While many people associate squirrels primarily with shades of gray or brown, the reality of their fur coloration is surprisingly diverse. Beyond the commonly observed hues, a spectrum of unique and less frequent colors exists.
Common Squirrel Colorations
Grey squirrels, specifically the Eastern Gray Squirrel, are widely distributed and typically feature a gray back with a white underside. Their fur often includes subtle brownish tints, creating a grizzled salt-and-pepper appearance that comes from a mix of black and white hairs, sometimes with brown hairs interspersed.
Red squirrels, such as the American Red Squirrel and the Eurasian Red Squirrel, display distinct reddish-brown fur, often with lighter undersides. The American Red Squirrel has a bushy, dark red tail. Eurasian Red Squirrels can range from vivid ginger to dark brown, with their belly remaining white year-round, and they are also known for their ear tufts in winter. These red squirrels are generally smaller than gray squirrels.
Black squirrels are a melanistic variant of the Eastern Gray Squirrel and, less frequently, the fox squirrel. Their dark coloration results from an excess of melanin. In some regions, like parts of southeastern Canada, black squirrels are predominant. While they are the same species as their gray counterparts, their striking appearance makes them stand out.
Fox squirrels are North America’s largest tree squirrel, often displaying a brownish-orange or reddish-brown coloration. Their fur can vary significantly, including shades of grizzled tan, and their bellies can range from cream-colored to reddish-orange. Many fox squirrels in the eastern United States feature a black head with white ears and nose, and their bodies can be almost any color.
Less Common and Unique Squirrel Colorations
White squirrels represent a rare variation, primarily falling into two categories: albino and leucistic. True albino squirrels lack all pigment, resulting in entirely white fur and pink or red eyes. Leucistic squirrels have a partial loss of pigmentation, leading to white fur but retaining normal eye color, typically dark. Leucism can manifest as completely white fur or a dappled mix of white with brown or gray patches.
Golden or blonde squirrels have lighter, often yellowish or golden fur. This coloration can be a genetic variation, where the production of darker melanin pigments is reduced, or simply a lighter shade within the red/brown spectrum. These lighter forms are sometimes a result of moderate levels of pigment production.
Piebald squirrels exhibit distinct patches of different colors, often white patches on a gray or black background. This patchy appearance is due to genetic variations affecting the distribution of pigment-producing cells. Unlike albinism, piebaldism involves a partial loss of pigmentation, meaning the squirrel retains some melanin production and typically has dark eyes.
Other regional or species-specific variations exist. For instance, Eurasian red squirrels can exhibit jet black to dull yellowy-brown fur, and even within typically colored morphs, there can be significant color variation. Some populations of Eurasian red squirrels in central Europe show a range of colors from red to black, while others, like those in Great Britain, are predominantly red.
Factors Influencing Squirrel Color
Fur color in squirrels is primarily determined by genetics, with specific genes controlling the production and distribution of pigments. Melanin is the main pigment, with eumelanin responsible for black and brown hues, and pheomelanin for red and yellow. Genetic mutations can lead to variations such as melanism, where there is an overproduction of melanin, or albinism and leucism, which involve a complete or partial lack of pigment. For instance, melanism in Eastern Gray Squirrels is linked to an incomplete dominant mutation of the MC1R gene, which results in darker fur.
Habitat and environment can influence the prevalence of certain color morphs within squirrel populations. Darker squirrels, such as melanistic Eastern Gray Squirrels, are more common in northern regions around the Great Lakes Basin and Canada, possibly due to a thermal advantage as black fur absorbs more heat in colder climates. Conversely, lighter colors may be more advantageous in arid regions or where lighter backgrounds are prevalent.
Camouflage plays a significant adaptive role, as fur color helps squirrels blend into their surroundings to avoid predators. For example, gray coloration blends well with the regenerating forests in much of the eastern United States. While white squirrels might seem more vulnerable due to their visibility, some theories suggest that certain predators may not recognize them as food. Research also indicates that different pelage colors can offer crypsis in various environments, such as dark pelage in dense, damp conifer forests for Eurasian red squirrels.
Fur color can also undergo slight changes with age or seasonally, typically due to molting. Eurasian red squirrels, for example, shed their coat twice a year, transitioning from a thinner summer coat to a thicker, darker winter coat, sometimes with gray tinges. These seasonal changes are less dramatic than genetic variations but contribute to the overall diversity in squirrel appearance.