‘Red in tooth and claw’: Inside the world’s longest predator-prey study

For more than 60 years, researchers have been studying wolves and moose on Isle Royale. But should humans be interfering with nature?
By Charnel Anderson - Published on Jun 24, 2021
In 1958, researchers began studying wolves and moose on Isle Royale. (Courtesy of Rolf. O. Peterson



In the midst of a polar vortex in late January 2019, a four-year-old, almost-70-pound female wolf with distinct black markings — known to researchers as wolf 003F — took advantage of Lake Superior’s ice cover to walk off the island where researchers had placed her a year earlier. 

Until her escape, wolf 003F had unknowingly been a participant in the world’s longest-running predator-prey study, taking place on Michigan’s Isle Royale National Park, a remote wilderness island roughly 24 kilometres from the shore of Lake Superior. Wolf 003F was one of 19 wolves relocated to Isle Royale in an effort, spearheaded by the U.S. National Park Service, to restore its wolf population — by 2016, there were only two animals, which were both father and daughter and half-siblings. 

The decision to relocate the wolves prompted opposition from those who believe humans should not interfere with the island’s natural balance — and forms the latest chapter in a decades-long research effort that has helped shape Ontario's approach to wildlife management.

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In 1958, Durward Allen, an ecologist at Purdue University in Indiana, launched what was supposed to be a 10-year study of Isle Royale’s wolves and moose. 

“It’s 62 years and running, in terms of annual monitoring of wolves and moose,” says Rolf Peterson, a wildlife ecologist and research professor at Michigan Tech University who has been involved with the study since the 1970s. “It’s continued to open up new questions and new frontiers for research. It’s not getting old.” 

a wolf lies on snow
Wolf 003F was captured in northeastern Minnesota in 2018. (Courtesy of Rolf. O. Peterson)

It is thought that moose arrived on Isle Royale in the beginning of the 20th century and that wolves followed, via ice bridge, in the 1940s. Prior to the wolves’ arrival, the island’s moose population went through a “big boom-bust cycle” twice, says Peterson. In order to prevent another boom-bust cycle, the U.S. National Park Service — unaware that wolves had colonized the island themselves — introduced wolves from the Detroit Zoo in 1952. 

The NPS’s effort was unsuccessful; most of the wolves from the zoo were trapped and killed because they caused problems with humans on the island. However, the wolves that naturally colonized the island were able to establish themselves, and “they became the managers of the island, and wolf predation moderated [the moose] population swings tremendously,” says Peterson. 

By 1980, the island’s moose population had been declining for almost a decade, while the wolf population was abundant — up to 50. Soon, however, the wolf population began to decline, and concluding that neither disease nor lack of sustenance was to blame, researchers considered whether a lack of genetic diversity, or inbreeding, could be the cause. 

Between 2000 and 2010, Isle Royale’s moose population declined to its lowest levels, while wolves began to rebound — thanks in part to a wolf that immigrated to the island in 1997 — but, by 2011, the were only nine wolves on Isle Royale, and, in 2016, there reduced to two. With an estimated 1,600 moose on the island, there was still plenty of food for the wolves to eat, so researchers suspected inbreeding was the culprit. 

“The inbreeding was severe enough that there was no hope of recovery,” says Peterson. “And it was determined by the National Park Service that, in order to protect the forest of Isle Royale from moose, they needed to be controlled by a top predator, like the wolf.” 

two wolves walking on snow
The last male island-born wolf (left) died in October 2019 after sustaining injuries from another wolf. (Courtesy of Rolf. O Peterson)

Starting in 2012, the NPS held forums and collected feedback from the public about whether they supported human intervention in order to save the island’s wolf population. Researchers compiled public responses and found that out of 465 comments analyzed, 88 per cent of people supported some form of intervention, while 12 per cent were opposed. 

Thomas Heberlein, a scientist and professor emeritus in the Department of Community and Environmental Sociology at the University of Wisconsin-Madison, was one of those who opposed the idea of relocating wolves to Isle Royale. In 2013, he wrote a letter to Peterson stating his position: “I believe science should watch and wait, observe and measure, and let nature teach us lessons, rather than get in there to control and manipulate to ‘save’ nature.”

He continued: “Should wolves go extinct in Isle Royale (and we don’t know if they will), it might be an important control to compare wolf and wolf-less ecosystems. It is possible the ancestors of these wolves made a bad choice for sustainability by migrating to Isle Royale, and that nothing could be more natural than for that population to end. We can learn from that.” 

Opposition to the wolf-relocation initiative also came from wilderness advocates, who, Peterson says, “believed that regardless of what happens in a forest or anything else, humans should not play a direct role in the future of wolves and moose on Isle Royale, and they cited the Wilderness Act [of 1964] as the legal basis for that.”

