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Title: Ecological Studies of the Timber Wolf in Northeastern Minnesota
Author: Mech, L. David, Winship, John W., Karns, P. D., Ream, Robert R., Frenzel, L. D.
Language: English
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USDA FOREST SERVICE
RESEARCH PAPER NC-52
1971

[Illustration]

Ecological
Studies of the
TIMBER
WOLF
in
Northeastern
Minnesota


NORTH CENTRAL FOREST EXPERIMENT STATION
FOREST SERVICE
U. S. DEPARTMENT OF AGRICULTURE



FOREWORD


The largest population of timber wolves remaining in the United States
(excluding Alaska) lives in northern Minnesota. Many of these wolves
inhabit the Superior National Forest, so protecting the habitat of this
endangered species is largely a Forest Service responsibility.

As the "Age of Ecology" broadens into the 1970's, wolves and wolf
habitat will become a subject of concerted research. Forest land
managers will have to know more about how the timber wolf fits into a
forest system. Building on nearly 50 years of research in northern
forests, we at the North Central Station intend to expand our studies
of wildlife habitat. We are happy to publish the enclosed papers as one
step in this direction.

                                        D. B. King, Director

North Central Forest Experiment Station
D. B. King, Director
Forest Service--U.S. Department of Agriculture
Folwell Avenue
St. Paul, Minnesota 55101



ECOLOGICAL STUDIES OF THE TIMBER WOLF
IN NORTHEASTERN MINNESOTA

L. David Mech and L. D. Frenzel, Jr. (Editors)


CONTENTS


Movements, Behavior, and Ecology of Timber Wolves
in Northeastern Minnesota
    L. David Mech, L. D. Frenzel, Jr., Robert R. Ream,
    and John W. Winship                                         1

An Analysis of the Age, Sex, and Condition
of Deer Killed by Wolves in Northeastern Minnesota
    L. David Mech and L. D. Frenzel, Jr.                       35

The Effect of Snow Conditions on the Vulnerability
of White-Tailed Deer to Wolf Predation
    L. David Mech, L. D. Frenzel, Jr., and P. D. Karns         51

The Possible Occurrence of the Great Plains Wolf
in Northeastern Minnesota
    L. David Mech and L. D. Frenzel, Jr.                       60


THE AUTHORS

     Dr. Mech, formerly with the Department of Biology,
     Macalester College, St. Paul, Minnesota, is now employed by
     the U.S. Bureau of Sport Fisheries and Wildlife, Twin
     Cities, Minnesota.

     Dr. Frenzel, formerly with the Department of Biology,
     Macalester College, St. Paul, Minnesota, is now employed by
     the Department of Entomology, Fisheries, and Wildlife,
     University of Minnesota, St. Paul, Minnesota.

     Dr. Ream, formerly with the North Central Forest Experiment
     Station (maintained in cooperation with the University of
     Minnesota), Forest Service, U.S. Department of Agriculture,
     is now employed by the School of Forestry, University of
     Montana, Missoula, Montana.

     Mr. Winship is with the U.S. Bureau of Sport Fisheries and
     Wildlife, Twin Cities, Minnesota.

     Mr. Karns is with the Minnesota Department of Conservation,
     Forest Lake, Minnesota.


For sale by the Superintendent of Documents, U.S. Government Printing
Office, Washington, D.C. 20402



MOVEMENTS, BEHAVIOR, AND ECOLOGY OF TIMBER WOLVES
IN NORTHEASTERN MINNESOTA

L. David Mech, L. D. Frenzel, Jr.,
Robert R. Ream, and John W. Winship


The largest population of wolves (_Canis lupus_) remaining today in the
continental United States outside of Alaska is in northern Minnesota.
As of mid-1970 this population was not legally protected, and the
species, which once ranged over almost all of North America, is now
considered by the U.S. Department of the Interior to be in danger of
extinction in the contiguous 48 States. Until the present research, the
only field studies of Minnesota wolves were those of Olson (1938 a, b)
and Stenlund (1955). Those investigations provided much useful general
information about Minnesota wolves and gave the present authors an
excellent background with which to begin more detailed investigations.

This paper reports on the basic aspects of a series of studies that
began in 1964, and concentrates primarily on wolf movements and
activity, social behavior, hunting behavior, and population
organization. Most of the data were collected during January, February,
and March 1967; February, November, and December 1968; and January
through August 1969. A total of 192 days was spent in the field.

According to a distribution map of wolf subspecies (Goldman 1944), the
race of wolves in our study area is _Canis lupus lycaon_. However,
evidence presented by Mech and Frenzel (see page 60) suggests that
there may be strong influence by _C. l. nubilus_, a more western race
of wolf formerly thought to be extinct (Goldman 1944).

Between 1965 and the present, wolves in the study area were neither
protected nor bountied, and the influence of trapping and hunting is
thought to have been negligible.


THE STUDY AREA

This study was conducted in the Superior National Forest (fig. 1) in
northern St. Louis, Lake, and Cook Counties of northeastern Minnesota
(92° west longitude, 48° north latitude), an area well described by
Stenlund (1955). Most of the data were collected from within and
immediately south of the Boundary Waters Canoe Area, a special
wilderness region in which travel by motorized vehicles is restricted.
The total study area encompasses approximately 1.5 million acres, and
numerous lakes and rivers comprise about 15 percent of this area (fig.
2). The topography varies from large stretches of swamps to rocky
ridges, with altitudes ranging from 1,000 to 2,300 feet above sea level
(fig. 3). Winter temperatures lower than -30° F. are not unusual, and
snow depths generally range from 20 to 30 inches on the level. However,
an important exception occurred in early 1969 when depths of 45 inches
and more accumulated in much of the area. Further details on snow
conditions in the study area during the period of this investigation
are given by Mech _et al._ (see page 51). Conifers predominate in the
forest overstory, with the following species present: jack pine (_Pinus
banksiana_ Lamb.), white pine (_P. strobus_ L.), red pine (_P.
resinosa_ Ait.), black spruce (_Picea_ mariana (Mill.) B.S.P.), white
spruce (_P. glauca_ (Moench) Voss), balsam fir (_Abies balsamea_ (L.)
Mill.), white cedar (_Thuja occidentalis_ L.), and tamarack (_Larix
laricina_ (DuRoi) K. Koch). However, as a result of extensive cutting
and fires much of the conifer cover is interspersed with large stands
of white birch (_Betula papyrifera_ Marsh.) and aspen (_Populus
tremuloides_ Michx.). Detailed descriptions of the forest vegetation
were presented by Ohmann and Ream (1969).

[Illustration: _Figure 1 (left half)--Map of the study area._]

[Illustration: _Figure 1 (right half)--Map of the study area._
BOUNDARY WATERS CANOE AREA SUPERIOR NATIONAL FOREST]

[Illustration: _Figure 2.--Lakes are common throughout most of the
study area. (Photo courtesy of L. D. Mech.)_]

[Illustration: _Figure 3.--Ridges, islands, swamps, and bays are part
of the variable topography in the Superior National Forest. (Photo
courtesy of L. D. Mech.)_]


METHODS

The observations discussed in this paper were all made from aircraft,
the method of flying being that reported by Burkholder (1959) and Mech
(1966a). The following aircraft were used (in order of size): Aeronca
Champ,[1] Supercub, Cessna 172, Cessna 180, and Cessna 206. The smaller
aircraft were excellent for holding in tight circles during
observations but had the disadvantage of being slow and cold; the
larger planes could cover the study area much more quickly and were
more comfortable, but were not as maneuverable during observations. For
radiotracking, to be discussed below, the best compromise seemed to be
a Cessna 172.

To make observations of wolves, we flew over frozen waterways until
tracks were found, and then followed the tracks until we lost them or
saw the wolves (fig. 4). Several times we located wolves directly just
by scanning the lakes. However, because there seemed to be a number of
packs in the area, and because most wolves were the same color (with
the exception of a few black or white individuals) (see Mech and
Frenzel, page 60), it usually was not possible to follow packs from one
day to the next and be certain of identification. Moreover, it was
impossible to locate any pack at will because most wolves also spent
much time inland.

[Illustration: _Figure 4.--An important technique used in the study
involved aerial tracking and observing of wolf packs. (Photo courtesy
of L. D. Frenzel.)_]

Therefore, to facilitate our observations and to obtain data on wolf
movements and extent of range, we began a radiotracking program in
1968-69. A professional trapper, Robert Himes, was employed to capture
the wolves. Using Newhouse No. 4 and 14 steel traps at scent-post sets,
he caught two wolves, and captured another with a live-snare similar to
that used by Nellis (1968); the senior author trapped two additional
wolves (fig. 5).

[Illustration: _Figure 5.--A wolf caught in a trap. (Photo courtesy of
D. L. Breneman.)_]

The four wolves held in steel traps were restrained by a choker (fig.
6), and then anesthetized by intramuscular injections (fig. 7A, B) of a
combination of 30 mg. of phencyclidine hydrochloride (Sernylan,
Parke-Davis Co.) and 25 mg. promazine hydrochloride (Sparine, Wyeth
Laboratories) as prescribed by Seal and Erickson (1969); these drugs
proved most satisfactory.

[Illustration: _Figure 6.--A choker was used to restrain wolves caught
in traps. (Photo courtesy of D. L. Breneman.)_]

[Illustration: _Figure 7.--A. A small hypodermic syringe is loaded with
drugs. B. The loaded syringe is used on the end of a pole. (Photos
courtesy of D. L. Breneman.)_]

The fifth wolf (a female), which was captured around the chest by the
live-snare, was handled without drugs. A forked stick was used to hold
down her head (Kolenosky and Johnston 1967), and she offered no
resistance (fig. 8). Evidently she went into shock or some other
psychophysiological state of unconsciousness, for after her release she
remained on her side and did not move for 1.5 hours, despite our
prodding during the first few minutes (fig. 9). Then suddenly she
leaped up and ran off.

[Illustration: _Figure 8.--Once pinned by the forked stick, the wolf
ceased struggling. (Photo courtesy of Richard Bend.)_]

[Illustration: _Figure 9.--After release, the wolf lay still for 1-1/2
hours before jumping up and running off. (Photo courtesy of L. D.
Mech.)_]

Each wolf was examined, outfitted with a radio transmitter collar 15
inches inside circumference (fig. 10) and tagged with identification
numbers in both ears (fig. 11). Each transmitter was of a different
frequency in the 150 MH_z range, emitted a pulsed signal ranging from
75 to 350 pulses per minute, and had a calculated life of at least 300
days (fig. 12). Two types of 12-inch whip antennas were used on the
transmitters: one type extended up the side of the collar and then
stuck out above for 6 inches; the other was fully attached inside the
collar and extended up one side, around the top, and partly down the
other side. The transmitter, batteries, and antenna were molded into a
collar of acrylic weighing 11 ounces (Mech _et al._ 1965).[2] All radio
equipment functioned flawlessly for at least 5 months, and one
transmitter continued operating for at least 9 months.

[Illustration: _Figure 10.--A radio transmitter collar was placed
around the neck of each trapped wolf. (Photo courtesy of D. L.
Breneman.)_]

[Illustration: _Figure 11.--Each ear of the wolf was tagged with
identifying numbers. (Photo courtesy of Richard Bend.)_]

[Illustration: _Figure 12.--Each radio collar had a different frequency
tuned to special receivers, which allowed each wolf to be identified.
(Photo courtesy of D. L. Breneman.)_]

For tracking radio-equipped wolves, a directional yagi antenna (fig.
13) was attached to each of the wing struts of an aircraft and
connected inside to a portable receiver. The usual tracking technique
was to fly at 1,500 to 3,000 feet elevation to the last known location
of the wolf being sought (fig. 14). If a signal was not obtained at
that point, the aircraft spiraled upward until the signal was found or
until 10,000 feet altitude had been reached. If the signal still was
not heard, a search pattern was flown at 10,000 feet. The range of the
signal from this altitude was 15 to 35 miles; at 3,000 feet it was 10
to 15 miles. Collars with antennas molded fully inside gave only about
two-thirds the range of those protruding partly, but could be expected
to last longer because the antennas could not break off. It is unknown
whether any protruding antennas did break during the study, but on
January 5, 1970, one wolf was recaptured, and its antenna had broken.

[Illustration: _Figure 13.--Directional yagi antennas fastened to the
wing struts of the aircraft were necessary to "home in" on the wolves.
(Photo courtesy of U.S. Bureau of Sport Fisheries and Wildlife.)_]

[Illustration: _Figure 14.--The tracking aircraft was usually flown at
altitudes of 1,500 to 3,000 feet.
(Photo courtesy of Dick Shank.)_]

When a signal was received, the aircraft was headed in the approximate
direction of the source until the signal strength reached a peak; a 90°
turn was then made in the direction the signal seemed the strongest. A
series of these maneuvers soon narrowed the area to the point where
visual search was possible. After practice and experience with this
technique, we could locate the approximate source of the signal within
10 to 30 minutes after first receiving it.

Even though the radiotagged wolves spent most of their time inland,
often in stands of conifers, they were frequently observed from the
aircraft. The technique was to circle at 300 to 800 feet altitude
around a radius of a quarter mile from the point where the strongest
signal emanated. From December through April, 65 percent of the wolves
located by radio were sighted; the rate was much higher for more
experienced personnel. A pack of five wolves that was tracked was seen
31 times out of 33 attempts during February and March.

Whenever wolves were located, radiotagged or not, observations were
made from an altitude that did not disturb them. Packs varied in the
concern shown the aircraft, but only one or two ran from it. The
radiotagged wolves, and a pack of 10 to 13 animals, were habituated to
the aircraft and usually could be observed from altitudes of 500 feet
and less without disturbance (fig. 15).

Almost all the radiotracking was done from aircraft, but when inclement
weather prevented flying, some attempts from the ground succeeded when
wolves were close enough to roads. The usual range on the ground was
0.75 to 1.50 miles. One wolf was approached to within 35 feet through
radiotracking.

[Illustration: _Figure 15.--The wolves studied soon became accustomed
to the aircraft and could then be observed during their natural
activity. (Photo courtesy of L. D. Mech.)_]

FOOTNOTES:

[1] _Mention of trade names does not constitute endorsement by the USDA
Forest Service._

[2] _The acrylic collar was fashioned by the Davidson Co., Minneapolis,
Minnesota, which also produced some of the transmitters. Other
transmitters and two radio receivers were manufactured by the AVM
Instrument Co., Champaign, Illinois._


RESULTS AND OBSERVATIONS

Aerial observations made during this study involved 490 hours
distributed as follows: January, February, March 1967--124 hours;
February 1968--10 hours; December 1968 through August 1969--356 hours.
Seventy-seven observations involving a total of 323 wolves were made
(table 1), excluding animals located through radiotracking.

One male and four female wolves were radiotagged, and they and their
associates were followed intermittently for periods of 5 to 8 months
(table 2). All except one initially suffered some injury to a foot.
Three of these animals were seen limping, but only in one case was the
limp judged extreme enough to have significantly affected the movements
or behavior of the animal. In that one case, the wolf (No. 1057) was
caught in a steel trap on an extremely cold night, and her foot froze.
After that she was often seen hopping on three legs. She was not able
to keep up with her pack, which consisted of 10 to 13 members, and her
movements were much restricted compared with those of other wolves.
However, she was frequently observed feeding on fresh kills, and may
even have made them herself.


_Table 1.--Sizes of wolf population units observed in northeastern
Minnesota_

#: _Number_
%: _Percent_

+------------------+-------------------------------------------+
|                  |             Wolf observations             |
|Population unit[3]+----------+----------+----------+----------+
|(number of wolves)|   Winter |   Winter |   Total  |Winters[4]|
|                  |  1966-67 |  1968-69 |          | 1948-53  |
+------------------+----------+----------+----------+----------+
|                     #    %     #    %     #    %     #    %  |
|       1             8   31    17   33    25   32    48   43  |
|       2             3   12     6   12     9   12    24   22  |
|       3             3   12     2    4     5    6     7    6  |
|       4            --   --     7   14     7    9     7    6  |
|       5             2    7     4    8     6    8     8    7  |
|       6             3   12     4    8     7    9     7    6  |
|       7             2    7     1    2     3    4     4    4  |
|       8             3   12     3    6     6    8     3    3  |
|       9            --   --     2    4     2    3     3    3  |
|      10             2    7     2    4     4    5    --   --  |
|      11            --   --    --   --    --   --    --   --  |
|      12            --   --     1    2     1    1     1    1  |
|      13            --   --     2    4     2    3    --   --  |
|                  --------------------------------------------+
|Total number                                                  |
|  of wolves        109   --   214   --   323   --   318   --  |
|Total number                                                  |
|  of observations   26   --    51   --    77   --   112   --  |
|Mean population                                               |
|  unit size          4.2 --     4.2 --     4.2 --     2.8 --  |
+--------------------------------------------------------------+

FOOTNOTES:

[3] Because wolf packs sometimes split temporarily, these figures may
not strictly represent actual pack sizes; nevertheless they should
provide reasonably accurate approximations.

[4] From Stenlund (1955).


