How Stable Is The Future Of Isle Royale National Park’s Wolf Population?
Submitted by Kurt Repanshek
When Dave Mech came to Isle Royale National Park to study wolves, they practically greeted him personally.
The closest I have ever been to a free-ranging wild wolf is fifteen feet, Dr. Mech, one of the country’s foremost wolf researchers, wrote in opening his 1970 book, The Wolf, The Ecology and Behavior of an Endangered Species. That moment was one of the triumphs of my life, for I had arranged the meeting, and the scheme had worked even better than I had hoped. Bush pilot Don Murray and I had been following a pack of fifteen wolves by air in Isle Royale National Park, and they were heading along one of their regular winter routes. If they were to continue, they would file across the ice of a little cove, fifty feet from an old fishhouse along the shore a couple of miles ahead.
They did. And we were in the shed awaiting them. With the door cracked open just enough for a camera lens, we watched as each of the fifteen animals strolled onto the ice in front of us. It was a marvelous spectacle — a rare glimpse into wolf society.
Today that island society seems on the verge of total collapse, as inbreeding, gender disparities, and even climate change seem to be conspiring to doom the wolves. Whereas multiple packs totaling 50 individuals roamed the island in 1980, today researchers say there are just 16 animals, and only two are known to be females. Newcomers to Isle Royale are hard to come by, as ice bridges that allow them to cross Lake Superior from Ontario to the island are few and fragile due to warming waters and somewhat mild winters.
And yet, it would be premature to eulogize the predators. Isle Royale Superintendent Phyllis Green is quick to point out that “the number that we have right now, we have 16, they’ve been down below that number 11 times. So I think we just need to wait and see what’s going on with them.”
What researchers have seen most recently is a wolf population that was split among four packs in 2008 drop to two packs in 2009. Today there might be just one. And while there where 10 females in the packs early in 2009, by the end of that year there were just four, according to Dr. Rolf Peterson, who long has studied the island’s wolf dynamics.
“We know two of those four died. So there’s no more than two adults, and there might be just one,” Dr. Peterson said recently during a conversation from Houghton, Michigan, where he teaches at Michigan Tech and from where he can regularly visit Isle Royale. “Now, there are two pups in the population, but their status is unknown and their gender is unknown, also.”
Complicating the numbers game is genetics. Isle Royale’s wolves haven’t had a refreshing infusion of off-island wolf genes since a Canadian male made that 15-mile ice bridge crossing in 1997. His arrival did provide a welcome burst of genes. He sired 34 offspring, which in turn have produced at least 22 of their own so far. But the passage of time without additional mainland interlopers is again narrowing the gene pool. Not only has that lack of stirring of the gene pool renewed inbreeding concerns, but the wolves’ relative isolation on the island has left their immune systems susceptible to disease.
They could be nearing the end of their chapter on Isle Royale, one that has enabled the world’s longest-running predator-prey study — wolves vs. moose — to run for 53 consecutive years.
“They could go extinct as soon as — completely gone now, even the males all gone — they could go extinct in four or five years,” says Dr. John Vucetich, who along with Dr. Peterson is co-director of the The Wolves and Moose Of Isle Royale project. “Completely gone.”
Wolf Pack Resilience
They also could bounce back.
Since wolves were first seen on the 45-mile-long island in 1950, having arrived via ice bridge, their numbers rose to as many as 50, back in 1980. Their current population ebb could simply be related to a corresponding ebb in the numbers of moose, which are now rebounding after numbering as few as 530 in 2009 from a high of about 1,000, also counted in 1980.
“They’ve (moose) been limited by heavy wolf predation for many years, and so I think they should be poised, with the wolf population dropping,” to rebound, said Dr. Peterson. “The moose look better, they’re a little bigger, the calves are bigger, the vegetation looks really nice. The trees have had several years off from heavy moose browsing, so as long as the climate cooperates, moose should be able to recover.”
When the moose population collapsed, he added, it was only a matter of time before the wolf numbers mirrored the decline.
“What’s happened is that the wolf has been living pretty well on old moose that were born in the early ’90s, when the population was expanding,” the biologist said. “There was a big baby boom of moose produced in the early ’90s, and then those animals got old, in the early 2000s, and the wolves kind of rode that wave out up until about two years ago, and then they kind of hit the wall.”
While there were two packs on the island coming into 2011, that didn’t last long.
“We started this year in January with two packs, one nine members, the other four,” said Dr. Peterson. “And then the nine decided to go to the other end of the island, and on their way back they killed the alpha male of the smaller group, and so the rest of them kind of scattered. So, we have one for sure. I’m not sure we have two.”
Should Nature Be Left To Take Its Course?
Though the answer to Isle Royale’s wolf woes might seem obvious — drop a few new wolves onto the island to both lessen the gender disparity and boost the genetic diversity — it’s not that simple. Debates — both philosophical and in terms of Park Service policy — quickly surface in discussing whether to leave the park’s wolves to their own fate or to intervene.
“We are bound by national park policies,” points out Paul Brown, chief of natural resources for the park. “We basically monitor the island and manage the island as a natural ecosystem, pursuant to the Wilderness Act. So we’re basically very hands off in our approach to the island.
“Many animals have come and gone from the island, it is an island ecosystem, and there’s no indication at this point that that’s (human intervention) something that we would be looking into in the near future,” he added. “But we haven’t made any decisions, and all management options are available to us should the need arise.”
From Dr. Vucetich’s perspective, there are three cases in which intervention might seem appropriate: The current scenario, in which there seem to be just two adult females on the island; a situation in which there are no females, only males, or; a situation in which the island’s wolf population blinks out completely.
