Richardson's ground squirrels are predominantly herbivores, with vegetation composing 80-100% of their total diet. The remainder is comprised mostly of insects. Richardson’s ground squirrels do not kill for food, but they sometimes nibble on easy-to-obtain meat such as road kills.
Richardson's ground squirrels primarily eat leaves, flowers and seeds, though the precise type of vegetation eaten depends on where they live. Because so much of the native prairie has been destroyed by human agricultural practices, it is now difficult to assess the natural and preferred diet. Forage grasses and legumes are major food items on overgrazed pastures in eastern North Dakota. In cultivated areas, where little native vegetation remains, Richardson’s ground squirrels have no choice other than to eat the seeds and seedlings of domesticated cereals such as wheat, barley and oats.
Ground squirrels feeding in cultivated
areas tend to be larger and bear more live young than those feeding in
native grasslands, presumably because more high quality food is available
in crop fields than on native grassland.