2023 Volume 2022 Issue 2 Pages 23-34
For a species reintroduction to be successful, understanding the minimum viable population number is important. We examined the occurrence of Eurasian otters (Lutra lutra) on isolated islands to assess whether they can survive in small, isolated habitats. Spraints were investigated, and DNA analysis of the cytochrome b region was conducted, to determine if genetic differences existed between the island and mainland otter populations. Moreover, people living on 13 islands were interviewed for a questionnaire survey. Of the 13 islands, otters were confirmed to occur on nine. Three of these islands seemed too far (≥18 km) for otters to reach by swimming across the sea. Huksan Island is most isolated, with a straight distance of 65 km from the mainland, a sea-crossing distance of 31 km. Yeoseo Island is smallest of the islands, an area of 2.5 km2. Our results validated that otter populations inhabited some of these islands. The genetic analyses of otter spraints detected four haplotypes. Furthermore, one type was found in feces from a river on the mainland, 60 km away from the coast. Isolated islands must be considered when establishing a plan to protect the otter population.
