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AN ANALYSIS OF THE AGE, SEX, AND CONDITION
OF DEER KILLED BY WOLVES IN NORTHEASTERN MINNESOTA
L. David Mech and L. D. Frenzel, Jr.
The selective effect of predation on prey populations is of significance in studies of evolution and population dynamics. Selective predation can be an important agent in the process of natural selection, and it influences the extent to which predators limit the numbers of their prey.
One of the predators most commonly chosen for investigating the selective effect upon prey is the wolf (Canis lupus). Because animals preyed upon by wolves generally are large, their remains can be more easily located and examined. It already has been established that in most areas wolves kill primarily young, old, and other inferior members of such prey populations as Dall sheep (Ovis dalli), moose (Alces alces), caribou (Rangifer tarandus), bison (Bison bison), and musk-oxen (Ovibos moschatus); evidence for this generalization has been summarized by Mech (1970).
However, only recently has it been shown that this generalization may extend to predation on the smallest hoofed prey of the wolf in North America, the white-tailed deer (Odocoileus virginianus). Pimlott et al. (1969) demonstrated a difference between the age structure of 331 deer killed by wolves during winter in Algonquin Park, Ontario, and 275 deer assumed to represent the actual population in the same area. Whereas only 13 percent of the deer from the population at large were estimated to be more than 5 years old, 58 percent of the wolf-kills were in this age category.
We employed a similar analysis for deer killed by wolves in northeastern Minnesota, but used a more refined aging technique and included comparisons of the age and sex structures of various subsamples of wolf-kills. Whereas the Ontario research involved a prey population unlimited by man, our work was carried out on both a hunted population and on one relatively unhunted. Further comparisons were made between deer killed during periods of normal snow conditions and those taken during unusually high snow accumulations. The incidence of various abnormalities in wolf-killed deer was also compared with that in hunter-killed animals.