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Archive for the ‘Carnivorans’ Category

Not so long ago, in terms of the history of our species and certainly not long ago in the history of the world, two “cheetahs” roamed North America, probably running the pronghorn and Odocoileus deer. They were fast and svelte like that cat of Africa and Asia, but they did not make it into the present fauna guild of this continent. 

The great extinction of the megafauna eventually wiped out the dire wolf and these running cats, which were replaced by the gray wolf sweeping down out of Eurasia and from the cougar recolonizing from South America.

Humans probably saw these cats and maybe stole their kills, maybe not though. They were running cats in the era when North America was like frigid Africa, where the faunal guilds of Eurasia and South America ran long and hard into each other. That of Eurasia eventually dominated in the end, but the opossum and the North American porcupine still made it, even though they were part of that austral losing team.

And where there were scores of fake antelope running about with our swift deer, there were two species of coursing cat to put them to flight.  
Miracinonyx was their genus, and M. trumani and M. inexpectus were the two species.  Trumani was more like a cheetah, and inexpectus was more like a very svelte cougar.

For much of my life, these animals were classified as American cheetahs, and there was a whole mythos about cheetahs first evolving in North America. And yes, it’s true that the cheetah’s closest relatives that still live today are the cougar and the jaguarundi, both of which are truly cats of the Americas.

But a few enterprising researchers were able to get some ancient mitochondrial DNA from trumani, and with careful comparison, they found that trumani was most closely related to the cougar. 

So we now think that the cheetah evolved in the Old World from an ancient cougar-like ancestor, but in North America, one form of ancient cougar begat two species with cheetah-like adaptations.

We call this sort of evolution “parallel evolution” in which two descendants evolve similar characters that are not shared by the common ancestor. It is similar to convergent evolution, which is the same sort of evolution without a direct relationship, but in convergent evolution, the common ancestor is so distant that it almost isn’t worth considering, such as the common ancestor of aardvarks and anteaters.

So North America never had any kind of cheetah. What we had instead were “coursing cougars.”

A piece of me longs to have seen one in the flesh, and for a time, cryptozoologists traveled around Mexico looking for such an animal. There were always references to “onzas” in the colonial literature of Mexico, and even today, onza is the term used for a particular cat in the countryside.  Onza means cheetah in Spanish, and there was always a hope that it referred to these old coursing cougars. 

But every lead led to a jaguarundi, which looks like an oddly-colored cheetah-cougar hybrid in miniature, or to really thin specimens of the cougar species.

So the coursing cougars went the way of the Smilodon and the dire wolf and the woolly mammoth.

But when you realize what was here some 12,000 years ago, it’s hard to not to be caught in flights of fancy. Our current wildlife seem picayune by comparison, but we once had all the majesty of the beasts of Africa south of the Sahara.

We’ve lost all these animals during that great extinction, and now we are looming into another one, this one definitely caused by our own actions.

And the cheetahs of Africa hold on by a thread. Those of Asia have almost gone entirely. They exist only in a narrow range in the north of Iran.  There may not be 50 of them left.

Extinction looms. We know it, and yet we feel so paralyzed by its inevitability, we wonder if we can act, if we can change, before it is too late.

To be a running cat is become a true specialist. To be a courser in a world already full of long-distance running dogs is to flirt with near extinction all the time.

But twice this form of cat evolved and ran long and hard across three continents.

Not a bad gamble in the terms of evolution’s blind whims.

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The notion that the black cats of parts of northeast Scotland are hybrids between Scottish wildcats and domestic cats is not controversial. The idea that they represent a hybrid species is, however, not something that has been considered. 

These black cats were anomalous, and during the tabloid-soaked years of the 1980s and 1990s, they became sort of legendary throughout Britain.  Eventually, some analysis was performed on some specimens, and it was decided that these animals represented hybrids between domestic cats  and Scottish wildcats. At the time,  these two animals were considered different subspecies but belonged to the same species.

