Isle Royale Wolves Hit a 47-Year High as Moose Herd Collapses

Isle Royale wolves are thriving and the island's moose are not, according to a survey released this spring by Michigan Technological University. The roadless wilderness in Lake Superior, reachable only by boat or floatplane, now holds an estimated 37 wolves, the most researchers have counted since the late 1970s. The moose herd, meanwhile, has fallen to 524 animals, a 75% drop from its 2019 high of around 2,000.

The 2026 Winter Study, run from January 22 to March 3, found the Isle Royale wolves and the island's moose pulling apart at a rate the long-running project has rarely recorded. Wolf predation accounted for roughly 24% of the moose population over the past year, close to the highest rate ever observed there. For the first time in 68 years of counting, the team observed no calves during the annual moose count.

How the island got here

Isle Royale sits far enough from the mainland that its wildlife arrives by accident or not at all. Wolves first crossed to it on an ice bridge around 1948, and researchers have tracked the island's wolves and moose since 1958, making the record one of the longest continuous predator-prey studies in the world. Inbreeding then nearly finished the wolves: by 2018 only two remained. The National Park Service translocated 19 wolves in 2018 and 2019 to keep the line from going extinct.

That rescue worked, and it worked faster than a headcount alone suggests. The 2026 survey found three packs, the West, East and Northeast packs, each carrying 10 to 13 wolves. All three raised pups the previous year and appeared likely to do so again this spring.

The forest is the third character

The rebound is not only about animals. Balsam fir makes up about half of a moose's winter diet, and heavy browsing from 2018 to 2021 hammered the island's young trees. Even with fewer moose now, the trees have not recovered. Researchers measured young balsam firs growing an average of just 2.7 centimeters over the past year, the slowest growth they have recorded; in low-browse years those saplings typically add about 20 centimeters. That lag is part of why the Park Service stepped in to restore the wolves in the first place.

Why it matters

Isle Royale behaves like a sealed experiment. The only large forces acting on its wolves and moose are weather, food and each other. When the island swings, researchers can watch a predator-prey cycle turn in real time, without the highways, hunters and development that complicate the story almost everywhere else.

The National Park Service frames those swings as a long-standing cycle: as wolves decline, moose rise, and the reverse. Its restoration plan anticipated 20 to 30 wolves, and the current count of 37 sits at the top of that band. The open question is what a high wolf count, a collapsing moose herd and a stalled forest mean together. Rolf Peterson, who co-leads the study, put the position plainly, saying the two populations are now approaching the edge of where they have been before, with moose low and wolves high.

His co-leader, Sarah Hoy, tied the numbers back to the ground she walks. She said she had seen only one moose calf in the past year, and that while the wolf recovery is welcome, watching both the moose population and the forest struggle is hard, though not unexpected.

What happens next

The island's history suggests the balance will move again. A hard winter can lock in an ice bridge and let new wolves in or let weakened moose die; a mild one can spare the herd. This past winter delivered an ice bridge from late January to mid-February, the kind of link to the mainland the island has not seen regularly since the 1970s. Researchers will keep counting, and the forest will keep its own slower ledger.

Isle Royale is not the only wildlife story moving this season. Great whites have returned off California, and a beluga died at a San Diego marine park. What sets this island apart is that its animals cannot leave; every swing in the count is a swing the researchers can watch from the air.

Sources: Michigan Technological University, "Isle Royale Wolf Population Nears Historic High as Moose Numbers Plummet," published April 27, 2026, at mtu.edu; U.S. National Park Service, "Wolf & Moose Populations," last updated September 18, 2026, at nps.gov; and the 2025-26 "Ecological Studies of Wolves on Isle Royale" annual report.