by Mary Free and Christa Watters, Extension Master Gardeners
Today is Squirrel Appreciation Day. Despite their sometimes-destructive behavior digging up the garden, eating cultivated plants and bulbs, appropriating bird seed, and gnawing on structures, these photogenic acrobats of our forests and backyards play important ecological roles in pest control and seed dispersal and propagation. Some of those seeds are contained in nuts, which squirrels famously cache. Many of these cached nuts grow into hard mast trees regenerating our forests. Nut also happens to be the newest word added to the Illustrated Glossary. However, just like the culinary use of the words fruit and vegetable, what we call a nut in the kitchen or supermarket may be different than what is considered a nut (click on the word to learn more) botanically.
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Can you identify the species of the squirrels pictured above?
If you answered eastern gray squirrel, you would be correct. Eastern gray squirrels (Sciurus carolinensis) are the most prolific squirrels in eastern North America. Their common name denotes the color most associated with their species and the center picture is what we visualize when we hear their name. Together, the black, white, and brown hairs of their fur coats appear as shades of gray that contrast with the white fur of their bellies.
In some regions, though, especially in the northern part of their range, small groups of melanistic gray squirrels occur. These squirrels have black fur (above left). Scientists have found that the variant of the gene that causes the black coloring probably originated in fox squirrels and transferred to gray squirrels through breeding. Although their number, estimated at less than 1% of the total Sciurus carolinensis population, remains low, in parts of the Washington DC area that percentage could be as high as 25% (Miller 2021). Some of these black squirrels are believed to be the progeny of the 18 Canadian black squirrels released by President Theodore Roosevelt on the National Mall in the early 20th century.
Less often we may see a white eastern gray squirrel and think it is an albino. Albinism is a genetic mutation that blocks the body from making melanin, the pigment that determines the color of an animal. But albinism is extremely rare and unless the squirrel has pink or red eyes and with it poor eyesight and low survivability, these white squirrels are more likely to be leucistic (above right) rather than albinistic. Although their coats are predominantly white, leucistic squirrels’ fur may also have patches of gray, black, or brown. Leucism, which can occur in humans and other animals, describes a genetic condition that results in a loss of pigmentation over parts or all of the body, but not the eyes.
Whether in coats of black, white, or shades of gray, Sciurus carolinensis are bound to be found digging around in a garden near you.
Reference
Miller ML. October 2021. What’s Up With White Squirrels and Black Squirrels? The Cool Green Science Newsletter. The Nature Conservancy.