Since that time, a new revision of felid taxonomy has been proposed in which the European and Caucasian wildcats are placed in one species (Felis silvestris) and the species that gave rise to the domestic cat is now called Felis lybica.  I generally agree with this new taxonomy, because of the deep division molecular division between these two cats, but I think that the domestic cat belongs as as part of Felis lybica in the same way dogs are part Canis lupus

If one adheres to this revision and accepts my little critique, then the so-called Kellas cats represent a hybrid species.  It would be great if more molecular studies were performed on these cats, but cats don’t seem to get as much fanfare or funding as dogs do when it comes to these sorts of studies.

I should also note that the Scottish population of European wildcats has significant introgression from domestic cats, so much so that in past 30 years, no Scottish wildcat DNA samples have shown to be free of domestic cat genetic markers.

If one defines a species as having no other crossed in, then we could say that Scottish wildcat is extinct in the wild, but we know that countless species exchange genes with close relatives,

This ecotype of the Lybica wildcat is much more adapted to the Holocene world than the European wildcat ever was. It is more than at home in agrarian landscapes, and it does well in urban environments too.

This story sort of parallels our own species, which came out of Africa into the land of the Neanderthals. We exchanged genes, but our species eventually swamped the land.

Maybe we will have better DNA studies of cats. Maybe we’ll find that European and European-derived domestic cats have traces of European wildcat ancestry.

One should have little hope for the pure European wildcat existing in Scotland or anywhere else where it currently roams, but maybe if we’re okay with the simple fact that hybridization exists, we can preserve what looks and behaves like a wildcat– and not worry too much about its DNA.

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The Tribe of Lybica

black cat

The August rains are autumn rains for me. The midday sun may boil the air a bit, but once a torrent falls from the sky,  air is astringent and cool and gives me just a little taste of the coming short days of October, when the sun will cast at the steepest angles through the crimson leaves on the trees.

Though the land is still in verdant summer, I feel this coming coolness and revel in it a bit. Just a few days ago, I was standing out in a bit of post-downpour reveling when I spied a black cat moving softly along the far end of the lawn.

Before we moved here, the cats lived in a paradise, feeding and fighting as ferals do,  and having their kittens on the old outbuildings that abut this property. The constant wanderings of dogs in and out of the house have put an bit of a damper on the cats constantly wandering here.

But every once in a while, I see one moving along the edge of the property, perhaps searching old haunts and checking to see if a giant coyote with a black muzzle still lived at this address.

On this day, though, the rain fell good and hard, and then the stooping August sun peared out to cast a yellow glow upon the land. And the sun rays cast upon the cat’s black coat, and its nearly pantherine form seemed to glow ethereally.

The cat glanced back at me, and I recognized its slender head and gracile form as belonging to a queen and not a tom.  Perhaps, it was the same queen I’d seen nearly month ago, moseying  through the summer grass with four kittens in tow.  Two black ones like their mother and two wildcat tabby ones cavorted all around their mother, who moved with the solemn determination of something wild and untouchable.

Their lives, like all things trying to be wild, are fleeting and harsh Hazards abound. Just few days later, I saw the flattened form of a black kitten on the highway just down from the house. I cannot know whether it was one of the four I’d seen cross the lawn, but I suspect that it was.

I am not a cat person. You will never confuse me with one, but I cannot help marvel at what they are. Many species of small wild cat exist in the world, but only a single form of wildcat managed set up shop in agrarian society.

This wildcat, now known by the name Felis lybica,  found that staking out granaries and wheatfields for mice and hamsters  was a pretty good way to survive. The grain ensured hordes of rodents for the stalking, and man’s hatred for all things large and predatory kept away all the wildcat adversaries or at least kept them at bay.

And over time the cat came to be man’s little wheatfield leopard, stalking and killing and living and traveling over the whole world as the ultimate mesopredator.

This is the Tribe of Lybica, the clan of little predators that don’t cause us much concern, and whole lineages of cats have passed before them. The mighty Smilodon and the American lion have fallen from the land. and even the squalling cougar has passed on from its haunts, though a few claim to see them slipping about in the undergrowth.