_Table 2.--Background information on five radiotagged wolves studied in
northeastern Minnesota_

#: _Number_

--------:---------:-------:--------:--------:-------:-------:-----------
  Wolf  :Estimated: Usual :Location:  Date  : Last  : Days  :  General
--------:weight[5]:associ-:captured:captured: date  :located: condition
 #  :Sex:(pounds) :ations :        :        :located:       :
----:---:---------:-------:--------:--------:-------:-------:-----------
                                                       #

1051  M     75     None[6] T62N-R7W   Nov.    Apr.    84   Good, but two
                           -S18       27/68   24/69        toes frozen in
                                                           trap; animal
                                                           limped lightly
                                                           for 5-6 wks.

1053  F     60     None    T62N-R8W   Dec.    Aug.    72   Thin; top of
                           -S13       10/68   29/69        foot cut in
                                                           trap but no
                                                           broken bones
                                                           or frozen toes;
                                                           limped for at
                                                           least 10 wks.

1055  F     60   Another   T61N-R10W  Jan.    May     65   Thin; two toes
                 wolf      -S26       5/69    30/69        lightly frozen;
                 intermit-                                 no limp ever
                 tently                                    noticed.

1057  F     60   Pack of   T66N-R5W   Jan.    Apr.    47   Thin; front
                 13[7]     -S33       8/69    24/69        foot frozen
                                                           in trap; lost
                                                           use of foot
                                                           and could not
                                                           stay with pack.

1059  F     65   Pack      T62N-R11W  Jan.    Aug.    51   Good but thin;
                 of 5      -S26       22/69   29/69        captured in
                                                           snare; no
                                                           apparent injury.
----:---:---------:-------:--------:--------:-------:-------:-------------

FOOTNOTES:

[5] Wolf 1059, when killed by a trapper on January 10, 1970, appeared
to be of the same size and condition as when radiotagged; she only
weighed 53 pounds, however, indicating that probably all the weights
are overestimated.

[6] Tracks of a pack of at least two other wolves came by trap where
1051 was caught; however, there was never any other indication that
1051 may have been a member of a pack.

[7] A frozen foot prevented 1057 from staying with her pack; but she
did associate with other wolves intermittently and with the whole pack
when it came by her restricted area.


The precise ages of the radiotagged wolves were unknown. All
individuals, however, had sharp unworn teeth, indicating that they
were all relatively young. No. 1051, the only male studied, had testes
2.0 cm. long and 1.5 cm. wide; their volume therefore would be less
than 4.5 cc. The small size of these testes, compared with the 7 to 28
cc. reported by Fuller and Novakowski (1955) as the volume of the
testes from wolves taken during fall, would indicate that 1051 had not
yet matured. Since the animal's testes and canine lengths were
considerably greater than those of pups caught in a later study, we
presume 1051 was 18 or 30 months old.

Two of the females, No. 1055 and No. 1059, both captured in January,
had vulvas that seemed to be beginning to swell. No. 1059 was killed by
a trapper about a year later, on January 10, 1970, and an examination
revealed that she had bred in 1969 and carried five fetuses. Sectioning
her incisors and reading the apparent annulations indicated that she
probably was 3+ or 4+ years old.[8]

Three of the wolves were basically lone individuals. One of these, No.
1051, was captured on a night when tracks of at least two other wolves
came by the trap, and this could mean that he had been part of a pack.
However, it is also possible that these were merely tracks of
non-associated wolves that were also traveling through the area. In any
case, 1051 was not seen associating with any other wolf until 4 months
after he was caught, and even then the association seemed to be
temporary and casual. It could be argued that capture, handling by
humans, or wearing a collar prevented him from regaining old
associations or making new ones. However, the wolves radiotagged by
Kolenosky and Johnston (1967) were quickly accepted back into their
packs, and so were two of ours. Thus we conclude that 1051 probably was
a lone wolf when captured.

When 1053 was trapped, her tracks were the only ones in the area, and
she was never seen closely associating with another wolf. No. 1055
probably was with another wolf when captured, as evidenced by tracks.
About a month after she was radiotagged she associated with another
wolf intermittently for about 2 weeks, after which she was only seen
alone.

No. 1057 and No. 1059 were both members of packs. No. 1057 was captured
during the night after a pack of 13 wolves was seen heading toward the
area; 5 days later she was seen with 10 other wolves, which no doubt
represented this same pack. This wolf's association with the pack was
interrupted, however, because of the foot injury sustained during
capture. When 1059 was caught, tracks of two other wolves were seen in
the immediate vicinity, and one of the animals was seen within a
quarter mile of the trapped wolf. Three days after 1059's release, and
perhaps sooner, she was back with her pack, with which she remained at
least through March.

The detailed histories of the associations of the radiotagged wolves
will be discussed in a later section.

Radiotagged wolves were tracked every day that weather permitted during
December, January, and February; every week during March, April, and
May; and once a month during June, July, and August (fig. 16).
Information was obtained for a total of 570 "wolf-days"--a wolf-day
being a day in which one radiotagged wolf was located; a pack of five
being located for 1 day would constitute 5 wolf-days.

[Illustration: _Figure 16.--Distribution of the days on which data were
obtained for each of the radiotagged wolves. Because tracking success
was 99 percent, this also represents the distribution of effort. During
June, July, and August, wolves 1053 and 1059 were located 1 day each
month._]

The last day that animals 1051 and 1057 were heard from was April 24,
1969. Both had traveled long distances during the previous week and may
have moved out of range. Signals from wolf 1055 were last heard on May
30; this animal had also been ranging widely. Circles with radii of at
least 50 miles around the last known locations of each wolf were
searched unsuccessfully for the signals. During all subsequent tracking
nights for the remaining wolves, the missing animals were also sought,
but to no avail. Before the last dates that signals from these animals
were heard, attempts to locate marked animals from the air had failed
in only three instances.

FOOTNOTES:

[8] _David W. Kuehn, Personal correspondence to L. D. Mech, 1970._


Daytime Activity Patterns

When radiotagged wolves were located, notes were kept on the type of
activity they were engaged in; the results are summarized in figure 17.
In a total of 171 observations made between 9:00 a.m. and 6:00 p.m.,
the wolves were resting 62 percent of the time, traveling 28 percent
and feeding 10 percent. They tended to travel more before 11:00 a.m.
and after 3:00 p.m., although resting still composed at least 45
percent of the activity during every hour (fig. 18).

[Illustration: _Figure 17.--Percentage of time spent by radiotagged
wolves in various types of activity throughout the day, from December
through April._]

[Illustration: _Figure 18.--Generally the wolves rested during most of
the day. (Photo courtesy of L. D. Mech.)_]

These results generally agree with the statement by Mech (1966a) that
wolves on nearby Isle Royale tend to rest about 11:00 a.m. and begin
traveling again about 4:00 p.m. However, it does appear that the
Minnesota wolves spend much more of the day resting than do the Isle
Royale animals. The difference may be caused by the difference in pack
sizes studied. The Isle Royale pack of 15 to 16 may have had to travel
more to find enough food to feed all its members than did the lone
wolves and pack of five in the present study.


Movements and Range

Wolf movement is greatly hindered by deep, soft snow, so during winter
travel, wolves frequently use areas where they sink into the snow the
least. In our study area, frozen waterways are used extensively where
possible, just as reported by Stenlund (1955). Where few lakes or
rivers exist, wolves follow railroad beds and logging roads, often soon
after a plow or other vehicle has driven on them. In cutting cross
country through deep snow, wolves travel single file and tend to stick
to windblown ridges and to trails of deer and moose. Wolves that have
ranges small enough to cover in a few days form a network of their own
trails, which they can maintain merely by traveling regularly over
them. Packs on Isle Royale depended a great deal on such a system of
trails (Mech 1966a), and so did Pack No. 1059 in our study area.

Wolf packs can travel up to 45 miles in a day but it is usually larger
packs that do so (Stenlund 1955, Burkholder 1959, Mech 1966a, Pimlott
_et al._ 1969). In our study area we sometimes saw evidence of long
moves by large packs along strings of lakes and waterways. However,
most of our movement data pertain to lone wolves and a pack of five.
The daily travel of these animals was usually much less than that
reported for large packs.

Our radiotracking data provide an index to the extent of travel for
each wolf rather than the actual amount of travel, for it is based on
straight line distances between consecutive points at which an animal
was found. This measure will be referred to as the "net daily
distance."

Much variation was found in the net daily distances of wolves, with the
longest ranging from 4.5 miles for 1057 to 12.8 for 1055 (table 3). The
mean net daily distance for each animal, excluding days with no net
movement, varied from 1.5 to 3.6 miles. The movements of these wolves
may have been affected by the snow depth and penetrability, for mean
and maximum net daily distances suddenly increased for all animals
between February 23 and 28, when snow penetrability had decreased to a
point where walking wolves would be expected to sink in only about 6
inches (table 4). Other possible explanations for the wolves' sudden
increase in movements will be discussed below.

The straight line distances traveled between consecutive weekly
locations (called the "net weekly distances") showed a similar
variation (table 3). The maximum net weekly distance for each wolf
varied from 4.6 miles for 1059 to 49.0 for 1055, with means ranging
from 2.9 to 15.6 miles for the same wolves. No doubt 1059's net weekly
distances were relatively short because her total range and that of her
pack were much smaller than those of the other wolves.

It is difficult to obtain comparable measures of the extent of the
ranges covered by each of the radiotagged wolves because their patterns
of travel varied so much. Thus the figures given in table 5 should be
regarded only as gross indicators of the minimum range of each animal.
The area figures are especially deceiving in the case of 1055, for she
had a horseshoe-shaped range, much of which apparently was not used.


_Table 3.--Straight line distances (miles) between consecutive locations of
radiotagged wolves_

#: _Number_
%: _Percent_

---------------------------------------------------:----------------------------
    :                                              :         Net weekly
    :             Net daily distances              :          distances
    :----------------------------------------------:----------------------------
    :        :        :        :        :Mean net  :     :     :        :
    :        :        :        :        :distance  :     :     :        :
    :  Days  :Days no :  Days  :Mean net:per day   :     :Weeks:Mean net:
Wolf:  data  :  net   :movement:distance:excluding :Range:data :distance: Range
  # :obtained:movement:        :per day :days of no:     :     :per week:
    :        :        :        :        :movement  :     :     :        :
    :--------:--------:--------:--------:----------:-----:-----:--------:-------
    :    #   :  #   % :  #   % :  Miles :  Miles   :Miles:  #  : Miles  : Miles

1051    54     13  24   41  76     2.0      2.6   0.0-12.0  22   12.7   1.0-46.0
1053    37     20  54   17  46     1.0      2.1   0.0-5.0   23    6.3   0.0-23.6
1055    46      7  15   39  85     2.9      3.6   0.0-12.8  21   15.6   1.7-49.0
1057    29     11  38   18  62     1.0      1.5   0.0-4.5   15    4.6   0.0-31.0
1059    26      1   4   25  96     2.5      2.6   0.0-5.6   18    2.9   0.0-4.6
----:--------:--------:--------:--------:----------:-----:-----:--------:-------


Nevertheless, one major piece of information is obvious from the
figures: 1059's pack of five wolves had a much smaller range than any
of the other uninjured animals--approximately 43 square miles when
figured by the minimum-area method (Mohr 1947). The next smallest range
was that of 1051 (excluding the area of his later dispersal--see
below), which was some seven times the size of the pack's range.


_Table 4.--Straight line distances (miles) traveled between consecutive
days ("net daily distance") by radiotagged wolves in northeastern
Minnesota during February 1969_

+-------+-------------------------+-------------------------+
|       |         Mean net        |       Greatest net      |
| Wolf  |      daily distance     |      daily distance     |
|number +------------+------------+------------+------------+
|       | Feb.  1-23 | Feb. 23-28 | Feb.  1-23 | Feb. 23-28 |
+-------+------------+------------+------------+------------+
| 1051       1.1          3.5          2.3          4.8     |
| 1053       0.7          2.5          3.0          5.0     |
| 1055       2.7          6.2          8.0         12.8     |
| 1057       1.0          1.5          4.0          4.5     |
| 1059       2.2          3.1          4.0          5.6     |
+-------+------------+------------+------------+------------+


There is little published information on the movements and ranges of
lone wolves with which to compare our data. Mech (1970) summarized
information regarding ranges of packs. Reported ranges varied from 36
square miles for a pack of two wolves in Minnesota (Stenlund 1955) to
5,000 square miles for a pack of 10 in Alaska (Burkholder 1959).
Considering only data based on intensive study in the same general
region (Minnesota, Isle Royale, and Ontario) as our study area, the
largest range reported was 210 square miles for a pack of 15 to 21
wolves on Isle Royale (Mech 1966, Jordan _et al._ 1967). On a per-wolf
basis, the ranges in this region varied from 6 to 28 square miles per
wolf. Our pack of five with its range of 43 square miles would have
about 9 square miles per wolf.

A more accurate assessment of the ranges of the radiotagged wolves
requires an individual discussion for each.

_No. 1051._--The range of 1051 was composed basically of three distinct
areas (fig. 19). Within 10 days after being released, the wolf left the
general area of his capture (Area A near Isabella Lake) and traveled to
Area B along Highway 1, some 17 miles to the southwest. From December 9
to January 4 wolf 1051 remained in Area B, which covers about 45 square
miles. Between January 4 and 6 he returned to Area A and stayed in 13
square miles until February 3. Between February 3 and 5 he shifted to
Area C east of Snowbank Lake, 11 miles northwest of Area A. He remained
in that 16-square-mile area until February 25, then suddenly left and
headed 8 miles to the northeast.


_Table 5.--Extent of ranges used by radiotagged wolves_

+--------+----------+----------+--------------+----------------------+
|  Wolf  | Greatest | Greatest | Total area[9]|Area[9] of intense use|
| number |  length  |  width   |              |  (before late Feb.)  |
+--------+----------+----------+--------------+----------------------+
|          _Miles_    _Miles_     _Sq. miles_    _Sq. miles_         |
|                                                                    |
|1051[10]   28.5       13.6          318          13 (Location A[11])|
|                                                 45 (Location B)    |
|                                                 16 (Location C)    |
|1053       31.1       22.0          392          31                 |
|1055       55.4       24.9          997          40                 |
|1057       32.3        3.8           77          14                 |
|1059[12]    8.4        8.0           43          39                 |
+--------+----------+----------+--------------+----------------------+

FOOTNOTES:

[9] Minimum area method (Mohr 1947).

[10] Before dispersal.

[11] See text and figure 19.

[12] Pack of five.


[Illustration: _Figure 19.--Locations and range of wolf 1051. Lines are
NOT travel routes; rather they merely indicate sequence of locations.
Only selected lakes are shown._]

From February 26 until April 24 the movements of 1051 were strongly
indicative of dispersal (fig. 20). His average weekly straight line
move during that period was 25 miles (compared with 6 miles per week
before this period), and until March 14 he maintained an almost
straight south-southwest heading to a location west of the town of
Castle Danger. After that the animal traveled a series of
northwest-southwest alternations that on April 3 took him east of Big
Sandy Lake to a point 129 miles southwest of where he had begun the
dispersal. There he remained for about 2 weeks, but between April 17
and 24 he traveled 26 miles northwest. We last saw him at 3:30 p.m. on
April 24 heading northwest through a swamp 15 miles southeast of Grand
Rapids, approximately 122 miles from where he had started. The total of
straight line distances between 16 consecutive pairs of locations taken
at intervals of from 1 to 8 days was 226 miles, which is the minimum
distance the wolf traveled during his dispersal.

[Illustration: _Figure 20.--Dispersal of wolf 1051. Lines merely
indicate sequence of locations. Only selected lakes are shown._]

We observed 1051 for distances of up to 5 miles during these travels;
he maintained a steady trot that seemed faster than usual, and he
appeared intent on heading in a straight line. He did chase deer
during his travels, and twice was seen feeding on carcasses. In the
area where he remained for about 2 weeks, he was twice seen closely
associated with another wolf. This relationship will be discussed
later.

An extensive search was made for 1051's signals on May 2 in an area of
at least 50 miles radius from his last known location, but it was
unsuccessful. On each subsequent tracking flight, the wolf's frequency
was also monitored with no success. Possible explanations for the loss
of the signal from this wolf include the following: (1) premature
expiration of the transmitter, (2) capture of the wolf and breakage of
the transmitter, (3) loss of the exposed antenna and consequent
reduction of range, and (4) travel of the wolf out of range of the
tracking aircraft.

During 1051's travels a number of interesting events took place:

     Nov. 27, 1968--Captured and radiotagged

     Dec. 4, 1968--Crossed road in front of tracking truck

     Dec. 8, 1968--Moved to Area B

     Dec. 9, 1968--Surprised on the ground at distance of 35 feet

     Dec. 18, 1968--Chased by loggers with axes

     Dec. 25, 1968--Almost shot by trapper who saw collar and
     withheld fire

     Jan. 5, 1969--Returned to Area A

     Jan. 13, 1969--"Bumped" twice on logging road by loggers in
     auto but no apparent injury

     Feb. 4, 1969--Moved to Area C

     Feb. 26, 1969--Began long-range southwest movement
     considered to be dispersal

     Mar. 14, 1969--Seen feeding on old carcass within 200 yards
     of houses, dogs, and a man walking

     Mar. 27, 1969--Chased two deer across 4-lane State highway
     53

     Apr. 3, 1969--Found with another wolf at point farthest
     south in his range

     Apr. 24, 1969--Last contact with this animal; was seen
     traveling NW

_Wolf 1053._--This wolf was basically a scavenger who subsisted for
long periods on the remains of old carcasses. She was known to have
visited the remains of at least four deer and three moose, and she
stayed near one moose carcass from February 8 to 20, at least during
the day. Between her date of capture, December 10, and February 28,
1053 traveled about in an area of 31 square miles in the Arrow
Lake-Maniwaki Lake region (fig. 21).

