The Northern Baja deer mouse (Peromyscus fraterculus ) is a species of deer mouse native to Southern California and the Baja California peninsula as well as several islands in the Gulf of California. P. fraterculus was previously considered a subspecies of the cactus mouse (Peromyscus eremicus ) prior to a 2000 study which identified genetic differences and suggested P. fraterculus is more closely related to Eva's desert mouse (P. eva ) than to P. eremicus.
