The primary prey of most wolves in our study area is the white-tailed
deer (fig. 29), but some moose (fig. 30) are also killed. We have
examined the remains of six moose that were eaten by wolves, two of
which were killed by them (fig. 31). One was found on February 25,
1967, on Gillis Lake and the other on March 7, 1969, on Twinkle Lake.
These locations are within 3 miles of each other, suggesting that a
wolf pack in that area may be more accustomed to preying on moose than
other packs. The other four moose carcasses were found in other parts
of the study area, but circumstances were such that the causes of death
of those animals could not be determined. A discussion of the details
of wolf-moose relations in our study area must await the collection of
additional data.
[Illustration: _Figure 29.--The main prey of wolves in northern
Minnesota is the white-tailed deer. (Photo courtesy of L. D. Mech.)_]
[Illustration: _Figure 30.--Moose are also killed by wolves. (Photo
courtesy of Allan Taylor.)_]
[Illustration: _Figure 31.--Only a few wolf-killed moose were located
during the study. (Photo courtesy of Laurence Pringle.)_]
The remains of 93 wolf-killed deer, and 49 probable wolf-kills, were
examined for age, sex, and condition and were compared with a sample of
433 hunter-killed deer from the same general area. The wolf-killed deer
were generally much older than the hunter-kills and had a significantly
higher percentage of jaw and limb abnormalities (see Mech and Frenzel,
page 35).
Until recently the only observations of wolves hunting deer were those
reported by Stenlund (1955) for northern Minnesota. He described two
reports of actual observations and two reports of interpretations of
tracks in the snow, all successful hunts. Since that time several
descriptions of successful and unsuccessful hunts have also been
published (Mech 1966b, Rutter and Pimlott 1968, Pimlott _et al._ 1969,
Mech 1970). Nevertheless, many more observations must be made before
generalizations can be formed.
During the present study we were able to witness a number of hunts from
the air and piece together others based on tracks. The following
descriptions are quoted from the field notes of Mech:
"26 January 1967. About 3/4 mile N.E. of Alice Lake.
"Jack Burgess [pilot] and I were following a pack of 8
wolves, when at 4:15 they veered from their former line of
travel, about 30 deg. They were then about 200 yards from 2
deer. They began wagging their tails when about 175 yards
from the deer. One deer, on the edge of a steep bank, was
lying, but one was standing about 75 yards N. of it in open
hardwoods. The wolves continued toward the latter deer.
"This deer remained standing in the same place until the
wolves approached to within about 100 feet of it. The lead
wolf stopped, when that distance from the deer, and the
others caught up but also stopped when within about 25 feet
behind the lead wolf. By this time the deer, whose body was
facing away from the wolves, had its head turned back over
its shoulder toward the wolves. The wolves and the deer
remained absolutely still while staring at each other, 100
feet apart, for 1-2 minutes, while we made several circles.
"Suddenly the deer bolted, and instantly the wolves pursued.
I am fairly certain that it was the deer that bolted first,
but could be mistaken. The action was almost simultaneous.
The deer headed toward the other deer near the top of the
high bank. This animal had been lying but had arisen when
the wolves were about 150 yards away.
"The lead wolf followed in the deer's trail, but the others
cut toward the bank. This flushed the second deer (near the
edge of the bank), which ran down the bank. Meanwhile when
the first deer reached the edge of the bank, it headed due
W. along the top of it. Only the lead wolf pursued this
animal. The other deer had headed down the bank to the S.E.,
and at least a few of the wolves followed it.
"We could not watch both deer, so we continued following the
first. The deer had no trouble in snowdrifts, but the wolf
was hindered by them. The wolf followed the deer for about
200 yards along the top of the bank, and then gave up after
losing ground. The wolf had run a total distance of about
250-275 yards. He then lay down and rested.
"We noticed at least 3 wolves stopped part way down the bank
in the trail of the second deer. However, we did not see
the remaining wolves or the second deer.
