Fauna Series No. 7

Fauna of the National Parks — No. 7 The Wolves of Isle Royale

RESULTS—THE TIMBER WOLF AND ITS ECOLOGY

NO WOLF or wolf carcass was handled during this investigation, so no vital statistics are available for the Isle Royale animals. However, these wolves undoubtedly are of the same subspecies as those on the nearby mainland—Canis lupus lycaon. Stenlund (1955) examined approximately 150 wolves of this subspecies from northern Minnesota and found that the body length of most males was 43 to 48 inches; the majority of females measured 41 to 45 inches. Females averaged about 61 pounds, and males about 78, although some males weighed over 100 pounds. Observations of most Isle Royale wolves from about 50 feet, and of one from 15 feet (figure 30), indicate that these animals are about the same size as those from Minnesota. All of the park's wolves are gray, with so little color variation that individuals are indistinguishable on this basis.

Figure 30—An Isle Royale timber wolf at 15 feet.

In most of the wolf's range, airplanes are used to hunt the animals. Minnesota wolf-hunters claim that wolves have learned to vacate open areas at the sound of an airplane, and Stenlund (1955) and Cole (1957) provide evidence for this contention. On Isle Royale, Cole found that the wolves reacted unpredictably to his light craft. At times they bolted for the nearest cover, but in other instances they calmly watched the plane pass several times within 100 feet.

The first time we encountered wolves they (six) showed little concern until the plane approached to within about 200 feet; then they arose from their beds (figure 31).

Figure 31—Attitude of wolves upon the initial approach of our aircraft.

Each time we passed within 100 feet, they rushed toward the craft. This continued until we left. When the plane drew near nine other wolves on a ridge a few miles away, they ran onto the ice and tried to chase the craft. A few hours later, the groups were together and responded to us as they had earlier. These wolves were seen again 2 days later; 200 feet below us, they showed little concern.

Throughout the rest of the first winter study period they remained oblivious to our presence, except once when continually buzzed at 75 feet. (Unless special conditions warranted, we usually flew at about 300 feet.)

This large pack apparently remained conditioned to the aircraft for a year, since low passes during the first day of the 1960 study period failed to disturb them. Even when we landed within 60 yards of the animals they stood their ground. Several ran back and forth on the ice for 1-1/2 minutes and started toward the plane a few times, but they all finally ran into the woods and howled. When relocated the next day, they were unafraid. Through out this study period the wolves appeared unconcerned at our presence (figure 32). Even when buzzed 10 times at about 40 feet on the last day, they merely stood around and watched.

Figure 32—The unconcern shown the aircraft by the large pack throughout most of the study.

Our first approach in 1961 frightened a few of the wolves in this large pack, but most remained unafraid. This disparity in behavior between individuals was noticed throughout February and March 1961, and probably resulted primarily from differences in social arrangement of the pack and the corresponding variations in social status of individuals.

Packs encountered less frequently showed more concern about the airplane. Apparently, wolves become conditioned by the continued presence of an aircraft that causes them no harm. Burkholder (1959) in Alaska found that wolves which were at first afraid of his craft eventually became accustomed to it.

Several times when the Isle Royale wolves were encountered while resting, they became aroused and began traveling a few minutes after the plane approached. They did not seem to be unduly concerned over the aircraft but may have been bothered by the noise. However, this was not considered enough of a disturbance of natural activity to complicate the results of our observations.

Wolves in most areas are known to be afraid of man, and experiences with Isle Royale wolves demonstrate the extreme to which this is true. On three occasions I chased 15 wolves from a moose carcass upon which they had just begun to feed. Although a few individuals were reluctant to leave until I approached to within, in one case, about 40 feet, all finally retreated and failed to return until several hours after the carcass had been examined. The manner in which the wolves left one carcass was especially interesting. When I approached to within 150 yards, most of the pack ran. Six animals continued tugging at the carcass until I got to within about 60 feet, and then two looked up at me and unceremoniously left. The other four, heads buried in the carcass, apparently received no signals from these individuals. They didn't detect me until I was about 40 feet away. Suddenly all jumped up and ran about 75 yards, stopped, looked back, and then continued to the rest of the pack, about 150 yards away.

On one occasion, after I had disturbed the wolves and examined their kill, part of the pack made a new kill while the others returned and fed on the old. The former animals apparently did not return to the original kill for about 2 days. The behavior of individuals during several other close-up encounters during winter and summer attested to the Isle Royale wolves' fear of man. A pack of three even were afraid of the human scent on a package of crackers tossed from the aircraft; each took one sniff and dashed off. However, the wolves were completely unafraid of docks, cabins, and other manmade structures which had no recent human scent.

Continued >>>

Last Modified: Thurs, Jul 4 2002 10:00:00 pm PDT
http://www.cr.nps.gov/history/online_books/fauna7/fauna5.htm