Because the data show that wolves in our study area tend to kill a
disproportionate number of older deer, it is not surprising to discover
that wolves also tend to capture a disproportionate number of
individuals with abnormalities and pathological conditions (table 8).
The explanation for such selection is obvious in regard to the
abnormalities of the lower limbs (figs. 14-17): deer with injured or
abnormal limbs simply cannot run as fast or as agilely as normal
animals (table 7). Our observations show that deer usually depend on
their alertness and speed to escape approaching wolves (Mech 1966b,
Mech _et al._, p. 1). Any trait or condition that tended to interfere
with either alertness or speed would decrease an individual's chance of
escape.
It is more difficult to explain how dental abnormalities or
pathological conditions of the mandible (figs. 8-10) would predispose
an individual to wolf predation. However, in the case of dental
abnormalities the genetic or environmental conditions that caused the
abnormality might also have caused some other trait that increased the
animal's vulnerability. Or the abnormal condition itself may have
caused a further, more critical, disruption of the animal's physiology
or behavior, which in turn predisposed it to wolf predation.
The finding of several wolf-kills with poor fat stores could indicate
that primary or secondary malnutrition was a factor in the animals'
deaths. However, it would take a statistical comparison between the fat
stores of the deer at large and those of the wolf-kills to establish
this.
The discovery that 13 percent of the fawns and 84 percent of the
yearlings killed during January, February, and March had not yet shed
their deciduous incisors and premolars, respectively, also fits well
with the rest of our information. Evidently some unusual factor had
caused the delay in tooth development and replacement. One possibility
is that the animals were born in August or September, much later than
normal. Although most deer in Minnesota are born in May and June, there
are records of births in July and August. In addition, a fetus 181 to
200 days old was found in a doe killed on September 26 (Erickson _et
al._ 1961).
An alternate explanation for the delay in tooth replacement
is that the animals were suffering from malnutrition or nutrient
deficiency. Severinghaus[35] has evidence that yearling bucks that have
not replaced their deciduous premolars during November, and thus are
aged at 17 months (Severinghaus 1949), generally have shorter, narrower
antlers and fewer points than 18-and 19-month-old individuals. Degree
of antler development in turn is considered related to nutritional
state (Latham 1950). Thus it is reasonable to conclude that animals
behind in tooth development and replacement, whether this is caused by
age or diet, are physiologically inferior.
Most of the abnormal conditions discussed above pertain to the skeletal
parts of wolf-kills. If the soft parts of a large number of kills could
be examined thoroughly, one might discover a much higher incidence of
diseases and other pathological conditions.
In conclusion, our data on both age and condition of wolf-killed deer
show that at least during winter, wolves in our study area usually do
not kill just any deer they discover, although they do try to.
Evidently, most deer can usually escape wolf predation. The most
frequent exceptions are those 5-1/2 years old and older, those born
late, those suffering from poor nutrition, those with abnormalities or
pathological conditions, and possibly fawns.
The above conclusions parallel those of Murie (1944), Crisler (1956),
Mech (1966a), and Pimlott _et al._ (1969) for wolves preying on Dall
sheep, caribou, moose, and deer respectively, and further substantiate
the claim by Mech (1970) that they can be extended to wolves preying on
most, if not all, species of large mammals under most conditions. It is
also apparent from the data presented above that deer over 5 years of
age and those with abnormalities of the jaw or lower limbs represent
such a small percentage of the total population that they are seldom
taken by human hunters. In this respect, competition between timber
wolves and human hunters appears to be minimal in the study area.