The Tribe of Lybica lives at the edge of human civilization, but it also lives in a much vaunted status as a companion animal. The internet worships them in almost the same garish way as the Ancient Egyptians did.  They filled their walls with many images of cats, while we fill our “walls” with memes of “kitters” and “cattos.”

The Anthropocene is the age where the little monsters thrive and the big ones live mostly in forgotten and inaccessible redoubts.  You’ve never seen an Amur tiger stroll down an alley in Pittsburgh, but you’ve surely caught the glance of one of the local ferals flitting away behind a parked car.

So the black cats will thrive well in my neighborhood. The speeding car is their only main concern.  They will stand starkly against the winter cold and driving rain, and we will consider them very little.

But they will thrive, and in the spring, the queens will have their kittens, and a whole new generation of the Lybica will inherit the grounds.

And this cycle will repeat long after I’ve moved on.

As much as I will rail that cats need to be kept indoors and kept neutered, they will thrive so long as human kind thrives.

And when our species goes the way of the dinosaur, their lineage will be spread across the globe. It might be cut down in size once the bigger predators return, or they could evolve into the new tigers and cougars that prowl the world post-humanity.

So the Tribe of Lybica’s fate is linked to ours, but perhaps not as much as we might assume.

Their connection to us will always be tenuous and fleeting but also linked and tied. A remarkable paradox, to be sure.

 

 

 

 

 

 

 

 

 

 

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red fox new jersey

New Jersey is a place I think of when I think of a place where animal rights ideology has become quite pernicious.  It is a densely-populated state that still has a lot of wild areas still left within its borders, but wildlife management decisions that include lethal control are quite controversial in that state.

For example, in my state of West Virginia, we have plenty of black bears. Black bears are state symbol, and if you go to any gift shop in the state, there will be black bears featured on so many different object. We love our bears, but we also manage them with hunting season.

New Jersey has the same species of bear, and this bear species is one of the few large carnivorans that is experiencing a population increase. Biologists know that hunting a few black bears every year doesn’t harm their populations at all, and in my state, bear tags go to promote bear conservation and to mitigate any issues between people and bears. Hunting these bears also gives the bears a healthy fear of humans, and it is virtually unknown for a bear to attack someone here. New Jersey has had a bear hunt for the past few years, but it has been met with far more controversy there than it ever would be here. Checking stations get protesters, as do wildlife management areas that are open to bear hunting.

Since the bear hunt began, human and bear conflicts have gone down dramatically. The population is thinned out a bit, and the bears learn that people aren’t to be approached.  But those potential conservation gains are likely to be erased sooner rather than later.

The animal rights people have become powerful enough in that state that no Democrat can make it through the primaries without pledging to end the bear hunt. The new Democratic governor wants to do away with the bear hunt.

But the bear hunt isn’t the only place where the animal rights people are forcing misguided policy.

A few days ago, I posted a piece about the inherent conflict between animal rights ideology and conservation, and it didn’t take me long to find an article about red foxes in Brigantine, New Jersey. Brigantine is an island off the New Jersey coast.

Like most places in the Mid-Atlantic, it has a healthy population of red foxes, but it also has a nesting shorebird population, which the foxes do endanger. One of the shorebirds that nests on the island is the piping plover, a species that is listed as “near threatened” by the IUCN.  Red knot also use the island on their migrations between South America and their Canadian arctic nesting ground. This species is also listed as near threatened, and both New Jersey and Delaware have enacted regulations and programs to protect them.

At Brigantine, people began to discover dead red foxes in the sand dunes, and because red foxes are canids and canids are charismatic. It was speculated that the foxes were poisoned, and the state DEP was asked if the agency had been poisoning foxes there.

The state apparently answered that it had no been poisoning foxes on Brigantine’s beaches. It has been trapping and shooting red foxes.

To me, the state’s management policy makes perfect sense. North American red foxes are in no way endangered or threatened. Their numbers and range have only increased since European settlement, and they are classic mesopredators.  Mesopredators are those species of predator whose numbers would normally be checked by larger ones, but when those larger ones are removed, the smaller predators have population increases. These increased numbers of smaller predators wind up harming their own prey populations.