[Illustration: _Figure 21.--Locations and range of wolf 1053. Only
selected lakes are shown._]

Between February 28 and March 6 she suddenly moved 13 miles to the
east-southeast near the Sawbill Trail, and during the next week she
traveled a straight line distance of 24 miles southwest to a point
southeast of the town of Isabella. Her subsequent travels eventually
took her over a much larger area. Before February 28, 1053's average
weekly straight line distance was 2 miles, but after that date it
increased to 11 miles.

_Wolf 1055._--The range of this animal from January 5, when she was
captured, to February 23 covered about 40 square miles near Stony Lake,
Slate Lake, and the Jack Pine Lookout Tower (fig. 22), and her mean
weekly distance was 4 miles. Between February 23 and 24, however, she
traveled 13 miles northeastward, the beginning of a series of long
moves. By March 5, 1055 had reached Crescent Lake, a point 39 miles
east-northeast of her previous area of intensive use. She then
gradually headed back toward the west and south during the next 10 days
and within the next month repeated this pattern. When her signal was
heard last on May 30, 1055 was near Martin Landing in the center of her
range. Her mean net weekly distance after February 23 had increased to
22 miles.

[Illustration: _Figure 22.--Locations and range of wolf 1055. Only
selected lakes are shown._]

_Wolf 1057._--The movements of 1057 cannot be considered normal
because freezing of a front foot prevented her accompanying the pack of
which she was a member. Nevertheless, even data from an abnormal animal
can provide some information. On January 13, 5 days after capture and
release on Red Rock Lake, 1057 was located 4 miles from the capture
point with a pack of 10 other wolves. She was limping and fell behind
when they moved. Five days later she was again seen with the pack 12
miles away between Knife Lake and Kekekabic Lake. She then remained in
about 14 square miles of that general area through April 17 (fig. 23).

[Illustration: _Figure 23.--Locations and range of wolf 1057. Only
selected lakes are shown._]

Suddenly on April 24, 1057 was found in Ontario some 31 miles northeast
of her location of the previous week. That was the last time we heard
her signal even though on May 2 we scanned an area with a radius of 35
miles from her last known location and listened for her signal during
every subsequent flight.

_Wolf 1059._--This animal was a member of a pack of three to five
wolves (see next section). The movements of the group varied little and
were concentrated in the August Lake, Omaday Lake, and Keeley Creek
area in about 43 square miles (fig. 24). Contrary to animals 1051,
1053, and 1055, this pack did not suddenly begin a series of longer
weekly movements in late February. Both before and after February 28,
the average weekly straight line movement of the pack was just less
than 3 miles.

[Illustration: _Figure 24.--Location and range of wolf 1059 and pack.
Only selected lakes are shown._]

Probably these animals did begin traveling more in late February, for
their net daily distances did increase at that time along with those of
the other wolves (table 4). However, the increased travel took place
within the restricted area of the pack's usual range rather than in new
areas as occurred with the other wolves.

Because 1059 was later found to have bred and carried five fetuses, her
movements during whelping season (late April and early May) are of
interest. Her locations on both April 24 and May 2 were within 250
yards of each other, which might indicate that she was denning. On May
9, however, she was 2.5 miles east of these locations, on the 17th and
21st was 2 miles west of them, and on the 30th was 3 miles north of
them.

In early January 1970, Wolf 1059 was killed by a trapper in the
southeast corner of her pack's 1969 range.

_Summer locations._--Signals from only 1053 and 1059 were heard during
summer, and then tracking attempts were made only on June 28, July 29,
and August 29. Locations for 1053 on those occasions were near Kelly
Landing and Isabella Lake, within her previous range. Wolf 1059 was
found each time within 2 miles outside of the southwest corner of the
pack's winter and spring range.


Wolf Associations, Social Behavior, and Reproduction

In our study area, population units of wolves exist as both single
animals (lone wolves) and packs. In a total of 77 observations, lone
wolves constituted 32 percent of the sightings (fig. 25), with packs of
from 2 to 13 members making up the remainder (Table 1). On the basis of
the number of wolves seen, rather than the number of observations,
lone wolves accounted for only 25 (8 percent) out of 323.

[Illustration: _Figure 25.--Only 8 percent of the wolves observed were
lone wolves. (Photo courtesy of L. D. Frenzel.)_]

These figures compare favorably with reports in the literature as
summarized by Mech (1970). In five areas studied, lone wolves made up
from 24 to 60 percent of the observations of population units, and from
8 to 28 percent of the wolves seen. In our study area during 1948 to
1953, lone wolves constituted 43 percent of the observations and 15
percent of the wolves (Stenlund 1955).

The average size of the population units observed during our study
(total number of wolves seen divided by the number of observations) was
4.2, which is significantly larger (95 percent level) than the average
seen in this area (2.8) from 1948 to 1953. This is also larger than
that reported from any other area of comparable size (table 6).


_Table 6.--Mean sizes of wolf population units reported from various
areas_

---------+------------+--------+------------+---------+---------------
         |            |        |Mean size of| Largest |   Authority
  Area   |Observations| Wolves | population |pack size|calculated from
         |            |        |    unit    |         |
---------+------------+--------+------------+---------+---------------
            _Number_   _Number_

Alaska         310      1,041        3.4         12    Kelly 1954
Alaska       1,268      4,823        3.8         21    R. A. Rausch[13]
Lapland        118        311        2.5         12    Pulliainen 1965
E. Finland     460        984        2.1         12    Pulliainen 1965
Minnesota      112        318        2.8         12    Stenlund 1955
Minnesota       77        323        4.2         13    Present study
----------------------------------------------------------------------

FOOTNOTES:

[13] R. A. Rausch. Personal correspondence to L. D. Mech, 1967.


The largest pack seen in our study area included 13 members, and there
apparently were at least two such packs. Although larger packs than
this have been reported, any group containing more than 8 to 10 members
is unusually large (Mech 1970).

Wolf sociology is a complex subject and is still not well understood,
so the following detailed observations of the associations between our
radiotagged wolves and others are given. Associations are defined as
relationships in which two or more wolves relate in a close, positive
manner.

As mentioned earlier, 1051 may or may not have been associated with
other wolves when he was captured. However, although this animal was
observed 55 times throughout winter and spring, only twice was he seen
associating with another wolf. Probably the same individual was
involved each time, because the location was about the same (the
vicinity of the juncture of Aitkin, Carlton, and St. Louis Counties).

The first occasion was on April 3. Wolf 1051 in the previous week had
moved 46 miles straight line distance from the northeast. He was then
observed lying peacefully within 15 feet of another wolf near a freshly
killed deer. The very proximity of the two animals implied a positive
relationship. On April 7, 10 and 14, 1051 was seen 1 mile, 10 miles,
and 8 miles from the kill and was alone each time.

However, on April 17, 1051 was back in the general vicinity of the
kill, and he and another wolf were resting on an open hillside about
100 feet from each other. As we descended for a closer look, the
smaller animal arose and headed to the larger, presumably 1051 because
he had not been disturbed by the aircraft. The larger wolf did not
arise for several seconds, but eventually followed the other into the
woods. No tail raising or other expressive posturing was seen in either
wolf. One week later 1051 was 26 miles northwest of the kill traveling
alone.

Wolf 1053 was never seen less than 80 yards from another wolf, and
there was no evidence that she ever associated with a conspecific. Even
when she was seen 80 yards from the other wolf, both were resting, and
when the strange wolf left, 1053 made no attempt to accompany or follow
it.

No. 1055 apparently had been traveling with another wolf when caught on
January 5, and tracks showed that the individual had remained near her
until we arrived to handle her. Tracks found on January 7 and 10
suggested that 1055 was with another animal, but that animal was not
seen during any of the six times 1055 was observed through February 1.
However, from February 5 to 19, 1055 was with another wolf on eight of
the 12 times she was seen. The two animals were observed resting,
traveling, hunting, and feeding together. On February 20, and
thereafter, 1055 was alone all 14 times she was seen.

It is possible that 1055's associate was killed between February 19 and
20. About March 6, a 63-pound male wolf pup was found dead (by Mr.
Charles Wick, USDA Forest Service) within about 50 feet of a highway
and less than a mile from where 1055 and her associate were seen on
February 19. Because of the snow conditions, it was judged that the
wolf had been killed (probably by an automobile) sometime in February.

Wolf 1057, whose foot froze during capture, was a member of a pack of
10 to 13 wolves, and was seen with the pack on January 13 and 18. After
that she was usually found alone, although on at least five occasions
she was with one or more wolves:

                 _No. of_
_Period_      _observations_  _Associations_

Jan. 13              1        10 other wolves
Jan. 14-17           1        None
Jan. 18              1        10 or 11 other wolves
Jan. 19-29           2        None
Jan. 30              1        1 other wolf
Jan. 31 to Feb. 2    2        None
Feb. 3-4             2        2 other wolves
Feb. 5               1        1 other wolf
Feb. 6-13            6        None
Feb. 14              1        3 other wolves
Feb. 15-22           5        None
Feb. 23              1        10 to 13 other wolves
Feb. 24 to Apr. 24   6        None

February 23 she was with the pack at a kill in her usual area, and
although the pack left that night, 1057 remained near the kill the next
day. Presumably this animal would have traveled with pack if she could
have.

No. 1059 was part of a pack that included three to five members (fig.
26). From January 25, the first time she was observed after release,
through April 2, the animal was seen 19 times with two other wolves,
eight times with at least three others, and eight times with four
others. She was never seen alone until April 17; both times after this
when she was seen, May 9 and 21, 1059 was also alone.

Some insight into the fluctuating size of this pack was obtained on
February 27 when the five animals were followed for 2 hours. During
that time two members (one of which was larger than the other) often
lagged behind the other three by as much as a mile. These two romped
and played considerably, with one carrying a stick or a bone part of
the time. Eventually they caught up again to the other three. The
behavior of the two lagging wolves would be consistent with the
hypothesis that they were either pups or a courting pair of adults. In
either case, they seemed to be an actual part of the pack even though
they temporarily traveled separately.

[Illustration: _Figure 26.--One of the radiotagged wolves was a member
of this pack of five. (Photo courtesy of L. D. Mech.)_]

The fact that 1059 was observed traveling alone three times from April
17 to May 21 may be further evidence that the pack had a den in the
area at that time. The presence of a den allows individual pack members
to venture off singly and return each day to a known social center, as
Murie (1944) observed, so they do not need to travel with each other to
maintain social bonds. Wolves in our area breed during the latter half
of February (see below), and the young should be born in the latter
half of April. Since dens are prepared a few weeks in advance (Young
1944), pack members might be expected to begin traveling singly in
mid-April.

Some information on social relations within our radiotagged pack of
five was also obtained. One of the members could often be
distinguished from the others by its reddish cast and this individual
appeared to be the pack leader or alpha male (Schenkel 1947). In
urinating, this animal lifted his leg, a position seen almost
exclusively in males. Except for only two temporary occasions, this
animal always headed the pack, which usually traveled single file. The
second wolf in line generally was noticeably small, possible a female,
and the third wolf was twice identified as 1059 on the basis of
sightings of her collar.

The leader often gained a lead on the other wolves, especially during a
chase (see below), much as reported for a lead wolf on Isle Royale
(Mech 1966a). Upon returning to the lagging members of the pack, this
animal usually held his tail vertically, an expression of social
dominance (Schenkel 1947). On two occasions he led chases against
strange wolves and demonstrated the highest motivation (see below).

The leader was also the most active in his reactions when scent posts
were encountered. Because the function of scent-marking behavior is
still unknown, it is important that detailed descriptions of the
natural behavior of free-ranging wolves around scent posts be made
available (fig. 27). Thus the following excerpt from field notes by
Mech dated February 27, 1969, is presented:

[Illustration: _Figure 27.--Feces, urine, and scratching in a
conspicuous spot indicate a wolf "scent post." (Photo courtesy of
L. D. Mech.)_]

     "When they [the three wolves] came to a small frozen pond,
     where the wolf trail [which they had been following]
     branched and there were some packed down areas, they became
     quite excited [fig. 28]. This was especially true of the
     reddish wolf. He nosed several spots, and scratched around
     them. Usually his tail was vertical. He defecated at one
     spot, and right afterwards another wolf did. After about 2
     minutes that pack went on.

[Illustration: _Figure 28.--A pack of wolves investigating a scent
post. The raised tails indicate their excitement. (Photo courtesy of
L. D. Mech.)_]

     "About 15 minutes later the 2 'satellite' wolves arrived at
     this spot, hesitated, nosed around but continued on after
     less than a minute.

     "The three wolves meanwhile came to a junction of 2 logging
     roads. There they nosed around, scratched, and acted much as
     described above. Again the reddish wolf was most active and
     had its tail up.

     "When the last 2 wolves came to this spot, they nosed
     around, ran back and forth, and 1 defecated. They then
     headed on a different branch of the trail than the first 3
     had gone on just 10 minutes before.

     "The first 3 wolves meanwhile were running along a logging
     road but eventually they circled and one other than the
     reddish one headed across a swamp toward the last 2. Then
     the reddish one and the other followed this one, and they
     met the last 2 on a ridge. There was the usual tail wagging,
     then all headed off together in a new direction. They passed
     the first scent post again and there was some nosing by the
     reddish wolf but little hesitation.

     "When they traveled, one wolf lagged behind by 150 yards.
     The wolf just ahead of it had its tail vertical part of the
     time, as did the reddish leader.

     "Soon the pack came upon another area packed with wolf
     tracks on a pond. There they followed every little trail,
     nose to the ground, wagged tails, grouped together often,
     chased each other, rolled over, etc. for 6 minutes. The
     reddish animal had tail up most of the time.

     "The wolves continued on, and we left them about 1 mile S.W.
     of the S.W. arm of Bald Eagle Lake [at 6:05 p.m.]."

Unfortunately it was not known whether the trails that the wolves were
following were their own or those made by other wolves.

Significant aspects of the above observation are (1) the spirited
initiative of the leader, (2) the amount of time spent in scratching,
urinating, and defecating, (3) the decision of the last two wolves to
take a different route from that of the first three even though their
goal seemed to be to catch up to the first three, and (4) the fact that
the scent posts were located at trail junctions. In the last regard, we
often noted from the ground that wolves urinated at the junction of
newly formed human trails heading perpendicularly from roads they were
following.

Copulation in wolves was only observed once during our study, on
February 19, 1969. Two members of a group of four were seen coupled for
2 minutes on Kekekabic Lake. On Isle Royale, which is at the same
latitude, copulations were witnessed on February 21, 24 and 27 (Mech
1966a).

On April 17, a den west of Big Moose Lake known to have been used at
least intermittently for 13 years was seen from the air to have fresh
activity of some kind in the snow in front of it, and on April 24 we
saw a wolf at the mound. A few days later, two local human residents
unaware of our interests approached this den and looked in. An adult
wolf, presumably the bitch, leaped over their heads and fled the area.
The men then dug up the den and removed six pups whose eyes had not yet
opened.


Intraspecific Intolerance and Indifference

Instances of chasing or attack by a pack of wolves on conspecifics not
a part of their group have been described by Murie (1944) and Mech
(1966a). Observations of such behavior are important in trying to
determine conclusively whether or not wolves are territorial. Pimlott
_et al._ (1969, p. 75) wrote "It still is not clear, however, whether
or not their use of range should be defined as territorial." Mech
(1970) summarized the available evidence for territoriality in wolves
and postulated that it may be spatiotemporal such that packs might
avoid each other at any particular point in time but over a long period
might cover the same area at different times. A number of our
observations are pertinent to this question, for we have evidence of
both, tolerance and intolerance between population units of wolves.

Two direct cases of intolerance were observed, both involving the
radiotagged pack and other wolves within the usual range of the pack.
Following is a direct quote from the field notes of Mech:

     "Feb. 7, 1969--about 11:30 a.m.--aerial and visual--1059 and
     2 other wolves traveling overland about halfway between
     Heart L. and August L. (R10W-T61 N. Sect. 17 center). They
     were traveling quickly and intently along a fresh wolf
     trail, with a lighter reddish individual in the lead. The
     other 2 animals were darker colored, and one of them was
     smaller than the other. One of them must have been 1059.

     "We soon found that about half a mile ahead of the pack was
     a dark wolf hurrying away from the three. This animal often
     looked back and ran whenever it encountered good running
     conditions. It soon became obvious that the pack of 3 was
     chasing this individual. Because it [the lone wolf] often
     broke its own trail, the pack gradually gained on this
     animal. The single wolf flushed a deer which ran when the
     wolf was about 75 feet away and floundered in the snow, but
     the wolf continued hurrying on by.

     "Although the deer ran only about 50 yards and stopped, the
     pack of 3 also hurried on by. The single wolf flushed
     another deer, ignored it, and continued by, as did the pack
     of 3. The chase continued for 2 miles as we watched, into
     the N.E. corner of Sect. 18 and then into the N. Central
     part of Sect. 8, and the pack got to within 150 yards of the
     single wolf.

