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Fauna Series No. 5








Dall Sheep



Grizzly Bear

Red Fox

Golden Eagle



Fauna of the National Parks — No. 5
The Wolves of Mount McKinley
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ONLY THOSE CONCLUSIONS involving major considerations are discussed here. It is hoped that the factual findings in this study will be useful not only in administering the National Park System but also lands having other objectives.

First, it seems apparent that the wolf is the chief check on the increase of the Dall sheep in Mount McKinley National Park. This conclusion is based on historical evidence, on the absence of indications that other factors such as disease or poor range operated sufficiently to curb the population, and on the fact that wolves spent much time hunting sheep successfully. Because of the limited survival of lambs during some winters, it appears that the predation on lambs is the most important limiting factor in stabilizing sheep numbers. Furthermore, it was found that the sheep preyed upon, other than lambs, were generally old or diseased and therefore already doomed to an early death.

During the period of this investigation the size of the sheep population was satisfactory from the standpoint of their survival as a species in the park. They were also present in sufficient numbers so that even from the highway many could be seen. Because there are so many fluctuating factors the future status cannot be predicted with certainty. The status of the so-called "buffer species," whether these be snowshoe hare or caribou, may change; also the effect of human activities within the park and adjacent to it cannot be predicted.

It appears that wolves prey mainly on the weak classes of sheep, that is, the old, the diseased, and the young in their first year. Such predation would seem to benefit the species over a long period of time and indicates a normal prey-predator adjustment in Mount McKinley National Park. These conclusions are based on a study of 829 sheep remains, mainly skulls, gathered on the range. Field observations of hunting methods and freshly killed animals support the conclusions drawn from the skull studies.

The caribou is the main food of the wolf, and a heavy toll of the calves is taken. Yet the park herd of between 20,000 and 30,000 animals is apparently maintaining its numbers. After the first few days in the life of the calves the hunting of them by wolves necessitates a chase which usually eliminates the slowest and weakest. Since the caribou and the wolf (and also the sheep and the wolf) have existed together for many centuries, it is not surprising that under wilderness conditions the two species are well adjusted to each other. The status of the caribou should be watched because the herds spend much time outside the park where they are in territory open to hunting. In respect to the sheep, the caribou is an important buffer species.

The moose in recent years, in the presence of a high wolf population, has increased conspicuously in Mount McKinley National Park and adjacent territory. This increase is generally attributed to a decrease of moose hunting by man.

The effect of the wolf and the eagle on the red fox appeared to be negligible. The fox was found to be flourishing in the presence of high wolf and eagle populations. All information indicates that seldom is the fox preyed upon by these two forms.

The coyote was so scarce in the sheep hills that it was not a factor. It seems to seek areas where the snowshoe hare is available, a fact in itself significant.

The predation of the golden eagle on the Dall sheep is negligible. During my 3 years of field work the eagles lived mainly on ground squirrels. Authentic studies in other regions also show that the golden eagle seldom preys on mountain sheep. The popular contrary impression probably arises from the fact that eagles have been known to kill mountain sheep lambs on some occasions and that they often swoop low over sheep, just as they may frequently be seen swooping low over wolves and grizzlies.

Sheep and caribou eaten by grizzlies are largely in the form of carrion. A very few young caribou may be killed by bears that happen to be living on the calving ground, but after the calves are a few days old they are generally too speedy to be caught by the grizzlies.

It is likely, judging from experience with the Mount McKinley wolves over a period of 3 years and from other information, that the Alaska wolf population has been at the saturation point for some time. It would not be surprising if, in the course of the little-understood population cycles, the Alaska wolf again declines. What the course of events will be during the next decade can not be predicted with certainty be cause many fluctuating biological influences are at work. But Mount McKinley National Park is a small part of Alaska (half of 1 percent) and wolves are plentiful in many parts of the territory. It becomes obvious therefore, that whatever policy is practiced in the park will have an insignificant effect on the wolf and other wildlife populations in Alaska as a whole.

In considering the wolf and the general ecological picture in Mount McKinley National Park it must be emphasized that national parks are a specialized type of land use. Wildlife policies suitable to national parks—areas dedicated to preserving samples of primitive America—obviously may differ from those applicable to lands devoted to other uses.

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Last Modified: Thurs, Dec 20 2001 10:00:00 pm PDT

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