This phenomenon is called “mesopredator release.” It is an important hypothesis that is only now starting to gain traction in wildlife management science. What it essentially means is that without larger predators to check the population of the smaller ones, it is important to have some level of controls on these mesopredators to protect biodiversity.

Animal rights ideology refuses to consider these issues. In fact, the article I found about these Brigantine foxes is entitled “These adorable foxes are being shot to death by the state.”   The article title is clickbaitish, because the journalist interviewed a spokesperson at the DEP, who clearly explained why the fox controls were implemented.

The trappers who took the foxes probably should have come up with a better way of disposing of the bodies. One should also keep in mind that New Jersey is one of the few states that has totally banned foot-hold traps for private use, so any kind of trapping is going to be controversial in that state. So the state trappers should have been much more careful.

But I doubt that this will be the end of the story. The foxes have been named “unofficial mascots” of Brigantine, and it won’t be long before politicians hear about the complaints. The fox trapping program will probably be be pared back or abandoned altogether.

And the piping plover and red knot will not find Brigantine such a nice place to be.

And so the fox lovers force their ideology onto wildlife managers, and the protection of these near threatened species becomes so much harder.

This sign was posted in 2016 after the first dead foxes were found:

save our foxes

But I don’t think many people will be posting “Save Our Piping Plovers.” Most people don’t know what a piping plover is, but red foxes are well-known.

They get their special status because they are closely related to dogs, and people find it easy to transfer feelings about their own dogs onto these animals.

This makes sense from a human perspective, but it makes very little sense in terms of ecological understanding.

And it makes little sense for the foxes, which often die by car strikes and sarcoptic mange, especially when their population densities become too high.

Death by a trapper’s gun is far more humane than mange. The traps used are mostly off-set jawed ones, ones that cannot cut the fox as it is held. The trap is little more than a handcuff that grabs it by the foot and holds it. The traps are checked at least once a day, and the fox dies with a simple shot to the head, which kills it instantly.

And the fox numbers are reduced, and the island can hold rare shorebirds better than it could before.

In trying to make a better world for wildlife, we sometimes have to kill. This is an unpleasant truth.

And this truth becomes more unpleasant when we start conflating animal rights issues with conservation issues. Yes, we should make sure that animals are treated humanely, but we cannot make the world safe for wildlife without controlling mesopredators and invasive species.

I think that most of the fox lovers do care about wildlife, but they are so removed from wildlife issues on a grand scale that it becomes harder to understand why lethal methods sometimes must be used.

My guess is these people like seeing foxes when they are at the beach and don’t really think about these issues any more than that.

It is not just the wildlife exploiters and polluters that conservationists have to worry about. The animal lovers who extend too much animal rights ideology into conservation issues are a major problem as well.

And sadly, they are often the people that are the hardest to convince that something must be changed.

I don’t have a good answer for this problem, but it is one that conservationists must consider carefully as the future turns more and more in the favor of animal rights ideology.

 

 

 

 

 

 

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golden wolf vs. black backed jackal

Not the best photo, but this is golden wolf on the left and a black-backed jackal on the right. I screen-captured this image from this documentary, which was made before the big golden jackal revision that happened a few years ago.

There is still a big debate on how classify the creature formerly known as the African golden jackal. It is clearly closer to gray wolves and coyote than to the Eurasian golden jackal, but the exact closeness requires further research.

The black-backed jackal on the right is a much older species. It has been known from the fossil record in Africa for over two million years, and the wolf-coyote-golden wolf lineage last shared a common ancestor with it around 4.5 million years ago.

Depending upon when we finally determine when the golden wolf diverged from the modern gray wolf, it may have evolved from larger ancient gray wolves that adapted to fit the generalist jackal-like niche, or it may have evolved from a African population of Canis mosbachensis.

The black-backed jackal is derived from the earliest wolf-like canids to have entered the Old World from North America. Those early wolves were all smaller and jackal-like, and its appearance and adaptations are of the primitive type.

