Relationship between Snow Depth and Gray Wolf Predation on White-Tailed Deer

Abstract

Survival of 203 yearling and adult white-tailed deer (Odocoileus virginianus) was monitored for 23,441 deer days from January through April 1975-85 in northeastern Minnesota. Gray wolf (Canis lupus) predation was the primary mortality cause, and from year to year during this period, the mean predation rate ranged from 0.00 to 0.29. The sum of weekly snow depths/month explained 51% of the variation in annual wolf predation rate, with the highest predation during the deepest snow. J. WILDL. MANAGE. 50(3):471-474 Wolves capture more prey during severe winters with deep snow (Pimlott et al. 1969, Mech and Frenzel 1971, Haber 1977, Mech and Karns 1977, Peterson 1977, Eide and Ballard 1982). However, except for extreme snow conditions, the relationship between degree of winter severity and wolf predation rate has only begun to be studied. Increased wolf kill of moose (Alces alces) has been related to increasing snow depths (Peterson and Allen 1974, Haber 1977, Gasaway et al. 1983), but no quantitative measure of this relationship between wolves and white-tailed deer has been made. This paper is the 1st attempt at analyzing such a relationship. This study was supported by the U.S. Fish and Wildl. Serv., U.S. For. Serv. North Central For. Exp. Stn., Mardag Found., Weyerhauser Found., and W. Dayton. Statistical help was provided by G. L. Hensler and R. E. McRoberts. We also thank the Minn. Dep. Nat. Resour. and several field technicians.