Great Basin Naturalist


Southwestern Idaho desert shrub-bunchgrass rangeland is being invaded by fire-prone exotic annuals that permanently dominate the landscape following wildfires. This study was undertaken to describe diets of Townsend's ground squirrels (Spermophilus townsendii idahoensis) at four study sites with varying degrees of exotic annual invasion to determine if the squirrels could utilize high proportions of exotic annuals in their diets. Townsend's ground squirrels were collected in March and May of 1987 and 1988, and stomach contents were analyzed using a microhistological technique. Grasses comprised 37–87% of Townsend's ground squirrel diets at the four sites. Native species, especially Sandberg's bluegrass (Poa secunda), winterfat (Ceratoides lanata), big sagebrush (Artemisia tridentata) and six-weeks fescue (Vulpia octoflora) constituted 7–96% (x̄ = 47.2%) of the diet, whereas exotic species, especially cheatgrass (Bromus tectorum), tumbleweed (Salsola iberica), and tansymustards (Descurainia spp.) made up 4–68% (x̄ = 48.0%) of the diet. At each site 2–4 species comprised >90% of the diet. There was no apparent correlation between the importance values of exotic species at a site and their importance in Townsend's ground squirrel diets.