     "However, at this point, the 2 darker members of the pack
     had fallen about 100 yards behind the lead one. The lead
     animal stopped and waited for them, as it had done a few
     times before. It then turned around and headed back to these
     animals. When they met, the reddish animal's tail was held
     vertically and there was much tail wagging by all for about
     1 minute. Then all animals lay down for a minute and then
     went up on a knoll. There was much activity and 'playing' on
     the knoll. (12:10 p.m.)

     "The single wolf continued running and looking back for at
     least another mile. We left at 12:21 p.m.

     "At 4:07 p.m. we saw a single wolf running across a small
     lake and looking behind it about 8 miles N.W. of these
     animals. The creature behaved the same as the one being
     chased today, and we wondered whether it could be the same
     animal."

On February 18, 1969, Ream made a similar observation, as follows
(quoted from his field notes):

     "Got visual sighting on 1059 with 3 other wolves at 11:55
     about a mile west of Omaday Lake and they were running along
     fairly fast on a trail. When we circled a second time we saw
     2 wolves curled up sleeping on a knoll ahead (south) of the
     running pack. We then realized the running wolves were on
     the trail of the sleeping wolves and when the pack of 4 with
     'red' in the lead was about 50 yards from the knoll the 2
     sleeping wolves jumped up and charged away in the opposite
     direction full tilt, and split and went in 2 directions.
     When the pack reached the knoll they started off on the
     trail of the wolf that headed N.E. and then changed and went
     after the one that headed S.W. The reddish wolf was in the
     lead and really picked up the pace. Although the reddish
     wolf seemed to gain on the chased one 3 or 4 times, the pack
     as a whole couldn't catch up, even though the single was
     breaking trail. The reddish wolf, after gaining, always
     stopped and waited for the others or went back to find them.
     They chased this wolf for 2-1/2 to 3 miles, all the way down
     to Highway 1 at a point 3.0 miles from the lab [Kawishiwi
     Field Station, U.S. Forest Service]. There was a dense
     patch, 10-15 acres, of woods just before Highway 1 and we
     lost sight of the chased wolf for a while and also the 4
     when they entered it, but shortly we found that the chased
     one had somehow doubled back and was heading N.E. again. The
     pack was apparently confused for at one point 3 of them were
     wandering back and forth on Highway 1, apparently looking
     for the trail of the chased wolf. Two of these paralleled
     the Highway for a couple hundred yards and then stopped on
     top of a hill, apparently resting. During this chase both
     the single wolf and the pack chased up deer from their route
     of travel and didn't seem to pay much attention to them,
     even though some were really floundering in the deep snow.
     We finally stopped watching all of this at 1:30 p.m. and
     proceeded on our rounds."

On February 21 we also saw a single wolf running and looking behind
several times on Ojibway Lake. Even when it saw a fisherman on the lake
within 1/8 mile, it continued across to the opposite shore seeming most
intent on avoiding whatever was on its trail. Presumably it had also
been chased by a pack.

The cases of tolerance or indifference that we witnessed between wolves
involved our lone animals. On January 27, 1051 was at a kill he had
made the day before, and another wolf was sitting within 100 feet
looking toward the carcass. Eventually the unidentified wolf left
without approaching any closer. A lone wolf was also seen near 1053 in
the general vicinity of a moose carcass, which probably both were
feeding on at different times. Three such observations were made, on
February 10, 15, and 18; and on February 21 another wolf was also seen
near 1053 some 2.5 miles away from the moose carcass. In all cases, the
two animals were 80 to 200 yards apart in open country and must have
been aware of each other's presence.


Hunting, Killing, and Feeding Behavior

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°. 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
--------------------------------------------------------------------------
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
--------------------------------------------------------------------------

FOOTNOTES:

[14] Kill rate per wolf.

[15] Figures for this animal are so low because she was basically a
scavenger.

[16] Average kill rate per wolf for all radiotagged wolves and their
associates, derived by dividing total number of wolf-days by total
number of kills.

[17] Average number of days that each wolf spent at each kill, derived
by dividing total number of wolf-days spent feeding by the total number
of kills.

[18] This figure probably is the closest to the actual kill rate during
most winters.


Therefore it is probable that the kill rate per wolf for members of the
pack of five is much closer to the usual average winter kill rate. It
can still be considered higher than the usual winter rate, however,
because this pack also was leaving some of its kills partly uneaten.

A reasonable approximation of the average kill rate during most winters
would be the rate found for our radiotagged wolves before February 1,
because the relations among the wolves, the deer, and the snow during
that period were not unlike those of most winters. The average kill
rate per wolf before February 1 was estimated at one deer per 15.7 to
20.3 days.

After this period, the rate increased to about one deer per 8.4 to 11.6
days, and an estimated 50 percent of the available food was left
uneaten (see Mech _et al._, page 51). This implies that the kill rate
during February and March was about twice as high as usual. On this
basis, the usual kill rate would be estimated at one deer per 16.8 to
23.2 days, which checks well with the rate found before February (one
deer per 15.7 to 20.3 days). Thus we feel that an estimated kill rate
of about one deer per 18 days per wolf is a close approximation of the
average kill rate for most winters. This is about 50 percent less than
the kill rate of one deer per 4 days estimated by Stenlund (1955) for
two packs of three wolves (one deer per 12 days per wolf). However, it
compares favorably with the actual kill rate of one deer per wolf per
17.6 days found for a pack of eight wolves in Ontario.[19]

Once the average rate of kill is known, the average food consumption
per wolf can be calculated. The average deer (considering both fawns
and adults) from the Superior National Forest during winter weighs
about 113 pounds (calculated from Erickson _et al._ 1961), and an
arbitrary 13 pounds can be deducted from this for inedible portions.
This leaves 100 pounds of deer per wolf per 18 days, or 5.6 pounds per
wolf per day. This figure is much less than the 10 to 14 pounds
estimated consumption rate for wolves feeding on moose on Isle Royale
(Mech 1966a). However, much variation can be expected in an animal
whose physiology must be adapted to a feast-or-famine existence.

Wolves can be maintained in captivity on 2.5 pounds of meat per day,
and large active dogs (_Canis familiaris_) require 3.7 pounds per day,
so it is likely that the minimum daily requirement for wolves in the
wild is about 4.0 pounds per day (Mech 1970). This figure agrees well
with the estimated consumption rate for our study area.

FOOTNOTES:

[19] _Kolenosky, G. B. Wolf movements, activities and predation impact
on a wintering deer population in East-Central Ontario. (Manuscript in
preparation for publication.)_


Relative Population Density

Censusing wolves in a 1.5-million-acre study area is a difficult task,
and we have no direct information on which to base a population
estimate. However, some deductions can be made about the relative
population densities in our study area between the period 1948 to 1953
and the period of the present study, 1967 to 1969.

R. A. Rausch (1967a) hypothesized that the frequency of large packs is
higher when population density is high, and presented evidence
supporting this idea. On this assumption, a comparison of pack-size
distributions between various periods can indicate relative population
densities between periods. The advantage of this method is that it
eliminates the usual type of year-to-year biases in wolf censuses such
as might result from differences in precise census route, type of
aircraft, skill of observers, and other conditions. Only a difference
that would cause a bias in the _size_ of the packs seen would be of
importance.

Therefore, we tested the difference in size distributions of population
units between the 1948-53 study period and the present period (table
1), using a Kolmogorov-Smirnov two-sample test (Siegel 1956). The
average "pack" size in the earlier years was 2.8, compared with 4.2 at
present; thus pack sizes are significantly larger at present (95
percent level). This indicates that the population density from 1967 to
1969 may have been higher than from 1948 to 1953. This apparent change
may be attributable to a reduction in snaring, trapping, and aerial
hunting that took place between the two periods as a result of changes
in State game regulations.

A similar comparison between our observations from 1967 and those from
1968-69 (table 1) shows no significant difference between these years,
so it appears that the density of wolves in our area has remained about
the same over the period of three winters. This agrees with the results
of several other studies summarized by Mech (1970) in which wolf
populations unaffected by man have been found to remain relatively
stable from year to year.


DISCUSSION AND CONCLUSIONS

The movements, behavior, and ecology of the wolves in our study area
during winter are variable, and are influenced considerably by snow
conditions. This may explain the fact that in late February 1969 wolves
1051, 1053, and 1055 suddenly extended their travels and range (fig.
F-34 and table 4).

However, increased travel may have resulted from other factors. For one
thing, the wolves apparently did not need to spend so much time hunting
as before. Because of the deep snow, the ability of wolves to capture
deer increased, and the animals had a surplus of food. Perhaps under
such conditions wolves may use more of their energy for traveling than
for hunting.

[Illustration: _Figure 34.--Net weekly (straight-line) distances
traveled by three radiotagged wolves._]

In this respect it is interesting that 1051 moved right out of his area
and traveled into country that presumably was unknown to him. Wolves
1053 and 1055 each ventured into an area that was almost devoid of deer
and that even had few moose in it. Without sufficient fat reserves in
all these animals, it would seem disadvantageous for them to have made
these travels.

Evidently wolves can obtain enough food in much smaller areas than
these three animals used after February. Both 1059's pack of five and
1057 lived in relatively small areas throughout the winter and seemed
to survive well. Before late February, 1051, 1053, and 1055 did also.
Thus some factor other than food must have influenced the movements of
these three animals from late February through April.

The fact that the increased movement began during the breeding season
makes one suspect a relationship between the two. One possibility is
that the factors increasing the hormonal flow associated with breeding
in adults stimulate a hormone output in immature or subordinate
individuals that causes an increase in their movements. An alternative
is that the breeding behavior of resident packs involves the beginning
of, or an increase in, aggression toward neighboring nonmembers. This
might force the lone animals to shift about over large areas in
avoidance of such aggression.

Whatever the cause of the changes in movements of these animals, the
fact that the pack used a much smaller area than any of the lone wolves
may be of central importance in trying to understand the organization
of the wolf population. The following pieces of information are also
pertinent to such an understanding: (1) the pack, which can be presumed
to include a breeding pair (Mech 1970), chased other wolves in its
area; (2) the lone wolves, which apparently did not breed, were
tolerant of, or indifferent to, other lone wolves in their areas; (3)
the ranges of the lone wolves overlapped considerably (fig. 35); (4)
the lone wolves seemed to avoid certain large areas that one might
logically think would have been visited by them (fig. 35); and (5)
packs of wolves were sometimes observed in these large areas (fig. 35).

[Illustration: _Figure 35.--Locations of all radiotagged wolves and
unmarked packs observed during winter 1968-69, except dispersal of 1051
out of the study area. Only selected lakes shown._]

From the above information it can be hypothesized that the wolf
population consists basically of groups of breeding packs defending
territories of limited size, with lone wolves and other nonbreeding
population units that are tolerant of each other shifting about in much
larger nonexclusive areas among these territories. The information from
Isle Royale (Mech 1966a, Jordan _et al._ 1967) is consistent with
this idea, but the area of that island (210 square miles) is too small
to allow untested extrapolations to be made about spacing in much
larger wolf populations. Data from Algonquin Park, Ontario (Pimlott _et
al._ 1969) also strongly suggest this hypothesis. However, the packs
studied there could not be identified with certainty, and little
information was obtained about nonbreeding population units.

To test the proposed hypothesis with certainty, a larger number of
identifiable breeding and nonbreeding population units from the same
general area must be followed during at least one winter. This will be
the main objective of our next study.


SUMMARY

During the winters of 1966-67, 1967-68, and 1968-69, aerial
observations of timber wolves (_Canis lupus_) were made in the Superior
National Forest in northeastern Minnesota, where the primary prey is
white-tailed deer (_Odocoileus virginianus_). In 480 hours of flying
during the study, 77 sightings involving 323 wolves were made. In
addition, during 1968-69, five radiotagged wolves and their associates
were tracked via receivers in aircraft for a total of 570 "wolf-days."
Visual observations were made during 65 percent of the times the wolves
were located from December through April.

The average size of each population unit (including single wolves,
pairs, and packs) observed was 4.2, although packs of as many as 13
wolves were sighted. Radiotagged wolves spent most of their daylight
hours resting during winter, and when traveling, hunting or feeding
during the day, tended to do so before 11:00 a.m. and after 3:00 p.m.

Considerable variation was discovered in the movement patterns of
individual wolves, with straight line distances between consecutive
daily locations ranging from 0.0 to 12.8 miles, and between weekly
locations, 0.0 to 49.0 miles. A pack of five wolves used a range about
43 square miles in extent, whereas lone wolves covered areas many times
this size. One animal in an apparent dispersal was tracked a straight
line distance of 129 miles between extreme points.

A reddish male wolf was the leader of the pack of five and led two
observed chases after alien wolves in the pack's territory. This
animal was also most active during scent marking by the pack. Lone
wolves were apparently indifferent to other wolves, and thus exclusive
areas, or territories, were not observed among lone wolves.

Hunts involving a total of seven deer were observed and described, and
two successful attacks on deer were interpreted from tracks in the
snow. Wolves generally consumed all the flesh and much of the hair and
bones from kills, except during February and March 1969 when extreme
snow conditions increased the vulnerability of deer to an unusual
degree. At that time kills were found that were partly or totally
uneaten. The kill rate by radiotagged wolves and associates during the
winter of 1968-69, based on 468 wolf-days of data, varied from one deer
per 6.3 days to one per 37.5 days per wolf, with the average being one
deer per 10 to 13 days. The rate was much lower per wolf for members of
the pack of five than for lone wolves, and much lower before February
1, 1969, than after. The average rate of kill during more usual winters
was estimated to be about one deer per 18 days. This is a consumption
rate of about 5.6 pounds of deer per wolf per day.

Indirect evidence based on comparisons of pack-size distributions for
different periods indicates that the wolf density in the study area may
have increased since 1953, but that it has remained the same from 1967
to 1969.

On the basis of data presented in this paper, the following hypothesis
about the organization of the wolf population studied is proposed: The
wolf population consists basically of groups of breeding packs
defending territories of limited size, with lone wolves and other
nonbreeding population units, tolerant of each other, shifting about in
much larger nonexclusive areas among these territories.


ACKNOWLEDGMENTS

This study was supported by Macalester College, the U.S. Bureau of
Sport Fisheries and Wildlife, the USDA Forest Service, the Minnesota
Department of Conservation, and the New York Zoological Society.
Special thanks are due the following for their help and cooperation
with this project: Mr. J. O. Wernham, former Supervisor, Mr. L. T.
Magnus, Wildlife Biologist, numerous District Rangers, and other
supporting personnel of the Superior National Forest, Mr. J. T. Morgan,
North Central Forest Experiment Station; and Mr. S. E. Jorgensen and
Mr. C. E. Faulkner, U.S. Bureau of Sport Fisheries and Wildlife.

Drs. C. T. Cushwa, L. F. Ohmann, Catherine Ream, and D. G. Schneider
aided in the field work. Mr. W. W. Cochran provided advice and
suggestions on the radiotracking technique, Dr. U. S. Seal furnished
the drugs and the advice on their use with wolves, and Mr. R. Himes
contributed significantly in the wolf trapping. Mr. L. Ringham, Ontario
Department of Lands and Forests, granted permission for research
personnel to radiotrack wolves crossing into Quetico Park, Canada.
Numerous students from Macalester College also contributed to the field
effort.

Thanks are also due pilots Robert Hodge, Pat Magie, Ken Bellos, Don
Murray, Jack Burgess, and several others, who along with
pilot-biologist John Winship, expertly flew the aircraft used in the
study.

This report was reviewed by the following biologists: Mr. G. B.
Kolenosky, Dr. P. A. Jordan, Mr. M. H. Stenlund, and Dr. D. L. Allen.

Mr. Wallace C. Dayton, Miss Elizabeth Dayton, and the Quetico-Superior
Foundation, all of Minneapolis, generously contributed funds to support
Mech during the preparation of the paper.


LITERATURE CITED

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Alaska. J. Wildl. Manage. 23: 1-11.

Erickson, A. B., Gunvalson, V. E., Stenlund, M. H., Burcalow, D. W.,
and Blankenship, L. H. 1961. The white-tailed deer of Minnesota. Minn.
Dep. Conserv. Tech. Bull. 5, 64 p.

Fuller, W. A., and Novakowski, N. S. 1955. Wolf control operations,
Wood Buffalo National Park, 1951-1952. Can. Wildl. Serv., Wildl.
Manage. Bull. Ser. 1, No. 11, 23 p.

Goldman, E. A. 1944. The wolves of North America, Part II.
Classification of wolves, p. 389-636. Washington, D. C.: The Amer.
Wildl. Inst.

Jordan, P. A., Shelton, P. C., and Allen, D. L. 1967. Numbers,
turnover, and social structure of the Isle Royale wolf population.
Amer. Zool. 7: 233-252.

Kelly, M. W. 1954. Observations afield on Alaskan wolves. Alaska Sci.
Conf. Proc. 5: 35 (and mimeo).

Kolenosky, G. B., and Johnston, D. H. 1967. Radio-tracking timber
wolves in Ontario. Amer. Zool. 7: 289-303.

Mech, L. D. 1966a. The wolves of Isle Royale. U. S. Nat. Park Serv.
Fauna Ser. 7. 210 p.

Mech, L. D. 1966b. Hunting behavior of timber wolves in Minnesota. J.
Mammal. 47: 347-348.

