Cactus Deermouse

Cactus mice are small cricetid rodents, with large eyes and ears, a pointed snout, and a long monocolor tail. Average dimensions for P. eremicus are as follows: total length, 160 to 211 mm (6.3 to 8.3 in); length of body, 72 to 100 mm (2.8 to 3.9 in); length of tail, 84 to 120 mm (3.3 to 4.7 in); length of hind foot, 18 to 22 mm (0.71 to 0.87 in); length of ear, 13.4 to 20 mm (0.53 to 0.79 in); greatest length of skull, 22.7 to 25.9 mm (0.89 to 1.02 in) and zygomatic breadth, 11.2 to 13.5 mm (0.44 to 0.53 in). Adults weigh between 18 and 40 grams (0.63 and 1.41 oz). 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 flesh-colored tails (as opposed to the furry bicolored tail common in most Peromyscus species), 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 slightly grayish. …

Cactus mice are found in dry desert habitats, steppe, and mountain foothills in arid regions of the southwestern United States and northern Mexico, as well as islands off the coast of the Baja California peninsula and in the Sea of Cortés. Low average temperatures and lack of the mesquite species Prosopis juliflora might limit northern expansion. The cactus mouse occurs sympatrically with five other deermouse species, including the California mouse, canyon mouse, Eva's desert mouse, mesquite mouse, and the western deermouse.

The cactus mouse feeds on seeds, mesquite beans, hackberry nutlets, insects, and green vegetation. In winter, they rely more on insects; on seeds and flowers in the spring; and seeds, leafy greens, and insects in the summer. In autumn, they transition to their winter diet.