"Eventually (after about 5 minutes), these wolves joined the
first, and all rested. At 4:25 p.m., one wolf started toward
a third deer, which had been lying under a tree while the
former chase took place. The deer was about 150 yards from
where the wolves rested, and it had stood before the wolf
started toward it. We could not see whether the deer or wolf
bolted first, but suddenly both animals were bounding away.
The wolf chased the deer about 125 yards and gave up after
losing ground. The other wolves followed slowly in its
trail, and all assembled and rested. The deer continued
running for at least 1/4-mile."
"27 February 1969. 2 miles N. of August Lake.
"1059's pack of 5 was heading N.E. at 4:10 p.m. when they
got to within 100 yards of 2 standing deer. The deer had
been standing alertly in a shallow draw, and when at least 2
wolves got to within 100 yards, they fled. The wolves began
running after them.
"The deer were in snow up to their bellies and had to
hesitate slightly at each bound. But they ran fast. We could
only see one wolf very much [of the time]. It was also
having a difficult time in the snow, and after a total run
of about 250 yards (100 to the deer's original location and
150 after the deer), the wolf lay on the snow and rested
about 10 minutes. The deer ran only about 200 yards more and
stood alertly for the next 20 minutes at least. The wolves
then went on.
"27 March 1969. About 2 miles S.E. of Central Lakes,
Minnesota.
"At 3:00 p.m. while we were following wolf 1051 by aircraft
in above location, we saw a deer running very quickly on top
of the crusted snow and then stand and watch its backtrail.
About 1-1/2 minutes later we saw 1051 running along the same
route. We did not see when the deer fled again, but saw it
running about 100 yards from the wolf and doubling back
paralleling its original route. When the wolf got near the
approximate doubling-back point, he lay down and rested for
about 5 minutes. The deer continued fleeing for about 350
yards, stopped, and for several minutes faced its backtrail.
The wolf finally continued on in his original direction,
giving up the chase.
"At 4:30 p.m.--1-1/2 miles S. of Central Lakes,
Minnesota--Wolf 1051 had come to within 100 yards of
[four-lane] Highway 53 and was hesitant to approach it.
Several cars were going by in both directions. Thus the wolf
headed S. parallel with the highway about 150 yards E. of
it.
"Suddenly two deer, which we had noticed S. of the wolf
earlier, fled across the highway. The wolf soon got to the
point where they crossed, hesitated about a minute and then
ran across. No cars came at that time.
"We could not always see the deer or the wolf when W. of the
road because there were several patches of evergreens. The
wolf did head straight W. after crossing the road. Then
about 250 yards W. of this point we saw a deer come out onto
an old woods road which lay in a N.W.-S.E. axis. The deer
ran N.W. on the road and then we saw the wolf where the deer
had come out onto the road. While the deer ran N.W., the
wolf cut into the woods to his right, N.E. We could not see
it then but presumed it was running N.W. paralleling the
road.
"After the deer had run about 50 yards up the road, it also
headed N.E. into the evergreens. Within a few seconds it
fled right back out and started S.E. down the road. The wolf
was about 50 feet behind it and began gaining.
"When the deer got back to where the wolf had headed into
the woods from the road before, it also headed N.E. into the
woods. The wolf was then about 20 feet away and the deer was
headed N. around in a circle with the wolf closing in on the
outside. The wolf did not emerge from the evergreens for at
least 15 minutes, nor did we see the deer, so I presume the
wolf killed the deer. [But see entry for April 1.]
"1 April 1969. Dan Frenzel and I searched the area described
on March 27 for 1 hour and found no sign of a kill. Old wolf
tracks were seen, but only a single wandering track. No
concentration such as usually seen at kills. Best conclusion
is that 1051 did _not_ kill the deer where seen from the air
March 27."
We also saw 1055 and her associate actually kill a deer, on February 6,
1969, but we did not realize what was going on and it happened so fast
that we only saw a wolf rushing and biting at the front end of the
downed animal. The chase had to have lasted only a few seconds.