Mech, L. D. 1970. The wolf: the ecology and behavior of an endangered
species. 389 p. New York: Natural History Press, Doubleday.

Mech, L. D., Kuechle, V. B., Warner, D. W., and Tester, J. R. 1965. A
collar for attaching radio transmitters to rabbits, hares, and
raccoons. J. Wildl. Manage. 29: 898-902.

Mohr, C. O. 1947. Table of equivalent populations of North American
small mammals. Amer. Midl. Nat. 37: 223-249.

Murie, A. 1944. The wolves of Mount McKinley, U. S. Nat. Park Serv.
Fauna Ser. 5, 238 p.

Nellis, C. H. 1968. Some methods for capturing coyotes alive. J. Wildl.
Manage. 32: 402-405.

Ohmann, L. F., and Ream, R. R. 1969 Vegetation studies in the BWCA--a
brief report on plant communities. Naturalist 20(1): 20-29.

Olson, Sigurd F. 1938a. Organization and range of the pack. Ecology 19:
168-170.

Olson, Sigurd F. 1938b. A study in predatory relationship with
particular reference to the wolf. Sci. Mon. 46: 323-336.

Pimlott, D. H., Shannon, J. A., and Kolenosky, G. B. 1969. The ecology
of the timber wolf in Algonquin Provincial Park. Ont. Dep. Lands and
Forests Res. Rep. (Wildlife) 87, 94 p.

Pulliainen, E. 1965. Studies of the wolf (_Canis lupus_ L.) in Finland.
Ann. Zool. Fenn. 2: 215-259.

Rausch, R. A. 1967. Some aspects of the population ecology of wolves,
Alaska. Amer. Zool. 7: 253-265.

Rutter, R. J., and Pimlott, D. H. 1968. The world of the wolf. 202 p.
Philadelphia and N. Y.: J. B. Lippincott Co.

Schenkel, R. 1947. Expression studies of wolves. Behaviour 1: 81-129.
(Translation from German by Agnes Klasson.)

Seal, U. S., and Erickson, A. W. 1969. Phencyclidine hydrochloride
immobilization of the Carnivora and other mammals. Fed. (Symp. Lab.
Anim. Anesthes.) Proc. 28: 1410-1419.

Siegel, S. 1956. Non-parametric statistics for the behavioral sciences.
312 p. New York: McGraw-Hill.

Stenlund, M. H. 1955. A field study of the timber wolf (_Canis lupus_)
on the Superior National Forest, Minnesota. Minn. Dep. Conserv. Tech.
Bull. 4, 55 p.

Young, S. P. 1944. The wolves of North America, Part I. 385 p.
Washington, D. C.: The Amer. Wildl. Inst.



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.

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._]


METHODS

The investigation began in February 1966 and continued through March
1969; the basic objective was to examine as many wolf-killed deer as
possible and compare their ages, sex, and condition with a large sample
of deer from the population at large in the same area. Wolf-kills were
examined only during December through March when they could be found
from the air. Aircraft ranging in size from an Aeronca Champ to a
Cessna 206 were used to fly over frozen lakes at altitudes up to 2,000
feet to locate wolves (fig. 2), wolf tracks, or kills (fig. 3). We
often discovered kills by tracking a wolf pack.

[Illustration: _Figure 2.--Wolves were located from the air, usually on
frozen lakes. (Photo courtesy of L. D. Mech.)_]

[Illustration: _Figure 3.--Wolf-kills were easily spotted from
aircraft. (Photo courtesy of L. D. Mech.)_]

During the winter of 1968-69 this method of finding kills was
supplemented by radiotracking five wolves and their associates via
aircraft (see Mech _et al._, p. 1). The latter technique resulted in
increased discovery of inland kills.

A deer carcass was judged killed by wolves if the death had been
recent, if tracks or other sign indicated that wolves had fed upon it,
and if no other possible cause of death was discovered. Carcasses fed
on by wolves but not clearly identifiable as kills were labeled
"probable" wolf-kills. Although the cause of death of the specimens in
this latter category could not be determined with certainty, there was
no reason to believe other agents were involved.

In addition to the wolf-kills examined by project personnel, data and
lower jaws from deer judged killed by wolves were contributed by other
biologists, game wardens, forest rangers, and others whose competence
was known. Nevertheless, if certain identification of carcasses as
wolf-kills was not possible, the data were relegated to the "probable"
wolf-kill category.

Whenever possible, kills discovered from the air were examined on the
ground (fig. 4). Often only skeletal parts remained, but soft parts
were also examined when available. Femur marrow, heart, lungs, liver,
kidneys, reproductive tracts, and omenta were usually inspected in the
field for fat, parasites, and abnormalities, and the degree of
subcutaneous back fat was also noted. Hoofs and lower legs were
checked, and those showing pathological conditions or abnormalities
were collected and examined by the Veterinary Diagnostic Laboratory of
the University of Minnesota. All lower jaws found were collected, aged,
and examined for dental abnormalities and pathological conditions.

[Illustration: _Figure 4.--As many wolf-killed deer as possible were
examined from the ground. (Photo courtesy of L. D. Mech.)_]

In November 1967 and 1968 hunter-check stations were operated on the
study area (fig. 5), and deer bagged by hunters were field-checked for
age (Severinghaus 1949) and hoof abnormalities. As many lower jaws as
possible were collected from field-checked deer and other deer killed
in the area for age determination and examination for abnormal
dentition.

[Illustration: _Figure 5.--Information about hunter-killed deer in the
study area was obtained through hunter-check stations. (Photo courtesy
of L. D. Frenzel.)_]

An assumption was made that the age structure and incidence of
abnormalities in the sample of hunter-killed deer would be _reasonably
representative_ of those in the population at large, an assumption also
implicit in a similar comparison made by Pimlott _et al._ (1969). In
this respect, the following statements by Maguire and Severinghaus
(1954, p. 109) about deer in New York State are pertinent: "It may be
concluded that, considering the open season as a whole, wariness does
not significantly distort the age composition of the [deer] kill in
relation to that of the corresponding wild population, except possibly
for buck seasons of only 1 or 2 days duration.... A reliable appraisal
of the age composition of the kill by hunting may be obtained through
the operation of roadside checking stations." However, in critically
reviewing the present paper Severinghaus stated that in States such as
Minnesota, with fewer hunters and higher hunter success rates, age
compositions of deer from checking stations may not be the same as
those of wild populations. Reviewers Peek and Downing also made similar
comments.

Nevertheless, for our comparison with wolf-killed deer it is not
necessary that the hunter-kill age structure be exactly representative
of the age structure of the actual deer population. All that is
required is that there be reasonable agreement between the two. The
hunting regulations in our study area allow a 9-day period of taking
deer of any age or sex, and a single hunter may legally shoot as many
deer as he and his party or associates have permits for. Thus there is
no reason for selective hunting, and we feel confident that the age
structure of the hunter-kill in our study area does basically represent
that of the deer herd at large.

Two laboratory techniques were used for determining the ages of deer
from the lower jaws or mandibles--a tooth replacement and wear
technique (Severinghaus 1949) and an incisor-sectioning method (Gilbert
1966). The tooth-wear technique requires only the molariform teeth but
it is more subjective and inaccurate, particularly in older deer (Ryel
_et al._ 1961). Incisor sectioning requires only incisors and appears
to be much more accurate.

However, because the incisors had been lost from many of the
wolf-kills, and because the tooth-wear technique was used at checking
stations, both methods were applied in the laboratory. Mr. David W.
Kuehn (1970) sectioned and aged the incisors. Fortunately there was a
sufficiently large sample of mandibles with molariform teeth and
incisors from both wolf-killed and hunter-killed deer to enable us to
devise a table showing the actual ages (based on incisor-sectioning) of
each of the jaws assigned to various tooth-wear classes. This table was
then used to distribute the ages of specimens that contained only
molariform teeth. For example, because it was found that 37 percent of
the jaws aged 4-1/2 years old by tooth wear were actually 5-1/2 years
old, we assigned 37 percent of the incisorless jaws aged 4-1/2 by tooth
wear to the 5-1/2-year category. Similarly, another conversion chart
comparing field age determinations of hunter-killed deer with ages
based on incisor sectioning of the same jaws was employed to distribute
the ages of field-aged, hunter-killed deer for which jaws or incisors
could not be collected.


RESULTS

We flew a total of 480 hours during this and related research, mainly
during January through March 1967 and December 1968 through March 1969;
about one-third of this time was devoted primarily to searching for
kills. Jaws were examined from 93 wolf-kills and 49 probable
wolf-kills.

[Illustration: _Figure 6.--All hunter-killed deer examined were checked
for age. (Photo courtesy of L. D. Frenzel.)_]

Hunter-check stations yielded information from 335 deer (fig. 6), and
data on 98 additional hunter-killed deer were contributed by other
hunters. Incisors were collected from 82 of 214 hunter-killed deer
checked that were older than yearlings; comparisons were then made
between ages of the deer based on incisor sectioning and those based on
field checks using the wear method. Similarly, incisors were sectioned
from 195 wolf-killed and hunter-killed deer older than yearlings that
had been aged by the tooth-wear method in the laboratory, so that these
two methods could be compared (Kuehn 1970). (Note: incisor-sectioning
is unnecessary for fawns and yearlings because animals of these ages
can be aged objectively by the progress of tooth replacement.)

Because age or sex distributions might differ in the various subsamples
of deer examined during this study, these parameters were compared in
subsamples of both wolf-kills and hunter-kills (table 1). No
significant differences were found in the age or sex structures between
the known wolf-kills and "probable" wolf-kills, so these subsamples
were pooled and considered wolf-kills for all subsequent comparisons.

Three significant differences in sex ratio were found among the
subsamples of wolf-kills: (1) wolves killed more female fawns than male
fawns, but more male adults than female adults (table 2); (2) more of
the adults killed in the hunted area were females, while in the
wilderness more males were taken (table 3); and (3) after January 1969,
when snow was unusually deep, 57 percent of the deer killed were
females, compared with only 38 percent before this date.


_Table 1.--Results of statistical comparisons between various samples
of deer kills from northeastern Minnesota_

%: _percent_

------:-----------:--:------:------------:--------------------:------------
      :           :  :      :            :      Results of    :
      :           :  :      :            :     comparisons:   :
Sample:           :  :Sample:            :--------------------: Direction
size  :Sample     :VS: size :Sample      : [20]Age  :[21]Sex  :    of
      :description:  :      :description :structures:  ratios : difference
------:-----------:--:------:------------:----------:---------:------------
      Wolf-kills:[22]       Wolf-kills:[22]

 93     Known          49    Probable      Nonsig.[23] Nonsig.     --

 42     Jan.-Mar.      83    Dec. 1968-    Nonsig.     Nonsig.     --
        1967                 Mar. 1969

 66     Male           61    Female        Nonsig.       --        --

 50     Wilderness     92    Hunted area   Nonsig.     Nonsig.     --
        area

 41     Adult,         64    Adult,          --        Sig.,    More
        wilderness           hunted area               99%      females in
                                                                hunted area

 96     Lakes[24]      32    Inland        Nonsig.[25] Nonsig.     --

 66     Before         77    After         Nonsig.[26] Sig.,    More females
        Feb. 1969            Jan. 1969                 95%      after Jan.

105     Adults         22    Fawns           --        Sig.,    More female
                                                       95%      fawns

      Hunter-kills:        Hunter-kills:

110     Field aged,   225    Field aged,   Nonsig.     Nonsig.     --
        1967                 1968

335     Field aged     98    Lab. aged     Nonsig.     Nonsig.     --

132     Lab. aged,     79    Lab. aged,    Nonsig.       --        --
        males                females

 89     Field aged,   246    Field aged,     --        Sig.,    More male
        fawns                adults                    95%      adults
---------------------------------------------------------------------------
433   Hunter-kills    142  Wolf-kills      Sig.,         --     Older deer
                                           99%                  in wolf-kill

321   Hunter-kills    118  Wolf-kills      Sig.,         --     Older deer
      excluding            excluding       99%                  in wolf-kill
      fawns                fawns
---------------------------------------------------------------------------

FOOTNOTES:

[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).

FOOTNOTES:

[27] _R. L. Downing. Personal correspondence to L. D. Mech, October 2,
1969_.


_Table 4.--Age and sex distribution of deer killed by wolves
and hunters in northeastern Minnesota_

-------:-------------------------------:-------------------------------
       :       Wolf-killed deer        :        Hunter-killed deer
  Age  :---------------------------:---:---------------------------:---
(years):     Number of:            :   :         Number of:        :
       :Males Females Unknown Total: % :Males Females Unknown Total: %
-------:---------------------------:---:---------------------------:---
Fawns     9     13       2      24   17   54     54      4     112   26
  1+      5      7       1      13    9   63     26      1      90   21
  2+      3      8       5      16   11   42     19      2      63   15
  3+      2      4       2       8    6   47     16      1      64   15
  4+      6      3       4      13    9   32     22      1      55   13
  5+     12      9      --      21   15   15     12      1      28    6
  6+      9      2       1      12    8    3     --     --       3   --
  7+     12      4      --      16   11    7      4     --      11    3
  8+      4      2      --       6    4    5      1     --       6    1
  9+      4      2      --       6    4    1     --     --       1   --
 10+     --      3      --       3    2   --     --     --      --   --
 11+     --      1      --       1 }      --     --     --      --   --
 12+     --     --      --      -- }  4   --     --     --      --   --
 13+     --      1      --       1 }      --     --     --      --   --
 14+     --      2      --       2 }      --     --     --      --   --

Total    66     61      15     142  100  269    154     10     433  100
-----------------------------------------------------------------------


Mandibles from the 142 wolf-killed deer and 259 hunter-killed deer were
examined closely for abnormal dentition (table 5, figs. 8-10) (Mech _et
al._ 1970) and pathological conditions (table 6), and the lower limbs
of 75 wolf-kills and 126 hunter-kills were also checked for
abnormalities and pathology (table 7, fig. 11). Statistical comparison
showed that the incidence of each condition was significantly higher in
the sample from wolf-killed deer (table 8).

Jaw necrosis found in our specimens was similar to that described by
Murie (1944) for Dall sheep and Mech (1966a) for moose. Generally
animals with this condition are old, and ours were no exception.

[Illustration: _Figure 8.--Deciduous first premolar (arrow), usually
not present in deer, was found in specimen M-31._]

[Illustration: _Figure 9.--A permanent first premolar (arrow) was
discovered in M-8._]

[Illustration: _Figure 10.--An extra set of fourth premolars (arrows)
occurred in specimens M-96._]

[Illustration: _Figure 11.--The jaws and legs of kills were inspected
closely for abnormalities. (Photo courtesy of L. D. Frenzel.)_]


_Table 5.--Abnormalities in the mandibular dentition of deer from the
Superior National Forest, Minnesota_

--------:---:-------:--------:-------:--------------------------------
Specimen:   :       :Cause of:Side of:
 number :Sex:Age[28]: death  :jaw[29]:        Abnormality
--------:---:-------:--------:-------:--------------------------------
             _Years_


 M-8      F    3+     Wolves   Right  P_1 present (fig. 9)
                               Left   Normal; no P_1 present outside
                                      or inside jaw

 M-31     F _17 mon._ Wolves   Both   Deciduous P_1 present (fig. 8)
                                      and permanent P_1 present inside
                                      left ramus; right side not
                                      examined internally

 M-45     M   _4+_    Wolves   Right  P_2 rotated 90°
                               Left   P_2 absent

 M-52     M    4+     Wolves   Right  P_2 absent
                               Left   Normal

 M-96     F   _2+_    Hunters  Right  2 permanent P_4s present; both
                                      crooked in orientation (fig. 10)
                               Left   P_2 diagonal; P_3 normal; P_4 below
                                      gumline, pointed posteriorly and
                                      wedged against M_1; appears to have
                                      pushed out original P_4 (fig. 10)

 M-117    M    5+     Hunters  Right  Third column of M_3 reduced

 M-191    M    4+     Wolves   Right  Third column of M_3 absent
                                      although rudimentary root present
                               Left   Third column of M_3 much reduced,
                                      peg-like, and almost separate

 M-225   --    4+     Wolves   Right  P_2 absent
                               Left   P_2 situated diagonally

 M-234    F    5+     Wolves   Right  Third column of M_3 reduced

 M-254    M    2+     Hunters  Right  P_2 slightly crooked in orientation
                               Left   P_2 slanting posteriorly and
                                      crowding P_3

 M-272    M    5+     Hunters  Right  Third column of M_3 reduced,
                                      peg-like, and almost separate
                               Left   Third column of M_3 peg-like and
                                      separated from second column by
                                      4 mm.

 M-296    F    5+     Wolves   Right  Normal
                               Left   Extra permanent P_4 crowding
                                      original P_4; much like M-96

 M-369    M    3+     Hunters  Right  Permanent P_2 still not emerged
                                      but appears to be wedged against
                                      root of P_3
--------:---:-------:--------:-------:--------------------------------

FOOTNOTES:

[28] Based on incisor sectioning method of Gilbert (1966) except that
_underlined_ figures are based on tooth replacement or wear (Severinghaus
1949).

[29] Where only one side is listed, the other was not available.


