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Isle Royale wolves are holding steady as researchers make a major new find

Courtesy of J. Vucetich
A single wolf photographed from far above, who is not running with a pack, not sharing a moose kill, but just sitting, maybe waiting, on a field of windswept snow.

The annual survey of wolf and moose populations on Isle Royale was published Wednesday, and it’s fair to say the outlook for key elements of the island’s ecological health is not improving.

Major findings from the report:

  • The number of wolves counted in the two-month winter study, which ended March 5, puts the island’s population up by just one wolf — to nine from its historic low point of eight in 2013.
  • It may have reached 11 at some point last year, thanks to the birth of three pups who lived past infancy, but two adults were lost: “Isabelle,” who left the island by ice bridge and was found dead, and another lone wolf who disappeared in unknown circumstances.
  • The nine are now grouped into a West Pack of six and a Chippewa Harbor Group of three, but only the larger is thought capable of reproducing. The smaller consists of an aging female and two middle-aged offspring, one male and one female.
  • Although researchers had reached a firm conclusion that no pups survived infancy in 2012, there was some question about whether there might have been at least one pup in 2011. Now they know, from genetic evidence, that neither year added pups to the population.
  • Because wolves are the only control on the island’s moose (except for starvation), the moose herd has probably risen above 1,000, more than doubling  in the past three years as wolf predation has fallen to just about zero.
  • This is especially bad news for Isle Royale’s balsam fir forest, which had only just begun to reach the capacity for sustained reproduction.
  • Oh — and the beavers are booming, too, also because of the wolves’ decline; the number of colonies has climbed by at least 70 percent since 2010.

In a way, the cover photo of this year’s report tells much of the story within: A single wolf photographed from far above, who is not running with a pack, not sharing a moose kill, but just sitting, maybe waiting, on a field of windswept snow.

Because release of this year’s report was delayed by more than a month past its scheduled appearance — held up by review as managers at Isle Royale National Park worked toward a decision about what, if anything, to do about the wolves’ decline — some wondered if the news was going to be still worse.

And in terms of one important, highly interesting research development, that may well prove to be the case. But to describe this discovery, we first need a bit of back story.

History shaped by inbreeding

The 65-year history of wolves on Isle Royale, and much of their current predicament, is shaped by inbreeding and a steady downward spiral in genetic diversity and health, consequences of living on a rocky archipelago in Lake Superior, isolated from mainland wolves.

The island’s first known wolves turned up in 1949 or so, and until quite recently it was thought that all wolves on the island were descended from a single female and one or two males. Then in the late 1990s advances in DNA analysis detected, retrospectively, the arrival of a new wolf who came across an ice bridge in 1997 and became famous as Old Grey Guy.

Old Grey Guy’s beneficial contributions to the wolves’ gene pool were substantial, widespread and persistent. Indeed, his injection of fresh genes has served as a practical illustration of how today’s wolves might recover toward their typical numbers of about two dozen if the National Park Service would permit a “genetic rescue.”

Though the details of such a program are unsettled, the basic idea is simple: Round up some mainland wolves and drop them on the island in a mimicry of how things happen in nature, or would happen if it weren’t for a changing climate and the shrinking frequency of ice bridges from Isle Royale to shore.

This approach is strongly favored by the wolf/moose research project’s current and former directors, John Vucetich and Rolf Peterson. But it poses complicated policy and legal questions for the National Park Service, which announced last month that it would hew to a hands-off policy unless the wolves became completely incapable of reproducing, at which point it might reconsider.

Discovery about the wolves’ gene pool

Against that backdrop, the really big revelation in yesterday’s report is a finding that Isle Royale wolves’ gene pool has been freshened frequently, over at least the last 30-plus years, by wolves arriving undetected from the mainland.

This analysis draws on mathematics and a measure of genetic diversity called heterozygosity, which reflects the number of ancestors that contribute to a wolf’s DNA, or a human’s. Here’s how Vucetich explained it to me:

If both my parents have blue eyes, then my gene pair for the trait of eye color is homozygous, because the pair’s two parts, one from each parent, are identical. But if one parent has brown eyes and one has blue, then my gene pair has mismatched parts and is heterozygous. This diversity is passed from me to my children, with additional matches or mismatches from their mother, and from them to their children, and so on.

Which means that by counting and comparing the number of matched and unmatched gene pairs in a line of humans, or wolves, over generations, you can arrive at a measure of heterozygocity that reflects how many different ancestors were contributing.

Courtesy of J. Vucetich
On March 1, 2014, the elderly one-eyed matriarch of the former Chippewa Harbor Pack stands in dominant display over her adult daughter, with her adult son viewing the action.

Fresh calculations by Phil Hedrick, a wolf geneticist at Arizona State, have shown that at the time of Old Grey Guy’s arrival, Isle Royale wolves had lost about 32 percent of their heterozygocity after not quite five decades of inbreeding. However, the expected loss over such a time period is 82 percent — more than twice as high.

The explanation?

