Black squirrels, with their striking dark fur, often spark curiosity due to their distinctive appearance. Their presence can seem unusual, prompting questions about their nature and prevalence in different environments. These animals are an example of genetic variation within common species.
What Are Black Squirrels?
Black squirrels are not a distinct species but rather a color variant of existing squirrel species, most notably the Eastern Gray Squirrel (Sciurus carolinensis) and, less commonly, the Fox Squirrel (Sciurus niger). They possess the same physical characteristics as their gray counterparts, including bushy tails, agile bodies, and keen senses. The difference lies solely in their fur pigmentation, which can range from a brownish-black to a deep, jet black.
The Science of Their Color
The dark coloration in black squirrels is a result of a genetic phenomenon known as melanism, which involves an increased production of melanin, the pigment responsible for dark colors. Specifically, in Eastern Gray Squirrels, this melanism is primarily linked to a mutation in the melanocortin-1 receptor (MC1R) gene. This mutation leads to the overproduction of eumelanin, the dark pigment.
This trait is inherited, and the MC1RΔ24 allele responsible for melanism is incompletely dominant. Squirrels with two copies of this mutated allele typically exhibit a jet-black coat. Those with one copy of the mutated allele and one wild-type (gray) allele often display a brown-black coloration. Research suggests that this specific MC1RΔ24 allele likely originated in fox squirrels and was later introduced into the Eastern Gray Squirrel population through interbreeding.
Where Black Squirrels Live
Black squirrels are found within the natural range of their gray and fox squirrel relatives, primarily across North America. While they can appear in various locations, they are particularly common in the northern portions of the Eastern Gray Squirrel’s range. This includes areas around the Great Lakes Basin, where they can constitute a significant portion of the squirrel population, such as in the Canadian province of Ontario and the U.S. state of Michigan.
Specific urban areas have also become known for their high concentrations of black squirrels. Examples include cities like Kent, Ohio, and Syracuse, New York, where they were sometimes intentionally introduced or have naturally thrived. Beyond North America, black Eastern Gray Squirrels were also introduced to other regions, notably parts of the United Kingdom, where they have established populations since the 19th and 20th centuries.
Are They Truly Rare?
The perceived rarity of black squirrels often depends heavily on geographic location and individual experience. While they are a minor percentage of the overall Eastern Gray Squirrel population in many areas, they are far from rare in certain “melanistic hotspots.” In places like Ontario, Canada, or specific cities in the United States, black squirrels can be quite abundant, even outnumbering their gray counterparts.
Their dark fur provides certain ecological advantages, particularly in colder climates, where the darker pigmentation can help them absorb more solar radiation, aiding in thermoregulation during winter months. Historically, their dark coloration may have also offered better camouflage in the dense, shaded environments of old-growth forests. However, in more open, modern forested areas, their dark coats can make them more conspicuous to predators. The prevalence of black squirrels in urban settings may also be influenced by reduced predation pressure and the urban heat island effect.