Isle Royale’s last wolves aren’t ready for their obituary just yet.
A trail cam placed by Michigan Technological University wolf researcher Rolf Peterson last month spotted a male and female wolf moving down a moose trail on the Lake Superior island, which also is a national park. It bolsters the finding in last winter’s annual Isle Royale wolf survey of two surviving wolves.
The remaining pair are a father and daughter, and they were born from the same mother, making them half-siblings and highlighting the severe inbreeding that has decimated the island’s wolf pack. Wolves came to the island more than five 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 recent years due to the physical and reproductive impacts of inbreeding.
The pair had an offspring two summers ago, but the young wolf was seen in that winter’s survey as small and unhealthy. It died shortly after the survey, said Michigan Tech wolf researcher John Vucetich, a member of the annual survey team. Any future offspring will have similar viability problems, he said.
“Imagine a brother and sister mating, let’s say they have a son and a daughter, and then they mated,” he said. “That’s how intense this (inbreeding) would be.”
The remaining pair seem relatively healthy, indicating they’ve been able to take down moose for food, Vucetich said.
“For the neighborhood of two years now, they’ve been pulling it off just fine,” he said. “They’ve demonstrated they know how to get food, and that means take down moose. It would be pretty extraordinary if they are just surviving off scavenging.”
George Desort, a Chicago filmmaker and photographer who has helped chronicle the island’s wolves for the Michigan Tech team, said it was “phenomenal” that Peterson was able to capture on camera the last two wolves on a 200-square-mile island.
“It just goes to show how well he knows the place; how well he knows the wolves’ behavior,” Desort said. “When he sent me the thumb drive” with the trail cam footage, “it was like Christmas morning coming early.”
But the momentary joy many feel in seeing the island’s last pair of wolves still making their way is tempered by the reality of what is inevitably coming: Wolves will soon vanish from the island altogether.
“I don’t know if” seeing the wolves still alive last month “is very heartening to even the most optimistic folks out there anymore,” Vucetich said.
“They are middle-aged wolves right now. Under normal circumstances, they could die in a year, or they could live three or four more years.”
The flip side to the vanishing wolves, one that has many researchers and others concerned, is what it means for Isle Royale’s moose population. Without wolves to prey on them, the moose population has exploded — growing about 20 percent a year; doubling to 1,300 moose; and on pace to double again in four more years, Vucetich said. The very limited wolf predation on the moose has made no dent in their numbers for the past four years, he said.
A single moose can eat up to 40 pounds of vegetation a day. They spend considerable time grazing in ponds and bogs, clearing them of plants relied upon by small fish and amphibians, and stirring up sedimentation that can further disrupt the ecosystem.
“Moose can cause really important damage to the forest if they are not under the influence of predation,” Vucetich said.
Both Vucetich and Peterson support a “genetic rescue” of Isle Royale’s wolf population, bringing in wolves from off the island to rebuild the pack size and fix the out-of-kilter predator-prey dynamic. But the National Park Service has taken a deliberate approach to studying the issue, stating they do not expect to have a decision until the end of next year. Two mandates of the service can be interpreted to contradict each other on the Isle Royale wolves: Don’t interfere with natural processes, and conserve the scenery and wildlife that exist.
“They have managed to make the process slow enough that genetic rescue is not really a feasible option anymore,” Vucetich said. “By the time they get around to doing something, you cannot rely on those two wolves still being alive.”
That leaves as options doing nothing or repopulating the island with wolves after they are gone, he said. But the rapidly growing, unchecked moose population will likely lead to a major moose die-off at some point, Vucetich said. That’s what happened in the mid-1990s, when, after a severe winter, about 2,000 moose died over a four-month period. The moose numbers had swelled in the 1980s and into the ’90s after wolf numbers dropped when humans introduced canine parvovirus to Isle Royale, he said.
A similar moose die-off due to a lack of wolf predation “is almost a certainty,” Vucetich said.
“It will be manifest more than likely through starvation,” he said. “It will be a needless starvation, because we could have prevented it. We have already seen this recently what happens when wolves are taken out of the picture, and we’re just bracing for it again.”