Iriomote IslandIriomote Island is the second largest island after the main island of Okinawa. Approximately 90% of the island is covered in subtropical virgin forest, and it is an extremely valuable academic site with 15 nationally designated natural monuments, including the Iriomote wildcat, the Crested Serpent Eagle, and the Yellow-margined Box Turtle. Approximately 40 rivers, large and small, flow through Iriomote Island, and many of them have mangroves near their river mouths. The mangroves in the Nakama River basin in particular are so majestic that they account for approximately one-quarter of the mangrove area in Japan as a whole.