Archive for the ‘Invasive species’ Category

feral horses

I make no bones about my view that the horses that roam the American West are feral and should not be regarded as native wildlife. This view shouldn’t controversial, but it is.

Lots of romanticism exist about horses and the West, including that brief time when Native cultures used horses as their greatest asset in hunting bison.

But the truth is that the horses one might see roaming the ranges of the American West are all derived from domestic horses that went wild on the range. The initial ones were all derived from Iberian/North African horses that Spanish colonizers brought into the New World, but these were later augmented with horses brought over from the rest of Europe.

If one were to say that the various forms of freely breeding swine in North America were feral, it would be easy to get agreement. Suids are not native to the Americas, though a sister lineage, the Tayassuidae, are native to North America. The tayassuids, better known as peccaries or javelinas, once ranged as far north as the Yukon, but since the Pleistocene, they have not ranged north of Texas, New Mexico, and Arizona.  Feral swine, though, exist over large sections of the country, and wildlife and agricultural departments spend lots of time, money, and manpower on controlling their numbers.

Feral horses, though, get special privileges, as do feral donkeys.  They receive a certain amount of protection not afforded to other feral livestock in the Wild and Free-Roaming Horses and Burros Act of 1971. The horses and donkeys are not controlled in the same way feral pigs are. There is no continuous open season on them in the way that most states manage feral pigs.  Indeed, it is actually a crime to kill or harass feral horses or burros on federal land.  Excess horses and burros are managed through roundups, where some of them are deemed adoptable and sold to the general public.

For those of us with a modern ecological mindset, which has a deep disdain for making allowances for feral livestock, this law makes little sense.

But there is a sort of argument for this act. It goes something like this:

The modern horse species evolved in its current form in North America. Some taxonomists contend that there was once a Holarctic distribution of this species during the Pleistocene, and with the latest ancient DNA studies, I tend to agree with this assertion.

The North American population of horses became extirpated at the end of the Pleistocene, and when European horses went feral on the Western ranges, this constitutes a rewilding event.

Now, I don’t buy this argument very much, but I can say that there are some things we might consider. North America’s original population of cougars became extinct at the same time. The cougars that live in North America are derived from South American cougars that recolonized the continent about 2,000 years later.

Further, conservationists and sporting groups spend lots of resources on restoring and protecting elk populations. Elk have a much shorter history on this continent than horses ever did. Different experts have estimated when elk have first arrived. 40,000 years ago has been suggested, but more recent data points to them colonizing North America only 15, 200 years ago.

If elk arrived in North America only that recently, their status as native wildlife exists only as a weird  accident of geography. Elk are the on Cervinae or “plesiometacarpal deer” in the Americas. All the other deer in the Americas are Capreolinae or “telemetacarpal deer.”  Sika, axis, red deer, and fallow deer are also Cervinae, but they were introduced after colonization.

Elk don’t live in far northeast of Russia anymore. The elk of North America are the genetic legacy of this ghost population.

So the feral horse advocates could at least through the recent arrival of elk in North America as something to consider when we say their favorite animal is not native. Horses have a long evolutionary history in North America, and we just happen to be at an odd point of the history of horses that no native horses exist here. The earliest horse, Eohippus, first appeared in North America 52 million years ago.

So the feral horse advocates could say that we have a species that derived from a lineage that was here for over 50 million years that has now been restored through feral livestock and thus deserves these protections.  And this animal has at least as much rights to be free and roaming in North America as a large deer that had no connection to this continent until the latest Pleistocene.

However, the extinction of the horse in North America likely stemmed from natural climate change at the end of the Pleistocene.  Horses became extinct because they were poorly adapted to the new ecosystems, and as we have seen, horses really don’t do that well out in the deserts and semi-arid ranges of the West. They require water tanks to get them through long droughts, and they eat lots of forage. Not as much as domestic cattle, of course, but on ranges that are heavily catered toward livestock grazing, the horses are just an extra set of grazers that are taking away forage from native wildlife.

And even if we were to accept that horses were restored native wildlife, why on earth would we ever extend these protections to donkeys? Donkeys, though of ancient North American origin, evolved in their current form in Africa.

So although I do think of horses as no longer being native to North America, I do think questions of them being native or introduced are complicated, much more so than the question of feral pigs or cats. And yes, there is something like an argument that can be made for the native status of horses, even though I think it’s mostly in error.

