Isle Royale National Park

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Wildflowers in Isle Royale National Park
Wildflowers in Isle Royale National Park (Travel Michigan)

Had we visited Isle Royale at the turn of this century, we would have found it quite different. We would have seen no wolves or moose. Instead, we might have seen a herd of caribou or glimpsed a lynx, no longer seen today. The forest undergrowth would be thick with American yew rather than thimbleberry. Since the turn of the century, the coyote has come and gone. The white-tailed deer was introduced and has since disappeared. Sometime early in this century, moose immigrated to the island, probably swimming from Canada's mainland. With abundant food and no predators, the moose population grew unmolested. By the early 1930s the moose had destroyed their food supply and began to die off in great numbers.

A fire in 1936 burned over a quarter of the island and by 1937 the moose population crashed. But the fire stimulated growth of new brush and the unchecked moose population began to grow, only to crash again when the food ran out. During the cold winter of 1948-49 an ice bridge formed between Canada and the island, and a small pack of Eastern Timber Wolves crossed to Isle Royale. Since then, additional packs have become established here as offshoots of the original pack. Individual wolves have ranged from 12 to 50. The population is now at the low end of that range.

The wolves are important in maintaining a healthy moose population. The very young, the very old, and those moose prone to predation because of illness or injury are the most likely prey. By culling weak and old, wolves contribute to the health of the moose population. When predators decrease, the number of prey increases and the dynamic cycle begins again. In lean years, the pack's reproduction and survival rates may fall off dramatically, but they usually increase when the moose in an aging population are more easily caught. So wolf and moose are held in balance.

Wolves are highly intelligent and social animals that form extremely organized packs. Every individual from the dominant pair to the weakest pup has a specific place in the pack hierarchy. Wolves are distinguished from other wild canines by their size. An adult male, bigger than a large German shepherd, may weigh close to 100 pounds. Its size is accentuated by the heavy gray coat of fur and mane-like ruff around the head. A wild wolf's normal lifespan is six to eight years and some individuals may live 12 years. Pack size varies from two to 15 individuals.

As parents, few wild animals can match the wolf's devotion to its young. In late spring, the pregnant female will dig a den and prepare it for the pups. Before and after the pups are born, the pack remains close to the den, supplying food to the female. When the pups are able to leave the den, they assume special status and are cared for by all pack members.

As a wilderness, Isle Royale is more than just a sanctuary for wolves and moose. As a national park it is more than a pleasuring ground for humans. The island's uniqueness lies in its complex yet simple system of natural processes, a system in which moose are dependent upon both wolves and beaver—wolves to control their numbers and beaver to provide dams and in turn the aquatic vegetation upon which moose feed. The beaver also serve as a summer food for the wolf and the beaver ponds eventually become meadows that support a variety of smaller animals. The red fox eats the hare who, if left unchecked, would destroy the forest that supports the moose that supports the wolf. In such a system, a dynamic equilibrium is struck in which each species has an important role. And man's part? We must leave this balance to natural law, observing but not manipulating. Isle Royale has been designated an international biosphere reserve under the Man and the Biosphere (MAB) program. Ninety-nine percent of the park's land area is legally designated as wilderness.

Published: 29 Apr 2002 | Last Updated: 12 Oct 2011
Details mentioned in this article were accurate at the time of publication


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