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Researchers forced to cut short an annual survey of wildlife on a remote Lake Superior island this winter due to unusually warm weather announced Tuesday that they managed to gather data that shows the wolf population is stable.

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, offering a rare opportunity to observe wolves and moose acting naturally without human influence.

Scientists have conducted an annual survey of the island’s wolves and moose since 1958. It’s been going on every year except for 2021, when the pandemic forced researchers to cancel.

Researchers typically conduct aerial surveys of the island to develop population estimates and observe animal behavior. The island doesn’t have a landing strip so the scientists use skiplanes that can land on the ice surrounding it.

A team led by Michigan Tech University researchers was two weeks into this year’s seven-week survey in January when unusually warm temperatures left the ice around the island unsafe for their planes to land. They were 

Data the team gathered before they left shows the wolf population stands at 30 animals, down from 31 animals last year but up from 28 in the winter of 2022. The scientists said they believe the wolves have divided themselves into four packs, with one pack numbering at least 13 wolves. At least one wolf appeared to be living alone.

The moose population, meanwhile, stood at 840, down 14 percent from last year. Overall, the moose population has declined by almost 60 percent since 2019, when the population peaked at a little more than 2,000 animals.

That year, the National Park Service relocated 19 wolves to the island, to try to restore balance between the two species, after the wolf population had dwindled and the moose population surged. 

While it’s still too early to determine the longer term consequences of the relocation, Michigan Tech University professor and project co-lead Sarah Hoy said so far the results are encouraging. 

“The number of wolves on the island and the number of moose that are currently on the island are about in line with what we would expect based on six and a half decades of observing the population,” Hoy said. 

“So it seems that those populations are at more sustainable levels than they have been in the past.”

Hoy said the surviving moose population also appears to be healthier, with fewer animals dying of starvation than in past years. Wolf predation is once again the main cause of mortality of moose. 

Moose can eat up to 40 pounds of vegetation daily and with low wolf numbers, the population grew unchecked and the creatures ate themselves out of food. 

Large numbers of moose eating huge amounts of food also severely limited the growth and survival of tree and plant species that moose prefer to eat, including balsam fir, researchers say. 

“It appears that restored wolf predation is now coming to bear on calf survival, greatly reducing the growth potential of the moose population, but offering hope that trees stunted by moose feeding might finally be able to grow,” said project co-lead Rolf Peterson.

Fewer moose are having calves, the research team said. Less than 6 percent of the moose the researchers observed this winter were calves. That’s higher than last year’s estimate of 2 percent, but still far below the long-term average of 13 percent.

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Dan Kraker

Wildlife researchers say the wolf population on a remote Lake Superior island is stable. But they announced Tuesday that the moose population had declined by 14 percent from last year. Scientists have conducted an annual survey of Isle Royale’s wolves and moose since 1958.

Remote Lake Superior island wolf numbers are stable but moose population declining, researchers say

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