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We like to think of our common fauna as having always had their current range. It would be news to most people that at the time of European contact, red foxes were uncommon south of New York State and were unknown south of the northern tier of Pennsylvania. The clearing of the forests allowed red fox to colonize southward. Similarly, the Virginia opossum did not range north of a line that stretches from extreme southern Ohio through to Virginia.  The expansion of agriculture, the killing of predators, and a generally warming climate have allowed the opossum to make it into Canada.

In recent decades, a new species has begun to shift its range.  The nine-banded armadillo is the only xenarthran found north of Mexico. This is a bit of an oddity in the history of mammals on this continent, because the US was once home to several species of ground sloths and a species of glyptodon. Until around the year 1850, there were no armadillos in the US.  But after 1850, the armadillo became known in Texas. Maybe it swam the Rio Grande. Maybe soldiers coming back from the war in Mexico turned them loose. We really don’t know.  But Texas became the epicenter of armadillo’s colonization of the United States.

It began its range expansion from Texas up through the central states. It is well-established in parts of Missouri, Southern Illinois, and Kansas.  They have also colonized Eastern Colorado. So these creatures are quite cold tolerant.

In the 1920s, it was introduced to Florida, and from Florida, it has launched its eastern colonization. Because it had a comparatively late start, this colonization northward has been quite a bit behind the colonization of the Central states.

But it is on its way.  We now have reports of them in the Smoky Mountains National Park, Smoky Mountains National Park, parts of Western North Carolina, and even sightings of them in Southwestern Virginia.

Milder winters are certainly helping their advance. Their diet is primarily insects, and when the winters fail to kill of their food, the armadillos have much easier time surviving in the cooler parts of North America.

This colonization is a sort of replacement. During the Pleistocene, a close relative of the nine-banded armadillo lived over a broad swathe of the United States. This relative, the beautiful armadillo (Dasypus bellus), lived from New Mexico to Florida and up to Indiana and Illinois. This remains of this species are quite difficult to tell apart from the modern nine-banded species, but it is likely that these animals behaved quite similarly.

However, because it lived in these regions during the Pleistocene, it had to have been even more cold tolerant than the nine-banded species.

So armadillos went extinct from much of the United States when the Holocene rose out of the Pleistocene, and now we have a very close relative restored during the Anthropocene.

Of course, the armadillo invasion means some potential risks. Nine-banded armadillos are a vector for leprosy, and it is quite possible for humans to catch leprosy from armadillos. As armadillos become more common in the United States, the potential for a rise in leprosy cases certainly exists.

So the armadillos have hit the Southern Appalachians. In a few years, we’ll hear of them in the Central Appalachians, and then they will reach their projected northern range limit in Pennsylvania and Ohio. They could potentially colonize the Eastern Seaboard as far north as Massachusetts.

So they march northward, armored up for protection.



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Raccoons in Ireland


Europe has no living native Procyonids.  Germany and the countries on which it borders do have a well-established population of raccoons, but the British Isles were thought to be raccoon-free. In fact, I refused to watch one version of 101 Dalmatians because it featured raccoons in England. Every English person knows there aren’t any raccoons running around.

However, the same cannot be said of Ireland. Rumors of errant raccoons have been filtering through the internet for quite some time. I got wind of it in 2011, when raccoons were sighted in County Cork. 

I didn’t think it was possible that there could be a breeding population in Ireland, but in recent months, a raccoon was hit by car in County Clare back in September.

In November, a raccoon was live-trapped and humanely euthanized in Cork.

These might be errant escaped pets, but errant escaped pets are the basis for a potential breeding population. And if you think that sounds far-fetched, well, Germany has a growing population of raccoons that were introduced in the 1930s.

Ireland has a much milder climate than most of North America, and this species of raccoon lives where the winters can be quite harsh.

These sightings could very well be the start of a real problem in Ireland. Raccoons are the ultimate mesopredator in that they relish raiding bird nests and even killing ground-nesting birds and poultry. Their numbers have flourished in North America since the widespread extirpation of wolves and cougars, and in Ireland, they would likely find a paradise. They would have to compete with badgers and red foxes, but because they are such adept climbers, they would also have access to food sources in trees.

We can hope that an established population of raccoons isn’t being founded in Ireland right now, but I almost wouldn’t bet against it.  They do very well on the continent. Ireland is ripe fruit, reading for the clawed hands to pick.

