When Squirrels Fly

From its aerodynamics to its eco-dynamics, the flying squirrel is a biological marvel.

| June/July 2005

Take an ordinary gray squirrel, shrink it down to about the size of a large chipmunk, equip it with night-vision goggles and a cape, and you’d have a pretty good approximation of not only Rocky the cartoon flying squirrel, friend of Bullwinkle, but Glaucomys the real flying squirrel, friend of woodland and suburban ecosystems throughout much of North America.

That you’ve probably seen Rocky far more often than you’ve seen a real flying squirrel is not so much a comment on our popular culture as it is the flying squirrel’s sleeping habits — or, more accurately, ours. Between the twilight hours of dusk and dawn, while we diurnal humans sleep, ebony-eyed flying squirrels glide the night skies like flat, furry leaves, flinging themselves from tree to distant tree in search of food or — according to some observers — just for the fun of it. By the time we wake up, blinking our eyes to the light of a new day, the night shift has ended and flying squirrels have hunkered down in bark-lined tree cavities or stick-built dreys for a long day’s sleep.

So it is that few of us think “flying squirrel” when we think of backyard wildlife. Yet in much of the United States and Canada, in suburban back yards as well as in deep forests, wherever there are mature trees, there are flying squirrels — often in greater numbers than the other tree squirrel species we commonly see during the day.

North versus South

Worldwide, there are more than 40 species of flying squirrels. Most of them are in Asia, where in the southeastern part of the continent you might catch a glimpse — and it would be a startling one — of one of the largest flying squirrels of them all: the yard-long and russet-furred red giant.

In North America, there are just two species of flying squirrels, both of which are reassuringly more diminutive. The northern flying squirrel (Glaucomys sabrinus) averages 11 inches — about as long as this page — from the tip of its sensitive whiskered nose to the end of its 4- to 5-inch-long tail. It weighs just 4 to 6 ounces, or about half the weight of a typical day-roaming red squirrel. The southern flying squirrel Glaucomys volans; is the smallest of all tree squirrels, measuring only 9 inches long and weighing a mere 2 to 3 ounces — half the weight of its Yankee cousin.

Aside from their noticeable size difference, both species look remarkably alike: They have soft, light- to deep-brown fur; a creamy-white underbelly; huge, dark eyes; and short, rounded ears. Unscientifically speaking, each species is as cute as a button.

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