Complicating the idea of intervention, though, is both the Park Service’s policy to, generally, let natural processes play out, and the Wilderness Act.
“Intervention kind of conflicts, at least prima facie, with basic wilderness policy,” notes Dr. Vucetich. “But I think that when you look at wilderness policies it’s clear that wilderness policy indicates that non-intervention is a value that sometimes conflicts with other values like ecosystem health, scientific values, things like this…I think that wilderness policy suggests that when it’s complicated, complicated in the sense of competing values, then you have to look at it carefully and think about it.”
Superintendent Green fully agrees.
“The question is, ‘When do we intervene in the natural processes of wolves maintaining themselves on the island?’ That is a question that we take very seriously, because as soon as you start tinkering you start entering more human factors into an equation,” she said.
Those human factors can range from how we view ecosystems, our concerns over the health of those ecosystems, even the value placed on the long-running wolf-moose study.
“Let’s imagine that they were extinct right now. Let’s imagine that. Then I think the competing values that you’re dealing with are things like ecosystem health,” says Dr. Vucetich. “I think you could make an argument that ecosystem health of Isle Royale would decline without wolves, and so now you have a wilderness value competing against an ecosystem health value, and that’s not something that you expect to happen too often. You expect those two values to line up together most of the time.”
While dropping some wolves onto the island might run contrary to Park Service policy and the Wilderness Act, the long-term good that might come out of helping the wolves maintain their presence on Isle Royale might be worth such intervention, he adds.
“If we learn what happens on Isle Royale under different scenarios, it will help for other conserved populations where they’re trying to go through genetic management of those populations,” Dr. Vucetich says.
Genetic Rescue Is Not Alien To the National Park Service
While supplying new genetic material through mainland wolves would be a first at Isle Royale, similar infusions have been done elsewhere in the National Park System. Most notably arguably most successfully it’s been accomplished in South Florida at Big Cypress National Preserve, where cougars were brought in from Texas in 1995 to bolster the Florida panther gene pool. In Yellowstone National Park, of course, wolves were returned there in the mid-1990s, not to refresh genetics but to re-establish a viable population of the predators, which had been exterminated in the first half of the 20th century.
Much thought, however, would preface any similar action at Isle Royale.
“If there was to be any intervention at all it would have to be something that the National Park Service wanted to do. They would have to make the next step, and I think a pretty thorough review of policy and specifics of the situation would be something they would want to consider doing,” Dr. Peterson says. “It would include the notion that, if they indeed went to zero females, yeah, you could pretty easily fix that and also put new genetic material in at the same time. That would be a manipulation that’s never been done at Isle Royale. It’d have to be some pretty thorough evaluation of that.”
And then there’s the existing proof that Isle Royale’s wolves can bounce back on their own.
“In the late ’80s, early ’90s, when the populaton was sinking really fast and got down to 12, actually, and hung onto 12, and we deliberated at that point whether to vaccinate them, what we should do,” recalls Dr. Peterson. “We had never even handled wolves before, trapped them, or blood sampled them, so there was a decision to live-trap some, get some blood for genetic and disease work, not vaccinate them, and then just study them.
“And as it turned out –the wolves had maybe no more than three reproducing females, and none of them were doing really well — as it turned out, in their last year of life all three reproduced,” he goes on. “So they got through that little squeeze chute, and then this new Canadian immigrant came in ’97, and so that kind of set the stage for the next 10 years.”
Climate Change Could Bottle Up The Wolf Genes
If anyone is counting on a naturally migrating wolf to rescue the island’s gene pool, those odds might be longer than ever due to the vagaries of the weather under ongoing climate change. Not only are ice bridges fewer and farther between, according to researchers, but those that do form can be too fragile and short-lived to support even an 80-pound wolf.
“One thing that’s important is not whether they form but how long do they form for,” points out Dr. Vucetich. “Some winters — this is before my time now, before I was working on the project — you might have an ice bridge that lasts for a month or five weeks or something like that. And so today, when they form they form for a few days or a week or something like that, because the ice isn’t very thick and the wind blows it away.
“… Nobody can say how many ice bridges will there be in the next 10 years,” he continues. “I mean, we could have a cold snap and there could be an ice bridge in every year the next 10 years. But you’re not going to be betting on that. You’re going to be betting on fewer than we’ve seen in the last 10 years, which is basically one in the last 13 years that lasted for any significant time.”
Superintendent Green said the erratic nature of ice bridges is something the park will take into consideration as it discusses how best to handle the island’s wolves. While the superintendent said her staff is currently consulting with outside experts in light of the decline in female wolves on the island, her chief of natural resources points out that it wouldn’t be the end of the world if wolves vanished from Isle Royale.
“You have to remember that Isle Royale has only had wolves for the last 50 years,” Mr. Brown points out. “And for the last couple thousand before that it was a lynx-caribou dominated ecosystem, and so wolves are a very new animal to the island.
“There’s a kind of public perception that wolves are out on Isle Royale and have always been out on Isle Royale, but that’s actually not the case,” he says. “They’re a very new animal.”
Still, offers Dr. Vucetich, an opportunity exists at Isle Royale to learn a great deal more about wildlife management, lessons that could be applied elsewhere in the world.
“I think on one hand a person could say, ‘Oh, in the big picture, in the big scheme of things, this is a tiny little island, and wolves aren’t globally endangered, and this is kind of small peanuts kind of thing,’” he says. “I think what’s important is that two things, the issues at stake, are big issues because National Park Service management, wilderness management, climate change, competing values in conservation, these are all big issues.
“As you know, a lot of people pay attention to Isle Royale wolves, and so I think this is a great case example of why don’t we take it slow and careful and do a really good job and set a good precedent and example for lots of other cases,” the biologist said.