So here we have two species that look like they might just be color phases of the same species but actually are divided by millions of years of evolution. One is a truly primitive member of its lineage. So primitive and basal that its now classified in a different genus (Lupullela). The other came from a more derived source that evolved parallel characteristics with the primitive one.

Parallel evolution is a hell of a thing, especially when it comes to canids. So much of this parallel evolution has been missed in paleontology and in the conventional methods of taxonomy that use only morphology. Not recognizing the parallel evolution issues is why we didn’t notice that coyotes and gray wolves were much more closely related than we ever could have imagined. It’s also why we thought bush dog belonged with the dhole and African wild dog, just because their teeth are so similar, and it is also why an affinity has been suggested between crab-eating foxes and raccoon dogs, even though they are in entirely different lineages. It is also why there was a suggestion that red wolves represent an ancient lineage of North American wolves, when they are now probably hybrids between coyotes and gray wolves.

Parallel evolution messes up a lot of things. Our eyes and our measuring instruments can fail us.

But the correction of these failures reveals a much more mysterious world.

That’s the inherent beauty of science. Each correction is a revelation.

 

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red panda mom

Mozilla Firefox is a browser with an interesting zoological name.

I think it’s a little strange that people don’t know what a “firefox” is, but it is an alternate name for the red panda. The company that developed the browser is quite into red pandas for this reason, but I don’t think the typical user of the product really thinks much about the name.

Red pandas are perhaps the most unusual carnivoran from a taxonomy perspective.  For most of the twentieth century, it was assumed that red and giant were close relatives. Both animals live in Asia, and both have this unusual “thumb” that is made out of one their wrist bones. The feature is used to grip bamboo, and it was just assumed they evolved this trait from a common ancestor.

Red pandas look a lot like raccoons, and it was proposed that they were procyonids, just because they looks so much like a more specialized form of raccoon. And if this animal is a raccoon and the giant panda is its closest relative, giant pandas are not bears.

The classification of the giant panda was resolved though a molecular and genetic measures that were published in 1985. Giant pandas are bears, though they are a very divergent form of bear. Further, the giant panda’s chromosomes were found to be mostly fusions of the typical bear karyotype.

Red pandas, though, were even more strange. They weren’t bears, and they weren’t procyonids either.  In this study, they were as divergent from bears and procyonids as bears and procyonids are from each other, but the techniques in those days were rudimentary and not conclusive.

However, this finding suggested that red pandas really are something else. They were given their own family name (Ailuridae), and researchers have spent several decades trying to figure out where these animals fit in the order Carnivora.

Of course, figuring out exactly where they fit they were took some time. In 2009, we finally got a good molecular study that looked at a relatively large same of nuclear DNA of red pandas, procyonids, mustelids (weasels, ferrets, otters, wolverines, martens, and mink), and mephitids (skunks and stink badgers).  It found that red pandas formed a clade with procyonids and mustelids. They are roughly as closely related to mustelids as they are to procyonids, so they definitely do deserve their own family name.

This is largely the consensus view on where red pandas fit, but there is an alternate view that has popped up as result of another molecular study.

In 2010, an analysis of the cytochrome-b sequences from 243 carnivoran species and subspecies found something unusual. The red panda was found to be most closely related to canids.

This finding is somewhat surprising, and because this study is based upon a very small part of the mitochondrial DNA from each sample, it is problematic. If you look at the phylogeny proposed in this paper, it puts the kinkajou outside of Procyonidae, and a clade is formed with the Ethiopian wolf, red wolf, and the coyote, while another clade is formed with the various subspecies of the Holarctic wolf and the golden jackal. These are problematic because full-genome comparisons tend to place the coyote as much closer to the Holarctic wolf than we ever thought, and the exact position of the other species still must be worked out.

But let’s just say that this study’s findings about the red panda are later confirmed in another nuclear DNA study or one that uses full-genome comparisons.

