Grey and Fox squirrels, naturally segregated?

Oak Park native Dan Protess, 42, has visited a redwood forest in Oakland, canoed the Bronx River in New York and followed coyotes along railroad tracks between Cicero and Chicago for a 16-webisode digital series he produces for WTTW called “Urban Nature.” 

The series, which premieres March 20 on, is about how wildlife thrives even amidst the density and concrete busyness of major metropolitan areas. Naturally, Protess couldn’t produce a series called Urban Nature without dedicating at least one webisode to squirrels.

“I knew I had to do something about squirrels because they’re the most common form of backyard wildlife in cities,” said Protess, a graduate of Holmes Elementary and Oak Park and River Forest High School.

For the series, he relies on the expertise of Joel Brown, a professor of ecology and evolution at the University of Illinois Chicago who happens to live in Oak Park. 

In 1997, Brown co-founded Project Squirrel, a website and mobile app that educates people on how to spot different squirrel species in their backyards and invites them to share their observations. So far, over 1,000 people have provided insights to the project. 

What Protess found as he drove around Oak Park and nearby Austin with Brown while filming the webisode was that in Chicago, even the squirrels are segregated — to an extent. 

There are hundreds of different squirrel species worldwide, but basically two, fox (or Sciurus niger) and gray (or Sciurus caroliniensis) squirrels, call the Chicago area home. 

The fox squirrel, the largest tree squirrel in the country, is distinguished by its rust-colored belly and its tint that appears tanned orange. The gray squirrel’s belly is usually white and it typically sports a large, bushy tail. 

“Austin is almost all fox squirrels, right up to the border in Oak Park, which mostly has gray squirrels,” Protess noted. 

“Joel found that there are correlations between squirrel populations and socioeconomics,” he said. “So in wealthier neighborhoods, there are more likely to be gray squirrels and in more affordable neighborhoods, there are more likely to be fox squirrels.” 

Brown and his collaborator, researcher and educator, Wendy Jackson, found 27 zip codes in the Chicago area where only gray squirrels were recorded, compared to only two zip codes where only fox squirrels were recorded. In 85 zip codes, both fox and gray squirrels were recorded. 

The distribution, they found, didn’t exactly mirror the distribution of humans along racial and socioeconomic lines. The two squirrel species have different preferences in trees and spatial densities. 

For instance, the results of the more than 1,000 observations submitted to Project Squirrel include “more fox and fewer gray squirrels than expected in areas with single-family homes. 

“This is in contrast to multiple-family units, high-rise buildings, parks and campuses, where the pattern was reversed and where more than the expected number of gray squirrel observations and fewer than the expected fox squirrel observations were made.”

Those results, however, don’t entirely explain why Protess found more gray squirrels in wealthier areas like the North Side of Chicago and Oak Park. 

“I live on the North Side and since I’ve [filmed the webisode], I’ve noticed that it’s entirely gray squirrels where I live,” Protess said. “I never see fox squirrels. You never notice it until you start walking around.”

So why, exactly, are gray squirrels and fox squirrels separated by Austin Boulevard? You’ll have to do a little digging on your own — or watch the Urban Nature webisode, starting March 20, to find out.


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