TRAVERSE CITY, Mich. — A gray wolf that was moved from Minnesota to Isle Royale National Park last fall has wandered back to the mainland, trekking more than 15 miles (24 kilometers) across the frozen surface of Lake Superior to reach her home turf, officials said Wednesday.
The female was among four wolves relocated from the Grand Portage Band of Lake Superior Chippewa reservation in September and October — the first steps in an effort to restore the species at the park, where a predator is needed to prevent moose overpopulation.
The National Park Service hopes to move 20 to 30 wolves to Isle Royale over several years.
The project has hit some early snags. One wolf captured for movement to the park died in captivity. Another perished a month after it arrived. Plans to transfer a new group from Michipicoten Island in Canada have been delayed, first by the partial U.S. government shutdown and then by rough weather.
Still, park superintendent Phyllis Green said such setbacks weren't unexpected and wouldn't thwart the operation.
"When we made the decision to restore the predator-prey relationship, we knew we would have to respectfully work with whatever curves nature threw at us, whether it's adverse weather or wolves working out where they choose to fit on the landscape," she said.
"We're going to continue the project for the next three years, a window we feel affords us the opportunity for successful restoration."
Scientists believe wolves originally crossed ice bridges in the late 1940s to reach Isle Royale, where they formed packs and feasted on moose. But they became inbred and their numbers dropped sharply in the past decade. Only two remained when the relocation began. They're believed to be alive, putting the current population at four.
The transplanted wolves were fitted with radio collars enabling researchers to track their movements. A team from Michigan Technological University arrived last weekend to begin their annual winter study of the wolves and moose.
During an aerial search, biologist Rolf Peterson found that two of the newcomers were still on the island. But the third transplant's signal directed them toward the lake and eventually the mainland.
Mark Romanski, the park's natural resources chief, used GPS data to confirm the wolf had left Isle Royale on Jan. 31 and was near the border between northeastern Minnesota and the Canadian province of Ontario.
Studies have shown that a wolf moved less than 80 miles (129 kilometers) from its original territory might try to return home, said Dave Mech, a U.S. Geological Survey biologist. However, those held in the new area three to four weeks usually stay put. That didn't happen this time.
"The Isle Royale wolf translocation is new territory in understanding wolf behaviors," Mech said.
Green said it was necessary to use Minnesota wolves — along with those from Ontario and Michigan's Upper Peninsula, which will arrive later — to ensure genetic diversity in the rebuilt population.
"The drama gets captured in how individuals behave," she said. "But what we're looking for is a healthy wolf population on the island."