Isle Royale wolf rescue faces longterm genetic challenge, researchers say

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By Kaley Fech
Capital News Service

Relocating wolves to Isle Royale may only be a temporary solution to the island’s diminishing wolf population, according to a recent study.

The population has declined rapidly in recent years. In 2010, 19 wolves lived on the island. By 2016, that number had dropped to two.

The researchers used blood samples collected over the past 30 years to analyze the wolves’ DNA.

“We thought it was time for full genome analyses for as many of these wolves as possible to try and figure out some of the genetic details of the genetic collapse,” said Rolf Peterson, a research professor at Michigan Technological University and a member of the study’s research team.

The researchers found that genetic rescue—the introduction of new genes into a population to increase genetic diversity—can reduce problems associated with inbreeding. But those positive effects may only be temporary.

They also discovered that genetic rescue created problems that led to the rapid decline of the island’s wolf population.

Here’s what happened:

In the late 1990s, a male wolf migrated from the mainland across an ice bridge to Isle Royale. He dominated the island’s native wolves and mated with a female from the island, according to the study.

Through the genetic work, the researchers found that the descendants of these wolves rapidly dominated the genetic ancestry of the population. The wolf from the mainland won out.

“At one point, almost 60 percent of the genes on the island were from him,” said Philip Hedrick, a population geneticist and conservation biologist at Arizona State University and a researcher on the study. “That’s astonishing. I’ve never heard of a situation quite like that.”

Eventually, the descendants began to breed with one another because no new wolves migrated to the island. That led to something called “inbreeding depression,” or the tendency for small, inbred populations to decline.

“All inbred populations tend to collapse,” Peterson said.

The introduction of a single wolf increased the population’s genetic diversity initially, but ultimately resulted in descendants that were extremely similar genetically and unable to produce viable offspring, which led to the population’s drastic reduction in size.

“I think this was kind of an extreme case where the positive effect was so strong that it ended up resulting in a negative effect,” Hedrick said.

Genetic rescue will likely only have relatively short-lived effects, Peterson said.

“It might be 20 years,” he said. “But it’s all temporary.”

The researchers think that the same thing may happen but at a slower rate with the current effort to restore wolves to control the exploding moose population.

“The island is almost totally isolated from the mainland,” said Jacqueline Robinson, an evolutionary geneticist at the University of California, San Francisco, and a researcher on the study. “It’s highly likely that over time, inbreeding will once again set in. It’s kind of inevitable.”

The National Park Service has begun relocating new wolves to Isle Royale to keep the island’s population from becoming extinct. They plan to relocate between 20 and 30 wolves to the island over the next few years.

Although 30 sounds like a lot, it would not be enough in the long run, Robinson said.

The wolves are from different source populations, which is a good thing, Peterson said.

“Instead of trying to copy nature and relocating a pair, this is a better founding population,” he said. “Then you start right away with a real mixed bag of genes.

“That’s better because you won’t see that inbreeding showing up quite as fast.”

If ice forms across Lake Superior and new wolves travel to the island, that will counteract the effects of inbreeding, Hedrick said.

However, without the formation of ice bridges and the movement of new wolves to the island, eventually all of the wolves would be inbred again.

With warmer, more windy winters as a result of climate change, ice bridges do not form as often as they used to, Peterson said.

Human intervention may once again be necessary to save the population.

“There may be a reason to periodically introduce wolves to the island to mimic what would have happened in the past,” Hedrick said.

A more regular introduction of new wolves to the island by humans would help prevent inbreeding, Robinson said.

Even if the effects are only temporary, Peterson said he believes it’s a good thing that humans have stepped in to save the population.

The wolves are the only natural predator for the island’s moose population, which has exploded in recent years due to the wolf population’s decline, Peterson said. Without wolves to hunt them, the moose will ravage the island’s forest and eventually begin to die of starvation.

“The National Park Service has taken it upon themselves to direct nature in what I consider to be a very positive direction,” he said. It’s crucial to save the island’s ecosystem.

“The real value of Isle Royale, in my mind, is not that it’s some kind of untouched wilderness, because that’s a myth,” Peterson said. “The value today is that it’s a system with a top carnivore, a large herbivore and a forest—none of which is being exploited by people.”

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7 thoughts on “Isle Royale wolf rescue faces longterm genetic challenge, researchers say

  1. The discussions about when to intervene and when to permit nature to “take its course” are interesting. It raises the fundamental question about whether nature and its selective pressures are the most ‘pristine’ ways to go. It also ignores, to some degree, that nature has already been changed by humans to a degree which we are probably underestimating.

