In the winter of 1948, a small group of wolves crossed a bridge of ice from the Canadian mainland onto Isle Royale, and then the ice broke up behind them. There was no going back for them, and for decades afterward there wasn't much coming or going for any wolf on the island at all, which is exactly what makes the predator-prey relationship that followed the longest and most closely watched of its kind anywhere on Earth.
Fifty Wolves, Then Two
Researchers began formally tracking Isle Royale's wolves and moose in 1958, when the project started out of Purdue University. It moved to Michigan Technological University in 1975 under biologist Rolf Peterson, and in 2026 it's in its 68th year, making it the longest continuous study of a single predator-prey system anywhere in the world. The wolves themselves were never native to the island. They arrived by that 1948 ice bridge and stayed only because Isle Royale, ringed by Lake Superior, doesn't let animals wander on or off the way they could on the mainland.
That isolation cuts both ways. It's what let researchers watch one uninterrupted population for nearly seven decades, and it's also what nearly ended the population outright. The wolf count climbed as high as fifty animals by 1980, but with no regular way for outside wolves to reach the island and refresh the gene pool, inbreeding set in. Deformities and low survival rates followed, and by sometime between 2016 and 2018, the island's wolves had fallen to just two, both closely related, effectively marking the end of genetic viability for the population that had made the ice crossing seventy years before.
- Study founded 1958, PURDUE UNIVERSITY
- Moved to Michigan Tech 1975, UNDER ROLF PETERSON
- Years running, as of 2026 68
- Wolf population, 1980 50
- Wolf population, 2016–2018 low 2
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Open the Trip PlannerNineteen Wolves, and What Came Back
Facing the end of wolves on Isle Royale entirely, the National Park Service relocated nineteen wolves to the island from the wider Great Lakes region across 2018 and 2019, a deliberate genetic rescue rather than a natural recolonization. It worked, and it worked fast. By the 2026 winter study, researchers counted thirty-seven wolves organized into three packs, West, East, and Northeast, each holding ten to thirteen animals, a population not seen since the late 1970s.
The moose are the ones absorbing the rebound. Their numbers peaked near 2,000 in 2019 and had fallen to 524 by 2026, a decline of roughly 75 percent, with wolf predation accounting for an estimated 24 percent of the moose lost over the past year alone. For context, the lowest moose count on record before this stretch was 385, back in 2007, so the herd isn't yet at its historic floor, but the direction is unmistakable: for the first time in the study's 68 years, researchers observed zero moose calves surviving to be counted in 2026.
- Wolves relocated 19, ACROSS 2018–2019
- Wolf population, 2026 37, IN 3 PACKS
- Moose population, 2019 peak ~2,000
- Moose population, 2026 524 (-75%)
- Moose calves observed, 2026 0, A FIRST IN 68 YEARS
Wolf arrival, study history, and the 2018–2019 relocation checked against the National Park Service's official account of wolves at Isle Royale. Current wolf and moose population figures, pack structure, and the 2026 zero-calf finding checked against the 2026 winter study results reported by Michigan Technological University and the National Park Service.
Another ice bridge formed between Isle Royale and the mainland in January and February of 2026, the same kind of frozen crossing that let the original wolves reach the island in 1948 and let researchers imagine, for a while, that recolonization might just happen on its own. It didn't need to this time. Nineteen wolves flown and driven in by people did the job the ice used to do, and did it faster than nature ever had, fast enough that the moose the wolves depend on may be the next number this study has to explain.