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indian rock python

I should note now that I really hate the way science journalism tends to overplay certain discoveries, and this week I saw a great example of “clickbait” science journalism run amok on what really is an interesting finding.

As long time readers know, I have been a bit obsessed with the successful colonization of Burmese pythons in South Florida. As someone who has lived his life in the true temperate zone of Eastern North America, which is usually called “humid continental” by some climate classification schemes, I have lived where most of the reptilian fauna are quite diminutive. The species that I will call a “black rat snake,” because of bizarre taxonomy boondoggle in which it is next to impossible to find a consensus on what one should properly call it, is the largest species of snake. The biggest specimens of that species can approach six feet in length. It’s an impressive snake for something in this cooler temperate zone, but it’s not a monster among squamates.

Florida, though, by a geographical accident, is a place where the lower parts of the peninsula have a climate much like Southeast Asia, and this area is connected to the 48 contiguous states.  This accident of geography means that Florida’s middle class had access to all the wonderful exotic pets that were popular throughout the country in the decades following the Second World War. The problem is that green iguanas and spectacled caimans cannot survive the winter in New Jersey or Michigan, but they can survive in Florida.

Burmese pythons became established in large swathes of South Florida around the year 2000. Lots of studies have gone into figuring out what the establishment of this large non-native constrictor could mean for biodiversity in Florida. A 2012 study concluded that massive declines in mammal diversity coincided with the establishment of the python in Everglades National Park. And a long-going debate still exists about how far north Burmese pythons will spread, a debate that started when the US geological survey released its analysis of how much of the southern US was actually quite good python habitat.

An experiment in which some Burmese pythons were kept outside year-round in South Carolina found the snakes just didn’t do well. The ten snakes died during a January cold snap, but the possibility exists that a more free range population could have found shelter in an armadillo burrow.

So maybe they won’t make it up through the South, but there has always been a catch in those studies. We assume that the Burmese pythons will remain pure, but various species of python do hybridize.  Burmese and African rock pythons do hybridize, and there are reasons to be concerned that a population of African rock pythons has also become established in parts of South Florida.  Many articles have been posted about the potential issues that could result if those two species hybridize, but thus far, no one has documented a hybrid of the two species in the wild.

But a study released a few days ago revealed that there was evidence that some of the feral Burmese pythons have mitochondrial DNA that can be traced to another species of python, the Indian rock python. It was the first study to do any kind of DNA analysis of the feral Burmese python population, and what it found was 13 Florida Burmese pythons out of the 426 sampled had Indian rock python mitochondrial DNA. The study did look at some nuclear DNA characters, and pretty much found that these odd ones still were overwhelming Burmese python in ancestry.

That is a quite small number, and the researchers were careful to point out that the hybridization event probably happened long before the pythons became established as invasive species.

I should note now that for most of my life, we regarded the Burmese python as a subspecies of the Indian rock python. Currently, there is a move to have the Burmese python raised to a full species status, but in the classical definition, the Burmese python was the subspecies of Indian rock python that evolved to live in humid and wetter places in Southeast Asia, while the Indian rock python proper lived in the more arid regions of South Asia.

The authors of the study that found the 13 pythons with Indian rock python mitochondrial DNA are using the paradigm of the Burmese python as a distinct species, so it does look like you have full species hybrid, even if it is just a mitochondrial DNA introgression.

This introgression could have happened in Asia, because it is not exactly clear how much hybridization happens in the wild where the ranges of the two species overlap. To make things even more interesting, the US Fish and Wildlife Service listed the Indian rock python as an endangered species through the ESA, and it was common for keepers of Indian rock pythons to cross them with captive Burmese pythons to avoid regulations on keeping and selling that species.

But the popular press’s understanding of what was discovered has been, well, not that nuanced.

Headlines, like The GuardiansSuper-snake: hybrid pythons could pose new threat to Florida Everglades” and Hello SWFL’sBurmese and Indian Pythons Breeding, Creating New Species,” lead one to think that this discovery is a sign that something really unusual has been discovered.

But the truth is that there is still a debate as to whether Burmese pythons represent a distinct species or not, and the authors have not found anything but some limited introgression of mitochondrial DNA from the Indian rock python in the feral Burmese population.

I should note that I do think that the Indian rock python and the Burmese python are distinct species, because the amount of genetic divergence between the two is pretty significant. However, they can hybridize and probably do so in the wild on a very limited basis. .

