Predator and Prey, a Delicate Dance


IN Lake Superior lies a remote island, Isle Royale National Park, 134,000 acres of boreal and hardwood forests where a life-or-death struggle between wolves and moose has been the subject of the world’s longest study of predators and their prey, now in its 55th year.

Joohee Yoon

Moose first appeared on this Michigan island in the first decade of the 20th century, apparently by swimming from the mainland. With no predator to challenge them, the moose population surged (interspersed by two crashes, from starvation) and devastated the island’s vegetation in search of food. Then wolves arrived in the late 1940s by crossing an ice bridge from Canada, and began to bring balance to an ecosystem that had lurched out of control.

Today, moose are essentially the only supply of food for the wolves, and wolf predation is the most typical cause of death for moose. But the wolf population is small, and decades of inbreeding have taken their toll. The ice bridges that allow mainland wolves to infuse the island’s wolf population with new genes form far less frequently because of our warming climate. With the number of wolves reduced to little more than a handful, they face the prospect of extinction.

The National Park Service is expected to decide this fall whether to save the Isle Royale wolves — a decision that will test our ideas about wilderness and our relationship with nature. This is because the park is also a federally designated wilderness area, where, under federal law, “the earth and its community of life are untrammeled by man, where man himself is a visitor who does not remain.” If we intervene to save the wolf, will we be undermining the very idea of not meddling that, since the passage of the Wilderness Act in 1964, has been the guiding principle behind the protection of 109 million acres of federal land?

The park service has three options: conserve Isle Royale’s wolf population by taking new wolves to the island to mitigate inbreeding, an action known as genetic rescue; reintroduce wolves to the island, if and when they go extinct; or do nothing, even if the wolves disappear.

As the lead researchers in the study of wolves and moose, we favor conservation or reintroduction. But more important than our view is the reasoning behind it.

Wilderness is conventionally viewed as a place where nature should be allowed to take its course, free of human interference. This is essentially the principle of nonintervention that has guided America’s relationship with wilderness areas for roughly 50 years.

Importantly, two of the architects of modern-day thinking about wilderness, the wildlife biologists Aldo Leopold and Adolph Murie, supported the idea of introducing wolves to Isle Royale in the 1940s — to conserve a habitat being overrun by moose — before wolves had arrived on their own.

The principle of nonintervention touches on fundamental conservation wisdom. But we find ourselves in a world where the welfare of humans and the biosphere faces considerable threats — climate change, invasive species and altered biogeochemical cycles, to name a few. Where no place on the planet is untouched by humans, faith in nonintervention makes little sense. We have already altered nature’s course everywhere. Our future relationship with nature will be more complicated. Stepping in will sometimes be wise, but not always. Navigating that complexity without hubris will be a great challenge.

These realizations have led a number of environmental scholars to consider new visions for the meaning of wilderness. One is of a place where concern for ecosystem health is paramount, even if human action is required to maintain it.

The future health of Isle Royale will be judged against one of the most important findings in conservation science: that a healthy ecosystem depends critically on the presence of top predators like wolves when large herbivores, like moose, are present. Without top predators, prey tend to become overabundant and decimate plants and trees that many species of birds, mammals and insects depend on. Top predators maintain the diversity of rare plants that would otherwise be eaten, and of rare insects that depend on those plants. The loss of top predators may disturb the nutrient cycling of entire ecosystems. In addition, predators improve the health of prey populations by weeding out the weakest individuals. Also, wolves are a boon to foxes, eagles, ravens and other species that scavenge from carcasses that wolves provide.

Given that moose will remain on Isle Royale for the foreseeable future, the National Park Service should initiate a genetic rescue by introducing new wolves to the island.

In a world increasingly out of balance, Isle Royale National Park is a place with all its parts, where humans kill neither wolves nor moose, nor log its forests. Places like it, where we can witness beauty while reflecting on how to preserve it, have become all too rare.

John A. Vucetich is a population biologist, and Rolf O. Peterson is a wildlife ecologist, both at Michigan Tech. Michael P. Nelson is an environmental ethicist at Oregon State University.


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