Michael's Rediscovery of Nature

Ramblings and observations of a former biologist and a lifelong naturalist, who has recently returned to his roots in east Texas. After a many years of working from coast to coast in an industry far removed from biology, it has been a pleasant change of geography, activity, and attitude. No stressful job decked out in a three piece suit. No city living. Instead there is a rediscovery of the woods, of something scurrying through the leaves, of the clear notes of a bird call, and of reliving the joy that I had when nature was a playground and a classroom.

Why Are My Red Squirrels Turning Black?

As I am want to do, I recently moved my RV to a new site. This time it is on the banks of Lone Star Lake only ten miles or so from the spot on Lake O' the Pines where I had been for quite a while. 

FoxSquirrelMelanistic 1This relatively short move revealed a lot of changes in the wildlife. Of course, at the old location, I was closer to some rather remote woods (a few hundred yards away in two directions). Here, it is more of a residential area. I knew there would be some differences with the wildlife that I was used to seeing and, indeed, there were some major changes.

In particular, there were far fewer birds, although it turned out that there are as many species, including some that I see here and didn't see there; and vice versa. The numbers are very different. Here, it is unusual to have more than ten birds at a time on my feeders (eight of them out right now) and before, that would be very few, dozens were more likely. 

At the old location, I had a group of squirrels who were rather tame. Some actually came into my RV when I left the door open, to help themselves to the peanuts that I kept for them. They would also readily take peanuts from my hand and actually came to me when I called. Well, when I made my little "thck, thck, thck" sounds that I always make when any wildlife is around. 

There, the squirrels were the more commonly seen, Gray Squirrels, that frequent all of east Texas and throughout much of the U.S. Ah, but here at Lone Star Lake, the squirrels were fox squirrels which are less commonly seen. They are noticably larger than the Gray Squirrels and usually reddish in color. There was one other very noticable characteristc. Some of them were black; some of them were brownish black; and only a few were red.  

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Many species of squirrels have black phases, including Gray Squirrels, but they are not common. 

Sometimes, animals may have genetic mutations which cause this black phase, which is referred to as being a melanistic phase. Without getting into the genetic details, I will just say that generally when the melanistic phase appears in a population, it usually affects 25% of the population  which would indicate that it is a recessive gene. Naturally, it is not all that simple. Genetics rarely are. 

The individual hairs from the fur of Fox Squirrels is actually not one color. It usually has red, brown, and black. This is the same with Gray Squirrels, but the natual colors with them have more gray than brown and less red. When the mutations occur, the individual hair may only be black with no red or brown, which makes a black squirrel. Sometimes, the hair may have the red replaced with black or brown, which makes the brownish black squirrels. 

This opens a whole lot of interesting possibilities for how this genetic change affects the overall population. If it were just genetics and no other factors, then with a recessive gene, you would have 1 in four Fox Squirrels with the black color and three with the usual reddish color. But let's look at other factors that affect the color distribution within the population.

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The small local population in my area consists of 9 Fox Squirrels in an approximate area of 5 acres. Of those 9, two are red, 5 are brownish black, and two are black. Genetically, with 9 squirrels you would expect 6 or 7 to be red and the rest combinations of black and blackish brown. Here we have the opposite. 

There must be other factors in place other than just genetics. Without careful study, there is no way to tell for sure what is causing that unexpected ratio. There well could be other factors to do with health and reproductive success that are also affected by the same genes that control the hair color. Genes often are pleiotropic which occurs when one gene influences two or more seemingly unrelated phenotypic traits. In other words, one gene may affect more than one trait such as fur color. That means that the same gene contoling the fur color may also control other factors that may make one color or the other less likely to survive to reproduce for any of many reasons. 

Of course, it is also likely that there is a definite difference in survivialability between the colors. It would be easy to test that which is related to studies that I was involved in many years ago as a biologist. But all that was for another time.  These days, I am content to merely sit on my steps and watch as these fun creatures play along the fence or on the nearby trees. I still think a bit about genes, pleiotropy, phenotypes, genotypes and all of that. But it is not near as interesting to me these days. I am perfectly content with trying to figure out how I am going to get that little black squirrel to get in the perfect light so he won't be too dark or reflect too much light so I can get a great picture of him and those curiously cool blue eyes. 




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Saturday, 14 December 2019
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