Nature Notes Gray Squirrel, Black Squirrel
At Thanksgiving time I was with my wife, Julie, staying in the Bronx looking after her mother, Grace, who is 94 years old and was recuperating from an illness at Providence Rest at the edge of Eastchester Bay just south of Pelham Bay Park. We parked in a restricted area and I stayed in the car with the motor running while Julie made a last-minute visit before we headed back to Sag Harbor. It was in a residential neighborhood called Country Club and mid-afternoon.
I was watching two eastern gray squirrels hunt for food in the largish treed yards of two residences. The gray squirrel (Sciurus carolinensis) is a member of the rodent family that ranges from the tip of Florida and south Texas all the way up to Alberta, Ontario, and the Canadian Maritime provinces and west from the Atlantic to the Dakotas, Kansas, and Nebraska. Gray squirrels are tree dwellers and the great prairies must have slowed their progress. They never got to the Rocky Mountains and never to California. The western gray squirrel, Sciurus griseus, probably got there from Asia by way of the ancient land bridge, Beringia, which linked Asia and North America during the height of the ice age when sea levels were lowest.
These squirrels were very busy going here and there, climbing up and down trees when my eye caught something black moving at the edge of the house. It was a cat, and then I saw another. The cats and squirrels didn’t pay much attention to each other and at times were motionless side by side.
Then I saw another black animal, presumably a cat, but a smaller one, and when I screwed up my eyes and took a closer look, it turned out to be a squirrel. It was joined by a second and except for their inky coloration they were of the same size as the gray squirrels and carried on similarly. I began to realize that I was a voyeur to the famous melanistic gray squirrels of New York City’s East Side and eastern Westchester County to the north.
One could plainly see that the black squirrels were as much at home as the gray ones in that microhabitat of trees and lawns less than 200 yards from a tributary of Long Island Sound. There wasn’t much interaction between the grays and the blacks, but every once in a while one of the cats would take a swipe at one of the black ones.
It turns out that the two colors keep to themselves with respect to reproduction, although in some other locations scattered across the Midwest and East some grays and blacks hybridize to give birth to brownish squirrels. According to several studies, two black squirrels never give rise to gray progeny; two grays never bear black young.
In some Midwestern populations where black squirrels have been introduced, the blacks have been out-reproducing the grays to the point where they outnumber them. Certainly the New York ones are native, as are many of the other local black squirrel populations. It is said, but never has been documented, that the original Kellogg, of Kellogg’s cereals, introduced black squirrels on the campus of Michigan University in order to eradicate the red squirrels there. They are so highly prized in other areas that they have become the official mascots of Haverford College in Pennsylvania and Kent State University in Ohio. The latter institution has a special Black Squirrel Day celebration annually. Even the Harvard of the West, Stanford University, has a thriving population of black eastern gray squirrels. Apparently, they appeal to college kids.
There are some pre-settlement accounts stating that black gray squirrels were already here when the first European white colonists arrived. Black gray squirrels have been introduced in several English communities and are apparently doing quite well. The British Isles’ gray squirrel population, itself, was a result of early introductions.
The success of the black squirrels is puzzling. There is a rule in mammalian ecology coined by Constantin Wilhelm Lambert Gloger in the early 1800s. It states that the more tropical the population of a given species or group of species that has a wide range, and the more tropical the individuals, the darker the members of that population.
Bears are a classic example of Gloger’s Rule, as are polar bears and foxes. In the far north they are white, while their relatives much to the south are brown, even black.
This rule apparently doesn’t apply to gray squirrels, as they are darker here than in the south.
On the other side, it has been argued by some that the blacker the hair, the warmer the mammal in colder climates. Dark bodies absorb more solar rays than light bodies. It has also been postulated that there were more black squirrels here in the early-17th century than now because the area settled by the Europeans was largely forested, thus dark, and later became cut over, exposing squirrels to more openness which would favor gray over black in evolution. Interestingly, of the four squirrel species in the genus Sciurus in the United States, the West Coast gray squirrel, confined to the very dark coastal coniferous forests from south to north almost all the way to Canada, is gray, not black.
I searched my foreign mammal books and could find no accounts of black gray squirrels in Asia, Europe, or Japan, where squirrels of the genus Sciurus are common and range widely. Many of those squirrels are brownish, but not black.
A few black gray squirrel sightings in Sag Harbor have been reported to me over the years and I once noted a black road-kill squirrel near Otter Pond in Sag Harbor. However, to my knowledge there are no enclaves of black gray squirrels resembling anything like the Country Club population and that of Stuyvesant Town-Peter Cooper Village in New York City.
Let’s hear it for black gray squirrels!