What explains this? One possibility is that wolves avoid breeding with close relatives … but, nah, they’re not that picky. Another is that natural selection works against wolves that are too inbred, which certainly happens, but not on such a short time scale. So, the report says,

The only remaining possible explanation for the slower-than-expected loss in genetic diversity is that wolves have periodically immigrated to Isle Royale on ice bridges that had once been common. In particular, theory suggests that retaining the diversity that the population had would require the population to have received on the order of approximately two migrants every three generations (12-15 years).

That circumstance prompted us to review field notes from the past four decades for the possibility that undetected gene flow had taken place in the past. That review revealed several plausible gene flow events [including a pack of wolves observed in the middle of an ice bridge to the island in 1977, and the known arrival of seven or eight wolves via ice bridge 10 years earlier].

The available evidence suggests that the Isle Royale wolf population had experienced periodic gene flow throughout much of its history. The concern is that gene flow is much less likely now because ice bridges form far less frequently, due to anthropogenic climate change.

To Vucetich, this is the most important finding of the past year’s work, and only in part because it argues, in his view, for a human-engineered genetic rescue.

I suppose it might have that effect, although I can imagine, too, how policymakers could reach an opposite conclusion: If getting to a single genetic rescue a la Old Grey Guy remains difficult for the National Park Service, what about the possibility that to genuinely mimic history, the rescue might have to be repeated again and again?

Vucetich’s perspective

I asked Vucetich why he placed Hedrick’s discovery at the top of his list, and he gave the kind of complex, personal/professional answer that always makes our interviews so rewarding for me:

There’s a certain joy in science when you have certain kinds of revelations or discoveries, and one of those is when you discover something that’s been kind of sitting under your nose all along, but then you share it with a colleague and he looks at it in a way you’ve never looked at it before.

And that discovery then causes you to think about things in another way, and lo and behold, the world is suddenly a little bit different than it was before. And for a scientist, that’s one of the greatest feelings you can experience. …

Prior to this year, we would have said things like, OK, there are fewer ice bridges and that means there’s less opportunity for wolves to come across — but there was still this lurking, unanswered question of whether those bridges were really all that important in the past, and we would have said, well, we think they must have been important, but we don’t really know.

And now we do know.

Comments (15)

  1. Submitted by James Hamilton on 05/01/2014 - 10:32 am.

    An heretical thought.

    Let nature take its course, rather than try to freeze conditions on Isle Royale at some arbitrary point in time. If the ancestors of the current wolf population did not arrive on the island until 1949, isn’t their presence the anomaly here, and their slow disappearance the natural conclusion of a failed migration? It seems so to me.

    If I understand the likley process correctly, the moose and beaver populations will stabilize over time, at levels consistent with the resources available to support them. The balsam fir will remain or disappear, depending upon how long it takes for the moose and beaver populations to decline. If the latter, they will be replaced by another species.

    We cannot micro-manage the Isle Royale environment. Even if we could, I’ve not read a convincing rationale for why we should.

    • Submitted by Steve Titterud on 05/01/2014 - 11:21 am.

      It’s the myth of “preservation” which abounds here.

      As Mr. Hamilton suggests, nature itself is the real manager of populations wolf, moose, etc. – and in a sense, you might say it is perfect in that role.

      Nature has no problem with continuous change – it is the author of the ephemera which people find so unsatisfactory. It’s people who cannot accept change. We intervene to attempt to steer things in the direction we’d like, in fruitless pursuit of preservation of a past, as in “the rescue might have to be repeated again and again”.

    • Submitted by Ron Meador on 05/01/2014 - 11:26 am.

      A worthy thought but hardly heretical.

      The arguments for nonintervention are in fact the orthodoxy at the moment and have been for many decades. The question is whether that will or should change.

      It’s the proposal for an engineered genetic rescue that qualifies as heresy. It’s also, at the moment, a distinctly minority viewpoint.

  2. Submitted by Ray Schoch on 05/01/2014 - 11:53 am.

    National Park

    If the goal is to “preserve” Isle Royale as a natural ecosystem in the guise of a National Park, then I have to agree with those above – it’s the intervention by humans that’s the problem. If the wolves die out, the Moose and Beaver will take over, to the temporary (or perhaps permanent) detriment of the Isle Royale environment that some humans have grown to love.

    That’s nature at work, folks. True, it’s not pretty to watch Moose starve, but if this were the year 1414 instead of 2014, they’d likely starve anyway. Much the same seems likely to happen to the Beaver when the last predator dies. I don’t know that it’s our job to try to manipulate an unfolding natural wildlife scenario to suit our humanitarian or aesthetic sensibilities. If WE were directly causing the casualties through hunting or trapping or some other method, then I might be interested in what an advocate for human intervention might have to say, but I’ve not come across any evidence of that, though it may exist. I claim no expertise here.

    Many, many thousands of years of biological history suggest that, when a species surpasses the ability of its environment to support it, it dies out – something humans might want to keep in mind over the remainder of this century.

    • Submitted by Nick DePilla on 05/01/2014 - 08:45 pm.

      We have had a direct cause in the decline of the wolf population. Humans introduced the canine parvovirus multiple times to Isle Royale; which is highly contagious. Wolves on the island once exceed 50, but the canine parvovirus decimated this population. Multiple wolf deaths, including three last year, were caused by drowning in man made mines which were abandoned on the island.