If the red panda is the closest living relative to the dog family, then we’ve got something interesting. Canids were an early diverging family in the order Carnivora. Their sister family were the amphicyonids, which are often called “bear-dogs” in English. This family consisted of plantigrade species that were sort like wolverine-lions. They went extinct 1.8 million years ago.

Dogs are not that closely related to rest of what are called the “caniform” carnivorans, so when the amphicyonids became extinct, they were the last of their lineage.

If the red panda really is that close to the dog family, its exact position with regard to both canids and amphycyonids is not entirely clear.  It could be that red pandas are actually a sister taxa to the extinct bear dogs, which would be an interesting find.

One should keep in mind that the red panda family used to include some pretty fell beasts.  Simocyon was a genus of cougar-sized predators that lived throughout Eurasia and was also found in North America and Africa during the late Miocene and Pliocene epochs. These creatures were fully carnivorous– and they had the wrist thumb that one finds on the red panda living today. The discovery of this thumb on this extinct relative with such a different ecological niche revealed that the red panda’s thumb came about far earlier than we expected. And it had nothing to do with gripping bamboo to eat.  It had more to do with climbing around in trees.

The giant panda’s thumb does have to do with eating vegetation.  A Miocene bear in the panda lineage from Spain called Indarctos arctoides already started to have some deviations with the bone that becomes the “thumb” in modern pandas.

The trait evolved without any common ancestry, and it is only one of those ironies of natural history that these two creatures have this feature and use it in much the same way.

So giant panda really is a bear, and the firefox might be a kin to the dogs.  (But probably isn’t).

 

 

 

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pronghorns

Our brains like simple answers. We love to see the cause and then the effect, and we constantly look for them in nature.  At one time, we believed that the appearance of comets in the sky would be harbingers of great doom. And even in the past century in my home state, it has long been claimed that the appearance of Mothman in the area around Pt. Pleasant corresponded with the Silver Bridge collapse.

Correlation does not equal causation. Chanticleer, that old rooster of English Medieval lore, believed that his crowing at dawn made the sun rise.  When two variables occur at the same time but don’t have any causal relationship, they are called stochastic. Stochastic is one of my favorite words from graduate school, and even today when someone posits a bogus relationship between two variables, I say “Those are stochastic variables.”  I get some odd looks, but that was the point.

In trying to understand the complex phenomena that comprise evolution, we are constantly looking for these relationships. Some of them make some good sense and are well-supported with the data. We know that predators are the driving force behind making the prey swift and nimble, and we also know that plant-eating animals are the driving force behind the development of thorns and toxic plants.

But sometimes, our desire to see patterns leads us astray.  One example of what may be an erroneous positing of stochastic variables involves one of North America’s most unusual animals.

If one were to go to Wyoming on a hunting trip, there is a good chance that the outfitter will tell you to buy “antelope tags.”  Tags, of course, are licenses that give permission to the hunter to take a particular species, and in Wyoming, there is great interest in the pursuit of antelope.

But the little secret is there are no antelope in Wyoming. Indeed, the only true antelope in the United States are gemsbok that have been introduced to specific part of New Mexico, and Texas game ranches are full of various species of Old World antelope.

But no true antelope is native to the Americas. The animal we call an “antelope” should be more appropriately called “the pronghorn.”  It is not an antelope at all, but it is the last survivor of a lineage of creatures that are much more closely related to the various giraffe species and the okapi.  The pronghorn and its extinct kin are placed in a superfamily of Artiodactyla called Giraffoidea. These animals have bony processes that stick off their heads. In the giraffe and okapi, these are called ossicones and are covered in hair. In the pronghorn, a sheath of keratin grows over the bone. This sheath is shed every year, which leads to the claim that the pronghorn is the only animal that loses its horns every year.

The animal we call a pronghorn is superficially quite similar to what we would call an antelope or gazelle in the Old World.  But these similarities arose through parallel evolution. Both gazelles and pronghorns evolved in the open land where all sorts of cursorial predators hunted them. Predation forced these animals into swiftness and nimbleness.

That part is not much up for debate.

