Slim Pickings for Wolves on Isle Royale

Moose and wolves have been studied on Isle Royale for 50 years now. It is of great scientific interest because the number of variables affecting predator and prey are much smaller than on the mainland (Isle Royale is a large island in Lake Superior, and a national park). Wolves are the only large predator and moose are they prey, and the populations of each have gone up and down many times of the fifty years. They do not move in in exact concert.

Now unusually warm summers have increased the tick population that debilitates moose in the winter on the island (and pretty much whereever moose live). Moose numbers are declining due to their weakness, and the wolves are getting hard pressed for food with interpack strife and they are declining in numbers too.

There are fox on Isle Royale too, and they are suffering as well.

I can’t help but hypothesize that some elements of this are present in the elk number decline and wolf number decline on the northern range of Yellowstone.

Story from the International Wolf Center. Slim Pickings for Wolves on Isle Royale

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  1. Jim Avatar

    Isle Royale is a perfect example of how wolves will never eat themselves out of house and home. Any decline in prey numbers below sustainable levels or to extinction requires human interference.

  2. elkhunter Avatar

    I think its kinda hard to use Isle Royal as an example, they have never had more than 50-70 wolves at any one time I think. Sometimes as low as only 25. Thats a little bit different than having hundreds of them in areas. I would think.

  3. Ralph Maughan Avatar

    There is always a higher danger of extinction on islands. That’s why people worry more about the “island” grizzly bear population around Yellowstone than the contiguous populations of Alaska. It’s not just a matter of numbers.

    Both the moose and the wolves could go extinct on Isle Royale. If it is only one, however, it will be the wolf.

  4. Jim Avatar

    Isle Royale is a perfect example because neither the wolves nor the moose can replenish their populations through migration. Wolf numbers have never reached a point where there were too many of them to be supported by the number of moose on the island. Without human interference this is what predator/prey relationships look like.

  5. Denise Johnson Avatar
    Denise Johnson

    Ralph, The tick infestation hypothesis you pointed out has substantional merit. I saw photos of the moose on Rolf’s website. Would love to post it to this thread… YUCK! Have heard the problem is just as critical in the GYE elk. From what I understand it’s attributed to drought.
    Sounds like things are going to be pretty bad out West with El Nino….better get those tick collars out for your dogs too.

  6. Jeff Avatar

    Elk Hunter – For a period of time in the early 80’s the Isle Royale wolf population rose to 50 animals. It soon crashed to 13-14 animals based on availability of prey and inter-pack strife. Isle Royale is a perfect example of why wolves will never deplete the prey base. Wolves and moose have coexisted on this island since the late 1940’s and both populations have fluctuated over the past 50 years.

  7. Ralph Maughan Avatar

    Jim and Jeff,

    I think you are correct, but islands are susceptible to extinctions, and the onset of the warm summers on the island is the very sort of thing that brings about extinctions, and it happens on the smallest islands first.

    The wolves and moose would probably go up and down for an indefinite period of time if there was not a change in outside conditions, but there has been a change. That’s the point I want to make.

  8. Jeff Avatar

    Ralph – I agree that island wildlife popuations are more susceptible to extinction whether it be due to disease, genetics, parasites, predation or some other envrionmental factor. However, the point I was trying to make is that some opinions expressed on this site try to make the case that a few thousand wolves in the rocky mountain west are going to have a devastating impact on the tens of thousands of elk/deer if the wolves are not “managed”.

    If anything, the wolf/moose dynamic on Isle Royale does a pretty good job at showing how a predator/prey relationship in a mostly “enclosed”, unmanaged setting hasn’t allowed for the wolf to decimate it’s prey base.

    It seems that Elk Hunter’s point is that we can’t use Isle Royale as an example because there are only 25-30 wolves on the island. I’m assuming he thinks that the moose population on the island numbers in the tens of thousands and that 25-30 wolves wouldn’t have much of an overall impact on such a large population.

    Well in 2005 the moose population was 540 and I believe the highest moose number was at one time @ 2500.

    With all the other factors mentioned above (disease, parasites, etc…) it would seem more likely that the wolf would have by now eaten every last moose, beaver, and snowshoe hare on Isle Royale. Yet this has not happened in 50 years.

    In fact I would bet you that most wildlife biologists would agree that wolf is more likely to become extinct on the island than the moose.

    Thanks for the clarification on my behalf.

  9. Jeff Avatar

    I neglected to mention that another factor in why the wolf populaton crashed from 50 animals to 14 animals in the early 80’s was due to a Parvo outbreak on Isle Royale.


Dr. Ralph Maughan is professor emeritus of political science at Idaho State University. He was a Western Watersheds Project Board Member off and on for many years, and was also its President for several years. For a long time he produced Ralph Maughan’s Wolf Report. He was a founder of the Greater Yellowstone Coalition. He and Jackie Johnson Maughan wrote three editions of “Hiking Idaho.” He also wrote “Beyond the Tetons” and “Backpacking Wyoming’s Teton and Washakie Wilderness.” He created and is the administrator of The Wildlife News.

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Ralph Maughan