Isle Royale transplants are settling in
Researchers encouraged by signs of litters of wolf pups
After a somewhat rough start, the wolves who survived being transplanted to Isle Royale in Lake Superior seem to have taken a liking to their new surroundings, producing multiple litters of pups.
Nineteen wolves were transplanted on the island national park between 2018 and 2019 to bolster its nearly vanished wolf population and counterbalance the island’s swelling numbers of moose.
Though the COVID-19 pandemic disrupted Michigan Technological University’s annual winter survey of Isle Royale wolves and moose for the first time in 63 years last winter, data gathered last summer and this spring and summer seems to show the transplanted wolves settling into their new home. Researchers last summer found evidence of two litters of wolf cubs born on the island’s eastern end, and possibly a third litter on the west side of the island, Michigan Tech research assistant professor Sarah Hoy said.
In January, a remote camera on the island caught footage of a group of four wolf pups on the island’s eastern end.
“That shows that at least one litter of the wolves had survived into winter,” Hoy said.
“This summer, we’ve had a lot of reports from visitors of pup tracks, and footage of a wolf pup on the west end of the island on social media. All of that taken together suggests the wolf population is reproducing and doing well.”
Wolves came to Isle Royale about six decades ago by crossing a frozen Lake Superior in winter. The island’s wolf population once reached 50 wolves, and averaged 25 wolves over decades, before a population crash in the 2010s because of the physical ailments and reduced ability to breed because of severe inbreeding. Changing weather patterns, leading to fewer and smaller ice-overs of Lake Superi
or, have meant fewer ice bridges between the island and mainland to potentially replenish the wolf population.
With the disrupted predatory-prey balance between wolves and moose, the moose population soared, threatening the island’s ecology with their voracious appetites for vegetation. In 2015, the National Park Service began to deliberate about whether it should intervene, and ultimately decided to undertake a “genetic rescue” of Isle Royale wolves with relocated wolves from the mainland. Between fall 2018 and fall 2019, 19 gray wolves were brought to the island from the mainland, from genetically diverse packs in Minnesota, Ontario and Michigan. Another Minnesota wolf died in the process of being captured and anesthetized.
Seven wolves died on the island within months, one from pneumonia, several from wolf infighting and others from unknown causes. But an unlikely group of the transplanted wolves emerged from the early hardships — seven of the eight wolves brought to Isle Royale from Michipicoten Island in Ontario. The undernourished wolves didn’t meet the health conditions set by the Park Service for the reintroduction program, but were granted exceptions as a sort of rescue mission because Michipicoten Island had run out of prey, Michigan Tech researcher Rolf Peterson said last year. Those wolves began to form packs, develop their ranges on the islands, and den and have pups.
Another transplanted wolf, a female from Minnesota known as 003F, brought to the island in fall 2018, decided Isle Royale wasn’t for her. By late January and early February of that winter, signals from her radio collar showed she had left the island, traveling north across a frozen Lake Superior. She ultimately reached the mainland in Ontario, near the Minnesota border.
Because of its remoteness and access only by boat, Isle Royale is the least-visited national park in the contiguous United States. The wolves and moose that live there are best surveyed by researchers in the winter, when leaves have dropped on the heavily forested island and the animals are more visible from the air, and when the wolves’ distinctive tracks can be analyzed in the snow.
The last surveyed count of wolf and moose, from February 2020, showed 12 to 14 wolves, and about 1,800 moose, Hoy said. Given the likelihood that a few wolves have died from natural causes, and with the new pups, Hoy speculates there may now be “15 to 20” wolves on the island, with moose down to about 1,500 to 1,600. “But that is a guess,” she said. “It will probably be this winter until we get a firmer idea.”
The moose population on the island, researchers suspect, “has either started declining, or is just about to decline,” Hoy said.
The high number of moose in recent years, and their ability to eat as much as 30 pounds each of vegetation a day, has significantly impacted their available food.
“Balsam fir makes up half of the moose’s diet on the island,” Hoy said. “In a good year, branches grow 5 or 6 inches. This year, it basically grew maybe 1 inch. It’s been severely over-foraged.”
Teams out hiking looking for moose bones found at least 15 carcasses that looked like they died from starvation, Hoy said. In a typical year, researchers would find only one or two moose that died that way, she said.
An additional factor in the increased moose mortality was an unusually high number of ticks over the relatively mild winter this past winter, Hoy said. The ticks attach to moose in late summer and early fall, and suck their blood over the winter. In a bad winter like this one, a single moose can have up to 70,000 ticks on it, feeding. The moose bite at their fur, trying to remove the ticks, often tearing off most of their winter coat.
“The moose use a lot of energy replacing that blood,” Hoy said. “And because it has lost its fur, it has to use more energy to generate body heat.”
Wolves seek out moose calves and sick or elderly moose, those easier to kill and providing less worry of injury to the wolves from the powerful, up to 1,500-pound, antlered animals.
“In theory, if the moose population is not in very good shape, that could benefit wolves,” Hoy said. “But the other thing to consider is that stressed, weakened moose may be less likely to reproduce.”
Temperature data indicates the Great Lakes region is warming faster than the rest of contiguous United States, and humangenerated carbon emissions have been identified as a key driver of the changing climate. That could be particularly hard on Isle Royale moose, Hoy said. Summer heat stresses moose, increases tick loads and is bad for their favorite food, balsam fir, she said.