Winter 2018 Conservationist

Hey, Rocky!

by Scott Meister, Natural Resources

You’re likely familiar with gray squirrels and fox squirrels and may have seen a 13-lined ground squirrel, chipmunk or woodchuck, all members of DuPage County’s Sciuridae family. But did you know southern flying squirrels share our forest preserves and backyards as well (and are more common than you might expect)?

Southern flying squirrels are almost exclusively nocturnal, so don’t be surprised if you haven’t seen one. Under the cover of darkness, these chipmunk-sized arboreal rodents travel from tree to tree to find meals and socialize. Their large eyes allow them to see in low light, making them well-suited for overnight operations. Long whiskers, which point forward as the animals leap, help the squirrels “feel” their way through the treetops.

Flying squirrels don’t actually fly; they glide. A special flap of furred skin called a “patagium” stretches between their wrists and ankles and serves as a gliding membrane (an adaptation applied to the design of suits used by extreme BASE jumpers who leap off cliffs). As a flying squirrel launches off a tree, it stretches its limbs and uses its patagium like a parachute to silently glide to the next trunk. It can coast as far as 100 feet, although 20 to 30 feet is more typical. As it moves through the air, it uses its flat, wide tail to brake and steer — even to make sharp midair turns. Since it can’t ascend as it coasts, once a flying squirrel lands, it climbs to the jumping-off point of its next high-elevation descent.

Because they’re so adept at life in the treetops, flying squirrels seldom touch foot to ground. When they do move about the forest floor, they’re clumsy and vulnerable to predators. Weighing just a few ounces, a flying squirrel can be an easy, tasty midnight snack for an owl, raccoon or cat. By remaining in the trees, they can dash and dart through the canopies, keeping adversaries at bay. As an added defense, once a flying squirrel lands on a trunk, it scurries to the opposite side to hide from any predator that may have spotted it “in flight.”

Southern flying squirrels are omnivores, which means they eat both plants and animals — fruits, fungi, insects, the occasional bird egg — but acorns and hickory nuts are their favorites. Like their more grounded cousins, flying squirrels stockpile food in fall in hidden caches so they have reliable inventories when winter supplies start to run short.

Flying squirrels nest in abandoned woodpecker holes or natural tree cavities, where each year they raise two broods, one in spring and one in summer. The young squirrels remain with their parents for up to four months, a longer-than-normal rearing period for mammals their size. One thought is that the extended stay gives the inexperienced gliders the extra guidance needed to learn how to navigate the trees and avoid predators.

On winter’s coldest days, groups of up to 20 flying squirrels huddle in similar natural shelters to keep warm and conserve energy. Like gray and fox squirrels, they’ll also inhabit residential attics, but routine home inspections to ensure openings near roofs and vents remain sealed can prevent squirrels — and other wildlife — from becoming unwanted tenants.

This past summer Forest Preserve District ecologists conducted a countywide survey to look for flying squirrels in the preserves. They strapped trail cameras to trees at 40 sites in 35 preserves and aimed them at nearby trunks baited with peanut butter suet. Surprisingly, 31 cameras at 29 preserves — from the isolated 14-acre Goodrich Woods to the 2,500-acre Waterfall Glen — captured the nighttime foragers. (The animals may have been at the other nine but merely dodged the camera lens.) Ecologists knew flying squirrels lived the preserves but now know just how prevalent the animals really are.

Because flying squirrels live in a variety of forested conditions throughout DuPage, if you live in a neighborhood with mature oak trees and plenty of acorns you may spot one in your own backyard. If you don’t have quite the right habitat, check out the calendar of events for a nighttime hike or cross-country ski trek, where you might witness flying squirrels and other nighttime wildlife firsthand!


closeup of a southern flying squirrelSouth to Some

Even though we consider this part of the state “northern” Illinois, our resident flying squirrel is southern.

Southern flying squirrels (Glaucomys volans), including those in DuPage, live in hardwood forests that offer plenty of tasty acorns. Northern flying squirrels (Glaucomys sabrinus), their cousins in northern Wisconsin, northern Michigan and Canada, instead prefer evergreen forests, where they eat more fungi. Image iStock.com/EEI_Tony