Fieldnotes: Life Among Isle Royale Wolves

Published December 20, 2014

Isle Royale rises from the icy waters of Lake Superior about 20 miles south of Ontario, Canada. This far north, temperatures often drop below 15 degrees Fahrenheit during winter. Since the late 1940s, gray wolves have carved out a niche on this narrow strip of protected wilderness, feeding mostly on moose.

Isle Royale wolves Photo credit: Rolf Peterson

Wolves first entered the island by way of an ice bridge that connected the island to the mainland. The few who came, thrived. Hunters at the time aimed to eradicate wolves on the mainland, but on Isle Royale, wolves faced no predators.

The Isle Royale wolf population tends to fluctuate as moose numbers rise and fall. But the most recent count, last winter, found only nine wolves surviving on the island — close to an all-time low — and scientists say they saw no evidence of successful breeding this summer. At its peak, Isle Royale supported a population of at least 50 wolves. Moose, meanwhile, have doubled their numbers to 970 individuals in just three years.

This annotated MODIS satellite image shows where an ice bridge formed during early 2014.

Wolf ecologist Rolf Peterson, 65, a researcher with Michigan Technological University, has tracked wolf and moose dynamics on Isle Royale since 1970. In partnership with population ecologist John Vucetich, 43, he now leads research touted as the longest-running study of any predator-prey system in the world. Over the years these wolves have survived viruses, famine, and the occasional counterattack from a 700-pound moose, but Peterson worries that climate change and a shrinking gene pool will end the era of wolves on Isle Royale before the end of the decade.

A wolf pack moves across breaking ice around Isle Royale. Photo credit: Rolf Peterson

Working the Island

Each winter, Peterson climbs into a small seaplane in Ely, Minnesota, with Vucetich, who joined the wolf-moose research project in the early 1990s. Pilot Don Glaser flies the two scientists to the island, which is also a national park. For two months, the three men live in a small lodge and spend many days in flight, chasing the radio signal from a collared wolf that can lead them to sites where wolves and moose interact.

In the summer, Peterson and Vucetich head to opposite ends of the island to study its diverse plants and mammals, including snowshoe hares and beavers. When they find a moose or wolf carcass, they perform a necropsy to discern the cause of death. But mostly, Peterson and Vucetich observe and document life among some of nature’s most elusive large carnivores.

Rolf Peterson skis to the site of a moose carcass. Photo credit: John Vucetich

“In my first season on Isle Royale,” Vucetich recalled, “Rolf gave me a list of things I needed to pay attention to and I couldn’t even believe that it was possible to take two steps in an hour down the trail and pay attention to all of these things.” They log the location and activity of moose and wolves spotted in the field, and collect fecal samples for genetic tests. They monitor other species, too. It’s important to track the number of gray jays, for example, because they are important scavengers of wolf-killed moose, explains Peterson, and so a drop in the number of moose carcasses in a given season could in turn hurt the gray jay population.

“We spend an incredible amount of time just getting into position to get a few seconds of observation,” Peterson said. “The number of hours during any year that we actually spend watching wolves, you can count those on one hand.”

John Vucetich measures a balsam tree, which is a dominant food source for moose in winter. “Understanding the relationship between wolves and moose depends greatly on also understanding the relationship between moose and the forest,” Vucetich said. Photo credit: Leah Vucetich

The Old Grey Guy

In the late 1950s and early 1960s, wolves could cross between Isle Royale and Canada by way of seasonal ice bridges, which formed during three out of the first four winters of the Michigan Tech study. But rising temperatures have made ice bridges increasingly rare. In the past two decades, only three winters have been cold enough for ice bridges to form. And only one of those seasonal links, in 1997, brought a new wolf to the island: a grizzled male that Peterson and Vucetich call the Old Grey Guy.

The Old Grey Guy may have saved the Isle Royale wolves from extinction. By the time he arrived, the island population had dropped to around 24 individuals and every wolf skeleton the researchers examined showed deformities in the spine. The population had fallen to 14 wolves by the time the first of Old Grey Guy’s progeny were born. But even a team of leading geneticists couldn’t pinpoint the root of the problem.

“We didn’t know what the problem was at that time,” Peterson said. But more wolf pups began to survive after the Old Grey Guy came into the picture, and Peterson’s team was able to prove that the population had been suffering from genetic depression. Simply put, without newcomers like the Old Grey Guy arriving from the mainland, the wolves of Isle Royale face a limited selection of mates, and they become inbred.

The Case for New Blood

The Old Grey Guy was the last wolf to migrate to Isle Royale from the outside world. If wolves are to persist on Isle Royale, Peterson and Vucetich say a genetic rescue will be necessary. In other words, they want to bring fresh DNA to the breeding mix by importing wolves from mainland populations.

This radio-collared wolf fell through ice around the island in 2005 and washed ashore in the following spring. Photo credit: John Vucetich

They see two imperatives for this move: First, because climate models point to a future of warmer winters in this region, the wolves are unlikely to survive another generation without intervention. Second, because wolves keep moose populations in check, the disappearance of this predator would have cascading effects throughout the island ecosystem, allowing growing moose herds to overgraze on plants that that are already suffering negative impacts related to climate change.

Other scientists oppose the idea of meddling with a population that offers such a unique opportunity to observe and analyze trends in a natural laboratory over the long term. “The best thing we can do, for scientific purposes, is to just watch the situation,” former Isle Royale wolf ecologist Dave Mech told me in an interview for Al Jazeera America last spring. He’s concerned that monkeying with the wolf population would taint the scientific record, which has thus far been based only on observing the species.

After completing a necropsy, John Vucetich waits for Don Glaser to pick him up in the research plane. Photo credit: John Vucetich (self-portrait)

Further complicating matters is Isle Royale’s designation as capital-W Wilderness — public land designated for the highest level of conservation protection under federal law. That designation makes it off-limits to intervene with the natural ecosystem. Peterson and Vucetich argue, however, that climatic changes are not, in fact, natural, but rather are proof of the ways humans are trammeling (to use wording from the Wilderness Act) on nature in indirect ways.

For now, the National Park Service is taking a wait-and-see approach. In April, Isle Royale superintendent Phyllis Green announced that the park service would be taking no actions in the near term to perform genetic rescue and that it would instead conduct a three-year environmental impact study to ascertain not only the impacts of climate change on the island’s wolves, but also its entire ecosystem. The study was supposed to begin this fall, but a lack of funding meant the study will not commence until 2015 at the earliest.

When Science and Advocacy Meet

When asked if he considers himself an advocate, Peterson says “We’re advocates for science and education, for sure.” What about for wolves? “Through science and education, yes. There are sometimes abusive decisions made — abusive to the conservation of wildlife. And it’s important to study those issues carefully and, where appropriate, make noise about them.”

Rolf Peterson inspects a moose vertebrae for signs of arthritis, which would have made it more susceptible to predation. Taken in February 2014. Photo credit: John Vucetich

Vucetich has written about the issue of advocacy in the sciences for the journal Conservation Biology, and endured criticism for it. “There are some people who tell us we should not be doing anything that scientists aren’t expected to do,” says Peterson. “Advocacy is one word, crossing the line is another phrase. Passion. They say it’s OK to be passionate but you gotta know when to say ‘enough.’”

Vucetich, however, is undeterred. He said controversy like this comes with the job. “I think there might be some self-selection early on among wolf ecologists, figuring out what their tolerance is in getting engaged [in social or policy issues].”

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