Influence of snow cover on wolf Canis lupus predation patterns in Bieszczady Mountains, Poland

Sex, age, bone marrow fat (BMF) content, degree of carcass utilisation and terrain features were analysed for I 18 ungulates killed by wolves Canis lupus in the Bieszczady Mountains, Poland, during the winters of 1992-1995 to assess the influence of snow depth on the wolves' predation patterns. In Bieszczady, the snow conditions during the study period were milder than average, with an average total annual snow depth of 1,372 cm and an average snow cover lasting for 94 days. Red deer Cervus elaphus were the primary wolf prey (81%), whereas wild boar Sus scrofa and roe deer Capreolus capreolus were killed less often (9% and 10%, respectively). The majority of prey (74%) was killed in creeks and ravines. The carcass exploitation by wolves was high; of the recovered prey, 55% was more than 60% consumed. The average condition of red deer, as based on BMF, was high (83.4%). BMF varied most among red deer stags and calves, and varied with annual snow depth (N = 29, P < 0.01; N = 28, P = 0.09) and monthly mean snow depth (tau = -0.37, P < 0.005; tau = -0.25, P = 0.06). Wolves killed adult red deer in creeks and ravines with the same frequency regardless of snow depth, whereas calves were killed less often in these places than should be expected from their overall proportion in the sample (N = 95, chi(2) = 24.34, P < 0.001). During periods with thinner snow cover, consumption of red deer carcasses was slightly higher than during periods in which the snow cover was deep (tau = -0.42, P < 0.045).