Southern flying squirrels (Glaucomys volans) are one of two species of flying squirrel found in North America; the other is the northern flying squirrel (G. sabrinus). Along with tree squirrels, chipmunks, ground squirrels, woodchucks and marmots, and prairie dogs, flying squirrels are members of the squirrel family, Sciuridae, which belongs to the order Rodentia, the rodents.
Flying squirrels have long, flat, fluffy tails that make up almost half their overall length. They have soft, thick, dark brown-and-grey fur above with white undersides. Although they do not actually fly, these squirrels glide, and they are distinguished easily from other squirrels by the large, thickly furred membrane stretching between their fore- and hindlegs, attached at the wrists and ankles. The shape of the squirrel with its membranes outstretched is very distinctive; the contrast of the light underside against the night sky gives the squirrel a ghost-like appearance as it glides between trees. Additionally, as an adaptation for their nocturnal behavior, flying squirrels have very large eyes, which are ringed with black fur. Where the ranges of the two species of flying squirrels overlap, distinguishing the species can be difficult. However, southern flying squirrels are smaller, measuring about 23 centimeters (9 inches), while northern flying squirrels are about 30 centimeters (12 inches) in overall length.
Flying squirrels are similar to many other sciurids, or members of the squirrel family, by being granivorous and arboreal, but the two species of Glaucomys are unique among squirrels in two notable ways. First, these squirrels glide, allowing them a form of locomotion beyond climbing, an excellent adaptation for their arboreal lifestyle. Second, flying squirrels are nocturnal. Their large eyes indicate the importance of vision as they navigate and forage at night. Because of their small size and elusive behavior, flying squirrels are difficult to observe, and oftentimes their presence at night is indicated only by their high-pitched chirps. However, these squirrels avidly visit birdfeeders offering high-quality foods, such as sunflower seeds, and may be seen foraging at these feeding stations. Unlike some sciurids, flying squirrels do not hibernate. Instead, they congregate in nests when resting to conserve energy during the winter months.
Flying squirrels are primarily granivorous, or seed- and nut-eating, and include other plant material, such as fruits and flower buds, in their diets. The squirrels also are carnivorous and are known to feed occasionally on insects, bird eggs and nestlings, and carrion. These squirrels specialize on nuts from masting trees (those that produce large seed crops on a periodic basis) and make optimal use of this food resource by exhibiting a dynamic foraging behavior. For example, in the fall, squirrels are able to meet nutritional requirements by eating acorns, a mast nut. Therefore, at this time of year they eat acorns immediately upon finding them and cache, or store, other nuts, such as hickories, in nests, other cavities, and occasionally the ground. In the winter, however, when nutritional requirements are higher in lower temperatures, hickory nuts are eaten upon encountering them during foraging and are taken out of fall caches. By selectively eating some nuts and caching others on the basis of nutritional requirements, flying squirrels are able to make best use of both types of available mast nuts.
Southern flying squirrels experience two peaks of reproduction annually, with mating occurring once in late winter (February and March) and again in summer (June and July), with individual females reproducing during one or both of these periods each year. Young females may become pregnant as early as 10 or 11 months of age. Litters may be as large as seven pups, although the average size is three. Gestation is 40 days long, and the young are born hairless with their eyes and ears closed. Fur appears by the third week, and the pups are weaned at five weeks. Females raise their pups without the aid of other individuals. The life span of flying squirrels in the wild is about 5 years.