In this image from April 2021, an emaciated and nutritionally stressed bull moose — who is also severely impacted by winter ticks — beds down on the island/Sarah Hoy, Michigan Tech

Too little food and too many ticks are adversely impacting the moose population at Isle Royale National Park, though a seemingly increasing wolf population could begin to play a role in producing a more balanced number of moose on the island.

This spring Michigan Tech researchers found that "most balsam fir saplings had been browsed so severely that they had either been killed or left with only a few green branches at the west end of the island. Researchers also found the bodies of 13 moose, when in a regular year they would typically find only one to two starved moose."

“Moose really struggled to find enough food this past winter,” said Sarah Hoy, a research assistant professor at the university who co-authored along with Rolf Peterson and John Vucetich the university's annual report on how Isle Royale's wolf population is faring. “Because there have been such large numbers of moose on the island over the last five years and moose ate branches faster than the trees can recover and replace them, the amount of food available to moose during winter has been getting progressively worse each year since 2017."

In addition, ticks last winter were a significant problem for the moose. The researchers saw "moose with very little fur left in spring — having scratched or bitten off almost all of their winter coats in an effort to rid themselves of the blood-sucking parasites. This is significant because blood loss to ticks can exacerbate the detrimental effects of food shortage. Despite the mild winter, depleted food supplies and ticks made life harder for the island’s moose this year," said a release from the university.

Under a plan adopted by the National Park Service in 2018, the agency worked to bring up to 30 wolves to Isle Royale over a three-year period in a bid to insert some genetic diversity into the park's few remaining wolves. 

Chronic inbreeding long impacted the health of Isle Royale's wolf population. There was hope that "ice bridges" that formed between the Lake Superior island and the Canadian mainland during the winter of 2013-14 would enable wolves to arrive from Canada with new genes. But no new wolves reached the island, while one female left and was killed by a gunshot wound in February 2014 near Grand Portage National Monument.

The Park Service and research partners estimated as many as 14 wolves were present on Isle Royale as of April 2020. Eight wolves died with the most common cause of mortality tied to fights between different packs. However, last fall they found evidence that an unknown number of pups had been born to wolves transported to the island.

This spring, footage from a camera trap on Isle Royale showed what researchers believe to be another litter of pups.

“We recovered footage of a group of four wolf pups taken in January 2021 by remote cameras at the east end of Isle Royale,” said Hoy in the press release. “Additionally, observations of tracks and scats left by wolf pups last fall at two different locations suggest that there were probably two different litters of pups living at the east end of the island in September 2020.”

As a result, Hoy and colleagues expect the wolf population to have grown slightly or moderately since the last survey count, so long as there hasn’t been an unusually high death rate.

Mark Romanski, biologist and natural resources program manager at Isle Royale National Park, said the Park Service will use the information collected by Michigan Tech researchers, along with that derived from genetic analyses conducted through the conservation genetics lab at Michigan Tech, to provide a formal wolf population estimate.

“We anticipate completing an initial summary of these data in July,” Romanski said. “Because of constraints placed on field activities during the pandemic, we are especially pleased to have multiple lines of evidence to enumerate the population.”

MTU’s research on the island’s wolf and moose is the longest running predator-prey study in the world. For 63 years, researchers have documented both species, noting in recent years a steady decline in the number of wolves and the resulting rise of the park’s moose population.

This year, due to the Covid pandemic, marked the first time in the study’s history that the researchers were unable to conduct research in person at Isle Royale during the winter. 

“This year, their research provided a picture that’s worth a thousand words. Snapshots of four wolf pups born on the island demonstrate that Isle Royale’s wolves are breeding and thriving," said Christine Goepfert, Midwest associate director for the National Parks Conservation Association. "This is a story of hope for the park ecosystem, one that scientists and conservation advocates have worked so hard to see realized.

“The Park Service’s plan to reach 20-30 wolves at the park is well on its way, not a minute too soon," she added. "While it’s welcome news that there are more wolves in the park to stem the growing moose population, researchers believe the overabundance of moose has already led to a serious problem. Without wolves on the park landscape, the moose population has been outgrowing its food sources. With too many moose and not enough balsam fir trees for them to live off, Isle Royale moose are starving to death.

“A healthy park ecosystem includes a variety of wildlife and abundant food sources. As wolves bounce back after nearly disappearing from the park, their presence as a predator on the island will help all wildlife and native plants thrive at Isle Royale,” said Goepfert.