The Long View

Isle Royale National Park draws visitors who like nature rugged and remote. It’s also the site of the longest-running study ever of a predator and its primary prey—even as global warming shows signs of upsetting the natur

The old wooden auditorium at Rock Harbor on Isle Royale’s northeast end, built in the late 1930s by Franklin D. Roosevelt’s Civilian Conservation Corps, looms out of pea-soup fog like a ghost ship. Perhaps the SS America, which delivered vacationers and goods to lakeside resort communities in the early 1900s, when the island was billed as “A Summertime ‘Bermuda’ Paradise in the Beautiful Superior Sea.” The 272-passenger America struck a submerged shoal and sank without loss of life in 1928, adding its ruptured steel hull to a list of famous shipwrecks attributed to Isle Royale’s dangerous waters and Lake Superior’s often-furious moods. This evening the lake is only agitated. Still, waves smacking boulders near the steamship’s old dock nearly drown out a choir of loons bringing down the curtain on a cold, dripping mid-June day.

The America had been an essential conduit for the island’s commerce, returning to Duluth laden with the catch of lake trout and whitefish from several thriving commercial fisheries, and the ship’s loss hastened the end of Isle Royale’s halcyon days. At the same time it fueled an incipient movement to preserve the largely uninhabited island, which sits in Superior’s northwest corner, as a wilderness park. By 1940 the federal government had acquired title to all 210 square miles of land; in 1946, after a wait for the end of World War II, Isle Royale National Park was formally dedicated. Ever since, park scientists and seasonal naturalists have used that old CCC hall to give talks about the local flora, fauna, and geology.

The least-visited national park in the lower 48 states, Isle Royale annually attracts about 17,000 tourists who arrive by boat or floatplane—the only ways to get there—during its three-month summer season. Many of them are backpackers heading to outlying campgrounds. But around Rock Harbor, the hub of park activities with its visitors’ center, marina, and the island’s one remaining resort, these lectures are the only evening entertainment for guests deprived of television sets, cell phones, and BlackBerries. (Plump red thimbleberries, however, will soon be ripe for picking along Isle Royale’s 165 miles of trails.) Last night’s presentation, for example, highlighted the island’s 31 species of wild orchids, including the rare calypso or fairy slipper, a dainty jewel found only in lichen-draped boreal forests.

Tonight’s program, however, might be rated “R” for graphic content. The topic: Isle Royale’s wolves and the moose that are their bread and butter. The wolves are literally the most famous Canis lupus population in the world due to the prescience and determination of Durward Allen (1910–1997), a towering figure among many eminent conservation biologists in the middle of the 20th century, and the work of the young scientists who answered his summons. For it was a half-century ago—in the summer of 1958—that Allen, then professor of wildlife ecology at Purdue University, launched what is believed to be the world’s longest-running study of a top predator and its primary prey.

Early on Allen recognized Isle Royale as a natural laboratory that was effectively isolated from human impact—and the only place in North America where hunter and hunted could be counted and their interactions studied over time. Allen first proposed the project in the early 1950s, when he was a top research scientist with the U.S. Fish and Wildlife Service. But Eisenhower-era political appointees had little interest in funding research. His frustration ended when he left the Fish and Wildlife Service for a faculty position at Purdue, winning a National Science Foundation grant for the venture.

A good friend and supporter during my years as Audubon’s editor, Allen once told me that he wanted to study Isle Royale’s wolves and moose because he came along a century too late to study wolves and bison on the Plains. I’m sure he was serious. But what he really hoped was that the study would help change the public’s perception of wolves as terrifying creatures that kill for fun in great orgies of slaughter, cutting out the best animals in the herd, hamstringing their victims, and eating them alive. All myths. Yet at the time the three Lake Superior states still paid bounties on wolves, which were on the verge of extirpation in Michigan’s Upper Peninsula and northern Wisconsin. (Minnesota had a viable population of about 600 in the 1950s.) Popular articles about the researchers’ findings, Allen knew, would be a big help.

