The little pocket mouse, Perognathus longimembris, is a small mouse that occurs in desert and shrubland habitats in the extreme western United States and northwestern Mexico. In Utah, the species can be found only in the western portion of the state.
As with other pocket mice, the little pocket mouse has external cheek pouches in which seeds can be stored until the mouse returns to its underground burrow. The little pocket mouse breeds in the spring, usually producing one litter of two to seven young per year. Gestation lasts approximately thirty days, and young are weaned in an additional thirty days. This mouse feeds primarily on seeds, and as a consequence, population levels are dependant upon precipitation and may fluctuate widely from year to year.