In 2012, Japan declared the native otter species to be extinct; however, there was a sighting of a Eurasian river otter in 2017. I am very interested in rewilding projects around the world, and among species Japan intends on rewilding, otters are among them. I was wondering if the Eurasian river otter population has grown at all on the island, as there have been no available reports online. If they have, has there been any arrival of them on mainland Japan, or are there signs of invasive otters like the Asian short-clawed otter making their way into the wild from the pet trade?
The 2017 sighting: https://mainichi.jp/english/articles/20171013/p2a/00m/0na/005000c
Edit: There was also a study in 2024 about a possible population of 4 otters on Tsushima, which they say may lead to a breeding population: https://ocsj.asia/2024/12/%e5%af%be%e9%a6%ac%e3%81%ab%e3%81%be%e3%81%a0%e3%82%ab%e3%83%af%e3%82%a6%e3%82%bd%e3%81%af%e3%81%84%e3%82%8b/
Edit 2: They have a list of sighting spots at the "Sago River basin in Kamiagata Town, Nita in Kamiagata Town, and Tomiura in Kamitsushima Town." They also have a plan for possible addressing the long-term presence of the animals should they be in Tsushima: https://www.env.go.jp/content/900511610.pdf
by Igiem