By: Cristina Ellis
Springtime is often associated with rebirth, a connection made even more potent by the presence of many baby animals in nature. On the Fieldston Campus, we are privy to seeing many of these small critters, including none other than our squirrels. Perhaps you have noticed that our squirrels differ from those you may see in the park. That is because our squirrels tend to be black, rather than grey. What causes this to happen?
As with all animals, a squirrel’s phenotypes are determined by its DNA. These critters are actually an extremely rare mutation of Eastern Grey Squirrels. Black hair is a recessive gene, meaning a squirrel needs two copies of the black hair gene (one from each parent). When two black squirrels mate with each other, it is guaranteed that their offspring will be black as well.
Any Fieldston student will have noticed that our school contains a disproportionately high number of Black Squrriels. Instead of the usual 1 in 10,000 grey squirrels who appear black, the majority of the squirrels within Fieldston’s walls are black.
The high concentration of black squirrels on our campus is the result of a biological phenomenon called the founder effect. The founder effect refers to the reduction in genomic variability that occurs when a small group of individuals separates from a larger population. When they breed, there is less genetic variability, meaning that all future generations share the same genetics as the initial group of that population’s founders. When our school was first built, several black squirrels must have found their way onto the campus and stayed. The squirrels then bred and produced many more generations of black squirrels, which continue to live on our campus to this day!
Fieldston’s black squirrels are truly something to marvel at! A combination of a genetic mutations and isolation from other squirrels has led to them becoming the campus critters we all love! Next time you see one skittering across the quad or dumpster diving for leftover food, take a minute to admire this product of nature.
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Featured Image Source: Smithsonian
The Fieldston Science Bulletin 
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