The problem comes with a specific claim about pronghorns.  One odd feature of this species is its speed. The top speed of an adult pronghorn is 55 mph (88.5 km/h). This speed far exceeds any of its predators that were around in historical times. A pronghorn can smoke a pack of wolves or coyotes and can easily outrun a cougar or a bear.

This high speed has vexed science for quite some time, but there has been an attempt to explain how it could evolved using predation as the driving force.

The hypothesis even points to a specific predator.

At one time the cougar lineage was much more diverse than it is now.  Right now, only three cats still exist in this lineage:  the cougar/mountain lion/puma/catamount/painter/panther (all names for one species), the jaguarundi, and the cheetah of Africa and Iran.

But during the Pleistocene, there were long-limbed cats that superficially resembled the cheetahs of the Old World. They were called “American cheetahs,” but analysis of mitochondrial DNA extracted from their fossils revealed they were much more closely related to cougars. Indeed, they were more closely related to cougars than cougars are to jaguarundi, which complicates the whole move to place jaguarundis in the same genus as the cougar. The two extinct American cheetahs are currently classified in the genus Miracinonyx, while the cougar is in Puma and the jaguarundi is in Herpailurus. Because these two American “cheetahs” are closer to the cougar, placing the jaguarundi in Puma creates a paraphyletic genus. This problem could all be solved if we just placed the two American “cheetahs” into Puma, but not everyone agrees with the mitochondrial DNA assessment of their phylogeny.

Let’s just say that the current pronghorn species lived at the same time as these lithe cougars, and it has been suggested that these cheetahs are the driving force behind the evolution of the extreme speed. The person who came up with this suggestion was a pronghorn expert named John Byers. Byers does not claim that these “cheetahs” were the sole force behind the development of speed in pronghorns. Instead, he lists them among a whole guild of running predators that could have placed selection pressures on pronghorns to force them into the evolution of speed.

The claim that these “cheetahs” were the driving force behind pronghorn speed has been picked up on the popular press though. Wildlife writer Dan Flores even made this claim recently on the Joe Rogan Podcast, and one can find countless pieces on the internet (including this blog when I was a lot more naive) that the extinct North American cheetahs are the “but for” cause of the pronghorn’s fleetness.

The problem with this claim is that it leaves out the nuance of the original hypothesis, and what we’re left with is a sort of cartoon version of evolution.

On the blog Laelaps, a great amount of skepticism is leveled at this hypothesis, largely because the popular understanding of how North American cheetahs might have affected pronghorn evolution.

One problem is that no one really knows how the two species of North America cheetah lived:

We don’t know very much about the natural history of either Miracinonyx species. Their skeletons are cheetah-ish, but that’s not nearly enough to pin these carnivores as the inspiration for artiodactyl agility. In fact, the ecological context of Miracinonyx bones hints that these cats were not simply speedy specialists who prowled open grasslands.

In their 1990 study, Van Valkenburgh and collaborators noted that later Miracinonyx bones have been found from Nebraska to Pennsylvania and Florida in deposits which accumulated under varying conditions. These cats were apparently just as at home among coastal savannahs as mountain stream valleys. More recently, at the 2010 Society of Vertebrate Paleontology meeting, John-Paul Hodnett and coauthors presented a poster about Miracinonyx that frequented caves in prehistoric Grand Canyon, Arizona. There was a distinct lack of fast-running, open-savannah prey animals during the same time period – the researchers noted that the extinct mountain goat Oreamos harringtoni was the most common possibly prey animal in the area. Rather than speeding over the grasslands, Hodnett and colleagues reported, the Grand Canyon Miracinonyx may have lived like snow leopards, bounding down sheer rock faces in pursuit of mountain goats.

This isn’t to say that Miracinonyx never bolted after equally-swift prey. It’s only to point out that we don’t know much about the cat’s ecology, feeding habits, or hunting strategy. There are a few ways we could find out a bit more, though.

