Isle Royale moose crashing as wolves thrive

wolves on Isle Royale — Part of a pack of Isle Royale wolves. As of last winter, there were two large packs on the island totaling 28 wolves, more than double the 14 wolves from 2020.

By John Myers

August 24, 2022 at 12:28 PM

HOUGHTON, Mich. 鈥� The number of wolves living on Isle Royale has nearly doubled to 28, a sign that the effort to transplant outside wolves to the Lake Superior island has taken hold.

The wolves 鈥� now all descendants of animals brought to the island from Minnesota, Ontario and Michigan 鈥� also are doing their job at reducing what had been a burgeoning moose population, with 2022 moose numbers down 28% from 2020 levels.

Those were the long-delayed findings from the 63rd annual winter survey held earlier this year by researchers from Michigan Technological University. It鈥檚 the longest running research project on predator prey relationships in the world.

It was the first full-scale survey of moose and wolves on the island since 2020 because of COVID-19 concerns for research crews. The seven-week expedition by ski and plane took place Jan. 25 through March 6 on the 850-square-mile archipelago located about 15 miles off Minnesota鈥檚 North Shore.

The report, usually released in April, was released Wednesday, with the reason for the delay unclear.

Wildlife researcher Ky Koitzsch stands next to a dead moose during last winter's annual survey of moose and wolf populations on Isle Royale. Several wolves had been feeding on the moose carcass when researchers arrived. Only about 10% of the dead moose on the island over the winter were killed by wolves, researchers found, and the rest succumbed to starvation and winter ticks.

At least five litters of pups have been born on Isle Royale since 14 wolves were translocated to the island in 2018-19, said Sarah Hoy, a Michigan Tech research assistant professor. The wolves appear to be living in two packs: one in the island鈥檚 western region and the other in the eastern.

鈥淓ach time we carried out aerial surveys this winter, we saw wolf tracks across many parts of the island and we also regularly saw groups of wolves traveling or resting together,鈥� Hoy said in this year鈥檚 annual report. 鈥淚t is such a pleasant change from five years ago when there were only two wolves on the island and the future of the wolf population looked pretty bleak. It just goes to show how quickly wolf populations are able to thrive in places where they are free from persecution.鈥�

moose with ticks — A scrawny bull moose fitted with a GPS transmitter collar on Isle Royale photographed last winter. The moose had rubbed off much of its hair, likely due to winter ticks. It also may be starving due to a lack of winter food on the island. Moose numbers declined 28% from winter 2020 to winter 2022.

But while wolves are thriving, moose are having a tougher time on the wilderness island National Park. After exploding in number for a decade, the moose population is heading headlong into another bust part of the continual up-and-down cycle. Only 4% of the moose counted during the winter survey were calves, the lowest number observed since 2007.

Researchers estimated 1,346 moose on the island last winter, down 28% from 1,876 estimated in 2020.

Researchers found that wolves killed less than 10% of the moose that died last winter. Most moose appeared to have died from malnutrition, in part because of blood-sucking winter ticks 鈥� each moose can carry hundreds, even thousands of ticks 鈥� but also because moose have run out of balsam fir, an important winter food. Moose became so numerous on the island over the past decade they literally depleted their food source. Meanwhile an outbreak of spruce budworm, an insect that eats the needles on balsam and spruce trees, also is occurring on the island.

鈥淥ver the past year, we found an unusually high number of moose that appear to have died due to malnutrition,鈥� Hoy said. 鈥淭he population appears to be suffering from a food shortage, especially in winter when moose don鈥檛 have many good options of things to eat.鈥�

Rolf Peterson, Michigan Tech researcher who has been studying wolves and moose on the island since 1970, said he鈥檚 not surprised by how fast wolves have expanded.

鈥淭hey have plenty to eat and I think we鈥檒l see their numbers continue to go up,鈥欌€� Peterson told the News Tribune. 鈥淲e鈥檝e had as many as 50 wolves on the island before so there鈥檚 still room for them to grow.鈥濃€�

Peterson noted that wolves also appear to be checking the island鈥檚 beaver population. When wolf numbers had crashed a decade ago, beaver numbers increased five fold to the highest level in at least a century, Peterson said. Now, beaver numbers are dropping as wolves increase.

鈥淏eaver are an important summer food for the wolves,鈥欌€� he said.

This winter, researchers worked in partnership with the National Park Service and Grand Portage Band of Lake Superior Chippewa to outfit 19 moose with GPS collars, part of an ongoing project to assess the influence of predation on moose now that the wolf population has been restored. Hoy, Peterson and fellow Michigan Tech researcher John Vuectich also worked with National Park Service biologists to place GPS-transmitting collars on several wolves to monitor their activities.