people or cast ashore by ocean currents from South Korea during storms, the ministry said.
“It’s not the Japanese river otter in a narrow sense, but there’s a good chance that Eurasian otters have been living on Tsushima naturally,” Sasaki said. “I think we can be happy that river otters have been revived in Japan,” he said.
The ministry is planning to continue to investigate the areas where the droppings and the footprint were discovered, and it is also considering installing a camera at the site.
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