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Posts Tagged ‘Eastern gray 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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My deer season was unproductive, but I spent enough time on oak-lined ridges to realize that this summer had produced a bumper crop of gray squirrels.

I prefer gray squirrel meat (yes, Americans eat squirrels) to venison anyway, and I managed to drop these three.  I shot them with an 20 gauge (Stevens Model 940D). I shot two out of trees, and the third came running up a log toward me while I was sitting down.

 

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Bounding squirrel

“Run to the forest, run!”

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Gray squirrel track:

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Rabbit tracks:

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Turkey tracks:

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Winter sunset:

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

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Two crows got on camera as they ate turkey leftovers, but a gray squirrel got captured too.

You’re gonna have to look hard to see him though.

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Squirrel selfie

Trail cameras do pull of some nice ones, every once in a while.

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This week we had several visitors on the trail cameras. Keep in mind that one of these cameras has a messed up clock, so the time stamp reads that the video was taken in 2068. These cameras are pretty good technology, but they aren’t that good!

Let’s start small.  Here’s a white-footed mouse or a deer mouse:

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I can’t tell whether it is a white-footed mouse or a deer mouse, which is hard enough to do in the broad daylight. These animals are in the genus Peromyscus, and although we call them mice, they aren’t closely related to the mice that originated in Old World.  New World rats and mice are more closely related to voles, hamsters, and lemmings than to house mice and Norway rats.

Then we got a light-colored opossum:

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A good close-up of a melanistic gray squirrel:

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And a large raccoon:

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Because of the size of the raccoon, I am assuming that this one was a male. He was coming to inspect a pile of sticks and logs that I have anointed with weasel lure.

 

 

 

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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.

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

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