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Why are there so many black squirrels in Philadelphia?

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In 2003 former Tuskegee Airman and pioneering Black journalist Chuck Stone wrote “Squizzy the Black Squirrel,” about a Philadelphia boy who bonds with a black squirrel in Fairmount Park. Squizzy was the only black squirrel the boy had ever seen in the park, but visitors today still spot them gathering acorns and running up trees.

As Stone wrote in “Squizzy,” black and gray squirrels are simply color variations of the same species, the eastern gray squirrel (Sciurus carolinensis). The darker squirrels (some are an intermediate chocolate-brown color) have more melanin in their fur, much as humans can have in their hair. Black fur absorbs more heat from the sun than the usual gray fur, helping the darker squirrels keep warm in the winter, an advantage balanced against dark fur offering worse camouflage against tree bark than gray.

The eastern gray squirrel isn’t always gray. The darker-hued rodents thrive in an urban environment. Photo courtesy of Brian Henderson/Flickr.

Today in the countryside the darker squirrels are easy to find in the north of the species’ range: around the Great Lakes, New England and southern Canada. Black squirrels are rare in the rest of their range outside of cities, but this might not always have been the case. Samuel N. Rhoads, in his 1903 book “The Mammals of Pennsylvania and New Jersey,” reviewed the earliest accounts he could find on the proportions of black to gray squirrels. “[I]t is worthy of remark that there seems to be a diminution of the relative number of blacks as the country becomes deforested and settled upon.” Whether this had to do with more-open terrain being warmer than dense forest or with predators, including human hunters, having an easier time spotting black squirrels, Rhoads couldn’t say.

It is tempting to think that Philadelphia’s black squirrels are relics of a time when they were more common in precolonial forests. But by the mid-1800s urban squirrels were considered rare and special, hard as it might be to believe today, when every garden in the city is besieged by the bushy-tailed tomato pirates. As historian Etienne Benson wrote in a 2013 paper on the history of urban squirrels, “the gray squirrel was effectively absent from densely settled areas.”

When the scientists transplanted both colors of urban squirrels into the countryside, the black squirrels were more than eight times more likely to die than their gray counterparts.

Those that did wander near humans often didn’t survive the encounter; squirrels were considered fair game and good eating. An 1867 writer documenting what food was for sale in the markets of New York, Boston and Philadelphia wrote: “The gray and black [squirrels] are found sometimes in plenty … in the months of September, October, November and December.” And if squirrels did make it into a city alive, they wouldn’t have found much good habitat in neighborhoods that, at the time, lacked mature street trees.

But squirrels aren’t just good to eat; they’re also fun to watch. When squirrels (usually escaped pets) did show up in city parks, they drew a crowd. City leaders decided to give the people what they wanted. As Benson found, Philadelphia was an early leader in a fad of releasing squirrels in urban parks for entertainment. In 1847 squirrels were released in Franklin Square and provided with food and nest boxes. More releases followed, with black squirrels included among the transplants. A release in Washington Square included at least one black squirrel along with the gray ones.

Photo courtesy of Kevin E. Fox/Flickr.

Black squirrels were famously targeted for release in Washington, D.C., where in 1900 the director of the National Zoo asked colleagues in Canada to send him some. They delivered. Similar black squirrel shipments populated cities in southern Michigan, and though I haven’t found documentation, it’s not hard to imagine Philadelphians with northern connections arranging similar introductions in our parks to vary the squirrel palette.

Not all of the releases stuck; as Benson describes, once the novelty wore off, squirrels sometimes annoyed people so much that they trapped and removed the original transplants. But landscape changes in and around cities allowed squirrels to move themselves around. Hunting became regulated to ensure sustainable populations of game species like squirrels. Trees grew up along streets and in parks, and we erected vast networks of cables strung on poles to transmit electricity and information, giving squirrels the ability to cross pretty much any street they wanted without touching the asphalt.

Photo courtesy of Eric Baratta/iNaturalist.

Plenty of squirrels nonetheless cross the street at ground level, and today cars are the primary killers of urban squirrels, versus predators that are responsible for most squirrel deaths in rural areas. Researchers in Syracuse, New York, suspected that this difference in how they die could help keep black squirrels relatively common in cities. A black squirrel stands out more than a gray one against tree bark in a forest, making it easier for a predator to pick out. Car tires, however, don’t discriminate based on fur hue. Sure enough, when the scientists transplanted both colors of urban squirrels into the countryside, the black squirrels were more than eight times more likely to die than their gray counterparts.

Today you can find black squirrels all over Philadelphia. I tend to see them most often in parks — one of my go-to black squirrel spots is along Belmont Avenue in Fairmount Park West — but they show up in street trees as well, a reminder of our complicated history with urban wildlife.

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