Coprolites attributable to Miracinonyx might contain identifiable bone fragments of the cat’s prey. And while such a find is a longshot, perhaps a trackway made by a Miracinonyx running or launching itself into pursuit could tell us about how these cats actually moved. Both lines of evidence suffer from the complexities of accurately attributing a particular trace fossil to a trace-maker, though. Another route may be to compare the isotopic clues in the teeth of Miracinonyx to those of their potential prey, as was recently done for two sabercats and a bear dog found in Spain. By ascertaining where herbivores were feeding, and how geochemical signatures of prey became locked in carnivore teeth, paleontologists could narrow down the preferred habitats and prey of Miracinonyx. Furthermore, a poster presented by Natalia Kennedy and coauthors at the 2012 SVP meeting outlined a new attempt to compare the spine of the modern cheetah to that of Miracinonyx and other extinct cats to see how skeletal anatomy influenced flexibility and lifestyle.

Miracinonyx might have been the reason for the swiftness of pronghorn. False cheetahs and archaic pronghorn overlapped in time, if not habitat, for as much as three million years. But saying Miracinonyx was certainly a speed demon that gave pronghorn a reason to run is only supported by the barest amount of evidence. If we’re going to understand the evolution and natural history of these animals, we must first untangle their histories and the specific details of their ecology. The Just-So story of how the pronghorn got its speed has yet to be tested by the evidence which resides in the fossil record.

So we really don’t know enough about the extinct North American “cheetahs” at all, and we certainly don’t know enough to make claims that they were the driving force behind the evolution of speed in pronghorns.

Further, if one reads Byers’s text on these predators, he does say that these cheetahs were “the principal agents of selection” behind the pronghorn’s speed, but the author does point out that things like dholes, wolves, and various species of Borophaginae could have been part of the mix as well.

Pronghorn don’t just have speed. They have endurance.  Endurance is one way that Old World antelope elude the speed of cheetahs, but the main way they elude them is through agile running maneuvers. Pronghorn are fast, but they don’t have the quick turns of a Thomson’s or dorcas gazelle.

If these North American “cheetahs” ran down their prey in the same way the Old World true cheetahs do, then one would expect the pronghorn to have evolved some of these tricks.

Instead, pronghorn are running machines. They can take off and go and go and go. An animal that evolved to do such a thing likely didn’t evolve to outpace a sprinting cheetah. It likely evolved to outrun endurance runners.

Dholes are known in North America’s fossil record largely from Beringia, but we do have remains of dholes from Mexico. So their distribution in North America was probably more extensive than we might have assumed, but their fossil record is still quite spotty. Dholes run down their prey in long endurance chases, and dhole predation could have been a pretty strong selection pressure on pronghorns to make them fast endurance runners.

But another species could have also provided this pressure, and its presence in North America is well-established. What’s more, it lived in roughly the same areas where pronghorn were common.

This animal was North America’s only hyena, Chasmaporthetes ossifragus. These hyenas were far less like the modern bone-crushing species of hyena. Indeed, they were quite dog-like and are part of a grouping of hyenas that were called “dog-like hyenas.” The only dog-like hyena still in existence is the aardwolf,  which eats almost nothing but termites.  Its extinct relatives, though, were pretty adept predators of ungulates. They are thought to have run down their prey in much the same way dholes and African wild dogs do today.

So it seems that the pronghorn’s speed and endurance are much more likely to have evolved in response to predation from these long-distance running predators.

Further, we really don’t know how early North American wolves hunted their quarry.  Edward’s wolf and Armbruster’s wolf were both pretty common in North America until 300,000 years ago. They may have also hunted in much the same way dholes and African wild dogs do.  We don’t know enough about their natural history either, so we can only speculate.

The truth is we really don’t know why pronghorns are so fast.  It is possible that the North American “cheetahs” were the principal driving force behind the pronghorn’s speed. It is possible, but the evidence still is wanting. Further, there are more likely candidates that should be explored as having some influence on evolution pronghorn predation avoidance behavior.

So it is possible, but right now, it looks like we have two stochastic variables. We need much more evidence for a causal relationship.

And like everything else in evolution, we need to be careful about looking for patterns where they might not exist.

 

 

 

 

 

 

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