Fifteen days passed before Peterson and his research crew spotted three resident wolves on the island, Michigan's only national park. They were the only three spotted this season — down from nine wolves the previous season, and the fewest in a 57-year study.
It was the gravest sign yet that the longest, continuous predator-prey study in the world could be coming to an end — or perhaps moving in a new direction. The wolves, which have survived by preying on Isle Royale moose, have offered scientists at Michigan Technological University an unprecedented opportunity to study a predator-prey system on an isolated island for more than half a century.
The National Park Service likely will determine the future of the Michigan Tech study, which has captivated the public, garnered the attention of scientists around the world and put the Upper Peninsula school on the map.
At least one of the researchers says it's already too late. "It's sad to see the end of a population so highly valued by society, knowing that it could have been saved," said Peterson, one of the study's co-principal investigators. "It's sad to see something end that didn't have to end."
Peterson has lobbied to bring more wolves onto the island to rejuvenate the remaining few.
But what happens on Isle Royale is up to the Park Service, which plans an environmental assessment of the island. And that process, which would include deciding what to do about the wolves, will take a few years.
Some wonder if nature could intervene with Isle Royale's wolves in the meantime. After all, two wolves crossed an ice bridge and visited Isle Royale from Minnesota this past winter, but only stayed six days.
What if more wolves visit again next year, stick around and mate with the wolves that are still on the island, questioned David Mech, who did the first three years of the study and now is a senior research scientist with the U.S. Geological Survey in St. Paul. "My main interest in the whole project is the science: What is it we can learn from all this?" Mech said. "We have learned so much all these years and we continue to learn. Once we interfere, then it's not a natural population. What we are learning is tainted by that." Everything ends eventually, even long research studies aimed at giving insight into some of the world's most vexing issues.
Michigan is home to some of the most respected longitudinal studies — those that collect data on a single group of subjects over a long time. For instance, the University of Michigan has surveyed American students and young adults since 1975 on behaviors, attitudes and values for the National Institutes on Drug Abuse's annual "Monitoring the Future" study. The High Scope Foundation in Ypsilanti has tracked the outcomes of high-quality preschool experience for nearly 50 years.
But long-term research studies can end, sometimes abruptly, when they get tangled up in politics, lose funding or when the person who is running them gets too old to continue. In one instance, scientists revolted when the Canadian government in 2013 stopped funding the Experimental Lakes Area, a research station that studied the health of numerous lakes in northwest Ontario for more than 40 years.
But what happens when the subjects of a study — like the Isle Royale wolves — start disappearing?
The Wolves Moose study, which began in 1958, has sought to understand how wolves affect the moose population on Isle Royale, a 45-mile-long island in Lake Superior off the Keweenaw Peninsula, accessible only by plane or boat.
The moose arrived on the island in the early 1900s and multiplied quickly without any predators. The population fluctuated for 50 years until wolves arrived in the 1940s. Freezing temperatures in Lake Superior led to the formation of an ice bridge from the island to mainland Ontario, creating a pathway for the wolves, which became the only predator of the moose. That simple, isolated ecosystem — with minimal human impact — created a natural laboratory for annual study of both species.
The number of wolves on the island reached a high of 50 in 1980, and over the years the average number has hovered around two dozen. But in recent years, the number of wolves has declined as the moose population keeps growing — up nearly 20 percent to 1,250 at last count.
Researchers have lobbied the Park Service to bring in wolves to add to the population many times, according to the park's superintendent, Phyllis Green. More wolves were requested in 1989, 1995, 2007 and during the last five or six years, when the wolf population has fallen rapidly, Green said.
"If we added wolves in 1989 or in 1995, we would have dramatically changed the course of the study and the things we learned might have been very different," Green said. "The Park Service has always tried to be very thoughtful about what we should do with this situation."
The Park Service will launch a formal planning process this summer, one that will examine issues besides the wolves, Green said. Those issues include climate change's impact on the island and how that affects the moose population and vegetation. "For some folks, it's really all about wolves," Green said.
This year, scientists thought two of the remaining three wolves were either a couple or surviving from packs that were once on the island, according to their annual report. The third wolf was thought to be a 9-month-old pup with unusual posture, and not expected to live very long.
Though the National Science Foundation recently renewed a $90,000 grant for the study for another five years, the future looks bleak to Peterson, a retired professor at Michigan Tech. "The population is doomed if it doesn't have a genetic rejuvenation because of severe inbreeding," Peterson said. "It looks like the population will die out ... We'll also lose symbolic value of this national park as a place where wolves and moose interact and continue to inform us about predator-prey relationship."