Healthy pups and frigid weather change the scientific debate on Isle Royale.
It’s only February, and already it’s been an extraordinary winter for the wolves of Isle Royale.
At least two new healthy pups, and perhaps three, have survived their first perilous months of life — proof that the famous wolves, which number less than a dozen, may not be dwindling after all.
And twice this winter, the bitter cold that has halted shipping across Lake Superior has also created temporary ice bridges across the 20-mile channel between Isle Royale and the Minnesota-Ontario mainland, raising the tantalizing possibility that once again wolves could either leave the island or arrive on their own four feet.
Both developments are likely to only confound a precedent-setting decision that faces the National Park Service: whether to intervene in nature’s course and bring new wolves onto the island in an effort to preserve them and the critical balance between the predators and their primary prey, moose. Conservationists say the decision could establish new policy on managing critical species in national parks everywhere and even change the definition of wilderness as a place where only nature is allowed to rule.
The wolves, which once numbered as many as 50, are at their lowest ebb since researchers first began tracking them in the 1950s and are closely followed by naturalists all over the world. Scientists running the Isle Royale wolf study today, from Michigan Technological University say they fear that even with the new pups, they could die out, largely as a result of inbreeding.
At best, the new pups “might extend the amount of time the population can bump along,” said Rolf Peterson, who has been studying the wolves and moose along with John Vucetich for years.
In a series of e-mails sent from the island this week, Peterson said that even now the number of wolves is too small to keep the moose population in check and the forest ecosystem in balance. Since 2006, moose numbers have more than doubled to nearly 1,000. That’s far less than their peak of nearly 2,500 more than 30 years ago, but the rate of growth is dramatic.
The huge mammals depend on balsam firs, one of the primary species of trees on the island, as a major part of their diet. If they eat too many, then other trees would take over and, in the long run, neither wolves or moose would survive.
But other wolf experts disagree, including David Mech, a wolf expert with the U.S. Geological Survey in Minnesota. Mech said that the wolves’ population is perilously low, but that it has bounced back before, and that the pups are evidence that it can again. Many of the wolves, he said, are only now at the best age for breeding, and this year could see even more and larger litters, he said.
“Those wolves are not nonreproductive,” he said. “In another year or two they could produce some more.”
In the meantime, scientists say they provide valuable information on reproduction, genetics and ecology. This week, the prestigious journal Nature weighed in with an editorial.
“A declining island wolf population underlines the influence that humans have on nature,” it read. It points out that the whole system is “highly artificial.” Wolves and moose have been on the island less than 100 years, and in the 1980s the wolf population was nearly wiped out by canine parvovirus, an infection likely brought to the island by someone’s pet. (Dogs are no longer allowed.)
Meanwhile, climate change — also caused by humans — is greatly reducing the chances for the ice bridges that brought wolves to the island in the first place, it said.
Once a near seasonal event, the bridges have become increasingly rare. The last one formed in 2008, when two wolves collared with tracking devices disappeared, perhaps to the mainland. The last bridge before that was in 1997, when a wolf named “Old Gray Guy” appeared on the island and went on to sire dozens of puppies, providing an infusion of new genes that researchers credit with saving the population from demise.
This year satellite images show that two bridges have formed and then been broken again by wind, the latest in early February, said Peterson.
Meanwhile, as humans fret about the wolves’ survival and the meaning of wilderness, Isabelle waits. She is, literally, a lone wolf on Isle Royale and a prime candidate to mate with a new arrival, should one come, or take off across an ice bridge, researchers said.
Isabelle was born in 2008 to one of the two packs on the island, but, as wolves often do, left the pack in 2012 to find a mate. The pickings are few — and all the males are related to her. That inhibits mating in wolves as well as people, Peterson said.
In addition, lone wolves are vulnerable to attacks from breeding packs in the relentless competition for the right to reproduce.
Because she wears a tracking collar, the researchers have been able to follow her lonely and persecuted life. Last year they saw three other wolves chase her to the edge of the water and attack her with all the ferocity they use to bring down a 900-pound moose. They left her wounded and bleeding on the edge of the ice. When the researchers left last winter, they weren’t sure if they would see her again.
“But she has survived,” Vucetich announced on the research study’s blog in late January. “It would not be surprising if she’s learned to kill moose by herself. A wolf that can do so is better than most.”
Isabelle is now 5, a prime age to mate. About one in 10 wolves will strike off on their own and try to start new packs, and some will travel for hundreds of miles in their search. On Isle Royale, however, the wolves are trapped — unless there is an ice bridge.
No one knows what’s in the heart of a wolf, but Peterson said he thinks it’s quite possible, that given the chance, Isabelle will head out. Mech said that as long as there are potential mates on the island, she’s more likely to stay put.
The chances that a wolf would come from the mainland are also very small, researchers said. It’s known to have happened only three times in the island’s history. And today mainland wolves face a treacherous path across roads, yards and urban areas — never mind 20 miles of shifting ice.
Still, the survival of the three pups and the renewed possibility of ice bridges may have bought the National Park Service some time. Phyllis Green, park superintendent, is weighing three options: doing nothing, reintroducing wolves if their numbers hit zero or a “genetic rescue” by bringing a few new wolves to mate with those that are in residence.
Peterson and Vucetich said they favor genetic rescue. And Isabelle, if she had a vote, would likely agree.
Josephine Marcotty • 612-673-7394