|Southern Flying Squirrel
Glaucomys volans (Linnaeus)
Photo courtesy of New York Zoological Park
Description and Size: 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.
Range and Habitat: Southern flying squirrels occur in the eastern half of the United States and Canada, ranging to the Atlantic with its western limit running between central Minnesota and central Texas. It ranges south to the Gulf of Mexico and throughout Florida; the northern boundary of its range runs roughly from northern Minnesota to central Maine and southern Nova Scotia. In Mexico and Central America, two distinct populations are known. One occurs in southeast Sonora, southwest Chihuahua, and northwest Durango. The other spans the higher elevations of central and southern Mexico, including Tamaulipas, Jalisco, Veracruz, Oaxaca, and Chiapas, and parts of Guatemala and Honduras.
The range of southern flying squirrels overlaps that of northern flying squirrels in its northernmost parts, including northern Minnesota, Wisconsin, and Michigan, New England, and southern Ontario, Quebec, New Brunswick, and Nova Scotia. There are isolated regions in West Virginia, Tennessee, and North Carolina where both species can be found.
In Kansas southern flying squirrels are found in the eastern third of the state, being fairly restricted to thick stands of deciduous forest. Populations are known from Cherokee, Doniphan, Douglas, Leavenworth, Sedgwick, Shawnee, and Wyandotte counties.
Pine and hardwood trees provide suitable foraging and nesting habitat for flying squirrels, while dead trees, called "snags", are also important nest sites. The squirrels construct nests in tree branches or in cavities excavated by other animals, often woodpeckers. They also occupy artificial nest boxes. Nests are used by the squirrels on a daily basis, where various combinations of adults and juveniles may share a single nest, or as maternity sites, where a single female will keep her litter. Nests are lined with shredded bark, moss, lichens, leaves, and feathers. Flying squirrels tend to occupy cavities with smaller entrance holes, while other cavity-nesters, such as eastern grey squirrels (Sciurus carolinensis) and fox squirrels (S. niger), prefer cavities with larger openings, reducing the number of cavities available to flying squirrels. As a strategy to reduce competition for nest sites, female flying squirrels may move away from higher-quality foraging habitat to construct maternity nests in snags.
Differing preferences for sizes of nest cavities are just one example of resource partitioning displayed by the various squirrels coexisting within a forest. Another such example is that of partitioning of foraging habitat. Flying squirrels are the most arboreal of the squirrels, meaning that they are least likely to descend to the forest floor and prefer to occupy the highest levels of the forest. Consequently, only mature forest stands with complete canopies are suitable for these squirrels; flying squirrels are rarely found in younger forests. The most preferred forest types have relatively open upper levels, for ease of gliding, with complex, covered lower levels for protection against predators. Additionally, flying squirrels do not respond well to forest fragmentation; continuous stands of forest with an area greater than about 5 hectares are required for this species. Conservation of flying squirrels in the face of forest harvest requires the maintenance of strips of mature forest, known as "greenbelts", and significant numbers of snags for nesting habitat. Occupation of artificial nest boxes by flying squirrels increases near fragmented areas, and the addition of these boxes may be an important facet in the conservation of flying squirrels in compromised habitat.
Reproduction: 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.
Habits: 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.
Food: 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.
Remarks: Cavities suitable for nesting are a limited resource not only for flying squirrels but also among other cavity-nesting animals. Flying squirrels may oust, or even kill, small birds in order to take over a nest cavity. However, larger birds are more formidable. Sometimes, large birds may exclude squirrels from an area. In other cases where squirrels cannot remove birds from their cavities, the squirrels and birds may allow each other to occupy adjacent cavities whereas such proximity is otherwise undesirable.
Flying squirrels include animal matter in their diets, placing them among the most carnivorous of the sciurids. In particular, bird eggs commonly are eaten, and flying squirrels have been identified as significant nest predators for several species of tree-nesting birds, including thrushes and woodpeckers.
Because flying squirrels are active at night, their highest risk of predation is posed by owls, another group of nocturnal animals. However, other significant predators of flying squirrels may be either diurnal or nocturnal, including raccoons, weasels, foxes, hawks, and snakes.
The scientific name of the southern flying squirrel means "grey flying mouse"; "glaukos" comes from the Greek for "grey", "mys" is "mouse" in Greek, and "volans" refers to flying in Latin.
Revised by Heather York Dec./2002
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