Distribution, Abundance, and Foraging Patterns of Ground Squirrels near Atkasook, Alaska

Abstract

Arctic ground squirrel (Spermophilus parryii) populations near Atkasook appeared to have very similar population dynamics to those reported for this species in other regions. In a favorable habitat, sand dunes, adult females bred every year and July densities reached about 1.5 ha^–1 after the young emerged. Young animals, particularly males, dispersed in late August, and less than half the female young and one-tenth the male young were represented by yearlings the following spring. Apparently, density was regulated at a relatively constant level by aggressive behavior and dispersal. Animals used larger home ranges, densities were lower (about 0.5 ha^–1 in July), and breeding effort was lower in less favorable habitat on a river bluff. This population appeared to vary more from year to year than that in the sand dunes; there were half as many adults and three times as many juveniles in 1977 compared to 1976.

Stomach contents indicated that the squirrels took a wide variety of plant materials; herbaceous dicotyledons formed the most important group (25 to 75% of the diet) and included over 40 species. These plants had the highest water content and were probably the most digestible and nutritious. Evergreen shrubs, lichens, and animal matter formed very little of the diet. In spring, when food abundance was lowest, the diet was most varied; mosses, deciduous shrubs, monocotyledons, roots, and animal matter contributed over half of the total. Distaste for evergreen shrubs, even though they were common in squirrel habitat, suggested that secondary compounds known to affect microtine rodents also influence the foraging patterns of ground squirrels.