FILE - In this Feb. 28, 2019, file photo, provided by the Ontario Ministry of Natural Resources and Forestry, the U.S. National Park Service and the National Parks of Lake Superior Foundation, a white wolf is released onto Isle Royale National Park in Michigan. Warm weather has forced the federal officials to suspend the annual wolf-moose count in Isle Royale National Park for the first time in more than six decades. (Daniel Conjanu/The National Parks of Lake Superior Foundation via AP, File)

A stretch of unusually warm weather has forced federal officials to suspend researchers' annual wolf-moose count in Isle Royale National Park for the first time in more than six decades.

Isle Royale is a 134,000-acre (54,200-hectare) island situated in far western Lake Superior between Grand Marais, Minnesota, and Thunder Bay, Canada. The park is a wildlife biologist's dream - it offers a rare opportunity to observe wolves and moose acting naturally without human influence. Researchers have conducted an annual survey of the park's wolf and moose population since 1958. It's been going on every year except for 2021, when the COVID-19 pandemic forced scientists to cancel it.

Scientists from Michigan Tech University returned to the island this past Jan. 19, planning to survey the wolf and moose populations from the air through March, said Sarah Hoy, a Michigan Tech research assistant professor who leads the project alongside John Vucetich, a Michigan Tech forestry professor, and Rolf Peterson, a retired Michigan Tech ecology professor.

Hoy said that the National Park Services suspended the survey on Tuesday and ordered everyone off the island. She said warm temperatures have left the ice around the island unsafe for the scientists' ski-planes to land.

“The ice on the harbor was starting to deteriorate, I guess,” Hoy said. “We lost some ice depth and a few holes and cracks were starting to appear. ... Everybody had to leave. So the island's now only occupied by wolves and moose and a bunch of critters. We're incredibly disappointed that we're not able to continue our work.”

Temperatures in the region have hovered above freezing since Jan. 24, about 20 degrees above average, according to the National Weather Service. The mercury hit 47 degrees Fahrenheit (8 degrees Celsius) in the area on Wednesday.

Hoy said helicopters aren't an option because they're expensive to rent and so loud they'll disturb the wildlife, she said. The team may return to the park if temperatures drop and the ice firms up enough to support ski-planes again, she said. It's too far to fly from the mainland to the island, complete survey circles and fly back, she said.

The team may return to the park in spring by boat, but trying to conduct the survey then will be far more difficult, Hoy said. The snow and bare branches makes tracking easy in the winter, but once the trees bloom, spotting the wolves and moose will be much more difficult, she said.

The scientist's 2022-23 survey put the number of wolves on the island at 31, up from 28 wolves the prior year, and the number of moose at 967, down 28% from 1,346. The team attributed the decline to lower survival rates for calves, starvation and wolf predation. The scientists estimated a wolf killed 0.52 moose every month last year.

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