Columbia Ground Squirrel in Subalpine Forest Openings in Central Idaho

Abstract

Columbia ground squirrels were studied in natural alpine forest openings. Three sites were selected having the same potential but presently with different vegetation due to differing levels of past domestic sheep use. Ground squirrel population was least in the light-use area and increased with vegetation change induced by increased sheep use. Juveniles were most plentiful in the medium-use site and least in the heavy-use area. Up to a point, ground squirrel population increased with plant retrogression. With continued retrogression the community became less suitable to support a healthy population because of less preferred forage species. Lupinus sericeus was the most preferred forb. Other species included Achillea millefolium and Descurania richardsonii, species not generally preferred by sheep. The discussion of sheep-ground squirrel relative impacts also considers metabolic requirement, grazing period and animal density of both grazers.