In addition to the above direct observations, we also were able to
piece together from tracks in the snow the chase and successful
encounter between a single wolf and a deer in two instances. In the
first case, on January 25, 1967 (11:50 a.m.), we arrived at the scene
(near Grub Lake, just N. of Snowbank Lake) within an hour of the
encounter, and the wolf was still feeding on the deer, which had been a
2-1/2-year-old female. Mech examined the area from the ground and made
the following observations:
"The deer had come S.W. down the middle of the lake at a
fast walk, turned around, backtracked a few yards and headed
to the N.W. shore of the lake. Meanwhile a wolf had come at
a trot along the deer's track, but it had cut to the N.W.
shore about 50 yards N.E. of where the deer had. When still
on the ice about 15 feet from shore, the wolf began running
as evidenced by his long bounds. He continued running inland
about 50 feet from shore toward the deer. The deer had
walked inland from the shore and may have stood there about
25 feet from shore. Suddenly it had bounded away. The
bounding wolf track was in the same trail as the deer's for
about 25 yards but then it paralleled the deer's about 5
feet away on the inland side. After about 125 yards from
where the deer flushed, the deer was pulled down. It was
_not_ on its side but rather had sunk into the snow in
more-or-less of an upright position.
"Apparently the deer had just about reached the shore when
the wolf noticed it, and it detected the wolf. At this time
the wolf must have been up the shore about 50 yards where
his tracks first showed he began bounding. There was no sign
that the wolf had spotted the deer on the lake and had tried
to cut it off from shore by running inland along the shore
and then waiting for the deer to come inland. Once the wolf
had begun bounding, he continued until he pulled the deer
down.... Sign showed that the deer dropped within about 20
feet of where she had begun bleeding."
The second case involved a 5-1/2-year-old buck, No. M-28, which had
arthritis of his right hind foot and probably had defective gait (see
Mech and Frenzel p. 35). The attack took place on Basswood Lake on
February 2, 1967, and excerpts from field notes by Mech follow:
"A single wolf had killed this deer after chasing,
following, or tracking the deer about 3.75 miles. The deer's
last 350 yards was a fast walk--the tracks were one in front
of the other and about 2 feet apart, and there was no
leaping or bounding. Same with the wolf--a fast trot.
"Where the tracks came together, the deer apparently had
fallen, but there was no blood. From there, the deer dragged
its feet or the wolf for about 25 feet and then went down
again. The wolf circled the deer, and for the next 150 feet,
the 2 animals had fought or scuffled and then the deer had
gone down where we found it.
"The 4-mile persistence of this wolf--whether tracking,
following, or chasing the deer--is remarkable [compared with
most chases] and makes me believe the wolf had good reason
to believe it could kill the deer."
Our observations of wounds on fresh kills confirm the following
description by Stenlund (1955, p. 31) of the location and manner of
attack of wolves on deer: "No evidence of hamstringing of deer was
found on freshly killed carcasses, although the possibility does exist.
Usually deer are run down from behind, the wolf or wolves biting at
the hind flanks and abdomen, or at the hind flanks and head region
simultaneously."
On each kill, all the flesh and much of the skin and bones were eaten,
at least during the winters of 1966-67 and 1967-68. This was also true
during December 1968 and much of January 1969. However, during February
and March 1969 when an unusual accumulation of snow had built up, most
of the kills were only partly eaten (see Mech _et al._, page 51). In
previous years deer freshly killed by single wolves were sometimes
found with only a few pounds of flesh or viscera missing. However, in
each case the carcasses were almost completely cleaned up within a few
days, often by packs to which the single wolves may have belonged (Mech
1970).
Usually the first parts of a carcass to be eaten are the hams and part
of the viscera from the coelomic cavity. In one case where a wolf was
interrupted while feeding it was apparent that the animal had been
stripping the omental fat from the carcass. This may be the wolf's
favorite part of a deer, for the stomach of one wolf that we examined
in January 1967 contained nothing but such fat.
The average consumption and kill rate of deer by wolves has not yet
been determined, but we have some information bearing on the subject.
