Wolves Rise, Moose Plunge on Isle Royale

The wolf population on Isle Royale is growing and thriving, while the island’s moose population continues a sharp and troubling decline, according to a new annual report from Michigan Technological University researchers.

Scientists estimate there are now 37 wolves on the remote Lake Superior island, an increase from recent years and a sign the predator population is stabilizing after past struggles with inbreeding.

At the same time, the number of moose, the wolves’ primary prey, has dropped to 524 animals, down 38% from 2024 and about 75% from a peak in 2019 of about 2,060 animals.

Researchers say the decline is being driven by a combination of poor reproduction and heavy predation.

For the first time in nearly seven decades of study, scientists observed no moose calves during annual survey flights this winter, a concerning indicator of the herd’s struggles.

The lack of young animals means the population is not replacing itself, even as wolves continue to hunt at unusually high rates.

This year, wolves killed an estimated 24% of the moose population, one of the highest predation rates ever recorded on Isle Royale and more than double the long-term average.

The wolf population is now organized into three packs, each with about ten or more animals. All three packs successfully raised pups last year and are expected to reproduce again this spring, further strengthening their numbers.

The resurgence follows a 2018–2019 effort by the National Park Service to reintroduce wolves to the island after the population nearly collapsed, with only two wolves.

The wolf reintroduction program has been so successful that wolf predation has become “a major cause of mortality for moose and has contributed to the ongoing decline in moose abundance over the past six years,” the report says.

If the trend continues, researchers warn the moose population could approach historic lows seen in the early 2000s. In 2007, scientists counted 385 moose on the island.

The long-running Isle Royale study, one of the world’s most famous examinations of predator-prey dynamics, highlights how closely the fortunes of wolves and moose are linked.

Featured photo: In this 1966 aerial photo, wolves surround a moose on Isle Royale in Lake Superior. The long-running study of wolves and moose on the island is one of the world’s most famous examples of predator-prey dynamics. Photo by L. David Mech – Wolves of Isle Royale, Public Domain, Wikipedia