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As Isle Royale wolves slide toward extinction, a call for ‘genetic rescue’

Eight wolves remain — and last year, for the first time, there were no new pups.

wolfprint
The population trend on Isle Royale for the last six years has been steadily downward, and this year’s late-winter survey found just eight wolves.

Isle Royale’s wolves appear to be at the brink of extinction, and over the next few months the National Park Service will decide whether to intervene and save them or leave their fate to nature.

Intensive study since 1958 has established that the island’s population of wolves rises and falls in a see-saw relationship with the moose herd they prey upon, averaging about two dozen. But isolation and inbreeding have introduced vulnerabilities, and canine parvovirus — from pets brought to the island in violation of park rules — has taken a toll in two waves, one from the 1980s into the 1990s, another since 2007.

The trend for the last six years has been steadily downward, and this year’s late-winter survey found just eight wolves. Four of them were female, which could work in favor of recovery, but all are middle-aged, which works against it.

Most alarming, and perplexing, is that the wolves added no pups last year — the first such reproductive failure ever recorded. A repetition this year could seal their fate, and set in motion a series of dynamics that most would regard as undesirable. Including, perhaps, the typical Isle Royale backpacker, who treasures the chance to hear a nearby wolf — but a trailside run-in with a moose? Not so much.

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Park managers’ options for intervening are limited and also have their challengers, who prefer that wilderness be managed in as “natural” a way as possible — that is, with minimal human involvement.

Recent arrivals

But what’s “natural” for moose and wolves on Isle Royale is a complicated question, because neither was present there until quite recently, by nature’s time scale.

Moose arrived there first, a little over 100 years ago,  apparently after swimming from the mainland. Their numbers surged in the absence of effective predators, and by the 1940s Aldo Leopold and other scientists of similar stature urged that park managers import wolves to save the island’s forests from fir- and aspen-eating moose.

Nature beat them to it. The first wolf pack came over via ice bridge at the end of the 1940s. Another pair was deliberately introduced in the 1950s, and at least one wolf has come over by ice since then.

Now the wolves’ plummeting numbers have virtually stopped moose predation, and the park service plans to decide by this fall whether to:

  • Let the wolves disappear (and possibly return on their own), or
  • Let them disappear and then deliberately reintroduce a new population, or
  • Attempt “genetic rescue” by adding a small number of new wolves to the remnant population.

The latter is the preferred option, at least for now, of John Vucetich at Michigan Technological University. He leads the 55-year-old Isle Royale Wolf-Moose Study, said to be the world’s longest examination of predator/prey relationships in a single ecosystem.

Last week Vucetich laid out the case for intervention in a New York Times op-ed, and on Monday we discussed his views in more depth. Excerpts follow:

MinnPost: For starters, I think readers might be interested in learning how you are able to know these wolves so intimately — not just numbers but gender, age, health, reproduction success and so on.

vucetich portrait
mtu.edu
John Vucetich

John Vucetich: Well, we count them very carefully. Every winter in January and February, for seven weeks, we fly every day the weather permits us to — every other day on average. The island is fairly small, so we’re able to make repeated observations of each wolf pack; most years, each pack has one wolf with a radio collar.

We can see their tracks in the snow, follow the tracks and find the wolf. This January we found a group of three at the west end of the island, and a group of four plus one loner at the eastern end.

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Counting the pups is done basically by collecting scat from kill sites, where wolves have killed moose. We get the DNA from the scat, and that gives us a DNA fingerprint for each wolf. And when a wolf shows up for the very first time in the fingerprinting, we presume that wolf is a pup.

MP: Is it true that DNA analysis has shown every Isle Royale wolf to be descended from just one female and two males?

JV: Pretty close. It started with one female in ’48 or ’49, and two males —one in the first group and a second we’re unsure of, whether he came in that first group or later, maybe 10 years later. Then we discovered just a few years ago that in the year 1997, another male wolf came from Canada, also walked on an ice bridge, which made three.

MP: The famous “Old Gray Guy”?

JV: Yep.

MP: How long has DNA fingerprinting been available to you for this work?

JV: We were into it full swing by 1999, but we had a trickling of samples through the 1990s. However, we also had much older samples preserved by [former project leader] Rolf Peterson, who was on the project since 1971, and his predecessor, Durward Allen. They had a penchant for collecting samples, not always knowing how or whether they would be used. We’ve been able to analyze DNA from those, too.

