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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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canada lynx

North America has two species of lynx, the widespread bobcat (Lynx rufus) and the boreal-adapted Canada lynx (Lynx canadensis). The two species do have some range overlap across the northern-tier of states, and when Canada lynx ranged down the Appalachians, their range overlapped much more extensively.

These two animals behave quite differently from each other. The bobcat is a generalist predator that hunts everything from mice and voles up to white-tailed deer, while the Canada lynx specializes in hunting snowshoe hares.

The bobcat is found in Mexico and throughout the southeast, especially in Florida.  Those southernmost bobcats are often not much larger than domestic cats, but the biggest bobcats, which are found in the Great Lakes states, are actually larger than Canada lynx.

It is well-known that bobcats and Canada lynx do hybridize. Hybrids have been produced in captivity, and hybrids have been encountered in Maine, New Brunswick, and Minnesota.  These hybrids are apparently fully fertile, which leads to the question of how much the two species really do hybridize.

A group of researchers looked into a big sample of bobcats and Canada lynx that came from across the continent. Of the 2,851 cats sampled, only 7 had any evidence of introgression from one species to the other.

This finding shows that bobcats and Canada lynx do hybridize, but it is virtually unknown in the wild. The authors caution that if Canada lynx numbers ever become low, bobcat introgression could swamp the genetics of that population, effectively making the species disappear through hybridization.

This finding is quite different from what has been discovered with gray wolves and coyotes. Gray wolves and coyotes have apparently exchanged genes across North America, and animals of mixed coyote and gray wolf genetics are pretty common.

Because we don’t have evidence of a hybrid swarm, which we do with wolves and coyotes, we have very good evidence to consider bobcats and Canada lynx quite distinct species.  And conversely, it is within reason to question the validity of coyotes and gray wolves as being distinct species

I would love to see a similar study to the genome comparisons performed on gray wolves, coyotes, and admixed canid populations in North america performed on Canada lynx and bobcats. My guess is that there will be some evidence of very limited hybridization between the two species, but it will not be like coyotes and gray wolves.

We don’t have a good handle on when bobcats and Canada lynx last shared a common ancestor. We need some more genomic data to make this claim, but what we know now is that Canada lynx and modern Eurasian and Iberian lynx are sister taxa.

The bobcat is thought to be more basal to the lineage.  Lynx species have been roaming North America since the Pliocene. Indeed, the earliest lynx fossils were found in North America, not Africa, as we previously believed.

The bobcat evolved in North America. It is the last survivor of the endemic North American lynx that gave rise to the other species in Eurasia, while the Canada lynx came back from that ancestral Eurasian lynx population some 200,000 years ago. 

These animals have likely been distinct from each other for a very long time, but they have not yet lost chemical interfertility. It will likely be a while before this happens, but if climate change continues to threat Canada lynx populations, the bobcat will move north into their range and hybridization could become a threat.

So stay tuned to see what happens, but the genetic data clearly show that bobcats and Canada lynx are two distinct species that do rarely hybridize.

 

 

 

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loggerhead sea turtle hatching

Recently, I’ve been using this space to play around with the fuzziness of “species.” Hundreds of species concepts exist, and because different researchers have somewhat different perspectives, you will sometimes get real conflicts about whether something is a species or a mere subspecies.

In canids, we get caught up in species discussions that are about what really amounts to very little genetic variation. For example, red wolves, Eastern wolves, gray wolves, dogs, dingoes and coyotes are all lineages that have only radiated in the past 50,000 or so years.

By contrast Old World and North American red foxes, including the ones allegedly derived by those set out by English colonists in the seventeenth and eighteenth, last shared a common ancestor 400,000 years ago.  This finding means that we probably should regard the red fox of North America as Vulpes fulva.

But 400,000 years of divergence is nothing compared to the 3 million years estimated for the Indo-Pacifica and Atlantic-Mediterranean populations of loggerhead sea turtle. There has been some gene flow between the populations. Matrilines have flipped around South Africa, once 250,000 years ago and an once 12,000 years ago.

So researchers who specialize in wolf-like canids are debating over very small genetic differences and relatively recent divergence times.  Red fox researchers are only just now realizing that there are likely two species in what was once thought to be a Holarctic species. And those specializing in loggerhead sea turtles don’t really care that their species has such a deep genetic difference.  The occasional gene flows between populations are enough for them to recognize only one species of loggerhead sea turtle.

This problem gets more interesting when we start talking about “living fossil species.” Take this article on Futurity.org, which is entitled “Evolution Hasn’t Revamped Alligators in 8 Million Years.” This article discusses the findings of some paleontologists at the University of Florida, who have found 8-million-year-old alligator fossils in North America, and they are remarkably similar to the ones we have today.