Because our data were obtained during a winter of unusually deep snow,
and it was obvious that wolves were killing more deer than they could
eat at the moment (see Mech _et al._, page 51), our figures should be
considered much higher than average. However, they should be useful in
that they probably represent the maximum kill rate not only throughout
the year but also throughout a period of many years.
By observing each of our radiotagged wolves whenever possible and
noting whether or not it was feeding on a kill, we learned that our
wolves generally remained close to their kills for periods of from 1 to
7 days, depending on how recently they had eaten (fig. 32). Thus, when
a wolf was found at a new location each day, the assumption could be
made that the animal did not currently have a kill.
[Illustration: _Figure 32.--Periods spent by radiotagged wolves and
their associates feeding on kills judged to be their own. This does not
include periods when they were known to be feeding on carrion._]
We assumed that wolves found at fresh kills (fig. 33) had made them
unless there was evidence to the contrary as with 1053, the scavenger.
When a wolf was found at one location for several consecutive days but
could not be observed, we assumed it was feeding on a kill, since
whenever wolves were observed remaining in the same location for
several days they were seen feeding. Thus a range of possible number of
kills per wolf was determined, with the lower limit being the known
minimum and the upper limit the possible maximum. When more than one
wolf fed on a kill, as with the pack, the figures were calculated on a
per-wolf basis.
[Illustration: _Figure 33.--Radiotagged wolf (upper left) found at kill
(lower right). (Photo courtesy of L. D. Frenzel.)_]
In this way we obtained data on a total of 468 wolf-days and found a
total kill of 35 to 48 deer (table 7). This averages out to a kill rate
of one deer per 10 to 14 days per wolf. The figure varied considerably
among individuals--1051 had the highest rate of one kill per 6.3 to 7.2
days, and each wolf in 1059's pack had the lowest rate (except for
1053, the scavenger) of one deer per 14.0 to 18.0 days.
It is significant that the pack of five wolves had a lower kill rate
per wolf than did single wolves and pairs. This is explainable because
the ability of wolves to kill deer during early 1969 was much greater
than usual (see Mech _et al._, p. 51). Thus single wolves probably
could kill deer just as easily as could packs, but they did not need to
share them. This differs markedly from the situation on Isle Royale,
where lone wolves usually feed only on moose remains left by packs
(Mech 1966a, Jordan _et al._ 1967).
That lone wolves had more of a food surplus than those in the pack is
confirmed by the figures on the average number of days that the various
wolves fed on kills (table 7). Wolf 1051 spent an average of only 2.2
to 2.4 days feeding at each of his kills, whereas 1059's pack of five
spent an average of 5.8 to 7.5 wolf-days at each kill. Further
confirmation is found in the fact that even when most wolves were
leaving their kills partly uneaten, a pack of 8 to 10 wolves (probably
that to which 1057 belonged) was seen completely devouring a kill.
_Table 7.--Kill rate of deer by radiotagged wolves and their associates_
#: _Number_
--------------------------------------------------------------------------
Wolf-days
Wolf Wolf-days Wolf-days Wolf-days feeding
# Wolves Dates of data Kills per kill[14] feeding per kill
--------------------------------------------------------------------------
# # # Mean # # Mean #
1051 1 Nov. 26 to 101 14-16 6.3-7.2 33-40 2.2-2.4
Apr. 3
1053[15] 1 Dec. 14 to 75 2-3 25.0-37.5 9-18 4.5-6.0
Mar. 27
1055 1-2 Jan. 9 to 61 4-9 6.7-15.0 13-25 2.8-3.3
Mar. 14
1057 1-13 Jan. 24 to 51 5-7 7.3-10.2 25-33 4.7-5.0
Feb. 28
1059 5 Jan. 25 to 180 10-13 14.0-18.0 75 5.8-7.5
Mar. 14
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Summary 22 Nov. 27 to 468 35-48 [16]9.8-13.4 145-181 [17]3.8-4.1
Apr. 3
Before 142 7-9 [18]15.7-20.3 39-56 5.1-5.6
Feb. 1
After 326 28-39 8.4-11.6 106-125 3.2-3.8
Jan. 31
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