_Table 6.--Pathological conditions in the lower jaws of deer
killed by wolves or hunters[30]_

--------:---:------:--------:-----------:-----------------------------
Specimen:   :      :Cause of:Approximate:
 number :Sex: Age  :  death :  date of  :       Condition
        :   :      :        :   death   :
--------:---:------:--------:-----------:-----------------------------
            _Years_

 M-70     M   6-1/2  Wolves   Feb. 1968  Lump in left side of mandible
                                         near M_1 and M_2

 M-192    M   7-1/2  Wolves   Jan. 1969  Large lump in left diastema
                                         apparently from healed fracture

 M-206    M   8-1/2  Wolves   Jan. 1969  Light necrosis around base
                                         of teeth

 M-218    M   3-1/2  Wolves   Feb. 1969  Large lump in left diastema
                                         apparently from healed fracture

 M-228    F  11-1/2  Wolves   Mar. 1969  Heavy necrosis around molars
                                         and extending into bone; half
                                         of each M_3 destroyed, both
                                         roots and crown

 M-236    F  14-1/2  Wolves   Feb. 1969  Light necrosis around base
                                         of teeth

 M-402    F  10-1/2  Hunters  Nov. 1968  Heavy necrosis and lumps on
                                         both sides of mandible
--------:---:------:--------:-----------:-----------------------------

FOOTNOTES:

[30] Not including dental abnormalities, which are described in table
5.


The following organs were excised from wolf-killed deer and examined
grossly in the field for parasites and abnormalities (fig. 12): lungs
(six animals, normal); heart (seven animals, normal); liver (four
animals, one small unidentified tapeworm cyst). Twin fetuses were found
in each of two adult does examined.

Twelve deer were checked for body fat in one or all of the following
areas: back (subcutaneous), kidneys, heart, omenta. Of these animals,
seven had large amounts of fat, but five were almost depleted of fat
from these stores. These five were all killed in February or March
1969; three were fawns, and two were yearlings that had not yet shed
their deciduous premolars.

Of 69 animals examined for femur marrow condition, two had fat-depleted
marrow. One was a fawn killed in March 1969 that had not shed its
deciduous first incisors, and the other was a 5-1/2-year-old buck
killed in February 1966.

A fawn and a yearling that had died in February 1969 from unknown
causes also had fat-depleted, marrow. These animals might have been
killed by wolves, for wolves had fed on them. However, they could have
died from malnutrition and been eaten as carrion.


_Table 7.--Pathological conditions in the lower limbs of deer
killed by wolves or hunters_

--------:---:-----:------:--------------------------------------------
        :   :     :Cause :
Specimen:Sex: Age :  of  :        Condition
 number :   :     :death :
--------:---:-----:------:--------------------------------------------
            _Years_

 M-28     M  5-1/2 Wolves Right hind foot: "Old healed ankylosis of
                          the pastern joint ... a spontaneously healed
                          bacterial arthritis with the destroyed joint
                          cavity filled in by solid bone. This deer
                          probably had defective gait"[31] (fig. 14).

 M-29     F  5-1/2 Wolves Front foot: "A 3×4×5 cm. fibrous mass in the
                          subcutis about the digital flexor tendon on
                          the volar surface of the metacarpus. The
                          surface was denuded, ulcerated, and
                          superficially infected by surface bacteria....
                          Probably did detract from the animal's speed
                          of flight"[31] (fig. 15).

 M-37     F  7-1/2 Wolves Hind foot: "Probable that the lesion was at
                          one time an active bacterial bone marrow
                          infection that had eventually fistulated to
                          the skin.... Regional tendons and their
                          sheaths were also present among this
                          inflammation and scarring, and it would be
                          fair to assume that the animal's agility was
                          impaired to some extent."[31]

 M-115    M  4-1/2 Hunter Right front hoof: Broken at tip.

 M-196    F  4-1/2 Wolves Left front foot: "Two severe transverse
                          lacerations on the volar surface. Each was
                          approximately 4 cm. in length. One was
                          located at the margin of the heel, and the
                          other was located several cm. proximad. The
                          more proximal wound had severed the flexon
                          tendons, and the consequent uselessness of
                          the limb was suggested by the splayed toes,
                          the unmarred hoof wall and unworn soles"[32]
                          (fig. 16).

 M-227    M  9-1/2 Wolves Left hind leg: "A diffuse swelling of the
                          distal metatarsal bone, the surface of which
                          was studded with small osteophytic spicules.
                          The major flexor and extensor tendons were
                          forced to assume a convex course over the
                          summits of the dorsal and plantar surfaces
                          of the defect, but the tendon sheaths were
                          clean and the normal wear on soles of the
                          involved toes suggested that functional
                          deficit and pain were probably minimal ...
                          quite certainly a callus from previous
                          fracture"[32] (fig. 17).
--------:---:-----:------:--------------------------------------------
1
FOOTNOTES:

[31] D. M. Barnes. Personal correspondence to L. D. Mech, April 11,
1967.

[32] D. M. Barnes. Undated laboratory report transmitted to L. D. Mech
in 1969.


DISCUSSION AND CONCLUSIONS

It has been established that wolves hunting Dall sheep (Murie 1944),
caribou (Crisler 1956), moose (Mech 1966a), and other species usually
have a low percentage of success. In the case of a pack of 15 wolves
hunting moose on Isle Royale during winter, only 4.6 percent of all the
moose detected by the pack were killed; considering only the moose that
the wolves caught up to or held at bay, the kill rate was 7.6 percent
(Mech 1966a).

What little evidence there is about wolves hunting deer indicates that
the success rate is also low with this prey species, at least in
winter. The senior author has now observed a total of 14 deer being
chased by wolves in northeastern Minnesota, mostly by packs of five,
seven or eight wolves (Mech 1966b, and see Mech _et al._, p. 1). In
only one case (6.7 percent) did the wolves (a pair) succeed in catching
their prey.

Low hunting success rates imply that the circumstances influencing
hunts are seldom favorable enough, or the prey animals encountered are
seldom vulnerable enough for the wolves to succeed. When the evidence
cited earlier that most wolf-killed animals are inferior members of
their populations is considered, the most cogent explanation for the
low hunting success of wolves is that relatively few prey animals are
vulnerable.


_Table 8.--Incidence of various abnormalities and pathological
conditions in wolf-killed deer compared with that in hunter-killed
deer_

#: _Number_
%: _Percent_

---------------------:----------------:----------------:-------------
                     :   Wolf-kills   :  Hunter-kills  :
                     :------:---------:------:---------:   Level of
     Condition       : Deer :  Deer   : Deer :  Deer   : significance
                     :  in  :  with   :  in  :  with   :
                     :sample:condition:sample:condition:
---------------------:------:---------:------:---------:-------------
                        #     #    %     #     #    %         %

Dental abnormalities   142    8   5.6   259    5   1.9    [34]90

Jaw necrosis, lumps,   142    6   4.2   259    1   0.4    [34]95
  or fractures[33]

Pathology of lower      75    5   6.7   126    1   0.8        95
  limbs
---------------------:------:---------:------:---------:-------------

FOOTNOTES:

[33] Two mandibles from wolf-killed deer had large lumps from healed
fractures in the region of the diastemas.

[34] If all dental and jaw abnormalities are pooled, the difference
between the incidence in the wolf-kill sample (9.8 percent) and that in
the hunter-kill (2.3 percent) is significant at the 99 percent level.

[Illustration: _Figure 12.--When internal organs were present in kills,
they were examined in the field. (Photo courtesy of L. D. Mech.)_]


Age Structure

Our data strongly indicate that in northeastern Minnesota wolves prey
much more heavily on the older members of the deer population, at least
during winter (fig. 7). Substantial vulnerability to wolves seems to
begin at about the age of 5 years (fig. 13), because the percentage of
wolf-killed deer in each year class increases from 9 percent for
4-1/2-year-old animals to 15 percent for 5-1/2-year-olds (table 4).
Indeed, 48 percent of the wolf-kills were aged 5-1/2 and over, which
compares favorably with the Ontario figure of 58 percent for these age
classes (Pimlott _et al._ 1969).

[Illustration: _Figure 13.--Relative rates of predation on deer of
various ages, based on comparisons of the ages of wolf-killed deer with
those of a theoretical population (dashed line) and those of the
hunter-killed population. See figure 7._]

These figures assume added significance when compared with a sample of
deer killed by hunters in the same general area (fig. 1). Only 10
percent of the hunter-killed deer were 5-1/2 years old or older, and
the percent killed in each year class dropped off suddenly from 13
percent aged 4-1/2 to 6 percent aged 5-1/2. If the age structure of the
hunter-kill sample is reasonably representative of the age structure of
the population at large, the wolf-kill data show that wolf predation in
our study area during winter has a definite selective effect on the
deer population.

There is no direct way of knowing that the age structure of the
hunter-killed deer represents the age structure of the deer population
at large. However, sampling hunter-kills is the most practical means
available for gaining an index to the age structure of the existing
herd. Further, there are three indirect pieces of evidence indicating
that the hunter-kill sample represents the actual age structure of the
population, just as Maguire and Severinghaus (1954) found in New York.
First, our sample has the basic theoretical form expected of a stable
deer herd; i.e., the youngest year class contained the most members,
and each older cohort included fewer (fig. 7). Second, the age
structure of our sample has the same form as most other deer age
structures from widely diverse areas, (Ontario, Pimlott _et al._ 1969;
southern Minnesota, Erickson _et al._ 1961; Massachusetts, Shaw 1951).
Third, there is no reason to believe that in our area rifle hunting is
especially selective for any particular age classes. In talking with
large numbers of hunters, we have learned that most shoot at any and
all deer they happen to see.

Even if the age structure of the hunter-kill sample did not approximate
that of the actual herd, the comparison of the wolf-kill with the
theoretical population dictates the same conclusion: the rate of kill
of older deer by wolves was several times greater than that of younger
deer, excluding fawns (fig. 13). In any case, if the actual deer
population in our study area had an age structure similar to that of
our sample of wolf-kills (which would be the only age structure that
would contradict our conclusion), its numbers would be declining by
orders of magnitude each year, and there would now be only a remnant
population. Such obviously is not the case.

The only other question that might arise from a comparison of the age
structure of our wolf-killed deer with that of the hunter-killed deer
concerns the area from which each sample was taken. Fifty of our
wolf-kills came from a region almost inaccessible to hunters (fig. 1).
However, the other 92 came from the same general area as the
hunter-kills. Nevertheless, there was no statistically significant
difference in age structure between the wolf-kills from the wilderness
versus those from the hunted area (table 1). This fact also suggests
that the human hunting in the area is relatively light and has little
effect on the age structure of the deer population in the area.

Wolves may also be taking a disproportionately high number of fawns,
although our data do not show this. Nevertheless, there may be a bias
against fawns in our method. It is not unusual to discover the remains
of a wolf-killed deer so completely eaten that there is no indication
left of the animal's age. Because fawns often are only about half the
size of adult deer, and their skeletons have not yet completely
ossified, the chances are better that fawns will be more completely
eaten. Pimlott _et al._ (1969) also recognized this possible bias,
although their data did indicate that wolves were killing a higher
percentage of fawns than occurred in the population.

Our study does support the other conclusion of Pimlott _et al._ (1969),
based on a study of 331 kills, that wolf predation on deer during
winter shows a definite selection for older animals. It does not agree
with the tentative conclusion of Stenlund (1955) that wolves in the
Superior National Forest do not prey disproportionately on old deer.
However, Stenlund's conclusion was based on 36 kills and on the
assumption that only deer at least 7 years old were "old." Deer 5 years
old and older composed 33 percent of Stenlund's sample, a figure
considerably higher than the 10 percent in these age classes in our
hunter-kill sample (table 4). Thus Stenlund's data do not contradict
our conclusion.

The age of 5 years seems to be the beginning of the period of
vulnerability for adult deer. Although 5 years might not seem
especially old, there are two aspects of significance concerning deer
of this age and older. First, they are in the second half of the life
span for most members of the species, and their alertness and ability
to bolt quickly away might be expected to decline. It is of interest in
this regard that Klein and Olson (1960, p. 87) believed 5 years of age
to be "the upper limit of physiological efficiency" of black-tailed
deer (_Odocoileus hemionus_) in Alaska. Second, up to the age of at
least 4-1/2 years, and perhaps beyond, the apparent
weight-load-on-track of deer increases with age (Kelsall 1969). Thus
older deer would sink farther into the snow than younger ones, and
their escape might be slowed and hindered more. For further discussion
of the effect of snow on the vulnerability of deer, see Mech _et al._
(p. 51).


Sex Ratio

Statistical tests comparing a number of subsamples of both wolf-killed
deer and hunter-killed deer showed a series of significantly different
sex ratios (tables 1-3). The ratio of males to females in the fawn
cohort of the hunter-kill, which is probably the most representative of
the actual fawn sex ratio, was even (table 2). With wolf-kills,
however, a significantly higher percentage of females was taken in the
fawn subsample (59 percent) than in the adult subsample (46 percent).
These results compare favorably with those of Stenlund (1955), who
found that from 1948 to 1953 in the same area as the present study 68
percent of 19 sexable fawn wolf-kills were females and 44 percent of 63
sexable adult wolf-kills were females.

If the sex ratio of fawns began even, and more females than males were
killed by wolves, then a higher proportion of males would be left in
the adult population, unless some other mortality factor kills more
male fawns. Thus it is not surprising that in the wilderness area,
where little or no hunting is done, the sex ratio of wolf-kills in the
adult cohort is significantly heavy toward males (71 percent: 29
percent). This was also true of the wolf-kills in Algonquin Provincial
Park, where males made up 57 percent of the total sexable wolf-kill
(Pimlott _et al._ 1969). The latter figure may even have been higher if
calculated for adults alone, for a preponderance of female fawns in the
Algonquin Park data (such as occurred in our and Stenlund's samples)
would tend to obscure the preponderance of males in the adult sample.

The adult subsample of hunter-kills also contained a higher percentage
of males (66 percent : 34 percent). Although this might also reflect
the influence of wolf predation on female fawns, it probably is more a
result of the greater movement of bucks during the hunting season,
which overlaps with the rutting season. Even the sex ratio of adult
deer killed in wolf-free areas shows a preponderance of males (Erickson
_et al._ 1961).

However, it appears that the higher harvest of bucks by human hunters
does markedly affect the sex ratio of the deer population in the hunted
area, for the wolf-kill of adults in that area contained a
significantly higher percentage of does (56 percent) than did the
wolf-kill of adults in the wilderness area (29 percent).

Evidently the hunter harvest is not heavy enough to affect the age
structure of the deer population to any marked degree, for no
significant difference in age structure was found between the wolf-kill
in the hunted area and that in the wilderness area (table 1). This does
not conflict with the conclusion that hunting affects the sex ratio of
the deer herd, because it would take much less to influence a
population characteristic having two classes (sex) than one having 14
(age).

One additional difference in the sex ratio was found between two other
subsamples of the wolf-kill--that is, the wolf-kill before and after an
unusually high snow accumulation, which reached its peak about February
1, 1969 (table 1). Of a total of 77 animals killed before this snow
condition occurred (including those from previous years), 38 percent
were females. Of 44 animals killed after the heavy accumulation, 57
percent were females. One possible explanation for this is that females
may normally be less vulnerable to wolf predation, for Kelsall (1969)
has shown that they probably have a lighter weight-load-on-track than
males. Thus when snow conditions changed greatly, making deer generally
much more vulnerable to wolves (see Mech _et al._, p. 35), a
preponderance of does suddenly might have become available. There is
some evidence that does may be generally less vulnerable under most
conditions, for all seven of our wolf-killed deer over 10 years old
were females, and the oldest was over 14.


Condition of Wolf-Killed Deer

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.

FOOTNOTES:

[35] _C. W. Severinghaus. Unpublished data_.

[Illustration: _Figure 14.--Arthritis in right hind foot of specimen
M-28. (Photo courtesy of University of Minnesota Veterinary Diagnostic
Laboratory.)_]

[Illustration: _Figure 15.--Infection and fibrous mass in a front foot
of specimen M-29. (Photo courtesy of University of Minnesota Veterinary
Diagnostic Laboratory.)_]

[Illustration: _Figure 16.--Injury to left front foot of specimen
M-196. (Photo courtesy of L. D. Mech)._]

[Illustration: _Figure 17.--Healed fracture of left hind leg of
specimen M-227. (Photo courtesy of University of Minnesota Veterinary
Diagnostic Laboratory.)_]


SUMMARY

White-tailed deer (_Odocoileus virginianus_) killed by wolves (_Canis
lupus_) during winter in a relatively unhunted wilderness area and in
an immediately adjacent hunted area of Minnesota were compared with
deer killed by hunters in the same general area, and with a
hypothetical population. Deer killed by wolves were significantly
older. Statistical comparisons also showed the following: (1) hunters
generally killed an even sex ratio of fawns, and a disproportionate
number of adult bucks, (2) wolves took a higher percentage of female
fawns than female adults, a disproportionate number of bucks in the
wilderness area, and a higher percentage of does in the hunted area.
The latter fact evidently reflects the higher hunter success on males
in the hunted area. Significantly higher incidences of abnormalities
and pathological conditions of both mandibles and lower limbs were
found in wolf-killed deer than in hunter-killed deer, and these
conditions are described. It is concluded that wolf predation on
white-tailed deer in the study area during winter generally is
selective in that it tends to remove members of the prey population
that are old, debilitated, or abnormal. Apparently these classes of
deer represent such a small percentage of the population that they are
seldom taken by human hunters.


