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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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Milling about on the lawn were both common phases of the Eastern gray squirrel.

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I got a better photo of a black squirrel on the trail camera this week.

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Melanism in Eastern gray squirrels does have some advantage in heavily forested environments. I have a lot harder time seeing the black ones against tree trunks and branches, especially if the leaves are on.

However, if one of these squirrels runs out in the open, it is obvious to every hawk that might be staking out the area.

 

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The really cold temperatures must be messing with the time stamp. Neither of these two videos came from 2068.

These are melanistic Eastern gray squirrel, and there aren’t many of them in West Virginia.

Source.

Two of them here, and you can see where black color is an advantage in deep cover:

Source.

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Miley treed a black squirrel (melanistic gray squirrel) today, but he was moving too fast from tree to tree for me to get a photo of him.

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I came across this little melanistic gray squirrel today, and naive as he is, he just sat there on that white oak branch and let me take a few photos and a few seconds of video of him.

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In this particular stretch of woods there are black variants and normal gray variants, but they come in more color variants than I can describe here.

Eastern gray squirrels have two litters per year. This one was born in the late winter winter litter.  Its mother is likely already pregnant with her midsummer litter which will be born some time next month.

As I mentioned, I did get a little bit of video of this squirrel before he darted off:

Source.

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As someone who has seen dozens of melanistic gray squirrels, I can say that this is one of them.

It is not unusual to find melanistic individuals with gray or brown banding on their hairs.

I have seen these black squirrels with red tails– and they definitely were not fox squirrels.   The tail was pure golden red like a golden retriever, not sabled like a collie, which indicative of a northern fox squirrel.

 

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As I have written earlier, many melanistic Eastern gray squirrels have red tails, which leads to bizarre conclusions that these squirrel are hybrid with fox squirrels. Melanistic eastern gray squirrels are generally found in the northern parts of their range, where the native fox squirrel subspecies isn’t black at all.

I’ve never heard of the two hybridizing. Eastern grays don’t even like fox squirrels, and although a single fox squirrel can easily beat a gray up, the grays often gang up the fox squirrels. I’ve seen this many times at bird feeders.

This paticular melanistic gray does have an unusual amount of red on it. I’ve never seen one like this before

The vast array of color phases that can be found in the Eastern gray squirrels is really quite remarkable. They come in normal gray. They come in albino, and they have the aforementioned melanistic form.  But there are other colors that are not often mentioned– probably because they aren’t all that widespread.

 

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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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Source.

Most of the melanistic grays I’ve seen have this reddish tinge to their coats.

As I’ve mentioned before, about a third of the grays around here are black. This one is in Canada.

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