And it shouldn’t be a surprise that people would cross related species of exotic pets. Campbell’s and winter white dwarf hamsters have been crossed quite extensively, and hybrids with captive-reared felids are also quite well-known to the public.

Further, there are issues that we don’t know about the evolution of Burmese and Indian Rock pythons. We don’t know which genes each species has that allow them to be adapted to arid or wetter conditions. If we knew about these genetic differences, then we could test those hybrid snakes to see if they had inherited any other genes from the Indian rock python that would make it more easy for the snakes to colonize other areas.

We also don’t know how much Indian and Burmese pythons have been interbred in captivity or in the wild.  It very well could be that having some captive Burmese with this Indian rock python mitochondrial DNA is actually pretty representative of the pet population.

But we don’t have that information yet.  What we do have is the discovery of this mitochondrial DNA in the Burmese population, and that’s a pretty amazing discovery.

But it is not sign of a new hybrid species of super python. I will gladly eat my hat if more evidence is discovered, but I think we have a good case of the press blowing a really interesting discovery totally out of proportion.

Which does happen, especially during the silly season of late August and early September.





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bones of the tabby.jpg

To die as a feral cat is to die so ignobly that your existence might as well have been nonexistence.

This feral cat fell to the motor car sometime earlier this summer. The maggots and carrion beetles made quick work of its flesh, and the sun pelting down upon the bones is bleaching them so white. All that remains of its tabby pelt is the hide on the face, which retains the striped markings of the generic wildcat in domestication.

We dream of cats now. The digital era has unleashed an epoch of cat worshiping not seen since the Egyptians. The urban and techy and prole youth are forced to forsake the noble dog for the ersatz carnivoran companion, and some do so willingly, because they like an animal with felid autonomy and wit, which a true dog person like me would never be able to appreciate.

But for every cat that is loved and coddled, at least one is out there trying to make a go of life as a wild animal. They are not so far removed from their Lybica wildcat ancestors to have lost their wild instincts and essence, and although we’ve certainly produced a few domestic strains that wouldn’t last five minutes in the wild, the vast majority of cats born into this world are still very much what their ancestors were.

And we can romanticize their wildness, their proclivities that allow such feral lives, but we cannot gloss over the fact that a domestic wildcat gone feral lives the life of a mesopredator. It is not the tiger of any urban jungle or farmstead. It is a predator that targets the small and the meek, for it is a small and meek predator.

Coyote jaws and speeding cars take out so many cats, as do the various communicable diseases that sweep through cat populations.

We love this animal, yet we allow so many of them to live such terror-filled and fleeting lives. We must surely be doing better by this species than we were several decades ago, but the vast throng of ferals living at the edges of our civilization are still with us.

And they will always be with us. So long as people let their queens roam and get bred in the great outdoors and so long as those same queens drop their kittens in the wild, never giving them a chance to become imprinted upon people, there will always be a supply to fill feral cat colonies.

And the cars and the coyotes and the feline leukemia and distemper will take out the excess.

And we’ll claim to love our cats and post beyond stupid memes about them online, and we’ll still cast a blind eye.

The crisis of cats is a big part of the pet overpopulation problem, such that it exists.  Yes, I would totally agree that our frame about pet overpopulation has been misguided and stupid for quite a long time. I generally support the goals of the No Kill movement, but I think that those goals can be applied only to dogs.

Dogs don’t readily breed out in the wild, and no place has the same tolerance for big populations of free-roaming or feral dogs as currently exists for feral cats.

It is always said that cats are more popular than dogs, but this statement is misleading, at least as it applies to Americans. More homes in the US have dogs than have cats, which is a better metric of which animal is actually more popular.  It’s just that there is a larger population of cats as a whole. If you like cats, you can keep scores of them, and no one will ever know. Dogs require some public display of their existence, and they are a lot more work than any cat.

So many cats are born feral and can never become socialized to humans, and the only hope for these cats is that they are part of one of those TNR programs. I remain hotly skeptical of TNR, simply because this problem is next to unsolvable, even with dedicated people trapping, vaccinating, and neutering thousands of ferals every year.

And I am leaving out the ecological aspect of what goes on with this most permissible and innocuous of mesopredator release.

This problem is usually trivialized with the wonderful fallacy of relative privation. Cats might kill billions of birds and small mammals, but cars and pollution and deforestation kill more.  True, of course, but it doesn’t take away from the fact that cats still kill all those animals, and if we had more rational and humane policies towards these animals we claim to love, we would not become so defensive.