ACKNOWLEDGMENTS

This study was supported by Macalester College, the New York Zoological
Society, the Minnesota Department of Conservation, the USDA Forest
Service, and the U.S. Bureau of Sport Fisheries and Wildlife. Pilots
Robert Hodge, Pat Magie, John Winship, Jack Burgess, Don Murray, and
Walt Neumann aided substantially in obtaining jaws from wolf-killed
deer. Students from the Macalester College Biology Department and
personnel of the USDA Forest Service and the Minnesota Department of
Conservation helped secure mandibles from both wolf-killed and
hunter-killed deer. The interest of Mr. John E. Peninger and of many
deer hunters in contributing the jaws is also greatly acknowledged.

Mr. David W. Kuehn sectioned the incisors of the deer jaws and
determined their ages. Dr. Donald M. Barnes of the University of
Minnesota Veterinary Diagnostic Laboratory examined the abnormal lower
limbs, described their pathology, and provided photos of specimens used
herein.

Mr. Wallace C. Dayton and Miss Elizabeth Dayton and the
Quetico-Superior Foundation, all of Minneapolis, financed Mech during
the preparation of this paper.

The following individuals read the manuscript and offered many helpful
suggestions: Mr. R. L. Downing, Mr. C. W. Severinghaus, Mr. J. M. Peek,
Dr. C. T. Cushwa, Mr. M. H. Stenlund, and Dr. R. R. Ream.


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Fauna Ser. 5, 238 p.

Pimlott, D. H., Shannon, J. A., and Kolenosky, G. B. 1969. The ecology
of the timber wolf in Algonquin Provincial Park. Ont. Dep. Lands and
Forests Res. Rep. (Wildl.) 87, 92 p.

Ryel, L. A., Fay, L. D., and Van Etten, R. C. 1961. Validity of age
determination in Michigan deer. Mich. Acad. Sci., Art, and Letters 46:
289-316.

Severinghaus, C. W. 1949. Tooth development and wear as criteria of age
in white-tailed deer. J. Wildl. Manage. 13: 195-216.

Severinghaus, C. W. 1955. P. R. Rep. W-28-R-9: Job 1A, April 13, 1955.

Shaw, S. P. 1951. The effect of insufficient harvests on an island deer
herd. N.E. Wildl. Conf. (Mimeo).

Siegel, S. 1956. Non-parametric statistics for the behavioral sciences.
312 p. New York: McGraw-Hill.

Stenlund, M. H. 1955. A field study of the timber wolf (_Canis lupus_)
on the Superior National Forest, Minnesota. Minn. Dep. Conserv. Tech.
Bull. 4, 55 p.



THE EFFECT OF SNOW CONDITIONS ON THE VULNERABILITY OF WHITE-TAILED
DEER TO WOLF PREDATION

L. David Mech, L. D. Frenzel, Jr., and P. D. Karns


Wolves (_Canis lupus_) and deer (_Odocoileus virginianus_) having
evolved together, no doubt have become adapted to contending with each
other's physical abilities. Thus it is not surprising to learn that
deer which succumb to wolf predation are generally weaker, older, or
abnormal compared with the total deer population (Pimlott _et al._
1969, also see Mech and Frenzel, p. 35).

However, the structural and behavioral adaptations of both species must
have evolved under environmental conditions that are average or usual;
otherwise, an adjustment of wolf to deer populations, and vice versa,
could not have been maintained over long periods. This implies that
extreme or unusual conditions might sometimes occur, to which either
the wolf or the deer is poorly adapted.

One of the most important environmental factors that can influence the
interactions of wolves and deer is snow. The total fall, depth on the
ground, and the density are all aspects of snow that may vary
considerably and affect the ability of wolves to capture deer. Recent
studies of wolves and deer in northeastern Minnesota (see Mech _et
al._, p. 1, also Mech and Frenzel, p. 35) afforded us opportunities to
investigate the relationships between snow and the interactions of
wolves and deer.


METHODS

Two principal methods of study were used in this investigation. The
first involved recording the snow depth and support quality
("penetrability") in feet and tenths of feet (Verme 1968). Snow
measurements were taken during the winters of 1966-67, 1967-68, and
1968-69, in which large differences in snow conditions existed. Ten
such measurements were made weekly near Isabella, Minnesota, in an open
aspen (_Populus tremuloides_) stand away from influences that might
have caused drifting or other unusual snow conditions; the measurements
were averaged. Penetrability was determined with Verme's
snow-compaction gauge--a 3-foot piece of 1-1/8-inch (outside diameter)
copper tube filled with lead to total 3 pounds, which gives a weight
per area of 211 gm./cm.^2. To obtain a measurement, the pipe is held
vertically with its lower end just flush with the snow, and then is
released. The depth to which it sinks is considered the penetrability
of the snowpack by a walking deer.

Although the snow conditions measured at Isabella are not
representative of the entire study area, year-to-year comparison in the
Isabella area should also apply generally throughout the region.

The second technique used in this study was observing the movements of
wolves and deer. This was usually done from low-flying aircraft, and
was facilitated by the use of radiotracking, as described by Mech _et
al._ (p. 1). Close inspection of wolf-killed deer was made from the
ground (Mech and Frenzel, p. 35).


RESULTS AND OBSERVATIONS

Snow measurements for each winter are shown in figures 1 through 3. The
winter of 1968-69 was the most extreme of the three in terms of
accumulated snow, and was generally regarded as having one of the
heaviest snowfalls and accumulations on record for the study area. Snow
depth on the level near Isabella reached 3.9 feet at one time, and from
January 3 to April 4 it exceeded 2.4 feet. The highest snow level
reached during 1966-67 was 2.4 feet, and the highest level reached
during 1967-68 was 1.4 feet. In the vicinity of Ely, some 30 miles from
Isabella, the 1968-69 peak accumulation was 39 inches, the highest
accumulation since 1948-49 when records were first kept.[36] Thus we
consider the winters of 1966-67 and 1967-68 to be within the normal
range for the study area, and the 1968-69 winter as being most unusual
(fig. 4).

[Illustration: _Figure 1.--Snow depth and penetrability by deer and
wolves near Isabella, Minnesota, 1966-67._]

[Illustration: _Figure 2.--Snow depth and penetrability by deer and
wolves near Isabella, Minnesota, 1967-68._]

[Illustration: _Figure 3.--Snow depth and penetrability by deer and
wolves near Isabella, Minnesota, 1968-69._]

The snow penetrability in 1966-67 remained high throughout January,
February, and March. During the following winter, penetrability
fluctuated more, but even at its greatest, it was relatively
unimportant to deer because the total snow depth was so low. During
1968-69, however, penetrability was a very important aspect of snow
condition. It was so high during late January and early February, when
snow accumulation was also at its peak, that a walking deer would be
expected to sink in 2.5 to 3.5 feet. Snow penetrability then decreased
through February and March to a point where a walking deer would sink
in approximately 0.6 foot on March 21. However, because snow
accumulation remained so high through February and March, the lower
penetrability during late February and March still afforded no relief
to running deer, because they must exert forces several times as great
as when walking. On the contrary, the low penetrability (which is an
indirect measure of density) could be expected to hinder a running deer
in deep snow, for it would cause much more resistance.

[Illustration: _Figure 4.--During the winter of 1968-69, the snow was
unusually deep in the study area. (Photo courtesy of L. D. Frenzel.)_]

Deer movements, like snow conditions, varied greatly during the three
winters of the study. During the first two winters, deer were generally
found singly and in groups of two to six, often around the shores of
lakes but also scattered about inland. In late January and February
1967, running deer were observed sinking deeply into snow, but their
movements still did not seem to be hindered, no doubt because of the
high penetrability (low density) of the snow that year (fig. 1).

However, during late January, February, and March of 1969 the deer were
much more concentrated, mostly in conifer swamps, along
southwest-facing slopes, or on lakes. Although groups of two or three
animals could be found in scattered inland "pockets" throughout the
winter, groups of five or six were not uncommon on lakes during
January. The tendency to concentrate continued to increase, and on
February 6, as many as 11 deer were observed on one lake; by March 13,
group size had increased to as high as 22 deer in the same area.
Throughout February and March, heavy concentrations of deer tracks
covered most wilderness lakes, further evidencing much greater use of
shorelines than had occurred in the two previous winters (fig. 5).

No doubt deer tended to concentrate on lakes because travel inland
became so difficult. On January 28, two deer were seen plowing through
snow up to their necks. Although the snow began settling in February,
and the penetrability decreased, by late February running deer still
plunged chest-deep and had to hesitate at every bound. These conditions
persisted until about March 26, by which time a surface crust strong
enough to hold a running deer had formed.

[Illustration: _Figure 5.--Under unusually deep snow conditions, deer
used lake shores heavily. (Photo courtesy of L. D. Mech.)_]

In considering wolf mobility in snow, two types of movement must be
recognized: the trot used during general travel, and the bounding used
while chasing prey. The trot is an easy gait of about 5 m.p.h. on firm
footing (Mech 1970), and can be continued for hours at a time. During
periods of deep snow and high penetrability, most wolf travel is on
frozen waterways, roads, snowmobile trails, and animal trails,
including the wolves' own pathways, which become well packed with
frequent use (fig. 6, 7A, B). Such travel was observed during each of
the three winters of this study.

[Illustration: _Figure 6.--Wolves travel single file in deep snow.
(Photo courtesy of L. D. Mech.)_]

[Illustration: _Figure 7.--(A) A single wolf must break his own trail
through the snow. (Photo courtesy of L. D. Frenzel.) (B) Regular use by
a pack keeps trails open. (Photo courtesy of L. D. Mech.)_]

The second type of wolf movement affected by snow is the leaping and
bounding associated with chasing prey. The shallower angle of the
wolf's bound (fig. 8) (compared with that of the deer) often causes the
wolf to flounder in snow that presents little hinderance to deer (Mech
1970). Such was the case in January and February 1967 in our study
area. During 1967-68 no observations of wolves chasing deer were made
by the authors, but reports by other field workers indicated that
running conditions were similar to those of 1967.

[Illustration: _Figure 8.--Wolves run at a shallow angle, thus
hindering them in deep snow. (Photo courtesy of D. H. Pimlott.)_]

During the winter of 1968-69, wolves also bogged down a great deal in
snow when chasing deer. However, after January 1969 the snow was so
deep that deer were floundering even more than wolves in many cases.
The fact that wolves could run in the trail broken by deer probably
also gave the wolves an advantage under the conditions that severely
restricted deer movements.

The above observations of snow conditions, deer movements, and wolf
movements during the three winters of the study are in accord with
observations made on the differences in the ability of the wolves to
capture deer during the same period. Two indices support the conclusion
that wolves had a much easier time catching deer during February and
March 1969 than earlier in the winter and in the two previous winters:
(1) the degree of utilization of wolf-killed deer, and (2) the kill
rate of radiotagged wolves.

During the winters of 1966-67 and 1967-68, and in December and early
January 1968-69, most wolf-killed deer found had been thoroughly eaten,
and the bones--if present at all--were well chewed and scattered at
each kill (fig. 9). All skin and flesh from the skull were eaten, and
the mandible was usually separated from the skull. During late February
and early March 1967, few fresh kills were even found, and wolves were
returning several times to old kills that had been cleaned up many days
before.

[Illustration: _Figure 9.--Usually the remains of a wolf kill are well
chewed and scattered before the wolves abandon them. (Photo courtesy of
L. D. Mech.)_]

[Illustration: _Figure 10.--During a period of especially deep snow,
wolves abandoned many kills before pulling apart the skeletons. (Photo
courtesy of L. D. Mech.)_]

However, in late January 1969 a substantial change began taking place.
The skeletons of most kills found were almost intact, the flesh having
been eaten from around the bones (fig. 10). Appreciably more skin was
usually left on the carcass, especially on the side lying on the snow,
and the neck and head were generally intact. This was true even of
fawns, which in the past often were almost completely consumed.

In several cases, only about half of the flesh had been eaten from the
carcasses. On February 2, 1969, four deer recently killed by wolves
were found along a 1-1/2-mile stretch of Birch Lake and nearby
Polaris Lake (Minnesota-Ontario border). One large doe was completely
uneaten and remained so for at least 24 hours after discovery from the
air. Further, one fawn had only a few pounds of flesh eaten, a yearling
doe was half eaten, and another fawn was about 75 percent eaten.
Hazardous landing conditions during this period severely limited the
number of carcasses that could be examined from the ground, but on
February 6 a yearling doe was discovered that had only about 5 to 10
pounds of flesh eaten, and on February 8 an adult doe was found that
was completely intact except for wounds.

In past winters some kills had been located that had been only partly
eaten, but in each case the carcasses were soon revisited and cleaned
up (Mech 1970). This was often not the case in 1969. For the rest of
the winter most of the deer killed by wolves in our study area were not
as completely consumed as in previous winters. Pimlott _et al._ (1969)
found a similar relationship between the severity of the winter and
the degree to which wolf-killed deer were utilized.

Correlated with the above information was the kill history of our
radiotagged wolves (Mech _et al._, p. 1). From December 1968 through
January 1969 No. 1051 had killed three or possibly four deer, and
generally had spent 6 or 7 days feeding on each. However, throughout
most of February this animal visited a new deer carcass (which
presumably he killed) every 3 days, and he spent only 1 or 2 days at
each. In two cases two new carcasses were found in the immediate
vicinity of this animal during the same day, and in each case the wolf
spent only 1 day in the area. A second wolf (1053) which had spent most
of December and January scavenging on the remains of both deer and
moose (_Alces alces_) that had died long before, made her first known
kill of a deer on January 31, 1969. The kill rate of the other three
radiotagged wolves also increased, although the data for them are less
complete. The average kill rate for all radiotagged wolves and their
associates was one deer per wolf per 16 to 20 days before February 1,
and one per 8 to 12 days after February 1 (see Mech _et al._, p. 1).

FOOTNOTES:

[36] _M. H. Stenlund. Personal correspondence to L. D. Mech, Oct. 10,
1969._


DISCUSSION AND CONCLUSIONS

Under usual snow conditions throughout most of the range of the
white-tailed deer, healthy vigorous individuals can probably escape
most attacks by wolves. Observations by Mech (1966), Rutter and Pimlott
(1968), and Mech _et al._ (p. 1) indicate that a high percentage of
attempts by wolves to kill deer during winter are unsuccessful. This is
further implied by the figures of Pimlott _et al._ (1969) and Mech and
Frenzel (p. 35) showing that at least during winter wolves tend to kill
a disproportionate number of old deer as well as those with various
abnormalities and pathological conditions.

However, during a winter with extremely deep snow, the usual
relationships seem to change somewhat. Fewer deer are able to escape
wolves, and a surplus is killed. This means that some individuals not
vulnerable under the usual snow conditions become vulnerable during
extreme conditions. There are two main possible reasons for this, the
effect of the extreme weather conditions on the health and vigor of the
deer, and the physical effect of the snow on the escapability of the
deer.

In regard to the first possibility, there was limited evidence that
during February and March 1969 some fawns and yearlings in our study
area were losing their fat stores. Two of three yearlings, and both
fawns intact enough for examination during this period lacked back fat,
and the marrow in one of six fawn femurs was partly fat depleted.
Nevertheless, the third yearling inspected still had back fat, and a
3-1/2-year-old doe had heavy omental, renal, heart, and back fat during
the same period. Thus, although an abnormal decline in the physical
condition of some deer in the late winter might partly account for the
increased kill by wolves during February and March 1969, the effect of
snow on the escapability of the deer probably was also involved.

The key difference in snow conditions between the two periods--(1) the
winters of 1966-67, 1967-68, and December-January 1968-69, and (2)
February and March 1969--was the heavy, persisting accumulation of snow
during the latter period, combined with the increasing density of the
snow. As our observations show, this greatly hindered the movements of
deer fleeing from wolves.

Under more usual conditions, a running deer might sink through the snow
to the ground and thus obtain a firm footing from which to spring
again. In discussing wolf-caribou relations in snow, Kelsall (1968, p.
249) stated the following: "While caribou (_Rangifer tarandus_) will
sink into snow even deeper than wolves, their longer legs permit them
to run efficiently where a wolf will bog down. Nasimovich (1955)
considered that roe deer and sika deer could be taken by wolves when
snow was not more than 30 cm. (11.8 inches) in depth. At depths above
that their pursuit becomes difficult or fruitless."

However, it appears that when snow becomes extremely deep, wolves then
gain the advantage. With 22 to 48 inches or more of snow to plow
through, a deer would have trouble even touching a firm foundation.
According to Kelsall (1969), deer measure only 20 to 24 inches from
hoof tip to chest, with legs extended.

It is true that wolves stand even shorter than deer and so might be
expected to flounder even more. However, this is where another factor
becomes important, the "weight-load-on-track" or total weight per area
of track. As Kelsall (1969) has pointed out, the mean
weight-load-on-track for deer is extremely difficult to measure
directly, because the actual under-surface of the deer's foot slants
vertically, and a much greater area may be used to support an animal in
snow than on a hard surface. This probably explains the discrepancy
between Kelsall's measurements and work done by Verme (1968) in
Michigan. According to Kelsall, deer weight-load-on-track (hoof only)
varies between 431 and 1,124 gm./cm.^2. However, Verme stated that
his compaction gauge (with a weight load of about 211 gm./cm.^2,
described earlier in this paper) sank in virtually the same amount in
snow as did deer. Under the snow conditions in our study area, we found
that the same type of compaction gauge generally penetrated to a depth
within a half inch of that to which deer were sinking. On this basis,
it seems reasonable to suggest that a deer in snow is supported by more
of its foot than just the hoof, and that the actual
weight-load-on-track of deer in snow is about 211 gm./cm.^2.

