Posts Tagged ‘fox squirrel’

black squrrel

As long-time readers of this blog know, the black coloration seen in North America and Italian wolves and in coyotes originated in domestic dogs. Indeed, the black coloration in North American wolves originated from a single introgression of a black domestic dog in the Northwest Territories or the Yukon between 1,598 and 7,248 years ago.  Of course, we now know that there is significant gene flow between dogs and certain populations of gray wolf and that this gene flow has been going on for some time.

I have often wondered about color genetics and gene flow between species. One species that is particularly beguiling for speculation for me was always the origin of melanism in Eastern gray squirrels. Melanistic Eastern gray squirrels are more common in Ontario, Quebec, and Michigan, but there are isolated populations south of these locations.

A new paper just published in BMC Biology revealed that melanism in Eastern gray squirrels most likely had its origins from hybridization with the fox squirrel.

Melanism has evolved twice in fox squirrels. The melanistic ones in the Southeast have a mutation called ASIP A3.  Melanistic Western fox squirrels have a mutation that causes a deletion in the MC1R. This allele is called MC1R∆24.

What is interesting is that melanistic Eastern gray squirrel have the same mutation.

The authors contend that the most likely explanation for this shared mutation is hybridization between fox and Eastern gray squirrels, although ancestral polymorphisms and earlier hybridization between gray squirrels and fox squirrels cannot be ruled out as possible origins either. However, The authors think it originated in fox squirrels because it resembles other fox squirrel MC1R haplotypes.

This finding is pretty interesting because I live where both species are common, and I use to live where there were lots of black gray squirrels.  I had read accounts of fox squirrels mating with gray ones, but the accounts I read said that no offspring resulted from the mating.

I assumed that the two species could not hybridize, and I still have not seen any literature that even suggests hybridization could occur until I read this paper.

More work is going to be needed to see exactly how this mutation originated and if there are other traits that originated in one species that now are found in the other.

And yes, there is that old wives’ tail that says that gray squirrels castrate fox squirrels to reduce the competition. What actually happens is that when squirrels are hunted in the early part of the season, the testicles shrink in size, so that they appear to have been castrated.

But I have never heard of these two species hybridizing. Indeed, it may be that the hybridization that transferred that particular mutation onto Eastern gray squirrels happened far back in the evolutionary history of both species, when they were still chemically interfertile.

However, they might still be able to hybridize. It is just that no one has ever documented a true hybrid between the two species.

But I am certainly open to the possibility.

So it is likely that black gray squirrels resulted from introgression, just as black wolves and coyotes do.

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Fox squirrel being sneaky


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Yeah, these pink things are baby fox squirrels (Sciurus niger).

A storm blew them out of a palm tree in Fremont, California, and they had to be hand-reared.

This is actually an introduced species to California, so there are some ethical concerns about hand-rearing this species for reintroduction into the wild.


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Many people don’t like that I consider dogs to be the same species as wolves.

And usually what they’ll do is accuse me of holding views I don’t have.

For example, I don’t say that the average person should keep a pet wolf. The chances of that going wrong are just too high, but it doesn’t mean that it will never work out.  I have to point to several cases of people keeping wolves and having no problems with them, most notably Wags, the tame wolf that Adolph Murie kept while studying the wolves of Denali. Wags was taken from the den of a wild pack, and she wound up becoming something like a golden retriever in wolf form. Wolves have also been trained as hunting dogs and working dogs, and at least one turned out to be a decent bird dog and retriever.

However, the chances of a human-wolf relationship going wrong are very high, so I do not recommend that people keep pet wolves without learning as a much as they can– and of course, getting the proper licenses.

The other attack I get is that I think dogs are wolves, and therefore, I must believe that we should use compulsory, alpha-based training regimes.

That’s a position I not only don’t have, it is a position I have denounced as utterly unscientific and untenable in the modern era. (See Mark Derr’s piece in the New York Times for a good explanation of why).

Now those first two are pretty easily dealt with, but a third one requires a bit more of an explanation.

This third argument requires a bit sophistication to fully understand, but it’s one that I think can be explained if we look at other cases in nature for comparison.

This argument is one that is made by Raymond Coppinger in his book on dog domestication and behavior. There is a chapter in the book in which he denounces any attempt to represent dog phylogeny in their scientific name, which is Canis lupus familiaris. Coppinger totally defends the old scientific name Canis familiaris because dogs and wolves occupy different ecological nichees.

It’s definitely true that lap dogs have a very different ecological niche than large moose- and bison-hunting wolves in Canada.

However, what about Middle Eastern pariah dogs and Arabian wolves?  Both animals scavenge for most of their food. Neither forms large packs based upon a mated pair, but they essentially  have the same ecological niche. And they do exchange genes quite a bit, although because the wolves are far less common, this gene exchange is much more limited than it might have been.

