Don’t call Chicago tree squirrels fat; they’re just well-prepared

If you’ve noticed a lot of fat and ravenous squirrels lately, it’s not your imagination: Chicago’s squirrels are racing against an internal clock to get as big as they can.

And two mild winters have led to more — and bigger — tree squirrels in the city.

“Squirrels are fatter than ever right now. They don’t have a Tom Skilling to talk to them about the weather; they need to get ready for winter, and the best way to store calories is on themselves,” squirrel expert Steve Sullivan said.

“The squirrel population this year is fatter than it was in colder years because they are not expending all that much energy to stay warm. At the end of this year, I expect there to be more squirrels because they haven’t frozen to death.”

When a squirrel’s preferred diet of acorns and walnuts is not easily available, squirrels will devour hamburgers, potato chips and whatever they can find to satisfy their demand for a high-fat diet.

Sullivan said he recently saw a squirrel in Denver, Colorado, chowing down on a bag of prepackaged curried salmon with coconut milk.

“Whatever high-fat thing we eat, they have the potential to eat,” he said.

A gray squirrel in Wicker Park. | Alisa Hauser/For the Sun-Times

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A squirrel in Denver eats a package of salmon. | Courtesy of Steve Sullivan

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A mama squirrel with newborns on Nancy Stark’s back porch last spring in Wicker Park. | Courtesy of Nancy Stark

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A fox squirrel buries some acorns in Wicker Park. | Alisa Hauser/For the Sun-Times

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A bold fox squirrel with no fear of the camera in Wicker Park. | Alisa Hauser/For the Sun-Times

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Chicago squirrels, which usually weigh about a pound, view humans as vending machines more than predators, Sullivan said.

To test this theory, Sullivan suggests going to a city park, breaking a stick into chunks and scattering the pieces.

“Squirrels will come running toward you. They think the chunks of sticks are peanuts,” Sullivan said. “Do the same gimmick in a forest preserve, or out in the country, and you won’t see a squirrel at all; they’ll think you are a predator.”

The two most common squirrels in Chicago are gray squirrels, which have gray fur, white bellies and tails, and fox squirrels, which are brownish with an orange rust-colored belly and a black-fringed tail.

Squirrels “live on the edge of survival” by balancing competing interests of acquiring food, avoiding predators and not freezing and/or starving to death, Sullivan said.

Squirrels have a lifespan of about 10 years, and a female can have three to six babies a year.

Wicker Park resident Nancy Stark, who is somewhat of a squirrel aficionado, documented a litter of newborn squirrels last spring on her back porch.

Stark says she’s counted as many as 20 squirrels in her yard at one time, eating a bird feed mix that she orders via Amazon and hangs from strips on a chain.

“Squirrels love it. They crawl along the chain and eat upside down from the feeders. My squirrels are always fat because I feed them,” Stark said.

Both gray and fox squirrels roam Stark’s yard, but the orange ones are “much more precocious,” she says.

“They’ll eat out of your hand, even if they’ve never met you [before]. The orange ones seem to survive better, they are crowding out the gray ones,” Stark said.

Sullivan is the director of the Hefner Museum of Natural History at Miami University in Oxford, Ohio, and oversees Project Squirrel, a citizen-based science effort that encourages people to track and observe squirrels in their backyards and elsewhere.

Sullivan said he’s more concerned about how the surging squirrel population will handle parasites as the squirrels cluster in groups to stay warm this winter. He says the squirrels’ girth will get back to normal by spring or summer.

“This week is as fat as they’ll get,” Sullivan said.

For more info on how to document squirrels in your neighborhood, visit Scistarter.com and search for “Project Squirrel” to get started.