The cactus mouse, Peromyscus eremicus, is a grayish-brown mouse native to parts of the southwestern United States and Mexico. In Utah, the cactus mouse occurs only in the extreme southwestern corner of the state, in southwestern Washington County.
Cactus mice eat seeds, fruits, flowers, green vegetation, and insects. The species breeds throughout the year. Gestation lasts for about a month, and females can produce several litters of one to six young each year. Cactus mice are nocturnal and may become inactive during hot, dry weather. Desert and pinyon-juniper habitats are preferred, and nests are constructed among rocks or in underground burrows.