Richardson's Ground Squirrels

Diet of Richardson's Ground Squirrels
(also known as gophers)

 

Richardson's ground squirrels are predominantly herbivores, eating a diet composed of 80-100% vegetation, supplemented by insects such as grasshoppers. Because so much of the natural prairie has been destroyed due to agricultural practices and urbanization, it is difficult to assess the natural and preferred diet of Richardson's ground squirrels. The precise vegetation eaten depends on the area in which they live, but primarily includes leaves of grasses and forbs, flowers, and seeds. In cultivated agricultural areas, Richardson's ground squirrels have no alternative but to eat the seeds and seedlings of domesticated cereal crops such as wheat, barley, and oats. In urban areas, they eat available vegetation in parks and boulevards.

Richardson's ground squirrels do not kill for food, but they sometimes nibble on easily obtained meat, such as road kill. Richardson's ground squirrels are not major predators of ground-nesting birds; they may occasionally eat eggs or chicks of small passerine birds, but larger eggs are not eaten unless already damaged or cracked open. In an observational experiment with several sizes of eggs, no ground squirrels were able to open pheasant eggs or domestic owl eggs; a few females occasionally opened Japanese quail eggs, but usually only if the quail shell was particularly rough.

ground squirrel opening a quail egg
Female Richardson's ground squirrel attempting to open a Japanese quail egg. This female tried to open 18 quail eggs but succeeded only once.
Source: Michener (2005)

On emergence from 4-8 months of hibernation, Richardson's ground squirrels immediately begin foraging on the senescent vegetation remaining from the previous year. By the time females are lactating, the new season's green growth has begun, supplying the mother with the water and nutrients necessary to make milk for her growing infants. Juveniles begin to eat vegetation immediately on emergence from the natal burrow at about 30 days of age, after which they soon stop drinking mother's milk. For all Richardson's ground squirrels, most of their above-ground time in the active season is spent foraging, first to meet the costs of reproduction (adults) or growth (juveniles) and then to fatten up for the hibernation season.

Richardson's ground squirrels have small cheek pouches in which they can carry clipped vegetation or seeds. If they find a bonanza of seeds, females fill their check pouches and retreat to a safe location to eat the seeds. Males also stash seeds in the check pouches, but they usually unload the seeds underground, then return for more until the supply is exhausted.

barley in ground squirrel's cheek pouch
Juvenile male Richardson's ground squirrel with barley in his cheek pouches. This animal was killed by a vehicle while crossing a road between his burrow system and the field where he found the barley.

Male, but not female, Richardson's ground squirrels lay in a store of seeds in the hibernaculum. Then, at the end of the hibernation season, in the few days between the end of torpor and first emergence above ground in spring, males eat the seeds that they had cached before hibernation. This source of energy allows testicular recrudescence and a build up of fat stores before the mating season starts.

Related Pages: Habitat
Annual Activity Cycle
Hibernation Behavior
Richardson's ground squirrels as Pests

Sources: PDFs of many of these articles can be downloaded from the Michener Publications page

  • Michener, G. R. 2005. Limits on egg predation by Richardson's ground squirrels. Canadian Journal of Zoology, 83: 1030-1037.
  • Michener, G. R. 1993. Sexual differences in hibernaculum contents of Richardson's ground squirrels: males store food. pp. 109-118 in Life in the Cold: Ecological, physiological, and molecular mechanisms. (eds. C. Carey, G. L. Florant, B. A. Wunder, and B. Horwitz.) Westview Press, Boulder.
  • Michener, G. R. 1992. Sexual differences in over-winter torpor patterns of Richardson's ground squirrels in natural hibernacula. Oecologia, 89: 397-406.
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