[2] It is endemic to Isla Santa Catalina off the east coast of Baja California Sur, an island with an area of about 40 km2 (15 sq mi), and it is the only native mammal on the island.

[3] It is named for Joseph Slevin, a curator at the California Academy of Sciences.

They have pale cinnamon fur, mixed with dusky hairs, over the body, head, and flanks, with near-white underparts.

They appear very similar to the related California mouse, but are paler in color and slightly larger.

However, it may be most closely related to the North American deer mouse.