Lake Superior's last caribou herds: Ontario rushes to move remaining herd to avoid wolves
The last few Lake Superior woodland caribou may be on the brink of extirpation thanks to the freakishly cold winter of 2014 and hungry wolves decimating caribou herds in their last two holdouts.
While wildlife enthusiasts mourn the loss of the last remaining wolves on Isle Royale, the opposite problem is happening on Ontario's Lake Superior islands just 100 miles or so away: Too many wolves for caribou to survive.
On the Slate Islands, where a remnant population of Lake Superior woodland caribou had thrived for decades with no predators, as many as 650 caribou roamed there in the 1990s and at least 100 in recent years.
Now, after just the three years with wolves on the island, only three or four bull caribou remain. A recent survey of the islands found zero cows and calves.
Farther east along Ontario's North Shore of Lake Superior, at least 450 caribou roamed Michipicoten Island as recently as 2014. Then a few wolves crossed the ice from Pukaskwa National Park. Wolves now number between 15 and 20, depending on how many pups survived this summer. They had already eaten their way down to about 120 caribou as of late 2016, the most recent survey data available.
"It's probably far fewer than 100 by now. We think all the caribou will be gone sometime later this winter. I don't think they can hang on any longer," said Gord Eason, a retired biologist.
Eason was part of the Ontario Ministry of Natural Resources and Forestry in 1982 when the agency transplanted several Slate Islands caribou to Michipicoten, which also had no predators.
The transplanted caribou thrived on Michipicoten, as the species had for centuries before European settlement.
But caribou simply can't cope with large numbers of wolves. Unlike moose, which are bigger and better able to defend themselves against wolves, caribou, a little larger than deer, are extremely vulnerable to wolf predation on the island where escape is difficult.
It's the wolf version of shooting fish in a barrel.
"Moose will stand and fight when confronted by a wolf, and a fair number of them survive," Eason noted. "Caribou, which are much smaller, are easy for a wolf to take down. They have no choice but to run, to flee. But they really don't have any place to go on an island."
In far northern Ontario, from Lake Nipigon north, wildlife experts say woodland caribou survive with wolves only because both animals are in such low densities that they rarely bump into each other. On the Lake Superior islands, wolf densities are far beyond the level caribou can survive. (The Slates are about 14 square miles total. Michipicoten is about 70 square miles. Both are about 9 miles off the mainland.)
"The islands went from having the highest woodland caribou densities in the world to the highest wolf densities in the world," Eason noted. "With the (small) size of the islands, even one wolf would be too many now."
Once fairly common across the Lake Superior region, as far south as Minnesota and Michigan into the early 1900s, this variety of woodland caribou may now face extirpation. Scientists believe the occupied habitat of woodland caribou is shrinking, with the line moving northward by about 20 miles every 10 years. Some experts say they may be gone from Ontario by the end of the century. (Migratory, barren-ground caribou that live on the tundra are considered a different species.)
That gradual decline of caribou around Lake Superior has been happening for over a century as railroads, highways, logging, more people, more wolves, moose and deer moved into the caribou's range. Now, the last caribou face a threat that has arrived with, in biological terms, lightning speed. Eason says action needs to be taken within weeks, not months or years, to save the genetic diversity of the Lake Superior woodland caribou in their last remaining island holdout.
"They are gone from Pukaskwa. They are gone from just about everywhere else around Lake Superior," Eason said. "They are a threatened species. We really should do something."
While there's also a movement to let nature run its course and let the wolves eat the last caribou on the islands, Eason said the human thumbprint on the problem already is too big to ignore. With connecting ice forming in fewer winters the island wolves and caribou become isolated and trapped.
"Back when we had had ice to the islands nearly every year, for most of the winter, the caribou and wolves could go back and forth. ... They probably did that for hundreds of years. Now, they are isolated. And we've done that," he said, citing climate change.
Brent Patterson, wildlife biologist for the Ontario Ministry of Natural Resources and Forestry and a professor at Trent University, is leading the government's effort to respond to the caribou crisis.
"This issue has risen to the highest levels of the (ministry) and of the government" of Ontario, Patterson said. "These are about the last animals left in that Lake Superior Coastal population of caribou. ... That we are running out of time is not lost on us. We fully understand the clock is ticking."
Eason at one point had hoped that the U.S. National Park Service might take some or all of the Michipicoten wolves for Isle Royale where wolf numbers have crashed from near 30 to just one or two because of genetic deformities due to inbreeding. (Isle Royale lost its last native caribou in the 1920s.)
Eason said he spoke with Rolf Peterson, Michigan Technological University researcher at Isle Royale, "and we really thought it might work to move Michipicoten wolves to Isle Royale."