    Creating a national park is simply one version of altering nature. This artificial construct does require management. If we wanted to let nature do its own thing, so to speak, we would let the moose overpopulate, destroy their habitat, decline and crash—an experiment in its own right, but probably not what resonates with what most visitors to a national park might expect and enjoy.

    Wildlife biologists look at this situation in terms of “carrying capacity”, which essentially translates to the maximum numbers of a species which are feasible in a given ecosystem on a sustainable basis. There are some well-documented case studies about predator/prey relationships to base management decisions on. The classic example of intervention gone awry occurred on the Kaibab Plateau in Arizona starting in the early 1900s. An active plan to eliminate predators (wolves, coyotes, mountain lions and bobcats) to enlarge the deer population there created a superabundance of deer. These efforts were compounded by prohibiting deer hunting in the region. The outcome was a huge, starving deer population, and 10s of thousands of dead deer that were destroying their range.

    Islands are typically susceptible to booms and busts of animal populations. If Isle Royale is to retain its so-called phenotype as a “pristine wilderness”, which it fundamentally isn’t, then some forms of active management are essential. And those efforts will not always be perfect in their outcomes. The more insular a population, the more monitoring and managing may be required, including introducing fresh genetic material to animal populations.

    To stretch this concept into an analogy that urban citizens might better appreciate, preserving the character of a city’s treasured buildings in old, beautiful neighborhoods requires ongoing maintenance, such as repairing roofs and porches, painting exteriors and periodic re-landscaping, in order to avoid their total demise.

  2. I guess your point is “let it be.” If not for southern borders with several states and northern border with Wisconsin, Michigan would be an island as well. So, what is really different from Isle Royale than the rest of our great state? I hasten to say that following that thread, we should take “management” out of the phrase “wildlife management.” I might be able to be convinced, but I am not ready now to put a cork on the Isle Royale “test tube” and just look through the glass for the rest of eternity. Maybe its global warming that has reduced the amount of ice bridge years we now have. Maybe its habitat loss that reduces the number of wolves that travel the ice bridge in years it is available. Said differently, maybe I should not mow my back yard, and just cork that test tube and see what happens over the years. So, all said and done, I see no reason that we should not actively manage our resources, including those on Isle Royale. Responsible intervention is never wrong, but needs to be applied in carefully calibrated doses, with the long term “health” being the goal.

  3. What a bunch of hogwash. One of the programs the park service puts on for visitors of Isle Royale is a talk on unique species. This is the fact that “island effect” is in full force on the island and creates slightly different species. This “survival of the fittest” island effect on the island is what has created a huge swath of unique species. The island of Australia is on the far end of the spectrum BUT small island like Isle Royal do most certainly contribute to those unique species. The fact that leaving moose, balsam and wolves alone would most certainly create moose that survive on balsam and unique balsam trees that survive over browsing is most certain. It is disgusting that these so called “scientist” care more about “wolves” then they do scientific discovery and study of the island effect.

  4. There is no permanent solution. Evidently the wolves have crossed the ice on many occasions historically. The populations are then isolated. They get inbred and die out. Then it happens again.

    Nature is dynamic.

    The wolf situation is no more to be mourned that winter following summer. We can manage the packs if we want more consistency. If we let “nature decide” nature will give us the booms and the die-outs.

    Maybe we can just welcome the impermanence, live with it, maybe savor the it or manage it.

  5. Nice comment, but each intrusion into an ecosystem is a complex and unique undertaking–only with guesses about the long term outcome.

  6. Nice article. I am not sure if an introduction of 20-30 wolves over the next few years is the right approach. Better would be a 30-50 year plan to introduce fewer wolves per year and to make sure each year’s introduction is from a disparate genetic population. That would blunt a genetic dominance and create a more robust genetic diversity within an evolving population of wolves. During the evolving improvement period, controlled harvest of moose may be needed–but must be carefully calibrated to achieve long term “balance goals”. Thanks for posting this and for allowing me comment.

  7. Relocating wolves on the island with help from humans is a good idea. It is done on the mainland all the time. Just recently the DNR relocated a lynx from southern Michigan to the upper Peninsula. Humans have dominated the landscapes and have created rapid changes in nature. We need to help bring back the balance.
    I thank the researchers and the NPS.

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