And the cars, at least, do take out quite a few cats, as the bones of this poor customer reveal to anyone with a bit of curiosity.

But the cars pass its bleaching bones and rarely cast a glance in his direction. For these are the bones of another feral cat that died so ignobly that he might as well have never been born. And so he is forgotten and the wheels keep turning.

And each night the wheels keep turning and taking out the surplus in this Malthusian world of the feral feline.



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arctic fox eating an auklet

Arctic foxes were introduced to the Aleutians where they waged war on the seabird population, such as this poor least auklet.

I am a speciesist. Yep. I accept the title. I do believe some individual animals of certain species do have certain privileges that others don’t.

Owned domestic dogs should be treated as individuals, as should anything else kept as an actual companion animal.

Individual animals that must be culled through hunting seasons, like white-tailed deer, get no individual consideration. What matters about those species is carrying capacity as determined by wildlife managers.

Invasive species anywhere should receive even fewer protections than the game species.

That’s because as a conservationist, I value biodiversity over individual animals.

So I really don’t care that conservationists have trapped and killed introduced arctic foxes in the Aleutians, feral cats in the islands of the Sea of Cortés, or red foxes in Australia.

I don’t care about the individual deer that are shot every year in the United States. I care much more about what they are doing to temperate forest ecosystems.  They exist in a world without predators, predators that will never be reintroduced in significant numbers, and it is vital that humans manage their populations.

I don’t think an absolute moral system can be applied to all animals. Indeed, I have issues with the concept of an absolute morality period.

I know, though, that we are but one chain of biodiversity on the planet. And it is out of this chain that we somehow became the dominant species on the planet. As the dominant species, we like to think we’re above all other species, when we’re just the ones at the top right now.

I don’t think every invasive or introduced species is a negative on the ecosystem. Ring-necked pheasants are mostly banal where they have been introduced. In North America, common carp are generally not an invasive species either.

But many things that have been introduced clearly are.

Especially on islands.

New Zealand had rabbits that were introduced, which ate down much of the good sheep grazing. Then stoats, weasel, and polecat-ferret hybrids were released to control the rabbits, and the mustelids wreaked havoc upon the ground-nesting bird population. New Zealand is a place full of unique ground-nesting birds, and it was once fuller of those species before the weasel horde hit its shores.

Therefore, to protect things like the kakapo, a massive ground-nesting parrot, it is necessary to kill these predators.

Animal rights ideology, which posits an absolute set of rights for individual animals, cannot allow for this killing.

So this ideology would rather have all the kakapo and native New Zealand birds go extinct, just because this ideology doesn’t want to see a guild of invasive predators killed off.

And I must say that I have to reject this ideology, because it clashes with my aesthetic, which requires us to maintain biodiversity as much as possible.

That’s because I know fully well that in a hundred years, that biodiversity will be reduced. Habitat loss, poaching, pollution, climate change, and invasive species will take their toll on a whole host of species.

And the diversity of life from which we descend will be reduced because of us.

Therefore we must kill invasive species to protect as much of life as we can.  It is this paradox that many people cannot understand, but failure to understand this concept is ultimately going to add to the many species that will go extinct.

But in the end, animal rights ideology and conservation are not the same thing. Hunters who oppose animal rights ideology should stop conflating the two systems of thought. Animal rights ideology has no room for hunters, but true conservationists, who want to protect wild places from rampant development, believe hunters are part of the solution.

And virtually everyone is a speciesist. I am one, and it is only a small minority who try to hold absolute values when it comes to animals.

We have these inconsistencies, but they are not without reason. And although most mammals are very much like your own pet dog, they don’t act in the ecosystem in the same way. Transferring one’s feelings about a pet dog onto a mongoose in Hawaii is not wise– that is, if you care about nene. If you don’t care about biodiversity, then go ahead.

But don’t pretend that these two concepts are consistent. They are not.

And they are very much in conflict with each other.

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Blooming invader

Multifora roses are in bloom this week.




This thorny plant spreads out like concertina wire along old roads and overgrown pastures. It was introduced in the 193o’s in attempt to create a naturally growing fence to contain livestock.

It turned out that the birds in North America that had a penchant for eating its hips were also very good at spreading its seeds, and it wasn’t long before multifora rose were everywhere.


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