Walk around the Rock Creek watershed and you’ll likely see the Eastern grey squirrel (Sciurus carolinensis). It’s one of the most abundant urban mammals and although commonplace for those who live in the area they still continue to excite our four-legged canine friends.
Black To the Basics : DNA
But there is a Sciurus carolinensis that’s also making our heads turn. Eastern grey squirrels can come in all shapes, sizes, and colors. A subgroup of the eastern grey squirrel that has a darker pigment (aka more melanin) is popping up all over the place. This darker squirrel, sometimes called the black squirrel, is not a different species. Like many other mammals, individual Sciurus carolinensis can have vastly different coloring.
Black squirrels have a mutation in one of their genes that change the pigment of their fur. If a black squirrel has two copies of that mutation it will be jet black but if it only has one copy it will be brown-black.
Won’t Black Down:
The black squirrels you see today are originally from Canada, their dark color may have given these squirrels an edge at hiding in the thick Canadian forests. They were introduced to Rock Creek Park in the early 1900s by the Smithsonian National Zoo, and they’ve been at home with their grey counterparts ever since.
When you look around D.C. you can tell that black squirrels are thriving. Why? Many think that their dark color and visibility keeps them slightly safer from Capitol commuters. Some believe it is due to a gene that makes them slightly more aggressive and therefore more desirable to the lady squirrels. Others think it’s because the darker fur can retain more heat, giving them a competitive advantage during cold winters.
Although no theory has been proven, we do know one thing: they’re in Rock Creek Park. And we’re welcoming them with open arms. Not only are they adorable, but they encourage all of us to look closer and reconnect with urban wildlife.
If you see one, snap a picture, post it, and #loverockcreek
Edit: We realized we were leaving out an important part of the squirrel story by not including their introduction into Rock Creek Park. Technically, the black squirrel isn’t native, as it is originally from Canada. They are still the same species, so this isn’t an example of a non-native invasive species in Rock Creek Park. We are still against the introduction of non-native species, so we ask the National Zoo to please not release any more curious mammals into the park. We couldn’t bear it.
Author: Arielle Conti - Program Manager - Rock Creek Conservation Corps