The Wolf-Moose Relationship on Isle Royale in Michigan’s U.P.
Naturalists believe moose first arrived at Isle Royale in the early 1900s, when several swam the 15 miles (24 km) from mainland Ontario. With ample vegetation for food and no natural predators, the moose multiplied rapidly, their numbers soaring to somewhere between 1,000 and 3,000 by the late 1920s. Soon after, their numbers depleted the available food sources. Starvation and a succession of harsh winters killed off hundreds of the huge mammals in the 1930s. A fire in 1936 prompted a regrowth of vegetation. With revived food sources, the moose population skyrocketed again, followed by another round of starvation.
The seesaw pattern might have continued for decades, but nature intervened in the form of the eastern timber wolf (also known as the gray wolf). During the exceptionally cold winter of 1948-1949, the lake iced over between Ontario and Isle Royale, and a small pack of wolves made its way to the island. The wolves found a bountiful food source in the local moose and multiplied, reaching a peak population of about 50 animals by 1970.
Since then the two species, fenced in by the waters of Lake Superior, have provided scientists with a fascinating study of the predator-prey relationship. In 2023 the island marked its 65th year of wolf-moose research and study. The study is a joint effort of the National Park Service and Michigan Technological University, and it has become the longest predator-prey study ever undertaken. In a large moose herd, wolves cull the sick, young, and old, preventing overpopulation. In fact, moose make up around 90 percent of the wolves’ diet. But the resulting moose herd—stronger and healthier—makes hunting more difficult, which in turn reduces wolf breeding.
Populations of both animals have fluctuated dramatically over the decades. Today, the moose population is around 2,600, up considerably from previous decades. Not surprisingly, hikers have an excellent chance of spotting these 1,000-pound mammals, which often feed in ponds and lowlands or along inland lakeshores. Hidden Lake, across Tobin Harbor south of Lookout Louise, is an exceptionally good place to spot them, since the moose have a taste for its mineral licks. If you’re lucky enough to come upon a moose, give it a very wide berth. Although they look cartoonish and friendly, moose can be exceptionally dangerous if approached too closely. Cows safeguarding their calves and males behaving aggressively during the fall mating season are capable of inflicting lethal blows with their hooves.
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Isle Royale’s wolf population plummeted in the 1990s. Although biologists did not fully understand the reason behind this, they feared a lack of genetic diversity may have been a critical factor. By 1998, just 14 wolves roamed the island in three packs. After a brief rebound between 2000 and 2008, the decline resumed. In the winter of 2017, only 2 wolves were recorded, and this low figure is cited as the primary reason for the increasing moose population.
In 2018, the National Park Service began a relocation program to introduce additional wolves to Isle Royale. Twelve wolves were captured in Minnesota, Canada, and the mainland Upper Peninsula and relocated to Isle Royale. Some have produced pups, with the current wolf population standing at 28.
Backpackers rarely spot the shy and stealthy wolves, and the “wolf howls” often heard at night are most likely the haunting calls of loons. But the notion that even a very few wolves are out there, somewhere, and perhaps even watching from deep in the forest, is compelling enough for most, especially those lucky enough to spot a paw print along the trail.
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