The cactus mouse (Peromyscus eremicus) is a species of rodent in the family Cricetidae. It is one species of a closely related group of common mice often called deer mice. Cactus mice are small, between 18 and 40 g in weight. Females weigh slightly more than males and are significantly larger in body length, ear length, length of mandible, and bullar width of skull. Cactus mice can be identified by having naked soles on their hind feet and almost naked tails, which are usually the same length or longer than the animals' body length. Their ears are nearly hairless, large, and membranous. Their fur is long and soft; coloration varies between subspecies and between different populations. Color of fur varies from ochre to cinnamon, with white ventral areas, and the sides and top of head slight