The sightings of three black squirrels during a winter’s walk around my block led me down a bit of a rabbit hole. I believe that it was about three years ago when I first spotted a black squirrel at the corner of Summer and Norwood. Until that point in time, I had really only seen a black squirrel during my visits to Toronto. It was a wonder how one had suddenly appeared in my neighborhood. It was only when I spotted three in close proximity, around the same time, that I began to ponder squirrel lineage.
An article in Life in the Finger Lakes titled “A Black ‘Gray’ Squirrel” offered some insight into the two phenotypes (or morphs) of the Eastern gray squirrel: gray and black. Author Gabrielle L. Wheeler not only pointed out the “whys” behind the distinctive black coloration, she also led me to seek out a citizen science project called Squirrel Mapper, which is headed up by SUNY College of Environmental Science and Forestry in Syracuse. Squirrel Mapper is a website that encourages citizens to track squirrels, to help determine the course of squirrel evolution. There are currently 10,000+ citizen scientists collecting and analyzing data, according to the website. To date, there have been very few documentations of black squirrels in Buffalo, which I don’t find odd. What I do find odd is the sudden appearance of three in such close proximity.
Apparently, black coats (melanic) gove squirrels an upper hand during the winter months, as the darker fur allows the squirrels (also playfully referred to as shade tails, nut smugglers, and tree chickens), to absorb more heat in cold northern climates. So one would think that the black fur trait would be dominant due to natural selection. On the flipside, a black squirrel is easier to spot in the snow, especially in a clearing. And Merlin falcons, which have made somewhat of a comeback on the West Side, have been known to eat squirrels on occasion, as have other birds of prey.
I learned that the gene causing black fur is often recessive, and that the black fur trait (melanism) often requires two recessive genes, but can also be dominant, especially where fox squirrels and gray squirrels mix.
To my knowledge, there aren’t any fox squirrels in my neighborhood, which begs the question: where are the black squirrels coming from, since the gene is typically considered recessive? Maybe Mother Nature (and natural selection) is providing for a thermal advantage after all?
It is interesting to note that at one time – 500 years ago – black squirrels were more abundant than gray squirrels in the US. This was the case because black squirrels thrived in dense, dark forests, where avian predators could not easily spot them from above. As forests were decimated, there was a shift from black squirrels to gray squirrels. Now, that trend may be reversing, for reasons yet to be fully understood…