Woodland caribou are medium-sized members of the deer family. In Canadian provinces such as Ontario, these shadows in the forest are listed as threatened – quickly vanishing.
Non-migratory woodland caribou – one of two Ontario caribou “ecotypes,” with the other migratory – stay in the boreal, or spruce-fir, forest year-round. Most of Ontario’s non-migratory caribou live north of Lake Superior, but a few are found along the lake’s coast. Some are on its islands. Are caribou on the wane there, too, or could good news be hidden on these dark isles?
Recent scientific expeditions to the islands, especially 17-mile-long by six-mile-wide Michipicoten, offer reason for optimism. And clues to possible détente in what’s been called a running battle between predator and prey: wolf and caribou.
Researchers at the Ontario Ministry of Natural Resources & Forestry (MNRF) estimate the province’s woodland caribou population at 5,000 animals. Since the late 1800s, more than 40 percent of the species’ Ontario range has been lost, mainly from habitat fragmentation by human activities such as logging and mining. At the current rate of decline, woodland caribou may be extinct in Ontario by 2100, some scientists believe.
In 2014, a dozen or more researchers at Guelph and Trent universities, the Canadian Forest Service and the Ontario MNRF released results of a four-year Ontario caribou population study. The State of the Woodland Caribou Resource Report lists 14 caribou ranges. Of these, only the Lake Superior Coast range has slashes through it. The lines signal “discontinuous distribution”: few to no caribou.
A look offshore, however, tells a far different tale.
More than a century ago in 1907, woodland caribou made their way across Lake Superior on a rare, eight-mile-long “ice bridge” from the mainland to the Slate Islands.
Today there are some 100 caribou on the Slates, according to Steve Kingston, a biologist at Ontario Parks. The number once may have been as high as 650. Then a severe winter in 1990-91 and a resulting shortage of caribou food such as lichen caused the dramatic drop.
Michipicoten Island’s rugged shoreline in winter. Ice bridges from the mainland to the island have formed in recent years. (Photograph: Brent Patterson)
Ice Bridge to Danger?
Long after the 1907 ice bridge, new frozen pathways reached the Slates – and transported more than caribou.
“The Slate Islands were free of predators,” says Kingston, “then ice bridges formed in the winter of 1994, and again in the winters of 2014 and 2015, opening passages for wolves.”
In January, 1994, a wolf was sighted on the ice next to Mortimer Island near the Slate archipelago. That spring, wolf tracks were recorded on Mortimer for the first time. “Signs indicated that two wolves were there,” Kingston says.
By the summer of 1996, one wolf had disappeared. The body of the second wolf was found in 1999. A necropsy showed that caribou did not make up the majority of its diet. Beavers were the wolf’s most frequent meals, but it also dined on snowshoe hares, red-backed voles, birds, insects and berries.
The frigid winters of 2014 and 2015 again led to the formation of ice bridges. Researchers soon confirmed the presence of three more wolves on the Slates. As of February, 2016, all three were still on the islands.
Wolves also found their way across the ice to Michipicoten.
A Michipicoten camper spotted two wolves in the summer of 2014. Months later, a naturalist photographed tracks of three wolves on a beach. The wolves likely made their way to the island in the winter of 2013-14, padding across an ice bridge that extended ten miles from the Ontario coast.
In February, 2015, Patterson and other researchers mounted their first expedition to Michipicoten. They found a pack of three wolves, two males and a female, and placed radio-collars on all three.
The signals showed that the wolves traveled together for most of that winter, says Patterson, “and snow-tracking evidence suggested that the larger male and the female bred on the island.”
Trail cameras the scientists mounted on Michipicoten trees revealed that by March, 2015, a fourth adult wolf had appeared. “We don’t know whether the fourth wolf was there all along, or if it crossed over on an ice bridge and joined the group later,” says Patterson.
In June, 2015, four months after the biologists’ initial trip to the island, they returned. During the harsh winter of 2014-15 only a few caribou were taken by wolves, Patterson says, “but many caribou died of malnutrition.”
The discovery may indicate that Michipicoten hosts more woodland caribou than its vegetation can sustain. “The poor condition of the caribou, along with very few sightings of cows with calves, suggests that caribou numbers have probably exceeded the island’s carrying capacity,” says Patterson.
“If the wolves preyed on caribou more often,” he adds, “conditions for the surviving caribou would probably improve. Caribou densities are high on the island due to the absence of predators for so many years. Fewer caribou should mean less competition for available food.”
In February, 2016, the team went back to the island. The biologists radio-collared the fourth wolf, an adult male, and located two pups. Ontario MNRF researcher Art Rodgers also fitted GPS tracking collars on 30 adult caribou. The scientists should soon have a handle on how the caribou are responding to the wolves.
What are Michipicoten’s wolves eating, if not caribou?
The island hosts a thriving population of beavers, an important food source for wolves during the ice-free spring-to-fall season – and in mild winters when ponds stay open, Patterson found when he again trekked to the island last month. “Like many other places this winter, there was very little snow and ice on Michipicoten,” he says. “Only a few caribou had been killed by wolves. Instead the wolves were likely eating beavers.”
Why would Michipicoten’s wolves hunt beavers when the island is awash in caribou? “Beaver meat has considerably more calories and fat per pound than caribou,” says Patterson. “Beavers are also probably fairly easy to catch, especially in spring and fall when they forage extensively on land.”
Wolves, beavers and caribou are in a complex dance on Michipicoten Island. Where will they wind up when the music stops?
“We don’t yet know,” says Patterson. “We’re just beginning to understand the interplay of these species.”
For now, Michipicoten, an Anglicized Ojibwe word for the region’s high bluffs, may spell hope for Ontario’s woodland caribou. And, perhaps, a newfound coexistence for caribou and wolves.
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