But the Park Service slowed its action on its wolf reintroduction plan for Isle Royale and now any wolf relocation likely would be too late to help the caribou. (Patterson said Ontario stands ready to quickly give the Park Service Michipicoten wolves for Isle Royale if and when the U.S. government makes a decision.)
Meanwhile, any proposal to cull wolves on the Ontario islands likely would be met with heated opposition in parts of province. "Wolves are very popular ... that would be a hard sell," Eason said of killing wolves to save caribou.
"Even for folks who lobby strongly for us to take action for the caribou, the idea of using lethal control on wolves is unpalatable," he said.
Move the caribou
If you can't kill the wolves or move them fast enough, caribou supporters are hoping a third option might work — moving the caribou to another island with no wolves.
Eason has suggested Leach Island, farther east along Ontario's shore of Lake Superior. But Patterson said that, ironically, the best option may be to move several Michipicoten caribou back to the Slate Islands. He said trail cameras this summer showed that, when caribou numbers crashed to near zero on the Slates, wolves died from starvation, unable to leave during recent warm winters.
"We looked at a lot of camera trap (trail camera) data and we couldn't find any evidence of any wolves remaining" on the Slate Islands, Patterson said. "We think they starved to death."
On Thursday, Ontario government officials announced they indeed were planning to move at least some Michipicoten caribou to safety. Ontario's Natural Resources Minister Kathryn McGarry said the province would work with the tribal wildlife officials of the Michipicoten First Nation to move the animals "soon."
"We will be transporting a suitable portion of the caribou population to the Slate Islands to ensure the continued viability of this important species on an island free from predators," McGary said in a statement. "We also plan on initiating a broader discussion to seek input into the overall approach for managing the Lake Superior Coastal Range of caribou."
Even if some of the Michipicoten caribou are transplanted to another safe island, however, it might be only a matter of time before wolves find them again if and when another ice bridge forms. Much depends on the climate and how the caribou respond to wolves. It's unclear how many more times the government may be willing to move caribou around the lake.
"We are going to focus on the now and act based on the situation now. We don't know what's going to happen in the future," Patterson said.
Still, Paterson said there's hope that at least some remnant population of caribou will continue in the Lake Superior region.
"On the mainland, the caribou face a whole suite of problems ... and the prognosis isn't good," he said. "But as far as the coastal islands, I think we can retain a viable herd of caribou on Lake Superior. We're going to try. We need some luck."
Minnesota caribou revival foiled by wind, deer
Northern Minnesota was home to woodland caribou for thousands of years, well into the 1900s. But their numbers dwindled and — other than an occasional sighting — they've been gone since the 1940s, pushed out by indiscriminate hunting, logging, fires, deer and wolves.
But an effort in the 1990s nearly succeeded in bringing them back. Whether they could have survived will never be known.
A nonprofit group called the North Central Caribou Corp. worked with the Minnesota Department of Natural Resources, the U.S. Forest Service and the U.S. Fish and Wildlife Service on a detailed plan to relocate woodland caribou from Ontario's Slate Islands on Lake Superior to the middle of the Boundary Waters Canoe Area Wilderness.
The forest in the middle of the BWCAW was old, with big trees, good for caribou but bad for deer. That made the proposed BWCAW release site near Little Saganaga Lake as far away from deer as possible in Minnesota, a critical element because deer carry a parasitic brainworm nearly 100 percent fatal to caribou. (The brainworm, called P-tenuis, is harmless to deer. It's often fatal to moose, too, but not to the same degree as caribou.)
Then the infamous July 4, 1999, windstorm hit. Thousands of acres of mid-BWCAW forest was trashed, died, burned and regrew. That younger forest is perfect for moose and deer, which have been increasing farther north into the wilderness a little more each year.
Now, wildlife biologists believe there are simply too many deer near the area for caribou to survive. More deer also have attracted more wolves, which also are hard on caribou.
Supporters of the Minnesota caribou reintroduction essentially gave up after the big blowdown and the idea hasn't been brought up since.
And now, the planned source of the caribou, the Slate Islands, which had upwards of 650 caribou in the 1990s, is now down to just a few, with those expected to be gone soon, thanks to an invasion of wolves in 2014.
About woodland caribou
- Life Span: 10-15 years
- Height: 3-4 feet tall at the shoulder.
- Weight: Adults average between 250-450 pounds; males are larger than females.
- Reproduction: Caribou mate in October and cows almost always have just one calf in early June.
- Diet: Tree and ground lichens, where available, but also shrubs, grasses and willows.
- Name: The name caribou originates from the Mi'kmaq word xalibu, which loosely translates to "the one who paws."
Source: Nature Canada