Arctic ground squirrels mostly eat vegetation, but they're opportunistic feeders that will eat everything from bird eggs and hatchlings to invertebrates like insects, spiders or small reptiles. They've also been known to eat carrion, collared lemmings and weaker members of their own species. Ground squirrels are foragers, which means they search for their food.
When it comes to plants, Arctic ground squirrels will eat members of the rose family, brassicas, willows, gentians, asters, ranunculus, true grasses, rushes, dianthus, figworts, sedges, sandalwoods and basically all manner of flowering plant. Sometimes, the Arctic ground squirrel will store these plants in its very extensive burrow to eat when plants become scarce.
The Arctic ground squirrel will also eat all parts of the plant, including the roots, tubers, leaves, stems, flowers, fruit and seeds.
Despite its varied diet, the squirrel has been shown to pick foods that are fairly high in polyunsaturated fatty acids. Biologists believe that this is because the squirrel hibernates and must keep a level of polyunsaturated fatty acids in its system while it undergoes this long sleep. However, foods that are abundant in polyunsaturated fatty acids can create compounds that can damage bodily cells. Somehow, the squirrel knows how to avoid these foods.