The Wilderness Act of 1964, written by environmental activist Howard Zahniser, created the legal definition of wilderness — “an area where the earth and its community of life are untrammeled by man, where man himself is a visitor who does not remain” — and led to the protection of more than 9 million acres of federal land in the United States. In Peterson’s view, though, the legislation “doesn’t prohibit the manipulation of things in wilderness areas.” 

a moose
There are up to two moose per square kilometre on Isle Royale. (Courtesy of Rolf. O. Peterson)

In fact, he adds, “hunting by humans — recreational hunting — is permitted in wilderness areas. So there can be some pretty heavy-handed manipulation of wild populations by humans.” In a paper Peterson co-authored with Douglas Smith, project leader of wolf restoration in Yellowstone National Park, the authors argue that “human effects caused reduced predation, so to stop and not intervene would have made these systems more unnatural, potentially requiring continual human intervention subject to human value judgments for decades to come.” 

The authors conclude that “not intervening, or inaction, often perceived as safer, would have had more damaging impacts to ecosystem functioning.” Wolf colonization on Isle Royale, they say, has moderated the boom-bust cycle of moose populations, which in turn lessens the impact moose have on the island’s vegetation. 

Despite the opposition to the wolf-relocation initiative, in 2016, the NPS drafted a plan to place between 20 and 30 wolves on Isle Royale. In 2018, crews began trapping wolves in northeastern Minnesota, the western Upper Peninsula of Michigan, and Ontario. 

In 2019, 11 wolves were captured in Ontario – including three wolves from Jostle Lake, near Wawa, and eight wolves from Michipicoten Island, the latter of which are “among the largest known in the Great Lakes region,” according to Brent Patterson, a research scientist with the Ministry of Natural Resources and Forestry. The wolves from Michipicoten Island had all but eliminated the island’s caribou population. (In 2018, a number of caribou on Michipicoten Island were relocated in an effort to protect the species, which is considered threatened under Ontario’s Endangered Species Act.)

closeup of a wolf
Wolves in Ontario are some of the biggest in the Great Lakes region, says Brent Patterson. (Courtesy of Rolf. O. Peterson)

The wolves were captured using net guns from helicopters, “chemically immobilized,” and flown to a handling station in Wawa, where they were examined, vaccinated, and fit with a GPS collar and ear tags, Patterson tells TVO.org via email.  Then they were moved to Isle Royale. 

According to a 2020 report from the NPS, of the 19 wolves relocated, eight died. The most common cause of death was other wolves, something that’s “pretty common,” says Mark Romanski, biologist and Natural Resources Program Manager at Isle Royale National Park. “Outside of human interference or human mortality, the primary mortality mechanism for wolves is other wolves, because they’re all about defending their territory.” 

By March 2020, between 12 and 14 relocated wolves were present on the Isle Royale and had formed social bonds and secured their territory. Patterson says the large wolves of Michipicoten have flourished on Isle Royale and “become a dominant force among the island’s wolf population.”

According to Peterson, the decades-long predator-prey study has allowed researchers to learn a great deal about wolves and moose. For example, most moose cannot be killed by wolves, he says: “It doesn’t matter whether there’s a pack of 15 or 20 wolves — they just can’t kill about 95 per cent of moose they run into,” as a healthy moose can typically outrun, or at least outlast, wolves. 

“Wolves are limited usually to calves less than a year old, and older moose, at least nine or 10 years old that tend to have a lot of physical problems, just like old people: arthritis, osteoporosis, periodontal problems,” says Peterson. “So that’s where wolves may actually control the density of moose.”

a pack of wolves hunting a large animal at night
Wolves are most successful at killing young and old moose, says Rolf. O. Peterson. (Courtesy of Rolf. O. Peterson)

The research coming out of Isle Royale has been used in Ontario to inform wildlife management. Ontario’s had one of the most dramatic efforts to reform moose hunting to mirror wolf predation,” says Peterson. “There’s been a good use of data from Isle Royale to try to model what smart hunting might look like … that would mean killing calves, for example, which is a big change for North American hunters, and killing moose — at least bull moose — in such a way that breeding bulls are not killed.“

Back on Isle Royale, plans to replace the relocated wolves’ GPS collars (all of which have failed by now) were interrupted by the pandemic, so in the meantime, researchers are relying on cameras and performing DNA analysis on scat in order to keep track of them. 

Wolf 003F, who had been captured in northeastern Minnesota and moved to Isle Royale in fall 2018, had spent much of her time exploring the island before becoming the first wolf to cross the ice bridge back to the mainland. According to GPS data, she travelled through Ontario to Minnesota and back again; she was last spotted near Atikokan in 2020. No one knows where she is now. 

This is one in a series of stories about issues affecting northwestern Ontario. It's brought to you in partnership with Confederation College of Applied Arts and Technology. Views and opinions expressed in this article are not necessarily those of the college.

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