National Geographic : 1947 May
"Flying" Squirrels, Nature's Gliders BY ERNEST P. WALKER Assistant Director, National Zoological Park, Smithsonian Institution, Washington, D. C. WHEN I was a boy, I climbed a big beech tree. The top was a dead snag with many woodpecker holes in it. When I got up to the snag I pounded it with my fist. Immediately, little gray faces with big eyes peered out of almost every one of the woodpecker holes for an instant. Then there were a scurry and a shower as between six and a dozen "flying" squirrels leaped out in all directions and glided to adjacent trees. As I think back, the incident reminds me somewhat of the shower effect produced by lawn sprinklers. This glimpse was far more than most people ever see of the so-called flying squirrels. Not until I became intimately acquainted with them did I fully understand the meaning of "gay abandon." These delicate and gentle little creatures are sprightly in their move ments and are attractive and lovable. They are highly specialized little squirrels, and plentiful throughout much of their range in North America.* Other flying squirrels, both much larger and smaller and closely or distantly related to them, inhabit Europe, Asia, and western Africa. Glider "Wings" of Membrane The flying squirrel of the eastern United States weighs about 3Y2 ounces. Head and body are about 5 inches long and the tail about 4 inches. Coloration above ranges from grayish buff to dark gray or slate. The under side of the head, body, and gliding membrane is white, except for delicate buff on the flanks. The flying squirrel's fur is fine and soft. Its eyes are large, and its tail is flattened and shaped much like a feather. Arms and legs are very long, but do not appear so because they are enclosed in the large, loose skin of the body and gliding membrane (page 672). At each wrist is a slender cartilage. It projects outward when the arm is extended and thereby extends the membrane just back of the hands (page 668). The small creature has the appearance, when sitting, of being very fat or of wearing clothes that are much too large for it. Ac tually, when it extends its arms forward and * North American flying squirrels comprise two dis tinct groups-the smaller species (Glaucomys volans), of the eastern United States and parts of Mexico; and a larger species (G. sabrinus), occupying timbered sections of the western United States and Canada, with one form ranging into northern New England and border States along the Great Lakes. out and its hind legs backward and out, it stretches the membrane so that its body takes on almost a square form and is flat. We then see that it is slender and delicate in build. Flying squirrels are so strictly nocturnal that many people do not know of their exist ence, even in regions where they are common. Few have seen them and very few indeed have observed their behavior in the wild. Oc casionally they appear at a bird feeding shelf. Sometimes, when a tree is felled, they are found living in a hole in its trunk or in one of the limbs. Again, they may dwell in a bird box or nest in an attic, where their activity at night annoys the human occupants of the house. Sometimes they come down a chimney into a family's living quarters and meet a sad fate at the hands of people who do not realize what gentle, inoffensive creatures they are. Seek Lofty Home Sites Usually flying squirrels live among trees, making their nests in hollow limbs, old wood pecker holes, or other shelters high above the ground. Their movements are not limited to climbing up and down the trees or merely leaping between objects, for their remarkable form gives them power to glide long distances. Glides of more than 50 yards have been recorded. To take off, they seek an elevated point, then leap out into space. Spreading their arms and legs, they take on the form of miniature gliders and steer themselves by raising or lowering their arms to warp their flattened forms. Perhaps the tail also plays some part in steering. Certainly it acts as a stabilizer and assists in making the upward swing. When approaching a landing, usually in a tree or upon some other tall object, they swing slightly upward to check their speed and bring their long arms and legs forward as shock absorbers. Upon alighting, they dart around to the other side of the tree or limb, probably as a precaution to escape any enemy that might be following them. They feed largely on nuts, which they gather and store in their nests or wherever they find a cavity large enough to hold a nut securely. Intimate observations of flying squirrels in captivity, even when they have a great deal of freedom, do not take the place of those in the wild, but many accurate deductions may be made by such close study.