Great Basin pocket mice consume primarily seeds, but eat some green vegetation. Prior to production of seeds, they also consume insects. Great Basin pocket mice do not use free water, they metabolize water from food. Pocket mice ("Perognathus" spp.) and other heteromyids are scatterhoarders, caching seeds in shallow depressions and covering the seeds with soil. The seeds are primarily those of grass species, and some preferred forb species. Indian ricegrass ("Oryzopsis hymenoides"), cheatgrass ("Bromus tectorum"), Russian-thistle ("Salsola kali"), antelope bitterbrush ("Purshia tridentata"), pigweed ("Amaranthus" spp.), and mustard ("Brassica" spp.) seeds are important Great Basin pocket mouse food items. In productive years, cheatgrass seeds formed a major portion of the diet of Great Basin pocket mice in southeastern Washington.