Ninja Squirrels: The Dark Side of NU's Famous Furballs

By Jessie Moravek Northwestern has ninjas. With their sleek black fur, bushy tail and taste for acorns, our ninjas aren’t your typical teenage turtle. But if you venture to north campus and take a moment to look around the fraternity quad, you might be rewarded with a fleeting glimpse of Northwestern’s stealthiest furry creature: A black squirrel.

Black squirrels aren’t actually ninjas, nor are they the product of crazy biology experiments gone awry. They are a natural part of the environment on our campus, and lots of students already know about them.

“I get very excited when I see the black squirrel near Bobb, and have taken pictures of it,” said Weinberg junior Cassie Sham.

But there are definitely more than one.

“I often see a pair of black squirrels running around together,”said Aarohi Shah, a McCormick senior. “It’s like they form their own cult.”

As cult-ish and unique as black squirrels may seem, they are not really that different from gray squirrels. In fact, they technically are gray squirrels. According to Joel Brown, an evolutionary biologist at the University of Illinois at Chicago, the Eastern Gray squirrel (Sciurus carolinensis) is the only species of squirrel at Northwestern. The black squirrels are simply rare “melanistic morphs” of this species, meaning they have a genetic mutation that makes them black instead of gray.

How do we know so much about black squirrels? In the Chicago area, scientists keep track of black (and gray) squirrels through a program called “Project Squirrel” run by Steven Sullivan out of the University of Illinois at Chicago. This website is a forum for “citizen scientists” (that means non-squirrel experts) to share squirrel observations and pictures, which helps researchers estimate squirrel population, behavior and of course, color.

According to Project Squirrel’s observation network, Northwestern isn’t the only place with black squirrels. In fact, these black ninjas are fairly common around the Midwest.

“As a general rule, the black morphs get more common as you go north… by the time you get to Toronto or Ontario, one-third to 40 percent of the squirrels are black,” said Brown. “This pattern even holds true in Chicago. Here on the North Shore, we have more black squirrels than neighborhoods on the South Side.”

Scientists aren’t exactly sure why there are more black squirrels in northern climates, but Brown said it might have something to do with the color of their fur. Just like wearing a black t-shirt in August can be uncomfortably warm, these heat absorption properties may help black squirrels keep warm in harsh northern winters.

Unfortunately for the squirrels, their dark fur also makes them easier to see.

“In the same way they’re conspicuous to us, guess what they are to a coyote, a fox, a red tailed hawk, a great horned owl,” said Brown. “They probably stick out like sore thumbs.”.

So, black fur is a tradeoff between warmth and safety. In places with lots of predators, or even loose cats and dogs running around, there are generally fewer black squirrels. But luckily for us, the Northwestern campus seems to be a safe-enough squirrel haven that at least a few black ones survive. The ninjas of Northwestern are here to stay.

[fbshare type="button"] [twitter style="horizontal" float="left"]