A pair of wolves whose home range is on the Grand Portage Indian Reservation in Minnesota recently used an ice bridge to cross 14 miles over Lake Superior to Isle Royale National Park, where they wandered for five days before returning to the mainland.
One of the wolves, a female, was wearing a radio collar that enabled researchers to monitor their travels. According to Seth Moore, director of biology and environment of the Grand Portage Band of Lake Superior Chippewa, on February 22 the wolves crossed the ice to Isle Royale National Park and on February 27 they returned to the mainland.
During their wanderings, the two wolves were spotted by long-time wolf researchers Dr. Rolf Peterson and Associate Professor John Vucetich, both in the School of Forest Resources and Environmental Science at Michigan Technological University in Houghton, Michigan. The two observed and photographed the animals. They found their arrival tracks on the north shore of Isle Royale, some activity at McGinty Cove, and then a track about 1 mile North of Hugginnin Cove.
Then the wolves followed the shoreline around the south shore to the northeast, according to a release from Dr. Moore.
Their tracks were picked up again on the north shore of Siskiwit Lake, then headed southwest to Mud Lake, where they exited along the south shore, crossed the thin part of Washington Island, where they made brief chase of a cow/calf, and then headed straight across the ice at 330 degrees heading for Pigeon Point.
The wolves returned to the Grand Portage Indian Reservation on February 27, said Dr. Moore. "These collared wolves have provided insight into how this isolated population has managed to maintain itself through cryptic or undetected immigration events. The declining frequency of ice bridges between the mainland and the island as a consequence of climate change gives rise to concern of loss of genetic diversity of Isle Royale’s declining wolf population," noted the biologist. "The concern about genetic diversity comes directly from genetic measures and genetically-caused physical defects. The loss of ice has ultimately reduced this precarious connection with the mainland."
Dr. Moore has since 2009 been leading a study to determine wolf densities, pack counts, and wolf diet on the Grand Portage Reservation. The Grand Portage Band of Chippewa have been studying moose and wolf populations on the reservation using GPS collaring technology for the last decade. The goal is to determine how climate change is altering the ecological structure of the Grand Portage Band’s boreal forest system.
The wolf study has indicated that at least three and likely four packs of wolves occupy the Grand Portage Indian Reservation. The largest pack is comprised of nine wolves as observed by helicopter survey conducted during the week of February 22, 2015. The collared wolf that traveled to Isle Royale was captured in early February 2014 and came from a pack of seven wolves that were feeding on a moose kill near the Pigeon River.
Diet studies conducted on Grand Portage wolves indicate that they eat moose (50% of diet), deer (35%), and beaver (15%). Adult moose predation rates have been low on reservation lands, but moose calf predation is very high and may be contributing to low populations of moose on reservation lands.
The Grand Portage Band has been studying moose populations and causes of mortality in adult moose and moose calves for six years. That research has indicated that brainworm is the leading cause of death for collared moose (40%) followed by winter ticks (20%), other health issues (20%); however, wolf predation only comprises about 6 percent of adult collared moose mortality. A related study to identify calf mortality causes indicated that about 70 percent of newly collared calves are preyed upon within the first two weeks of life, about half of that predation is due to wolves.
Officials at Isle Royale National Park, where it's feared the resident wolves will die out due to a lack of genetic diversity, are developing and initiating a planning process to evaluate how to manage the wolves, moose, and vegetation on Isle Royale. In the meantime, the general public can provide comments on this issue by sending an email to firstname.lastname@example.org. Concerns of climate change causing a reduction in frequency of ice bridges like the one used by these collared wolves have catalyzed these discussions.
The Grand Portage Band has a long history of using Isle Royale and has had claims to the land since prior to the treaty of 1842. "Clearly, both humans and animals used the ice bridges historically and Grand Portage Indians subsisted on moose, woodland caribou (prior to arrival of moose), moose, and many fish species – lake trout, whitefish, herring, sturgeon, suckers, and brook trout," said Dr. Moore. "Grand Portage people also went to 'Minong' –their name for Isle Royale—to make maple sugar and gather plants for food and medicinal purposes. Portagers also trapped furs (otter, marten, beaver) through time and collected stones and copper found in a near 100 percent pure state."
Wolf 13264* Captured and collared on February 3, 2014* Female, weighed 62 pounds, had approximately 50% hair loss due to mange* Darted from a helicopter, immobilized* GPS collared and released (4 hours data collection, three-year life span of collar)* Core home range is in Grand Portage and southern Ontario*Furthest distance across locations is 100 miles*Made multiple trips > 50 miles*Likely den site localization from 2/12/14 to 3/13/14* Returned to den multiple times over this time span* Traveled to Isle Royale 2/22 to the northwest side of the island* Traveled along of the west end of the island, following the Lake Superior shoreline*Traveled to Siskiwit Lake on 2/26* Left on 2/27 and is currently in Grand Portage