Response by wolves to prey variation in central Ontario

Abstract

The influence of variation in prey availability in a wolf–moose–deer–beaver predator–prey community was studied from 1987 to 1992 in Algonquin Park, Ontario, Canada. Density, food habits, and movements of 57 radio-collared gray wolves (Canis lupus) were compared among three regions of varying moose (Alces alces) and white-tailed deer (Odocoileus virginianus) spatial and temporal abundance. Relative moose and deer availability was determined annually from 16 track surveys (5 km each), 150 pellet surveys (300 × 2 m), stratified aerial surveys (2 or 3 each winter), and prey carcass data. One region contained high moose abundance and virtually no deer year-round. The second region had high moose levels with moderate levels of deer, and a third region varied in deer winter abundance annually. Wolf use of deer was high, based on the proportion of deer in winter scats (9.3–32.1% frequency of occurrence; 4.3–22.5% total biomass) and the number of deer predation cases (50 carcasses) that occurred in all three regions, even in areas where deer were considered to be very rare. Wolf use of deer was positively correlated with increases in winter deer abundance (r2 = 0.66). Wolf density correlated with deer numbers (r2 = 0.74). In winter, deer in the third region migrated to a deer yard 15 km from Algonquin Park. A remaining overwintering deer density of less than 0.02/km2appears to have prompted a movement of wolves to the deer yard. Of the 41 moose consumed by wolves in winter, most (71%) were scavenged animals that had died with infestations of winter tick (Dermacentor albipictus). Beaver (Castor canadensis) apparently acted as important buffer prey species when deer numbers were low. The Algonquin wolf's reliance on smaller prey items appears to be a function of the fluctuating prey base, which promotes alternative hunting strategies, and the small size of the Algonquin wolf, which makes it an inefficient predator of moose. Even though moose were relatively constant in availability, and a major food item, the wolf population was responding primarily to the availability of deer.