For wolves, this measure varies from 89 to 103 gm./cm.^2 (Foromozov
1946). This means that for the same amount of force applied during
running, a wolf would have twice as much support as a deer. It also
means that in deep snow a walking wolf generally is much less
restricted than a walking deer. Late in February 1969, for example,
when deer were seriously limited in their ability to travel, wolves
were able to travel widely (Mech _et al._, p. 1).

Even though wolves have much greater support than deer, when running
they still sink into the snow almost as much as deer under most
conditions, probably because both run with such force that snow usually
offers little support. Nevertheless, with extremely deep snow, the
difference in support factor between wolves and deer could become
critical, and this is probably what happened during February and March
1969. With deer seriously restrained by the deep snow, even a slight
advantage in favor of the wolf could increase hunting success. A high
snow density during that period would accentuate this advantage. This
is because until the snow becomes dense enough to hold a running deer,
each increase in density would further the advantage of the wolf, which
would require only half the density to support it, while it would
hinder the deer.

One result of the extreme snow conditions of early 1969 was that deer
tended to gravitate to lakes, where snow was shallow and footing was
firm. Initially upon disturbance by human beings, and probably by
wolves, these deer usually headed inland, but it is apparent from a
number of kills examined that when pressed hard by wolves inland, deer
headed out onto lakes where possible. Apparently they could run there
with better footing. However, frozen lakes also provide wolves with
good running conditions, and even seem to give them an advantage
(Rutter and Pimlott 1968, Mech 1970), so many of these deer were killed
(fig. 11).

Stenlund (1955, p. 44) reported as follows on years of low snowfall,
the opposite condition, which demonstrated the same relationship
between snow depth and kills on lakes: "The winters of 1951-52 and
1952-53 were abnormally mild with little early snow. As a result, few
wolf-killed deer appeared on the lakes and most deer attempted to
outrun wolves in the woods."

[Illustration: _Figure 11.--On frozen lakes, wolves often seem to have
the advantage over deer, such as in this case where the wolf (center)
has just killed a deer and is trying to discourage a raven from joining
him in the feed. (Photo courtesy of L. D. Frenzel_.)]

Thus it appears that extreme snow conditions in our study area increase
the vulnerability of deer to wolf predation in three ways: (1) by
causing a decline in the health and nutritional state of some members
of the deer population; (2) by hindering the escapability of the deer;
and (3) by causing deer to congregate on frozen lakes where wolves have
the advantage in running.


SUMMARY

During the winters of 1966-67, 1967-68, and 1968-69, the interactions
of wolves (_Canis lupus_) and white-tailed deer (_Odocoileus
virginianus_) were observed in northeastern Minnesota from aircraft.
Snow depth and supporting ability were also measured during these
winters, and the ability of wolves to capture deer was compared for a
period of usual snow conditions versus a period of extreme snow
conditions.

It was found that during February and March 1969, when snow remained
from 2.5 to 3.9 feet deep and failed to support running deer, wolves
were able to capture deer more easily. This was evidenced by kills that
were left partly or completely uneaten, and by a higher rate of
predation by radiotagged wolves and their associates.

Although both wolves and deer floundered in the extremely deep snow,
the relatively lighter weight-load-on-track of wolves evidently gave
them a greater advantage than under the usual snow conditions, when
wolves were observed floundering more than deer. This factor, plus a
decline in the health and vigor of some segments of the deer population
and a tendency for deer to congregate on frozen lakes, where wolves
have an advantage, help explain the increased vulnerability of deer to
wolf predation during the winters of deep snow.


ACKNOWLEDGMENTS

This study was supported by Macalester College, the Minnesota
Department of Conservation, the USDA Forest Service, the U.S. Bureau of
Sport Fisheries and Wildlife, and the New York Zoological Society.
Pilots John Winship, Pat Magie, Jack Burgess, and Don Murray flew the
observation planes during radiotracking. Miss Elizabeth Dayton, Mr.
Wallace C. Dayton, and the Quetico-Superior Foundation, all of
Minneapolis, financed Mech during the writing of this report.

Thanks are also due L. J. Verme, J. P. Kelsall, and J. M. Peek for
their helpful reviews.


LITERATURE CITED

Foromozov, A. N. 1946. The snow cover as an environment factor and its
importance in the life of mammals and birds. (Moskovskoe obshchestvo
ispytatelei priroda) Materialy k poznaniyu fauny i flory SSSR, Otdel.
Zool. n. 5 (XX). (Translation from Russian published by Boreal
Institute, Univ. Alberta, Edmonton, Alberta.)

Kelsall, J. P. 1968. The caribou. Can. Wildl. Serv. Monog. 3, 340 p.

Kelsall, J. P. 1969. Structural adaptations of moose and deer for snow.
J. Mammal. 50: 302-310.

Mech, L. D. 1966. Hunting behavior of wolves in Minnesota. J. Mammal.
47: 347-348.

Mech, L. D. 1970. The wolf: the ecology and behavior of an endangered
species. 389 p. New York: Natural History Press, Doubleday.

Nasimovich, A. A. 1955. The role of the regime of snow cover in the
life of ungulates in the U.S.S.R. Moskva, Akademiya Nauk SSSR. 403 p.

Pimlott, D. H., Shannon, J. A., and Kolenosky, G. B. 1969. The ecology
of the timber wolf in Algonquin Provincial Park. Out. Dep. Lands and
Forests Res. Rep. (Wildl.) 87, 92 p.

Rutter, R. J., and Pimlott, D. H. 1968. The world of the wolf. 202 p.
Philadelphia and New York: J. B. Lippincott Co.

Stenlund, M. H. 1955. A field study of the timber wolf (_Canis lupus_)
on the Superior National Forest, Minnesota. Minn. Conserv. Dep. Tech.
Bull. 4, 55 p.

Verme, L. J. 1968. An index of winter severity for northern deer. J.
Wildl. Manage. 32: 566-574.



THE POSSIBLE OCCURRENCE OF THE GREAT PLAINS WOLF
IN NORTHEASTERN MINNESOTA

L. David Mech and L. D. Frenzel, Jr.


The timber wolf (_Canis lupus_) of northeastern Minnesota occupies an
area within the range given by Goldman (1944) for the eastern timber
wolf (_C. l. lycaon_ Schreber). However, this area is within 150 miles
of the eastern edge of the former range of the Great Plains wolf (_C.
l. nubilus_ Say), and there is some question as to whether the
Minnesota wolf is really an intergrade between these two subspecies.
Writing of _nubilus_, Goldman (1944, p. 444) stated: "Specimens from
eastern Minnesota and Michigan seem more properly referable to
_lycaon_, but relationship to _nubilus_ is shown in somewhat
intermediate characters."

In describing _lycaon_ as basically a gray wolf, Goldman made no
mention of the occurrence of black or white color phases in that
subspecies. However, in discussing _nubilus_, Goldman (1944, p. 442)
wrote the following: "Many color variations are presented. Individuals
may be nearly white at any season, except for a sprinkling of black
hairs over the back, a small, narrow, but conspicuous, black patch over
the tail gland, and a more or less distinctly black tip. Black
individuals may occur in the same litter with those normally colored."
Goldman also referred to _nubilus_ as "now probably extinct."

[Illustration: _Figure 1.--A few wolves observed in the study area were
jet black. (Photo courtesy of L. D. Mech.)_]

In the eastern part of the range of _lycaon_, color phases other than
gray appear to be rare as Rutter and Pimlott (1969, p. 188) attest:
"The uniformity of the color of timber wolves in many areas is
evidenced by the work in Algonquin Park, in Ontario. There, over the
past eight years, dozens of packs have been observed from the air.
However, we have never been able to discriminate between any of them on
the basis of the color variation of individual animals."

Thus it seems significant to report on incidences of black and white
color phases in wolves that we have observed in northeastern Minnesota
during some 480 hours of flying associated with wolf research (Mech _et
al._, p. 1). The observations took place in the Superior National
Forest, in northern Cook, Lake, and St. Louis Counties during the
winters of 1966-67, 1967-68, and 1968-69. A total of 309 sightings were
made of wolves that could be classified by color; of these, 11 (3.6
percent) were jet black (fig. 1) and two (0.6 percent) were creamish
white, with the cream color the most intense on the back. No doubt some
of the grays, and perhaps the blacks and whites, were repeated
observations, but the figures should provide a reasonable approximation
of the incidence of these color phases in this area. All black or white
animals except one were observed with gray wolves (table 1 and fig. 2).

A number of black wolves, and a few white wolves, have been seen by
other observers, all in the three counties listed earlier. To gain some
idea of the past incidence of these color phases in the same general
area, we asked Conservation Officers Robert Hodge, Robert Jacobsen, and
Frank Baltich of the Ely, Minnesota, area about the numbers of each
phase that they took before 1960. They reported killing an approximate
total of 580 wolves, of which four were black and three were white or
creamish white.


_Table 1.--Observations of wolves of black and white color phases_

+--------------+-------------------------+--------------------------+
|    Date      |      Location           | Color combinations       |
|              |                         | within each pack         |
+--------------+-------------------------+--------------------------+
|Feb. 24, 1967  T64N-R8W-S1 Vera Lake      3 grays; 1 black; 1 white|
|Mar. 4, 1967   T63N-R9W-S27 Lake Two      3 grays; 2 blacks        |
|Dec. 18, 1968  T63N-R8W-S35 Lake Insula   2 grays; 2 blacks[37]    |
|Jan. 17, 1969  T65N-R8W-S27 Carp Lake     1 gray; 1 white          |
|Feb. 1, 1969   T63N-R8W-S13 Lake Insula   4 blacks; 2 grays[38]    |
|Feb. 5, 1969   T63N-R8W-S8 Benezie Lake   1 black                  |
|Feb. 6, 1969   T63N-R10W-S33 Clear Lake   3 grays; 1 black         |
+--------------+-------------------------+--------------------------+
FOOTNOTES:

[37] These animals were near the shore of the lake, so others may have
been inland where they could not be seen.

[38] This group might well have been the same as that seen on Dec. 18,
1968.

[Illustration: _Figure 2.--A pack of four blacks with two grays (first
and third). (Photo courtesy of John Winship.)_]

Because black and white color phases have rarely if ever been reported
for _lycaon_, yet were well known for _nubilus_, it is not unreasonable
to conclude that the race of wolves now occupying northeastern
Minnesota does show strong _nubilus_ influence. Goldman examined the
skulls only of 10 Minnesota specimens assignable to _lycaon_ and only
one referable to _nubilus_. Because wolves in the known range of
_nubilus_ are thought to be extinct, and because the animals in
northeastern Minnesota are legally unprotected and subject to a control
program, it seems highly desirable that the question of their taxonomy
be studied intensively while specimens are still available.


ACKNOWLEDGMENTS

This study was supported by Macalester College, the New York Zoological
Society, the Minnesota Department of Conservation, the U.S. Bureau of
Sport Fisheries and Wildlife, and the USDA Forest Service. Mr. Wallace
C. Dayton and Miss Elizabeth Dayton, and the Quetico-Superior
Foundation, all of Minneapolis, financed Mech during the preparation of
this paper. We would also like to thank Dr. J. L. Paradiso, Dr. H. L.
Gunderson, and Mr. M. H. Stenlund for reviewing this manuscript.


LITERATURE CITED

Goldman, E. A. 1944. The wolves of North America, Part II.
Classification of Wolves. p. 389-636. Washington, D.C.: The Amer.
Wildl. Inst.

Pimlott, D. H., Shannon, J. A., and Kolenosky, G. B. 1969. The ecology
of the timber wolf in Algonquin Provincial Park. Ont. Dep. Lands and
Forests Res. Pap. (Wildl.) 87, 94 p.



SOME RECENT RESEARCH PAPERS OF THE NORTH CENTRAL FOREST EXPERIMENT
STATION


Tree Improvement Opportunities in the North-Central States Related to
Economic Trends, A Problem Analysis, by David H. Dawson and John A.
Pitcher. USDA Forest Serv. Res. Pap. NC-40, 30 p., illus. 1970.

Relation Between the National Fire Danger Spread Component and Fire
Activity in the Lake States, by Donald A. Haines, William A. Main, and
Von J. Johnson. USDA Forest Serv. Res. Pap. NC-41, 8 p., illus. 1970.

Thinning and Fertilizing Red Pine to Increase Growth and Cone
Production, by John H. Cooley. USDA Forest Serv. Res. Pap. NC-42, 8 p.,
illus. 1970.

The Impact of Estimation Errors on Evaluations of Timber Production
Opportunities, by Dennis L. Schweitzer. USDA Forest Serv. Res. Pap.
NC-43, 18 p., illus. 1970.

User Evaluation of Campgrounds on Two Michigan National Forests, by
Robert C. Lucas. USDA Forest Serv. Res. Pap. NC-44, 15 p., illus. 1970.

System Identification Principles in Studies of Forest Dynamics, by
Rolfe A. Leary. USDA Forest Serv. Res. Pap. NC-45, 38 p., illus. 1970.

Skiing in the Great Lakes State: the Industry and the Skier, by William
A. Leuschner. USDA Forest Serv. Res. Pap. NC-46, 42 p., illus. 1970.

Proceedings of the Ninth Lake States Forest Tree Improvement
Conference, August 22-23, 1969. USDA Forest Serv. Res. Pap. NC-47, 34
p. 1970.

A Water Curtain for Controlling Experimental Forest Fires, by Von J.
Johnson. USDA Forest Serv. Res. Pap. NC-48, 7 p., illus. 1970.

Wildness Ecology: A Method of Sampling and Summarizing Data for Plant
Community Classification, by Lewis F. Ohmann and Robert R. Ream. USDA
Forest Serv. Res. Pap. NC-49, 14 p., illus. 1970.



ABOUT THE FOREST SERVICE....


As our Nation grows, people expect and need more from their
forests--more wood; more water, fish, and wildlife; more recreation and
natural beauty; more special forest products and forage. The Forest
Service of the U.S. Department of Agriculture helps to fulfill these
expectations and needs through three major activities:

[Illustration]

    · Conducting forest and range research at over 75 locations
      ranging from Puerto Rico to Alaska to Hawaii.

    · Participating with all State forestry agencies in
      cooperative programs to protect, improve, and wisely
      use our Country's 395 million acres of State, local,
      and private forest lands.

    · Managing and protecting the 187-million acre National
      Forest System.

The Forest Service does this by encouraging use of the new knowledge
that research scientists develop; by setting an example in managing,
under sustained yield, the National Forests and Grasslands for multiple
use purposes; and by cooperating with all States and with private
citizens in their efforts to achieve better management, protection, and
use of forest resources.

Traditionally, Forest Service people have been active members of the
communities and towns in which they live and work. They strive to
secure for all, continuous benefits from the Country's forest
resources.

For more than 60 years, the Forest Service has been serving the Nation
as a leading natural resource conservation agency.

       *       *       *       *       *



Transcriber's Notes


This is a compilation of four separate reports, each having their own
table and figure numbers. I have retained the original table and figure
numbers due to all the references made to them within the text. However
I did reindex the footnotes for the complete compilation. I made minor
punctuation corrections, modified the table formats, moved some
illustrations, and made the following typo corrections:

Table of Contents: Changed "Occurence" to "Occurrence".
  Originally: The Possible Occurence of the Great Plains Wolf in
  Northeastern Minnesota

Page 5: Added missing parenthesis after "individuals".
  Originally: the same color (with the exception of a few black
  or white individuals (see Mech and Frenzel, page 60)

Page 27, Deleted repeated word "the".
  Originally: When still on the the ice about 15 feet from shore,

Page 34, Literature Cited: Changed "Vegetatation" to "Vegetation".
  Originally: Ohmann, L. F., and Ream, R. R. 1969 Vegetatation studies
  in the BWCA

Page 37: Changed "repreductive" to "reproductive".
  Originally: lungs, liver, kidneys, repreductive tracts

Page 40: Changed "wildnerness" to "wilderness".
  Originally: while in the wildnerness more males were taken

Page 41: Changed "decidous" to "deciduous".
  Originally: The deciduous first incisors of fawns and the decidous

Page 42: Changed "end" to "and".
  Originally: from wolf-killed deer end examined grossly in the field

Page 42, Figure 9: Changed "discoverd" to "discovered".
  Originally: A permanent first premolar (arrow) was discoverd in M-8.

Page 47: Changed "wildnerness" to "wilderness".
  Originally: not surprising that in the wildnerness area

Page 57, Footnote 36: Deleted duplicate "to".
  Originally: Personal correspondence to to L. D. Mech, Oct. 10, 1969.

Page 58: Changed "diffference" to "difference".
  Originally: Nevertheless, with extremely deep snow, the diffference

Page 59, Literature Cited: Changed "roll" to "role".
  Originally: Nasimovich, A. A. 1955. The roll of the regime of snow





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