Wolf-Caribou Relationships In A Multiple Ungulate Prey Ecosystem

Abstract

Winter wolf (Canis lupus) predation and functional response in wolf - caribou (Rangifer tarandus) dynamics were investigated in a multiple ungulate prey ecosystem in Gates of the Arctic National Park, Alaska. Prey selection, prey availability, prey switching, kill rates, and food availability for 4 wolf packs were estimated in March 1989, March 1990, and November 1990. Estimates for these study periods reflected near record, average, and early winter snow conditions, respectively. Wolves killed predominately caribou even if moose (Alces alces) or Dall sheep (Ovis dalli) were more abundant. Prey selection varied with study period; however, per wolf kill rates and food availability did not. Length of intervals between kills was correlated with pack size and the biomass of the previous kill. Kill rates indicated a destabilizing Type II functional response. Modeling with a linear numerical response revealed wolf predation to be an increasingly important limiting factor at low caribou densities. However, little potential for regulation of caribou by wolves was observed. <p>