One of the researchers is quoted in the article says,”We were surprised to find fossil alligators from this deep in time that actually belong to the living species, rather than an extinct one.”

I would be just a hair more careful in my language. Although one can certainly see that these ancient alligators looked and probably behaved very much like the current species, 8 million years is a long time. I doubt that current alligators and those from that time could even interbreed if they encountered each other today. From a biological species perspective, it makes little sense to call them the same species, but from a paleontological perspective, it makes more sense, simply because paleontology is more interested in morphology and ecology over the entire time a population has existed.

So yes, “species” is a nebulous concept, and that is a good thing.  It makes some legal aspects with conservation difficult, because we have an Endangered Species Act that is about a hard and fast definition of a taxonomic entity.  In reality, the whole nebulous side makes for interesting levels of inquiry. If the Neo-Darwinian synthesis correctly describes the origin of biodiversity, then we would expect these discussions and debates to be commonplace.

They certainly are quite common in taxonomy and systematics. They probably always will be. Part of what defines a species are the biases of the classifier, which can often be contradictory.

For example, I have no problem with the new taxonomy of wildcats that posits the European wildcat into a different species than the Near Eastern/North African species. However, I disagree with the position of the domestic cat, which derives fro the Near Eastern/North African species, as its own unique species.

That bias may come from the simple fact that I am more familiar with domestic dog taxonomy, and I have come to accept that domestic dogs are best classified as a divergent form of gray wolf. If the domestic cat derived from its wild ancestor much more recently than the dog derived from its wild ancestor, why would it make any sense to classify the domestic cat as its own species?

So in zoology, we have all these different perspectives on how to classify species. Specialists in sea turtles are able to tolerate a genetically quite divergent species, while experts in wolf-like canids will debate over much more recently divergent lineages. These researchers really don’t talk to each about their ideas.  Indeed, the only time loggerhead sea turtle researchers worry about what specialists on the wolf-like canid side are doing is when they need to figure out how to stop coyotes from destroying the turtles’ nests. But they don’t need to know the complexity of the systematics to find an answer.

However, it is amazing how different specialists come to tolerate variation within one species. That nebulous nature of the various species concepts makes for some interesting variations on what specialists accept as normal.

Specialists often have very different ideas in mind, depending upon what they are used to, and I find it beautiful, even if it a bit confusing at times.

 

 

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sea mink

Depending upon how one understands the red wolf, the United States has had only two native carnivoran species go extinct. One of these was the Caribbean monk seal, which was one of three species of monk seal that once swam the warmer waters of Hawaii, the Mediterranean, and Florida, the Gulf of Mexico, and the West Indies.  The Mediterranean monk seal still holds on, and I’ve laid eyes upon a few Hawaiian monk seals. But the Caribbean species is gone. Sightings still persist in redoubts throughout the West Indies, but virtually every expert believes the Caribbean monk seal to be extinct.

The second species we lost is a bit of a mystery, and yes, there is a bit of a debate as to whether it really was a species at all. The North American mink is a fur trade staple. It has been bred in captivity almost as extensively as red foxes have, and it has been accidentally introduced on more than a few occasions.

In its native range, it is quite widespread, and studies of North American mink and their predation upon muskrats were the basis of early predator-prey ecological studies.  These animals are even undergoing a sort of domestication and training as hunting animal in Utah.

But that common species of North American mink may have not been the only one on this continent. Another mink species was described along the rocky coasts of Maine and the Maritimes.  It was called the sea mink, and unfortunately, it was not described until 1903, when it was already extinct.  The trappers of Maine and the Maritimes knew the mink of the coast was somewhat different, but they had already trapped it out by 1894. The animals were described as being very large mink, measuring 36 inches in length and possessing a reddish coat.

When they were eventually described as a distinct species in 1903, much of the data backing their taxonomic status was based upon skulls taken from shell middens of the Native Americans. Their dentition was different enough for some scholars to maintain that this mink with the big teeth was indeed its own species. The current consensus is that there was a sea mink, and this consensus is made upon an another more sophisticated comparison of its dentition with other North American mink.

It should be noted that not everyone agrees with this species status based upon dentition alone. Richard Manville has long maintained that the sea mink was a unique subspecies of North American mink. Manville examined several specimens, including one that he thought was intergrade between the sea and “wood” mink form, and he concluded that the sea mink was nothing more than a subspecies.  Manville noted that purported sea mink remains dating to around 4,000 years ago were found in inland Massachusetts, well south of where the sea mink was supposed to range. Further, they were found so far from salt water, which led Manville to question whether the sea mink was so regionally distributed and so connected to the ocean as was believed.

