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.
The study was carried out in the Superior National Forest in northern
St. Louis, Lake, and Cook Counties of northeastern Minnesota (fig. 1),
in conjunction with other aspects of wolf research (see Mech _et al._
p. 1).
[Illustration: _Figure 1.--The study area showing locations where
wolf-killed and hunter-killed deer were taken. Line arbitrarily
separates the hunted area from the wilderness area._]