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.