There are no animals on this island.
Rum Runner Isle is actually an archipelago, consisting of a few forested islands and some barren sandbars. Because of its small size, it is possible to access every island and sandbar in Rum Runner Isle from another location in Rum Runner Isle without swimming, by wading across the shallow channels that separate them.
Rum Runner Isle is of special interest due to its close proximity to the North Star Seapost. If you travel to the northeasternmost sandbar on the Isle, you will find a telescope and astronomical charts and books that almost certainly belong to Sudds, an NPC astronomer and recent immigrant to the Sea of Thieves from the world beyond the Shroud, who is also the shopkeeper of the North Star Seapost to the immediate south of Rum Runner Isle. Sudds, knowing that the night sky in the Sea of Thieves has different stars than elsewhere in the world, takes it as his personal mission to map the night sky and name the unique constellations. It is likely that Sudds uses Rum Runner Isle as his base to conduct astronomical research. Unfortunately, players cannot use the telescope at this time.