Miyakojima is the least interesting of larger Ryukyu Islands (all but one native mammals are extinct), but I checked it out it anyway.
The only remaining forest on the island is Ono Forest, with a trail network radiating from 24.804706 N 125.315014 E. The Southern Ryukyus subspecies of Ryukyu flying fox is extremely common there, as is Oriental house rat. I also saw one house shrew.
Elsewhere, found a Japanese weasel in Shimajiri Mangroves (24.877879N 125.288292E), and one flying fox in Ihema Wetland (24.935413N 125.242212E). Polynesian rats have been collected on Miyako in the 1950s, but I didn’t see any. Hihashi Henna lighthouse (24.722569N 125.468869) is good for seawatches: the guy at the ticket office said he sees dolphins a few times a year, but I don’t know what species.