LAUSR

This article aims to introduce the reader to the charm of Iriomote island. Iriomote island is in the subtropical region of Japan. I have been visiting the island since 2015, for four consecutive years. I have also been taking graduate students with me to provide them with field experience with mountains, rivers, and the sea, all together in one place. The students belong to the Kyoto University Leading Graduate Program in Primatology and Wildlife Science (PWS), a 5-year PhD program (http://www.wildl ife-scien ce.org/index -en. html). Iriomote island is located 4°17′33′′ N and 123°51′43′′ E. Its area covers 289.61 km2. The highest point is Mt. Komi, at 469.5 m. About 90% of the island is covered by subtropical rainforest. As of March 2018, the population was only 2376 residents. Therefore, population density is only 8.2 persons per square kilometer. Thus the island is a sort of semiclosed ecosystem with little human disturbance. We have been exploring the island using the facility of the University of the Ryukyus as our home base (Fig. 1). Iriomote is at the southern end of the Ryukyu islands, only 200 km from Taiwan (Fig. 2). The Ryukyu islands stretch across about 1000 km in the area between Kyushu and Taiwan, and consist of 198 islands (defined as land larger than 0.01 km2). Among them, Yakushima island (504.88 km2, 1.7 times the size of Iriomote island) is home to the so-called Yakushima monkey (Macaca fuscata yakui), a subspecies of the Japanese monkey. Besides Yakushima, there are no monkeys in any of the other Ryukyu islands. Incidentally, there is another macaque species, called the Taiwanese monkey (Macaca cyclopis), in Taiwan. Thus, the Ryukyu islands in a way represent a gap in macaque distribution. Primatologists have been carrying out research on Yakushima since the 1950s because of its monkeys (Maruhashi 1980). Many publications have resulted from this work, which continues to the present day (e.g., Pelé et al. 2017). In contrast, they paid very little attention to the other Ryukyu islands. Nonetheless, it might be interesting