      This coupled with the ecological needs of Isle Royale further convince that genetic rescue is the right course of action; and something which I hope is implemented sooner rather than later. If humans never set foot on Isle Royale, there is a compelling case that the wolf population would be much more vibrant.

    • Submitted by Nick DePilla on 05/01/2014 - 08:53 pm.

      Pro Genetic Rescue

      Humans have contributed to the decline of the wolves on Isle Royale by introducing the canine parvovirus numerous times, which decimated the population that once numbered over 50. Humans also built mines on the island, which after being abandoned have caused multiple wolves to drown.

      A case could be made that the wolf population would be much more vibrant if humans had never visited the island. It’s imperative that genetic rescue be implemented sooner rather than later to restore ecology of Isle Royale.

  3. Submitted by Tom van der Linden on 05/01/2014 - 01:53 pm.

    Vucetich has a scientific point that can’t be denied

    Having a background in agriculture, wildlife biology and genetics/microbiology, I have learned to give credence to science, over lightly considered opinions. Especially when biological research bumps up against the old saw: is it preservation or is it conservation? An argument which will never be settled. (A favorite topic to discuss over beer when I was in college in the 1970s, and apparently still the case today).
    Facts: The climate has warmed, Lake Superior is warmer, fewer ice bridges are formed, and the wolves’ genetic pool is “trapped” if you will, as a result. Vucetich has established a scientific fact, at least as far as the wolf pack.
    Not managing the apex predator/prey relationship apparently is causing dramatic, ecosystem-wide changes to the Isle Royal forest, which will affect all the creatures living on the island, not simply the mammals.
    To suggest we don’t manipulate everything in our environment already is daft. We manipulate the wildlife populations in Yellowstone and other national parks. We also manipulate wildlife (all game animals to list just a few) throughout Minnesota today. Why should Isle Royal be treated any differently from these much larger areas?
    Now that the gene pool question has some real answers, It is not pie-in-the-sky “preservation” to suggest that new wolf genes is a modest, practical strategy that may retain and promote a more healthy ecosystem on Isle Royal. Not a proven hypothesis, but worthy of testing, I’d think.

  4. Submitted by Eric Snyder on 05/01/2014 - 02:02 pm.

    As usual…

    a fine piece of reporting, Ron. Thank you!

  5. Submitted by george desort on 05/01/2014 - 08:17 pm.

    2 Isle Royale Films

    Fortunate Wilderness, the wolf and moose study of Isle Royale explores the history of the study.

    Fifty Lakes One Island is a personal exploration of Isle Royale complemented with an interactive website that can be found on a website of the same name.

  6. Submitted by Bruce Young on 05/01/2014 - 09:48 pm.

    Always a shot at global warming

    “due to anthropogenic climate change” If we apparently didn’t regularly have ice bridges before 1949, what caused the warm weather back then?

  7. Submitted by Linda Rolf on 05/02/2014 - 12:01 am.

    Rescue Wolves and the Island

    Adding a few wolves to Isle Royale means adding new genetic material not a whole new species. This endless study of what to with the wolves borders on the absurd. How about letting the actual scientists who study this population shape the policy instead of the national park management? The quality of life for all flora and fauna on the island depends on it. Humans have already altered the possibility of new wolves crossing to the island over ice bridges because of climate change. Adding fresh blood to the resulting inbred wolf population is a drop in the bucket in comparison.

  8. Submitted by Paul Udstrand on 05/02/2014 - 08:34 am.

    Skewed logic

    Nature put wolves on Isle Royal via ice bridges and maintained genetic diversity more than likely for thousands of years. I doubt wolves had never ever before found they’re way to Isle Royal until 1949. Man made global warming and predation of wolves on the mainland (and possibly Isle Royal itself when fisherman first settled on the Island) has created the current situation. Intervene? We already intervened, there’s nothing “natural” about this decline or the extinction of wolves on Isles Royal or elsewhere. Near as I can tell the argument against saving the packs on the Island pretty much mimics the argument against having an endangered species act in the first place, after all, isn’t extinction natures way?

  9. Submitted by Paul Udstrand on 05/02/2014 - 08:37 am.

    Ron, a question

    One thing that has always puzzled me: how do the wolves know the Island is out there, they can’t see it, and conversely, when they leave the island, how to do they know what direction to go? I mean, if they went the wrong direction they’d head out into Lake Superior and perish, unless they made it all the way to WI.

  10. Submitted by beryl john-knudson on 05/06/2014 - 06:40 pm.

    Local myth/fact (who knows ) with a touch of humor ..

    Native local lore from the 1960’s…lived in G.M. village for a few years and while stopping for lunch at a little roadside cafe near the border we noticed the extremely large black wolf skin hanging above the fireplace.

    Story told by the owner/manager is that it was the carcass of a Russian wolf; as few were planted on the island by Isle Royal scientific management team sometime earlier but they forgot about the ice bridge and so adventurous wolves left the island and mingled with some of the grey wolves. One above the mantel was one of the first island transplants

    Native lore touched up with enough humor at the time on the ‘professionals’ who didn’t remember that ice freezes over in winter.

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