The same goes for the wolves and stray dogs of Italy. These dogs and wolves don’t hunt prey, because there aren’t many prey species about. Instead, they hang out at garbage dumps and live on that. The wolves of Italy are much more interbred with dogs than people realize. Dog genes for black coats and dewclaws on the hindlegs are working their way into the wolf population.

If we actually take Coppinger’s argument out to its logical end, then wolves themselves represent several species, even though genetically they comprise just a single species. Wolves in the high arctic hunt muskoxen, while wolves in the Middle East hunt gazelles and hares and mainly scavenge. The newly discovered African wolf subspecies (Canis lupus lupaster) isn’t even the top predator in its ecosystem, and it subsists largely by scavenging kills and hunting small prey.

Yet they are all classified as wolves (Canis lupus).

If wolves can occupy such a wide variety of ecological niches and still be considered the same species, why on earth would we not broaden it out and allow dogs to be classified as wolves?

Just as Arabian wolves are adapted to living in the deserts and arctic wolves have adapted to living in polar regions, domestic dogs are wolves that have adapted to live with humans.

I don’t know why this is so hard to accept, but there is a lot of resistance in some quarters to considering dogs a subspecies of wolf.

But that’s exactly what they are.

Now, in other species, there are different subspecies that have different ecological niches, but no one contends that they should be separated into distinct species on the basis of their differing niches.

Let me give you one that is pretty close to home.

To me, this is a fox squirrel (Sciurus niger).

Eastern or northern fox squirrel (Sciurus niger vulpinus).

It’s a big squirrel with thick tawny gold tail and belly.  They live on the border of pastures and hardwood forests, and they are more common along river valleys in West Virginia than ridgetops. Densely forested ridges tend to have mostly Eastern gray squirrels, which are smaller and usually have gray tails with white banding. In my area, these are the two most common squirrels, although one sometimes see American red squirrels (“fairydiddles.”)  The fox squirrel is the largest tree squirrel in North America, and it is from this subspecies that they get their common name. Their tales actually look like those of a red fox, and their full scientific name reflects this similarity– Sciurus niger vulpinus. This subspecies is found from the interior Mid-Atlantic states and the Appalachians north and west to the prairie provinces.

However, this is also a fox squirrel:

Southern fox squirrel (Sciurus niger niger).

This is the Southern fox squirrel, and it is the subspecies one will find in Eastern North Carolina and most of South Carolina.

They superficially look nothing like the fox squirrels I know so well, but they are considered the same species.

However, the two subspecies are quite different from each other.

The vulpinus subspecies is quite adaptable. They have been introduced to California, where they have thrived, and if you can live from Applachia to Saskatchewan, you can do pretty well no matter what the conditions are.

The niger subspecies is in decline. They are almost entirely dependent upon the long-leaf pine forests that once covered much of the Southeast. For those of you who have not been in this part of the South, most of the land is dominated by subtropical pine forests. Historically, the long-leaf pine has been the dominant pine, but these old growth long-leaf pine forests have been cut– and the land was replanted with more commercially lucrative short-leafed and loblolly pines.  The fox squirrels prefer the more open understories that the long-leaf pines provide, and the short-leaf and loblolly forests are much better suited for Eastern gray squirrels.

In states that have both vulpinus and niger fox squirels, the vulpinus subspecies prefers to live in any available oak-hickory forests, while the niger subspecies prefers to live where there are stands of subtropical pine– especially if it’s long-leaf.  In some parts of the Piedmont, these two different kinds of forest can be relatively close to each other, but as far as I know, no transitional zones between vulpinus and niger fox squirrels have been documented. They probably do exchange genes where their ranges overlap, but because niger fox squirrels are so habitat specific, there likely isn’t much of one.

No one consideres vulpinus fox squirrels a separate species from niger fox squirrels, even though they have very different ecological niches. The niger subspecies is also quite a bit larger than the vulpinus subspecies, which is in conflict with Bergmann’s rule. In other normal situations, taxonomists would at least try to consider them to be different species.

In fact, they have a better claim to having a separate species status than dogs and wolves, but I don’t think anyone would seriously consider these fox squirrels to be different species.

After all, there are several different subspecies of fox squirrel besides these two.  The most famous is the critically endangered Delmarva fox squirrel (Sciurus niger cinereus), which looks like a giant Eastern gray squirrel, which even more habitat specific than the Southern fox squirrel. They also are specialized to living in the Mid-Atlantic pine forests from Southern New Jersey to the Virginia’s Eastern Shore. It currently is found only in Eastern Shore portions of Virginia and Maryland.

Vulpinus fox squirrels are much more habitat generalists than either the Southern or Delmarva fox squirrels. They have a different ecological niche, and if one really wants to play around with Coppinger’s adamant defense of Canis familiaris, then we have to split up the fox squirrel species.

Ecological niche can be used to determine species status, but to rely upon it alone, as Coppinger does in his defense of the usage of Canis familiaris, is to inadvertently open up whole taxons to splits that are pretty hard to justify on face value.

So if one isn’t willing to say that there are multiple species of fox squirrel, we are going to have go with Canis lupus familiaris.

