Oak Openings Region Conservancy Creature Feature
By Michelle Grigore,
Published in the November Issue of Oak Openings Region Conservancy, “Sand Tracks”, A Green Ribbon Initiative Partner
For as many decades as I’ve spent in our local forests, there is one critter that I’ve seen only once in its natural habitat. The flying squirrel is nocturnal, shy and a tree-dweller, unlike our fox and gray squirrels which spend most of the daytime active and are often found on the ground foraging. In fact, flying squirrels are so clumsy on the ground that they have developed the ability to glide from tree to tree, enabling them to spend a majority of their time in the tree canopy. Rather than actually fly—these 5 1/2” mammals have a patageum, which is a fully-furred flap of skin that runs from wrist to ankle. Flying squirrels use their patageum to glide through the air and steer with their tail.
I happened to surprise a flying squirrel during the day on the trunk of a tree, which is highly unusual. These squirrels have large eyes, great at seeing in the dark. The daylight must have been blindingly bright. Typical of most squirrels, the little flying squirrel I spotted quickly hid behind the trunk of the tree and rapidly vanished. I would have loved to see it glide! There are reports of flying squirrels making 90 degree turns in midair to avoid obstacles and they alter their limbs to slow their glide and parachute onto the next branch or tree trunk.
What I saw was the Southern Flying Squirrel, Glaucomys volans. This little squirrel ranges from the temperate forests of Michigan and Ontario south to the Gulf of Mexico and west to the Great Plains. Its cousin, the Northern Flying Squirrel has a range as far south as mid-Michigan up to the northern edge of the evergreen forests in northern Canada and Alaska. Where the hardwoods and evergreens mix, you can often find the two species overlapping. Both species prefer eating seeds, but will also buds, tree sap, flowers, fruits, insects, bird eggs and even small animals.
Southern flying squirrels have a creamy white belly, brown-gray upper parts, dark gray gliding membrane, and gray head and neck. Their large, black eyes are set off by black eyelids—making them seem even bigger. This species prefers oak-maple-hickory-beech forests with large mast (nut/seed) crops. Flying squirrels favor holes in trees, but will make a leafy nest if none are available. They spend daytime in their dark nests and emerge at night—with a home range of roughly a football field. In Ohio, researchers estimate a density of six individuals per acre in productive forests.
Flying squirrels breed in Feb/Mar and again in Jun/Jul—triggered by changes in photoperiod. After a gestation of roughly 40 days, up to six young are born in a tree cavity lined with soft material, like lichen. The mother moves her offspring often to avoid predators and the young are weaned at 65 days. At 90 days of age, young flying squirrels are able to practice gliding skills and by 120 days they are independent. Adult squirrels also change nests frequently and, in winter, a number of flying squirrels may den up together. Food caches help get flying squirrels through the winter– often using holes smaller than the gray and fox squirrels that also seek out tree cavities.
This habit of stock-piling food for the winter makes fall the ideal time to look for flying squirrels. The changing photoperiod triggers nightly foraging and you may detect flying squirrels in the dark because they are noisy both vocally and in rustling the leaves as they awkwardly seek out nuts on the ground. While some of their vocalizations are ultrasonic, we can hear their chirping and barking calls. And red light is not terribly disturbing to nocturnal animals, but can allow us a better view of one of the Oak Opening’s most secretive tree-dwellers. You can also install squirrel boxes with small holes in your woodlot if you want to help out this species, as dead trees are often cut down.
To end on a fun fact, humans have studied the flying squirrel and made sports gear that mimics the patageum. Don’t believe me? Then look at the suit Base Jumpers use when they leap off precipices. Minus the tail, those Base Jumpers are using flying squirrel aerodynamics to sail through the air!