Effects of hunting group size, snow depth and age on the success of wolves hunting moose

Abstract

To study factors important to the success of wolves, Canis lupus, hunting moose, Alces alces, we analysed data from more than 4000 km of snow tracking of wolves during 1998–2003 in Scandinavia. We used two methods to estimate hunting success for 17 wolf territories from 185 observations of wolf attacks on moose. On average, hunting success was estimated at 45 and 64% for the two methods, respectively. We used a smaller data set (N = 142) to examine the effect of age of breeding wolves, hunting group size, snow depth and moose density on hunting success. Multiple logistic regression showed that age of breeding males was the only variable significantly related to hunting success, with maximum hunting success at 4.5–5.5+ years of age. We also studied prey selection of radiocollared adult wolves over successive winters in two wolf packs that lost one of the breeding wolves. Whereas the surviving adult female switched to prey on roe deer, Capreolus capreolus, the surviving adult male continued mainly to select moose. Our results suggest that the positive effect of male age on hunting success reflects both increased experience of attacking prey and possibly the greater size of adult male wolves (25–30%) compared to adult female wolves.