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Posts Tagged ‘woodland caribou’

isle royale wolves

One of the classic studies in wildlife management happened on island in Lake Superior. Isle Royale, part of the state of Michigan but much closer to the state of Minnesota and Northwest Ontario, is home to a population of moose. These moose either swam across from Minnesota or were stocked there in the early 1900, and they found themselves in a paradise. No predators existed on the island, and the island was full of birch trees and aspen colonies.

Over time, the moose denuded the aspens and the birches, and they were forced to eat balsam fir. In 1949, when Lake Superior was frozen over, a pair of wolves crossed to Isle Royale, and they were the foundation for a wolf population that specialized in hunting moose.

This island became of interest to ecologists early on.  It had been made a national park in 1940, and as a national park, it has no permanent residents. Because wolves and moose live on the island without any chance of humans hunting them,  early predator-prey researchers went to the island to see if Paul Errington was right.

Paul Errington was professor of zoology at Iowa State University. He had studied bobwhite quail population dynamics while a student at the University of Wisconsin, during which time he became close friends with Aldo Leopold. Leopold was not faculty member, but Errington learned so much from him during his time at the university. Errington was

Errington’s most famous research was performed in the marshes of Iowa. There, he studied the population dynamics of muskrats and American mink. Muskrats, which are giant water voles, are a major prey source for the mink, and one would think that mink would severely reduce muskrat population. However, Errington’s research found that mink predation had no real depressive influence on muskrat numbers.  He found that the mink tended to take young and infirm. Most healthy muskrats  were generally left alone.

This research, which was published in 1943, was the hottest idea in the nascent science of ecology, and researchers were looking for places where this hypothesis could be tested on a grander scale.  Isle Royale fit the bill, and the first studies of wolf and moose dynamics on the island started in 1958.

Initially, the research found similar findings to Errington’s muskrat and mink study.  Moose and wolf populations fluctuated over the years. When the moose became too numerous, they were forced to eat more and more balsam fir. The fir is not nutritious, and the moose gradually become emaciated. Because the moose require lots of nutrition from their bones to grow their antlers, they also wind up suffering from arthritis.  Emaciated, arthritic moose are easy prey for wolves, and wolf numbers increased when the moose hit this stage.  The wolf population would then increase, and after a few years, it would begin to pare back the moose population to allow birches and aspen to recover.

But at the same time, there weren’t enough weak moose for the wolves to hunt, and the wolf population would crash. The moose would find themselves in a situation with more limited predation and better forage, and their numbers would increase again. And the cycle would start again

When I think of Isle Royale’s wolf and moose dynamics, I think of the work of Rolf Peterson, who made a career out of studying the wolf and moose population fluctuations.  He began to notice that the balsam firs on the island were not regenerating through each moose and wolf fluctuation.

These findings meant that Isle Royale would not be able to continue on through constant moose and wolf fluctuations as one might have hoped, and this problem became worse when the wolf population really crashed.

Lots of debate exists about how well wolves can withstand inbreeding. Climate change has meant that ice bridges that connect the island to Minnesota and Ontario no longer form, and those that do form aren’t around very long. So the wolves have been inbreeding on the island for decades. They were able to withstand this inbreeding for decades, but in the 1990s, the population really began to suffer from this inbreeding depression.

In 1997, a lone male wolf, “Old Gray Guy,” wandered onto the island, there was hope that his genes would be a genetic rescue on the island.  He apparently did introduce some much needed genetic diversity to the island, because by the 2010s, 56 percent of all wolf genes on the island could be traced to him. Wolf fertility did not increase as the result of his arrival, and although a debate exists as to whether there was anything like a genetic rescue on the island, it should be noted that Old Gray Guy was very much like a popular sire in a purebred dog. The population was already quite inbred, and the influx of only a single male that winds up contributing that many genes to the population isn’t going to save the population

By the first decade of this century, a genetic disorder of the wolves’ spines became rampant in the population.  The wolves began to die at early ages, simply because they were unable to walk or because movement was painful for them.

At that time, a real debate existed about bringing in wolves from the mainland, but caution was exercised. There was a hope that natural selection would purge the spinal deformities, but this purge never came. When the ice bridge formed during a polar vortex collapse in 2014, there was also real hope that wolves would walk over to the island. However, all that happened was that two Isle Royale wolves left the island, and one was found dead on the Minnesota mainland.

Further, because the purpose of the studies on wolves and moose on Isle Royale was to see what predator and prey relations are like without the use of human intervention, there was very real resistance to introducing more mainland wolves.

However by December 2017, only one wolf was thought to be living on the island, and the moose population exploded.   However, the moose themselves were physically smaller and would very likely eat themselves out of forage in short order.

This past September, a plan was hatched to restore the wolf population to Isle Royale.  Wolves from the UP of Michigan and northeastern Minnesota would be released upon the island.  Yes, after decades of allowing nature to take its course, man would finally intervene in these predator-prey dynamics.

Things are not off to a good start, however.  One of the first three wolves released on the island has already used the formation of an ice bridge in the most recent polar vortex collapse to escape back to the Minnesota mainland.

However, wildlife managers aren’t giving up. Currently, there are plans to release six wolves from Ontario’s Michipicoten Island onto Isle Royale.  These wolves, which also live on an island in Lake Superior, have a bit of a storied reputation.

On their island, there was once a thriving population of woodland caribou, but the wolves have reduced their number from over 900 to just 30 individuals.  The  caribou were not native to the island, however.  A bull just happened to pop up on the island, and other woodland caribou were stocked to create a population, which thrived until the winter of 2014-2015.