Thus 46 years ago, when I was outdoor editor for a small Michigan newspaper, I sat in the front row at the Rock Harbor auditorium with pen at the ready as biologist Dave Mech—the first Purdue graduate student chosen for the Isle Royale project—set up a Kodak Carousel projector. The tray was filled with dramatic slides of wolves on the hunt in the dead of winter, shot by the often airsick researcher with a simple Argus C3 camera from a low-flying, ski-equipped Piper Cub; scenes of snow-drifted moose carcasses and skeletons picked clean by foxes and ravens; and close-ups of the skulls of aged moose showing extensive tooth wear. His audience that evening was sparse. The resort was about to close for the season and Mech had already given his talk several times. Still, his enthusiasm was palpable as he explained how the wolf packs culled old and infirm moose in winter and calves in summer, keeping the herd from overbrowsing the forest. The big carnivores, he emphasized, paid no attention to the circling aircraft, and he could watch them pursue prey and make kills without influencing the outcome. Nor were they belligerent when Mech snowshoed to a fresh kill. The pack simply ran off, returning to the feast a day or two later.

Mech went on to considerable fame, studying wolves and their prey in Minnesota, Alaska, and Arctic Canada, and founding the International Wolf Center in Ely, Minnesota. In time the Isle Royale work would provide a baseline for virtually all wolf–moose research in the world, especially in Scandinavia, where Canis lupus is staging a comeback. It was also a template for the long-term wolf study in Yellowstone National Park, where the much-needed predators were reintroduced in 1995. In the meantime, we have truly seen a sea change in most Americans’ attitude toward wolves, from loathing to love. Today there are large wolf populations in Wisconsin and northern Michigan as well as in Minnesota—so many that the eastern gray wolf, one of the first animals on the federal endangered species register, was recently delisted.

Alas, the Isle Royale ecosystem turned out to be less isolated from outside influences than Allen believed. The dynamic balance between wolves and moose has been shattered twice during the study’s 50 years. First by the introduction of a deadly canine disease, and now by global warming, which threatens the survival on the island of these two ecologically entwined animals.


Isle Royale National Park is actually an archipelago of some 100 named satellite islands, islets, and rocks encircling the rugged 45-mile-long, 9-mile-wide main island. Its spine is Greenstone Ridge, which runs for more than 40 miles and tops out at 1,394 feet. There are several large lakes gouged out by the last ice sheet and a 20-square-mile lowland swamp. Fast-flowing streams are few, but bogs and their carnivorous plants abound. Indeed, the island’s botanical life is incredibly rich. Hike Greenstone Trail and you’ll pass through a variety of forest habitats from spruce-fir to sugar maple with a rich variety of North Country wildflowers. My favorite: bunchberry, with its radiant white flowers in spring and clusters of scarlet fruit in late summer. Moose treats. Moreover, you’ll have great views of lower ridges, coves, harbors, and bays, and especially the lake, which Longfellow called the Shining Big-Sea Water. Plus, you’ll probably be alone. With so few people on the island at any one time, you’re as likely to bump into Bullwinkle as another hiker. I have. Nose to nose, on a blind jog in a trail.

There are no roads on Isle Royale—99 percent of the island is dedicated federal wilderness—and Park Service personnel travel around by boat. Big, fast boats bought with Homeland Security dollars and used by heavily armed rangers who check state fishing licenses while looking for terrorists from Canada. Or open outboards like the one Rolf Peterson ties down today at the Rock Harbor dock. He and his wife, Candy, who is also his research assistant, are clad in bright-yellow fishermen’s slickers and broad-brimmed rain hats. They’ve navigated the eight choppy, foggy miles from the wolf research camp with the aid of a handheld GPS unit because Rolf, who has led the wolf–moose study since the 1970s, is tonight’s star attraction. 

During the first 12 years of Durward Allen’s dream project, Purdue graduate students (some of whom worked mainly on Isle Royale’s smaller mammals such as beavers, foxes, red squirrels, and snowshoe hares) completed their doctoral work and moved on. Rolf, who retired in 2006 as professor of wildlife ecology at Michigan Technological University in Houghton, came aboard in 1970 to refocus the study on its original subjects and stayed, with Allen turning the project (and the constant scramble for funding) over to him in 1975.

A supremely fit Scandinavian from Minnesota with sparkling blue eyes and a gray-streaked blond beard, Peterson was nine years old when the study began, and like most lads of that age, he was clueless about the natural world. But a National Geographic article by Mech and Allen piqued his curiosity about Isle Royale. He hiked its trails twice while a college student. And as Rolf tells the story over a lake trout dinner at the lodge, he wrote to Purdue in his senior year and inquired about doing graduate work there. “The thick packet they sent back didn’t mention Allen or wolves, so I figured the study was over. Then I saw a TV documentary called Wolfmen and realized I had written to the wrong department.” This time Allen got the letter and offered Rolf the next time slot for graduate work on the island.

