Isle Royale wolf packs struggling
HOUGHTON – Researchers for the Isle Royale Wolf-Moose Study counted nine wolves at the end of last winter, one more than the year before but not nearly enough to keep the island’s moose population – now over 1,000 – in check.
That data was released Wednesday in the study’s annual report, which showed the moose population has more than doubled over the past three years. According to one of the study’s lead researchers, John Vucetich, if that type of growth continues the moose could permanently change the island’s ecosystem.
“The wolves are no longer limiting moose, and there’s no reason to expect they’ll be limiting moose in the foreseeable future,” Vucetich said. “If moose are able to grow in unlimited fashion, they’ll begin to over-browse the island and cause harm to the forest that’s there.”
In particular, he said, the moose could destroy most of the island’s balsam fir trees, none of which have grown to the seed-bearing canopy stage on most of the island.
The problem, according to the report, is that the wolf population, which once peaked at 50 in 1980, over the last three years are at their lowest population since the study began in 1959. They’ve also become less successful hunters and breeders, due to genetic inbreeding.
“Observations we’ve collected show (the wolves) aren’t able to perform their ecosystem function to limit the moose growth,” Vucetich said.
Vucetich said the best solution to restoring ecological balance is reinvigorating the wolves’ gene pool by introducing “new blood” from the mainland. A stronger wolf population, he said, could keep wolves in check. That solution has been on the table for a few years, but the Park Service has so far resisted any intervention after officially considering the issue last fall.
“It’s a natural population and we see it as a natural process, not necessarily as a problem,” said Isle Royale National Park Administrative Officer Betsy Rossini. “We are concerned about the populations of the wolves and the moose, but at this point we’re going to continue to monitor it and see how it plays out.”
“As long as there is a population out there, we’re just going to wait,” she added. “I think it’s a dynamic environment, and a lot of things could have an effect including a changing climate.”
Vucetich said putting off a response until forests began to show signs of over-browsing would be a bad idea, as the moose population’s growth momentum could make any response too late.
“Waiting any longer is an unnecessary risk to the ecosystem health of Isle Royale,” he said.
The report showed that three wolf pups were born on the island in the last year, almost certainly from the same litter, and brought the West Pack number up to six wolves. Another three wolves were counted in the Chippewa Harbor Group, which scientists believe is incapable of reproduction.
Despite the successful litter, Vucetich said it was unlikely the wolves would be able to rebuild their own population naturally, due to genetic issues.
One lone wolf, not counted in the study’s end-of-season total, crossed this winter’s ice bridge to Lake Superior’s north shore, where it died in Minnesota as the result of a pellet gun wound. Researchers had hoped the land bridge would offer opportunities for new wolves to migrate to the island, but Vucetich said none had been spotted and it was highly unlikely any had remained hidden or crossed in the few days the ice bridge remained after the researches left the island.
Vucetich said moose population growth, on the other hand, would be limited only by the severity of winters, and would likely continue to grow at the same pace as in the last few years. The only thing stopping that growth, he said, would be would be when the moose exhausted their food supply.
Rossini said that despite any differences of opinion between park officials and study researchers on how to move forward, the study has long been a great resource for understanding ecological relationships on the island.
“Absolutely, it’s been a very valuable study,” she said.