Could Isle Royale save Lake Superior’s native caribou?

In the town of Rossport, on Lake Superior’s northernmost shore, there is a local history museum housed in a caboose. Tucked away in a corner of the caboose is an undated, black-and-white photograph showing the carcasses of three, trophy-sized woodland caribou lying on a dock. The photo is captioned, “Island Caribou.”

Rossport is situated about midway between a string of islands running from St. Ignace in the west to the Slate Islands archipelago in the east. At the time the photo was taken, it is likely caribou inhabited all of the islands and were found on the mainland, too. Apparently, they were abundant enough at the time to warrant hunting. Now caribou, the native deer of Lake Superior’s North Shore, are found only on the Slate Islands and Michipicoten Island, which lies further east off the Pukaskwa Peninsula. According to a recent report in the Duluth News-Tribune, the continued existence of those caribou may be only a matter of weeks.

What happened? During the cold winter of 2013-14, wolves crossed the frozen lake from the mainland and took up residence on the islands. They began preying on caribou, the only food source other than beaver, decimating the small populations. The Duluth News-Tribune says a recent survey found only three or four caribou bulls remaining on the Slates and no wolves, because the predators likely died of starvation. Michipicoten Island is believed to have less than 100 caribou and 15-20 wolves.

Last week, the Ontario provincial government announced it will relocate some caribou from Michipicoten Island to the Slates in hopes of preserving the native species and restoring the island’s population, which numbered up to 650 animals as recently as the 1990s. Ironically, caribou had been reintroduced to Michipicoten Island from the Slates during the 1980s. At least 450 caribou were living on Michipicoten Island as recently as 2014.

Caribou exist in Ontario north of Lake Superior, but the gap between the North Shore and the mainland caribou range grows ever wider. The Duluth News-Tribune reports the caribou range is retreating northward about 20 miles every 10 years. Caribou and human development such as logging and related road-building don’t mix, because the altered habitat attracts more southerly ungulates such as moose and whitetail deer, which in turn allows wolves to thrive. Woodland caribou are more susceptible to wolf predation than either moose or deer. They are also highly susceptible to the brain worm transmitted by white-tailed deer.

The loss of caribou from the Lake Superior region has been ongoing for more than a century. Scattered bands hung on in northern Minnesota until the 1940s. In the early 1980s, up to a dozen caribou wintered near the North Shore community of Hovland, then disappeared. On Isle Royale, native caribou were extirpated in the 1920s. Local anecdotes and genetic research suggests moose were introduced to the island as a replacement species. When moose began to overpopulate the island, a mostly unsuccessful introduction of wolves was attempted to control their numbers. Wolves are thought to have crossed on the ice to the island a few years later.

The changing wildlife dynamics of three North Shore island groups should offer opportunity in the face of impending disaster, provided we choose to make the most of it. On Isle Royale, generations of inbreeding have caused the island’s wolf population to collapse. The most recent reports indicate one wolf is left on the island. The nearly inevitable outcome is the moose herd, lacking predation, will overpopulate, destroy its food source and then crash due to mass starvation. The solution presently under consideration is to stock wolves on the island, which is an artificial manipulation of a wilderness area. Ontario has offered to provide wolves for the stocking effort from the Michipicoten Island population, according to the Duluth News-Tribune, but the decision process on the U.S. side can’t move fast enough to save that island’s rapidly dwindling caribou from wolf predation.

In the press, the loss of Isle Royale’s wolves is largely portrayed as a tragedy, because the extirpation of wolves will bring to an end a famed, long-running, predator-prey study. But what if we chose to see the loss of the island’s wolves as a blessing in disguise, providing an opportunity to restore a native species: the woodland caribou. The diets of moose and caribou differ. Moose are browsers, while caribou exist on lichens and moss. Even if moose over-browse Isle Royale, caribou would still have food and habitat.

To the best of our knowledge, caribou long existed on the island prior to being hunted out and replaced with moose. Given the cold, year-round temperatures of Lake Superior and the chilling effect they have on the island’s climate, it is possible caribou could be restored to Isle Royale even in the face of climate change. If successful, these animals would become the only resident caribou population in the Lower 48. I haven’t seen anything to indicate such a strategy has been contemplated or presented to the public. Instead, we’ve seen an increasingly political debate about whether wolves should be stocked on Isle Royale, which is a national park and federally designated wilderness area.

Lake Superior is often described as pristine, which not only means its water is clean and clear, but that all or nearly all of its original biota is intact. During the past 50 years, we have witnessed popular and successful efforts to preserve and restore Lake Superior’s native species; from the lake trout, brook trout and lake sturgeon swimming in its waters to the white pine and white cedar growing along its shores. This begs the question: Why aren’t we doing everything possible to preserve and restore the crown jewel of Lake Superior’s native species, the woodland caribou?

I have never seen a Lake Superior caribou. Once or twice, on a lonely sand beach in view of the Slate Islands, I’ve happened upon blurred tracks that seemed a little small for moose. More often, I’ve been in places where you can still feel the echo of their passing; rocky outcrops carpeted with lichens and caribou moss. In those places is a tangible wildness, as though the caribou just walked away. If woodland caribou are extirpated from the North Shore, they’ll take that wildness with them. And Lake Superior will be pristine no more.



By Shawn Perich