Sorry, folks. Dogs are wolves.  The arguments on the contrary make no sense in the light of what we know about other species.

Update: It turns out that all these subspecies of fox squirrel have only diverged in the past 14,000 years.


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Our mystery squirrel is one of those strange creatures.

Everything about it is counterintuitive.

I remember being taught that the best way to tell the difference between fox and Eastern gray squirrels is that gray squirrel have white banding on their tails that makes them look gray. Fox squirrels– at least those in West Virginia and the northern and central parts of their range– tend to have orange-gold banding on the hairs of their tails. Their tails are usually much fuller than those of the gray squirrels, and they are usually at least 25 percent larger.

Of course, all of that applies for normal phases of gray squirrel.

Eastern gray squirrels are a bit like red foxes, American black bears, and gray wolves. Not all individuals are the color that their names would indicate.

Eastern gray squirrels come in three distinct phases: normal gray, melanistic (black), and albino. I’ve seen variations on all of these colors. I have heard of normal grays with solid white tails, and I knew a very light-colored normal gray squirrel in Buckhannon, West Virginia.  It was almost the color of a Siamese cat.

It is not unusual for gray squirrels to have a red tinge to their coats. This is particularly true for melanistic individuals. (Another one here).

Our mystery squirrel is one of these melanistic Eastern gray squirrels that has a lot of red coloration on its tail.   Such squirrels are not incredibly common, but when one turns up, people think they are looking at fox squirrel or perhaps some new species that has not yet been documented.

The first melanistic gray squirrel I ever saw had a red tail, and it looked very similar to this one.  Most of the melanistic ones I’ve seen since have been solid black or had only a slight reddishness to them.

It is certainly true that fox squirrels vary in coloration, and there are solid black fox squirrels (which is why their scientific name is Sciurus niger). Where I live, it is nearly impossible to mistake a fox squirrel for a gray, because fox squirrels come in only the orange-tailed and agouti coloration. Gray squirrels are come in gray and black. The fact that the fox squirrels are so much larger means that it is so hard to mistake the two species.

However, if you have just a photo of a squirrel with no size reference, the best way to tell them apart is look at their heads.

Fox squirrels have longer heads than grays do.  They have an almost Roman-nosed appearance (Look at the head. Ignore the color.)

Eastern grays are shorted headed. They have more delicate and “cuter” features than fox squirrels do.

Of course, I’ve seen so many different fox and Eastern gray squirrels that I can tell them apart very easily.

In the real world, the size difference alone is all one needs to tell them apart.

In photos, just look at the head.

It is amazing how much these two very common squirrels vary in appearance.

Gray squirrels are not always gray, just as black bears are not always black.

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This is the form I’m most accustomed to seeing. It actually is orange or reddish on its tail and belly. Its tail somewhat like that of a red fox.


However, other forms look  like this:


And others look like this:


There is also a Delmarva fox squirrel (from Maryland and Virginia’s Eastern Shore and Delaware) that looks a lot like a gray squirrel. It is an endangered subspecies of fox squirrel.

So when I say fox squirrel, I think of the animal in the first video. When you think of fox squirrels, it could mean a different animal entirely.

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Generalists are very interesting, for as cute as the Abert’s squirrel is, they don’t live off the North American continent. It is very specialized to its habitat and to is peculiar food source.

Eastern gray squirrels are found in many European countries. South Africa has a few of them. And Australia did have them for a while.

If you can eat anything, you’ll be able to live anywhere. When I was in undergrad, I watched the local grays raid the dumpsters. They would run off with pancakes, pieces of bread, and anything else they could find.

Abert’s are found only in parts of the Southern Rockies. The Kaibab squirrel, a subspecies of the Abert’s, is found only on the North Rim of the Grand Canyon and a small area of the Kaibab National Forest. It is a good example of geographic isolation producing a unique subspecies. (It was the textbook example of the phenomenon in my sixth grade science textbook.)


As I’ve written previously, the poor mast year has put the local squirrels on relief for the whole winter. The regular snowfall that we’re now receiving has forced them into eating lots of birdseed and corn out of our feeders.

We have two fox squirrels here who are so fat that they look like small groundhogs.

I’ll try to get photos of them, but these squirrels are hunted every year. They have a very real fear of people. They are nothing like suburban squirrels or those inhabiting parks.

In my immediate area, about one third of the grays are melanistic. Unfortunately, not a single one of them has come to our feeders. We’ve got a gray one with a blackish face, but no black solid black ones at all. When we’ve fed them in the front yard, we have had a few black ones show up, but virtually no fox squirrels visited. In the backyard, the fox squirrels dominate.


Please note, that we have American red squirrels here, although they are not that common. I prefer to call Sciurus niger the “fox squirrel,” while  I call Tamiasciurus hudsonicus is the “red squirrel.” I know this might cause some confusion for those regions of the country where the fox squirrel is called a red squirrel. To me, it’s not a red squirrel. It’s a fox squirrel. A red squirrel is something different.

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