Jeju striped field mouse

The Jeju striped field mouse ("Apodemus chejuensis") is a field mouse found only on Jejudo, an island in the northern East China Sea off the southwestern coast of South Korea. It was originally described in 1965 as a subspecies of "Apodemus agrarius". However, a 1992 study of mitochondrial DNA found that it was in fact a separate species.
The Jeju striped field mouse is one of the most abundant mammals on Jeju. It has brown fur with an eel back, hence the name.