Rates of capture in live traps set for snowshoe hares (Lepus americanus) were used to index population trends of four mustelids (Mustek frenata, M. erminea, M. vision, Mephitis mephitis), three sciurids (Tamiasciurus hudsonicus, Glaucomys sabrinus, Spermophilus franklinii), and the porcupine (Erethizon dorsatum) at Rochester, Alberta, during 1965–1975. The Mustela species (weasels and mink) had a 10-year cycle synchronous with that of the snowshoe hare. About 81% of the annual variation in weasel numbers, as indexed by capture rates, was attributable to fluctuations of hares, voles (Microtus and Clethrionomys), and mice (Peromyscus). Onset of the cyclic decrease in hares was followed within 2 years by declines in sciurid, skunk (Mephitis), and porcupine populations that may have been a consequence of predator switching as hares became scarce.