Many comparisons have been made between the sea mink and the North American mink that live on the Alexander Archipelago of Alaska. Those contemporary mink are quite large and live very similar lives. Like the sea mink, this large Alaskan mink relies upon cold, boisterous seas for its food. Shellfish feature also prominently in its diet, and it could be argued that the two forms evolved in parallel of each other.

I am leery of modern species being described solely off of morphological characters alone. Because sea mink remains definitely do exist that could be used for DNA extraction, one wonders why no one has tried to use this method to resolve this question.

Now that this large mink is now extinct, its taxonomy is less urgent.  This larger-sized sea mink was in demand because of its coarse fur, which would have been in demand to make fur coats, and its larger size meant that fewer mink would have to be trapped to make the same size of garment. It was definitely trapped out of its range, and all that was left was that other form of mink, which the New England trappers called the “wood mink.”

If this sea mink was just a subspecies, it likely exchanged genes with the local wood mink, and there is a distinct possibility that we could find its genes in some “wood mink” living today.  Even if it were a distinct species, it is possible that the two forms didn’t lose chemical interfertility.

So maybe the US lost two species of carnivoran in historic times. Or may we’ve lost only one. Just like the species status of the red wolf, the sea mink is still contentious in the literature, but unlike the red wolf, there are no molecular studies that have attempted to resolve this problem.

And we are left wondering about the mystery of what has passed, once again.

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Great Lakes gray wolf on Wisconsin’s Stockton Island.

An extensive camera trap survey of the Apostle Islands in Lake Superior has revealed a great diversity of carnivorans, including gray wolves and American martens. These islands, located just off Wisconsin’s Bayfield Peninsula, are among the few places left in the Eastern and Midwestern US that still retain an intact predator guild, and because all but one of the islands is protected as a national lakeshore, these islands will be protected from most exploitative development.

I love living in a country that still has room for wolves and wild places. Our natural heritage is every bit as important to us as a nation as our constitution and rule of law, and it should be protected with the same ferocity that we use to protect our republicanism.

Also of importance is the Great Lakes wolf in the trail camera capture that was part of the survey. This wolf looks to be one of wolves with some amount of coyote introgression. Great Lakes wolves can have quite a high amount of coyote ancestry, and the earliest estimated introgression of coyote genes into gray wolves that has been documented is from these Great Lakes wolves. This introgression happened as early as 963 years ago.

Coyotes and gray wolves are found on the islands now, and one wonders if they still occasionally interbreed. The Great Lakes are also the region that experienced the beginnings of the hybrid swarm we call the Eastern coyotes.

So these islands could be a new Isle Royale from which to study the new and evolving wolf and coyote of North America.

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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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We don’t really think of antlers as being practical weapons. No species of deer that has them has them year round, and in only one species, caribou/reindeer, do both sexes have antlers.

We tend to think of antlers as being used to attract the opposite sex and for ritualized combat between conspecifics, usually just competing males during the rut in all species but caribou/reindeer. In that species, the females retain antlers well into the winter, which they use fight for preferential feeding areas, a great asset in feeding the calves they carry through the long northern winters.

But we don’t normally think of them as weapons to be used against predators. After all, predators are a problem that plagues deer all year, not just during the rut, and if they were widely used in fighting off predators, one would think they would evolve to hold onto them permanently or at least for longer periods of the year.

Well, a recent paper in the journal Nature examined how these factors work with regard to elk living in Yellowstone, where wolf predation is a significant factor in elk survival.

The authors found that bull elk that lose their antlers relatively early tend to be in better physical condition than those that retain them, and those that lose their antlers early tend to grow larger antlers than those that retain them, simply because they have more time to grow their new antlers in the coming year.

The authors found that there is a massive trade-off for how long elk hold onto their antlers. Those bull elk that lose their antlers are preferentially targeted by wolves. Yes, even though they are in better physical condition than those that retain them, the wolves go for elk that lack antlers as weapons.

Predation from wolves could be driving elk in Yellowstone to hold onto their antlers longer, and it could explain why elk in general hold onto their antlers long after their breeding season.

This study has some interesting implications, because wolves could indirectly be selecting for smaller antler size in elk, simply because the elk that lose their antlers sooner tend to have bigger racks in the following year. Further, because the elk hold onto their antlers longer when they are in poorer physical condition, the wolves could be selecting for weaker elk that are much poorer foragers than they might otherwise be.

These questions were not addressed in the paper, but I’m sure the questions did arise as the researchers looked at their data. More work is going to have to be done, but it is clear that wolf predation is a lot more complex in how it selects for fitness in the elk population than we might have assumed.

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