That is when wolves walked across an ice bridge n Michipicoten, and they found it a paradise for wolves. Finding a vast horde of ungulates was a boon for their numbers, but by it took them just a few years to drop the caribou numbers. The caribou are now being taken off the island, but the wolves have had virtually no options. the wolves have had virtually no options.

These Michipicoten wolves are large-bodied creatures that definitely have the ability to hunt large ungulates, so there are very real hopes that these wolves will be able to reduce Isle Royale’s moose population.  New studies on their population dynamics can begin, and this experiment continues on.

That is the hope, anyway.  Whatever happens in the next few months, it should be noted that Isle Royale and the related Michipicoten experiences is that both are studies in a really controlled environments that no longer exist in North America, if they ever did at all.

Moose, caribou, and wolves are all at the mercy of a human-dominated world.  These islands give us an idea of what the world would be like if predator and prey dynamics were left alone, but they aren’t necessarily indicative of how these dynamics would exist on a continent in which human interests have great knock-off effects upon ecology.

After all, the Isle Royale moose and wolves are not directly affected by human hunting. They are still controlled by climate change.  Warmer than normal winters mean that the ice bridges don’t form, and the collapse of the polar vortex, which is also caused by climate change, means that the inbred wolves just don’t want to stay on the island. Moose are getting weaker and weaker as the ticks spread through the populations, and without long periods of cold, the ticks are able to infest the moose, weakening them in greater numbers every year.

The Isle Royale studies are the studies of an island where hunting isn’t allowed, but virtually every place where wolves and ungulates exist on this continent, hunting is a major point of human interest. Humans want more ungulates on the ground, and if their numbers ever drop, wolves will be blamed.  Wolves certainly can have an effect upon prey numbers, and even more than that, they have an effect upon prey behavior. Trophy cervids are just harder to kill if they spend much of the year being harried and herded by wolves.

Maybe what we can know from Isle Royale is limited, but in those limitations, we might get an idea of how to mitigate all these competing interests and have some way of keeping large predators as part of our North American wildlife heritage.

If wolves are not restored to Isle Royale, the landscape will likely be denuded of trees, and all that will be left is a population of tick-invested, diminutive moose.  They will always be on the edge of famine.

Restoring wolves gives a potential hope, but nothing is guaranteed.

But the saga goes on. Maybe for just a bit longer, or maybe new, bright future exists for this most storied of predator and prey studies.

 

 

 

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We think of caribou as being an arctic species. We know all about the vast herds of Alaska and the barren lands of Canada, but the truth of their range once came much deeper to the south.

South of those famous barren ground caribou are those caribou that inhabit the boreal forest, the great taiga that runs across the northern tier of Eurasia and North America. There are many herds of caribou in the North American stretch of this forest, and these caribou are often called “woodland caribou” to differentiate them from the arctic herds.

But woodland caribou were not always restrained to the boreal forest. They came into what are called the “mixed woodlands” that lie in transition between the boreal forests and the widespread temperate forests of mid-latitude North America. Caribou ranged through virtually all of Canada and also into the northern tier of states. They were found in Maine, New Hampshire, Vermont, and northeastern New York State. They also ranged through northern Minnesota, northern Wisconsin. the UP of Michigan, and the northern tip of the LP of Michigan.

Those herds of northern New England, New York and the Great Lakes states have disappeared long ago. The last of these southern herds ranged down into Idaho, Montana, and eastern Washington State.

These herds, too, dwindled away until only a single herd existed in the Selkirk Mountains of Idaho, Eastern Washington, and British Columbia. For most of my life, the last herd of woodland caribou to wander down into the Lower 48 were of this South Selkirk herd.

Over the past few years, the caribou in this herd have dwindled down. , These caribou live in an inland rainforest, where they specialize in eating tree lichens grow only in this old growth forest. Logging and road-building have destroyed much of the good lichen-growing habitat, and snow mobiles disturb the caribou from their grounds. Wolves, which have recolonized the area, have also been blamed for reduced the caribou herds.

This spring, the entire herd had been reduced to just three individuals, all cows. And now, just one exists. This single cow was just recently captured, and British Columbia has placed her in a breeding facility in hopes of getting her genes into captive caribou that could potentially be reintroduced to the wild.

Attempts have been made to bring woodland caribou to the Selkirks to add genetic diversity, but caribou from other areas are not as well-adapted to the Selkirk forests.

Caribou are much like sheep raised in traditional ways in England and Scotland. The sheep of Scotland and Northern England have been running their ranges for centuries. They know the best grazing at the right time of the year, and they do not typically leave the ranges to which they have been so adapted. Such sheep are called “hefted” to the land, and if environmental or agricultural policy in the UK were to close down traditional sheep grazing, the sheep would ultimately lose their knowledge about living on the land. Enclosing sheep make them lose much of their historical sheep know-how.

The end of this South Selkirk herd ends much of the caribou know-how to these inland temperate rainforests. The remaining cow has been placed with a similarly “hefted” herd of caribou from another mountain range in British Columbia, called the Purcell. These caribou are very similar to those of the Selkirk Mountains, and if this cow mixes well with these caribou, then there may be hope of someday restoring them to these mountains.

But as it stands right now, we have no more caribou in the Lower 48. Gone from Maine, Michigan, and now Idaho, their grunts will not be heard in our northern tier for a long time.

Maybe never.

As someone who does support wolf recovery as much as possible, I was always open to some limited wolf controls in the region where these caribou ranged. Wolves would not have made much a difference had the rainforests of the Selkirks remained largely intact, but the downfall of the original old growth forests made wolf predation an adversity the caribou couldn’t handle.

So the wolves will do fine as avatars of wilderness. But the caribou have slipped off into the misty fogs of history, perhaps never to return again.

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