Not surprisingly, there’s a minuscule cast of mammals on this isolated island, including just one species of mouse, and only five amphibians. How they arrived is anyone’s guess, but as Rolf points out, “They had 10,000 years to do it after the glaciers retreated.” Woodland caribou, Canada lynx, and marten were once present but disappeared in the early 1900s. Moose, however, seem to be relative newcomers, judging by the absence of bones at ancient Indian campsites. These large ruminants are strong swimmers, and biologists believe the ancestors of today’s population paddled over from Canada, a distance of 20 miles, about 1900. They found a moose paradise: a virgin forest with no predators. But within three decades their numbers had swelled to several thousand, the forest had been browsed to nubs, and a disaster loomed. By 1935 only 200 starving moose were left on Isle Royale. Then a forest fire created a brand-new forest and the herd slowly regained its health if not its former numbers. However, reports of new moose starvation in the unusually hard winter of 1949 prompted a clamor for control measures, either through hunting or by introducing wolves.

Nature, however, had already intervened. That winter a mated pair of wolves crossed over an ice bridge linking the island to Ontario. “It was an extraordinary event,” Dave Mech told me years later. “The water would have to be cold and calm enough for the lake to freeze over. Then you need wolves predisposed to make the long trek. Chances of that happening are pretty remote or Isle Royale would have had wolf packs before the 1940s.” In short time a balance between predator, prey, and vegetation was established on Isle Royale. It lasted until the summer of 1981, when a strict rule barring pets from the park was ignored.


The Petersons’ research base sits across the long, narrow harbor from Daisy Farm, Isle Royale’s largest campground and the first night’s stop for most backpackers. They live in a simple cabin built of logs laid atop beach rocks by Jack Bangsund, one of the island’s last commercial fishermen. Rolf flies the Norwegian flag over the camp in Bangsund’s honor. He’s also erected a yurt (“a Mongolian nomad’s home”) back in the trees, where he can work secluded from the hundreds of visitors who are dropped off by a tour boat and stare in awe at a yard full of moose bones, skulls, and antlers. But the Bangsund site has been more than a workplace since the Petersons arrived. As Candy writes in a book in progress, it also served as a summer nursery, home base, and launching pad for their two sons.

The couple’s mission from May to October involves a lot of footwork, including trapping and radio-collaring a wolf from each pack (there are three at present); tracking their movements with antennas from high points on the ridges; and locating wolf dens and counting pups. (Three summers passed before the Petersons found their first den, in an old dry beaver lodge.) Then there’s scouring the island for the bones of both moose and their tormentors, a task now largely assigned to Earthwatch Institute volunteers. The bones reveal a great deal more than stories about the owner’s life and death. For example, that an aged moose had severe arthritis or a broken jaw due to infection when wolves brought it down. Scientists, Rolf explains, have discovered that both animals are “biological time capsules.” Plants incorporate carbon dioxide from the air into leaves and twigs that are eaten by moose that will probably be eaten by wolves. They also accumulate traces of other environmental pollutants. Thus the animals’ teeth store a record of large-scale ecological change, from radioactive fallout during the period of Cold War nuclear tests to a sharp decline in levels of lead and mercury and—most notably—the inexorable rise of atmospheric carbon dioxide levels from our relentless burning of fossil fuels. Unknowingly, moose and wolves have mapped the road to global warming that now threatens their survival on the island.

It’s standing room only tonight in the Rock Harbor hall, unlike on my first visit in 1962. Rolf’s aerial shots of wolf–moose encounters in midwinter, taken from an altitude of 500 feet with a long, stabilized telephoto lens—are breathtaking if, well, pretty vivid. Red on white. A wide-angle close-up of a coal-black raven guarding a moose carcass that’s mostly skeleton elicits some laughs. Rolf’s laptop computer—the Kodak is obsolete—projects a graph on the screen showing that there were 20 wolves and 570 moose on Isle Royale when the study began and that the score was 20 to 1,250 when he arrived. And as the biologist explains, predator and prey numbers cycled in tandem, with the wolf population peaking about a decade after the moose herd when there were a lot of aged animals to bring down on the snowy killing fields. (That’s not as easy as it sounds. The front legs of a 900-pound moose are formidable weapons, and Rolf once watched an old, blind bull stand its ground against a pack of wolves for three days until they gave up and decided to look elsewhere for a meal.)