MP: I want to ask about your comment, in your paper on these issues for the George Wright Forum, that “studying simplified food webs is critical to ecologists’ understanding of nature.” Nonscientists might assume the opposite, that studying complexity is more productive than examining the one predator, one prey relationship on Isle Royale.

JV: I wouldn’t want to imply that studying simple things is the only thing we need. You need to study complicated things and simple things. But studying simple things fills a niche you can’t fill any other way, and provides a stepping stone to further studies.

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Yellowstone makes a great comparison to Isle Royale. There you have three top predators — grizzlies, mountain lions and wolves — and two especially important prey, bison and elk. And then humans are involved, through hunting, and influencing all those creatures. So you have all of those interactions and it’s bewildering to try to sort them out.

MP: While we’re on hunting — if wolves do go extinct on Isle Royale, could hunting in some form provide effective moose controls?

JV: If the goal is to protect ecosystem health, no, because hunting is not considered to be a good substitute for things that wolf predation does. Not that hunting is bad by any means — it’s just not substitutable in preserving ecosystem health.

MP: Because wolves tend to prey on the young, the old and the ailing moose, where hunters will take more of the biggest and best?

JV: Yes, and that’s probably the most important difference, but your question leads a person to another thought, about culling.

Yellowstone had a period of time, before wolves were reintroduced, where government sharpshooters would kill elk to control their numbers, which was controversial and turned out not to be such a good thing to do. And there is some culling in the Apostle Islands, on one or two of the islands for whitetail deer removal, to protect Canada yew and other plants.

If you were to try to control moose on Isle Royale with culling, I imagine you would have to kill something like 150 moose a year, and I don’t think hunters could do it. You’d have to be really close to the shoreline or you’re not going to get any of that meat out, and you’d be doing it in October, November, when Isle Royale is a pretty unforgiving place for that kind of activity.

If you were to go the sharpshooter route, killing that many moose and leaving them to rot in place, I think — heh-heh — the public would be pretty strongly opposed to that. A hypothesis to be evaluated, but that would be my guess.

MP: What is the time window for acting to preserve the surviving wolves?

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JV: The window could be closing kind of quickly. Each of these wolves has a few more years in ’em, but not a lot more years. Each year, a wolf has about a 25 percent chance of dying, so you could lose a good chunk in one year just by accident. The gender balance is not a concern at the moment. But if you, by a bad roll of the die, lost all four females, you’d be done for. Or three of the four — things would be very precarious.

Remember, too, that a genetic rescue or other response would require some logistical planning time, and administrative time, for something that’s not just an afternoon project. It’s hard to find the right adjective but you would almost want to treat this as urgent.

MP: Why do you feel that genetic rescue — adding a small number of new wolves to the existing population — is the best option of the three?

JV: There are basically two or maybe three principles that make me think it’s liable to be the better choice, but I’m readily willing to change my mind on further reflection.

One would be: Conserving something is preferable to restoring it. If something’s valuable, why wouldn’t you try to keep it rather than let it go extinct and then try to put it back?

Second idea: Some people have said this decision should be rooted in science. I don’t believe that’s the only value, but one important consideration is, what will we learn the most from? We already know a lot about extinction processes. We won’t learn anything new by documenting the precise point when Isle Royale wolves go extinct.

But genetic rescue is a potentially important tool for managing populations all across the planet, and it’s not very well understood, it’s more theory now. Here you have a population that you know so much about, for so many decades in advance, and then you do the rescue and see what happens with a situation that is not so common in nature.

When Old Gray Guy came in 1997 that was a genetic rescue that happened all on its own, and it ranks as one of the two or three most important findings of the entire study.

The third idea is essentially there’s a risk to continuity in predation if we allow wolves to go extinct. In Yellowstone, for example, when wolves were absent beavers just flourished, remaking the ecosystem structure in ways that weren’t easy to change back. And bringing wolves back didn’t restore the previous condition.

We’re already at a point for the last one to two years where wolf predation has fallen to where it’s no longer having an impact on moose population — not delivering ecological services. On Isle Royale, the percentage of moose killed by wolves each year averages 15 percent and can be as high as 24 percent. The last two years it was more like 2 percent. More moose than that die of pneumonia.

So even if wolves stumble along for another few years and then go extinct, and then, you know, funding is a little tight for reintroduction right now, and then you run into an obstacle with logistics, and some other little delays — you can easily image a decade-long period that probably began last year, of essentially no significant wolf predation, and that might be a problem we’d have trouble reversing.