Virginia Northern Flying Squirrel

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Virginia Northern Flying Squirrel

Glaucomys sabrinus fuscus

ListedJuly 1, 1985
DescriptionA medium-sized arboreal, nocturnal, gliding squirrel.
HabitatTemperate hardwood-coniferous forest.
FoodLichens, fungi, seeds, buds, fruit, insects, and other animal material.
ReproductionBears one litter per year in a nest in a tree-cavity.
ThreatsOccurs in small, isolated habitats subjected to destruction or disturbance by human activities.
RangeVirginia, West Virginia


The Glaucomys sabrinus fuscus (Virginia northern flying squirrel) is a small, nocturnal gliding mammal 10-12 in (25-30 cm) in total length and 3-5 oz (88-148 g) in weight. Its long, broad, flattened tail makes up 80% of the body length. It has prominent eyes and dense, silky fur. The broad tail and folds of skin between the wrist and ankle form an aerodynamic surface used for gliding. Adults are gray with a brownish, tan, or reddish wash on the back, and are grayish white or buff white ventrally. Juveniles have a uniform dark, slate-gray back, and an off-white underside. The northern flying squirrel can be distinguished from the southern flying squirrel (Glaucomys volans ) by its larger size; the gray base of its ventral hairs as opposed to a white base in the southern species; the relatively longer upper tooth row; and the short, stout penis bone of the males.

The Virginia subspecies of the northern flying squirrel (G. s. fuscus ) averages 10.5 in (27 cm) in total length with a 4.3 in (7 cm) tail. It is generally gray-brown above and gray-buff beneath.


Little information about reproductive biology is available for this subspecies. More northern sub-species have two litters of two to six young per year and a gestation period of 37-42 days. However, trapping data from the southern Appalachians suggest a single annual litter in early spring. Northern flying squirrels are relatively gregarious and are known to share nests; however, the large winter nesting aggregations reported for the southern flying squirrel are unknown for this species. Northern flying squirrels apparently live in family groups of adults and juveniles. Over much of its range, the northern flying squirrel can apparently subsist on lichens and fungi, but also eats certain seeds, buds, fruit, staminate cones, insects, and other animal material.


The northern flying squirrel occurs primarily in the ecotone (or transition zone) between coniferous and northern hardwood forests. Both forest types are used in the search for food, while the hardwood areas are needed for nesting sites.

Because of the small size of the squirrel, the climatic severity of its habitat, and the abundance of avian and mammalian predators, nesting sites represent a critical resource. During the cooler months, squirrels commonly occupy tree cavities and woodpecker holes, but may also construct and use leaf nestsespecially in the summer. The interior of both types of nests is lined with lichens, moss, or finely chewed bark. They also sometimes enter burrows in the ground, although the extent of their use is not yet known.


The Virginia northern flying squirrel is known from isolated localities in the mountains of eastern West Virginia and nearby Virginia. The northern flying squirrel is typically a species found in more northern areas of the United States, and it was well into the 20th century before the species was found to occur in the eastern United States to the south of New York. Only a few specimens have been captured since that time. This subspecies may have been declining since the last ice age, when the climate began warming and left the remaining suitable habitat limited to a few scattered areas at high elevations. The closest relative of the Virginia northern flying squirrel is the Carolina northern flying squirrel (Glaucomys sabrinus coloratus ), also classified as endangered, and known only from a few areas in North Carolina and Tennessee.

No population estimates are available, but the Virginia northern flying squirrel is extremely rare and difficult to study.


Because the Virginia northern flying squirrel is adapted to cold, boreal conditions, its range has probably been shrinking due to natural conditions since the last ice age. Populations are now restricted to isolated areas at high elevations, separated by vast areas of unsuitable habitat. In these surviving occupied zones, the squirrel and its habitat are coming under increasing pressure from human disturbance, such as logging and development of skiing and other recreational facilities. Logging and other clearing activity has also resulted in the colonization of former northern flying squirrel habitat by the southern flying squirrel. Regrowth in cleared areas, if any, has tended to be deciduous forest favored by the more aggressive southern flying squirrel. Research on captive animals suggests that the northern flying squirrel may be displaced by the southern subspecies in certain hardwood habitats where their ranges overlap.

The southern flying squirrel, though smaller than the northern flying squirrel, is more aggressive, more active in territorial defense, and dominant in competition for nests. When the two squirrels meet in an ecotone between coniferous and deciduous forest, the southern species would be expected to force the northern flying squirrel out into the purely coniferous zone, which lacks favorable nesting sites and would, therefore, reduce reproduction. Also, the southern flying squirrel is apparently the natural host for a nematode parasite, Strongeloides robustus, and has developed an immunity to its ill effects. However, when the northern and southern flying squirrels were held together in captivity, the parasite was transferred to the northern flying squirrel with lethal results. Contact between the two squirrels, as a result of habitat disruption, has created conditions suitable for spreading the parasite to the northern flying squirrel and may be contributing to its decline.

Conservation and Recovery

Two courses of action are of particular importance in preserving this subspecies. First, much more information is needed on its distribution and basic biologyhabitat requirements, diet, demographic characteristics, and relations with other speciesin order to understand the animal well enough to formulate effective management actions. Second, despite the shortcomings of the available data, efforts must be made to protect and manage areas of known or potential occupancy, especially those areas where the squirrel has been recently observed. Any known habitat on public land (federal or state) should be strictly protected. Private habitat should be acquired and designated as ecological reserves, or conservation easements negotiated with the landowner.


U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
300 Westgate Canter Dr.
Hadley, Massachusetts 01035-9589
Telephone: (413) 253-8200
Fax: (413) 253-8200

U. S. Fish and Wildlife Service
Asheville Ecological Field Office
160 Zillicoa Street
Asheville, North Carolina 28801-1082
Telephone: (828) 258-3939
Fax: (828) 258-5330


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U.S. Fish and Wildlife Service. 1985. "Determination of Endangered Status for Two Kinds of Northern Flying Squirrel." Federal Register 50(128):26999-27002.

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Weigl, P.D. 1975. "Parasitism as a Possible Biological Weapon Affecting the Ranges and Interactions of the Flying Squirrels, Glaucomys volans and G. sabrinus." Abstract of Paper Presented at 55th Annual Meeting, American Society of Mammalogists, University Montana.

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Weigl, P.D. and D.W. Osgood. 1974. "Study of the Northern Flying Squirrel, Glaucomys sabrinus by Temperature Telemetry." American Midland Naturalists 92(2):482-486.

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Virginia Northern Flying Squirrel

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Virginia Northern Flying Squirrel