Nature Note #146: Encounters with Audubon's Mammals (The Melanistic Squirrel of the Carolinas)

Sciurus Niger, Black Squirrel

When you move to a new place, it often comes with new sights and scenes. One of the more unexpected examples has been the color of the local squirrels. Squirrels in the northeast are already named for their predominant colors (with the exception of flying squirrels), but as the picture to the left shows, they also come in black.

While they seem like a different species, these "black" squirrels are actually a melanistic morph of the regular Eastern Grey Squirrel (Sciurus carolinensis). In the past, this didn't prevent prominent scientists and naturalists from labeling them as such however. 

Even though color morphs were certainly known about in the 1800s, there was still the constant taxonomic war known as "lumping and splitting". Even today, there are still battles and hypotheses being waged about certain species either being regarded as unique from one another or as simply being a subspecies. In biology, species and subspecies can refer to the same animal. For example, the Tiger (Panthera tigris) has several different subspecies that superficially all resemble one another, but are subtly different in terms of distribution, coloration, and size. For example, the most common subspecies, the Bengal Tiger (P. t. tigris) is found on the Indian subcontinent, while their more northerly, the Siberian or Amur Tiger (P. t. altaica) is found exclusively in Russia's Far East. 

While there are obvious morphological differences within the species, those subspecies are still able to breed with other subspecies in the genus. If there were two different species in the same genus, then they could hybridize producing sterile offspring in most cases. One contradictory example is the Mallard (Anas platyrhynchos). They hybridize regularly with other waterfowl such as American Wigeon (A. americana), Northern Pintail (A.acuta), and increasingly (and to the detriment of this last species) American Black Duck (A. rubripes). In fact, the Mallard is breeding with Black Ducks so aggressively, that there are fears that the latter will be bred out of existence.

Black squirrels don't have this problem. They are neither a subspecies nor a full species as some might have believed them to be. They are simply a color morph. But why black?

One school of thought suggests that because they live in a more northerly climate, their black fur gives them an advantage allowing them to absorb more heat from the sun during the cold winter months. This allows them to inhabit cooler, dryer areas that standard greys would have a hard time tolerating. 

Another interesting aspect of their color morph is that throughout the Eastern Grey's range, you are likely to see a black squirrel at some point. However, there are certain parts of the country that you are more likely to see one. Here in Syracuse, you are very likely to come across them. They are also quite common in London, Ontario, Kent State University in Kent, Ohio, Stanley Park in Westfield, Massachusetts, and Van Wert, Ohio. While they are common enough in the wild, they have been brought to other parts of the country for novelty reasons. I mean, who wouldn't love a black squirrel nibbling on handouts in your local park? 

Even if you think you wouldn't give a squirrel a single thought, I bet you'd still look twice if you saw a black one ambling on by!

Credits:

Rare Book Division, The New York Public Library. "Sciurus niger, Black Squirrel. Natural size. 1. Male, 2. Female." The New York Public Library Digital Collections. 1845 - 1848. http://digitalcollections.nypl.org/items/510d47da-7812-a3d9-e040-e00a18064a99

All other images were taken by myself and belong to me.