Black squirrels, such as the one above, are a color morph of the eastern gray squirrel — an introduced species.
Color morphs are a common form of polymorphism, which is the presence of two or more distinct characteristics within a single interbreeding population. Seasonal changes in coloration such as that of the short-tailed weasel, which possesses a white coat in the winter, or genetic conditions such as albinism are not considered color polymorphism.
Juan-Carlos Solis, director of education at Wildcare, said that black squirrels are not common in California but when they are seen it’s more likely in urban areas and parks.
“Eastern grays (regardless of coat color) are prevalent only in urban areas and parks in California, and not in more rural areas away from human habitation,” he said. “Their association with humans appears to be the key to their survival and not any variation in color and/or other traits.”
Wildcare’s wildlife rehabilitation hospital has seen a few dark brown or black squirrels, around four blondes and recently, several mottled gray, white and red squirrels most of which have come from San Anselmo. They have also encountered blonde and silver-coated racoons.
Unlike eastern grays, it is unusual for western gray squirrels — native to California — to display color polymorphism.
Read more about color polymorphism here.
A bird? A bug? Something strange in the natural world nearby? Ask us and we’ll find the answer!
Most recent in Ask the Naturalist
Moths often get sidelined as the country cousins of butterflies. But they have their own beauty and utility as some of the best pollinators around.
Ask the Naturalist | Wildlife: Invertebrates, Reptiles, Amphibians
When temperatures crank up, an unusual ecological adaptation begins to play out among our native Monterey pine. We explain why in our latest installment of our reader-funded Ask The Naturalist column.
Ask the Naturalist | Plants and Fungi