EFFECTS OF FOOD AND PREDATORS ON THE HOME-RANGE SIZES OF ARCTIC GROUND-SQUIRRELS (SPERMOPHILUS-PARRYII)

We used radiotelemetry to study the effects of food addition and preda tor reduction on the home-range sizes of adult Arctic ground squirrels (Spermophilus parryii) on large-scale experimental grids in the borea l forest of the southwestern Yukon Territory. Home ranges were 2-7 tim es smaller on food-supplemented grids than on nonsupplemented grids, r egardless of whether large mammalian predators were present. Similarly , core areas (where 50% of activities occur) were 8-11 times Smaller o n food-supplemented grids. Food availability rather than predator pres ence primarily determined the sizes of home ranges and core areas of A rctic ground squirrels.