 By the winter of 1980, he relates, a record high of 50 wolves in five packs prowled the island, while the moose herd had slowly declined to 750 animals. But researchers were astounded to find only 14 wolves when they arrived at their winter camp, at Windigo on the island’s southwest end, in January 1982. Canine parvovirus, a mutant disease that would ravage domestic dogs on the mainland, had swept Isle Royale. National Park Service policy explicitly bans pets from the park. But as Rolf later learned, a clueless Chicago man had brought his sick dog along on a fishing trip over the previous Fourth of July holiday. For a decade, the wolf population staggered along at a dozen or so animals and grew top-heavy with old wolves that had little success at breeding. At times Rolf wondered if they were on a fast track to extinction. And the impact of the tragedy is still being felt.


During a lifetime of 10 to 12 years, an Isle Royale wolf will feed on 200 or more moose kills. But now that the packs were decimated by disease, the herd exploded as it had in the 1920s, peaking at 2,400 animals in 1995. The next winter was especially severe, with blizzards bearing down in December. Moose, infested with tens of thousands of blood-sucking winter ticks that can weaken even a big bull, struggled through three feet of snow to find scarce food. From his plane, Rolf watched the starving animals leaning over steep cliffs for a mouthful of browse—and falling into Lake Superior. “The real clincher,” he tells me over coffee the next morning, “was that snowmelt occurred six to eight weeks later than usual. Moose simply ran out of fat and died before any new forage was available.” Only 500 moose were left by the winter of 1997, most of the old animals had perished, calves were few, and the handful of surviving wolves were digging up old carcasses and eating the sun-dried hides.

The next few years proved less tumultuous. The island’s battered forest was recovering, and the moose herd rebounded to an estimated 1,100 by the winter of 2003. The wolf population likewise surged, to 30 animals in 2005. By then, however, moose numbers were again heading downhill and wolves followed their slide due to a lack of prey. Last winter’s survey tallied just 385 moose and 21 lean wolves. And John Vucetich, a population biologist at Michigan Tech who has been Rolf’s research partner since 2000, blames climate change. Five of the past six summers, he notes, were the warmest since the Isle Royale study began in 1958. “Hot summers are particularly hard on moose,” Vucetich explains. “They tend to rest more and don’t eat enough forage to get through a long, bitter winter.” A warm spring or fall, he adds, can also trigger a devastating tick infestation. It’s not unusual for a hiker to encounter moose that have lost most of their hair because of ticks. Another sign of global warming: No snow fell on Isle Royale for a month last winter when researchers were at the Windigo camp.

Playing devil’s advocate, I ask Rolf if there’s anything more to be learned by continuing the study into another decade or beyond. “We’re not simply watching moose and wolf populations go up and down,” he answers. “The dynamics of the predator-prey relationship on Isle Royale are extremely complex, involving subtleties of weather, parasites, snow conditions, the food base. That’s just for starters. Then pivotal events occur with effects that are felt for decades. Finally, each 10-year period of this study has been unique, bearing little resemblance to other decades. So we don’t put much stock in predictions anymore. That’s especially true in a world where accelerating climate change will influence virtually everything.”

One example: Ten years ago Rolf told me that hikers seldom encountered wolves. “They’re terrified of us,” he said. Today that’s no longer true. While wolves have never touched a visitor, they occasionally saunter along asphalt paths at Rock Harbor or poke into unoccupied tents. And in late September, Rolf wrote me that the Park Service had closed the Daisy Farm campground. “Wolves were eating green apples falling from trees dating back to copper mining days in the 1850s,” he said. “There have been too many wolf–human contacts, and people are likely to do foolish things to get a photo.” One of the wolves, captured by Rolf’s remote camera, “was starving so badly that its pelvis was clearly outlined through its skin.” And he added, “While it’s mating season, moose are so rare that we haven’t seen a single bull with polished antlers looking for a brawl.”

In mid-January Peterson and Vucetich, along with bush pilot Don Glaser, returned to Isle Royale for another winter survey. History suggests they’ll be surprised by what they find. Today, though, I have one last question for Rolf: Will there be moose and wolves on Isle Royale in another half-century?

“Warming temperatures mean long-term trouble for the moose,” he replies after some thought. “I think they’ll tough it out. But sooner or later their numbers could drop even lower than they are now. If that happens, there’s a good chance the wolves won’t make it.”