[20] Kolmogorov-Smirnov two-sample test (Siegel 1956).
[21] Z test (Downie and Heath 1959).
[22] Because test showed no significant differences in age or sex
structure between sample of known wolf-kills and probable wolf-kills,
these were combined for all subsequent tests and the pooled sample
considered "wolf-kills."
[23] At 95 percent level or greater. (NOTE: Lack of a significant
difference does _not_ prove that no difference exists. Rather, it means
only that the available evidence does not allow the positive conclusion
that a difference does exist.)
[24] Wolf-kills found on lakes were compared with those located inland
because of the possibility that kills on lakes may not be
representative of kills in general.
[25] Sample too small for test, but no apparent difference.
[26] No significant difference in entire age structures. However, when
the percentage of yearlings is compared between the two groups, the
difference is almost significant at the 95 percent level.
_Table 2.--Sex ratios of hunter-killed deer and
wolf-killed deer from northeastern Minnesota_
-------:--------------------------:-------------------------
Age : Hunter-killed deer : Wolf-killed deer
-------:--------------------------:-------------------------
Number Percent Percent Number Percent Percent
male female male female
Fawns 108 50 50 22 41 59
Adults 315 68 32 105 54 46
------------------------------------------------------------
In the comparisons of the subsamples of hunter-kills, the only
statistically significant difference found was that the adult subsample
had a higher proportion of males than the fawn subsample. No
significant difference was found in the age structures of the
subsamples, so these were all pooled into a sample of 433 hunter-kills
for comparison with the wolf-kills. For the same reason, the entire
sample of 142 wolf-killed deer was used for a comparison with the
hunter-killed sample.
_Table 3.--Sex ratios of wolf-killed deer from wilderness areas
and from hunted areas_
#: _Number_
%: _percent_
-------:-------------------:------------------:-----------------
Age : Wilderness area : Hunted area : Total
-------:-------------------:------------------:-----------------
# % % # % % # % %
male female male female male female
Fawns 4 0 100 18 50 50 22 41 59
Adults 41 71 29 64 44 56 105 56 44
----------------------------------------------------------------
Wolf-killed deer in our sample, with an average age of 4.7 years, were
significantly older (99 percent level) than hunter-killed deer, with an
average age of 2.6 years. For example, deer 5 years of age and older
made up 48 percent of the wolf-kills but only 10 percent of the
hunter-kills (table 4). The oldest hunter-killed deer in our sample was
9-1/2 years old, but the oldest wolf-killed deer was 14-1/2 (fig. 7).
[Illustration: _Figure 7.--Comparison between the age structures of
deer killed by wolves, deer killed by hunters, and a theoretical
population from the same general area of northeastern Minnesota_.]
Because of a possible bias against fawns in the method of collecting
data from wolf-kills (to be discussed later), the age structure of the
sample of wolf-kills excluding fawns was tested against that of the
sample of hunter-kills excluding fawns. The result once again was a
highly significant difference between these two age structures (table
1).
As an additional test of the degree to which the age structure of the
wolf-killed deer might differ from that of the actual population, we
compared our wolf-kill age structure with the age structure of a
hypothetical deer population. This was considered advisable just in
case the hunter-kill data were poorly representative of the age
structure of the actual deer herd. Several hypothetical age structures
were constructed and compared according to advice from Downing.[27]
In all cases, the comparisons produced the same basic results as the
tests with the hunter-killed sample. An example of one comparison is
given in figure 7.
A further result obtained by aging the wolf-killed deer pertained to
the young individuals killed. The deciduous first incisors of fawns and
the deciduous premolars of yearlings are usually replaced with
permanent teeth by December (Severinghaus 1949). Of 24 wolf-killed
fawns examined, however, three (13 percent) taken during January,
February, and March had not yet replaced their deciduous first
incisors. Of the 13 yearlings found during this same period, nine (70
percent) had failed to replace their deciduous premolars, and two (15
percent) had just replaced them (one deer killed in February and one
killed in March).