Glaucomys volans - Southern Flying Squirrel

Physical Description:

The Southern flying squirrel (Scuridae) family contains 15 genera and 24 species that are found throughout the world. Southern flying squirrels (Glaucomys volans) may also be known by other common names such as asapan and assapanick (when colonized), eastern flying squirrel, fairy diddle, glider squirrel, small eastern flying squirrel, smaller American flying squirrel, and white bellied flying squirrel (Jackson 1961).

G. volans is nocturnal and easily confused with the northern flying squirrel (Glaucomys  sabrinus). Both species exhibit a redish brown coat, and have large dark eyes.  The G. volans displays a completely silky white underside, whereas G. sabrinus displays a darker grey color on the underside. The large eyes allow for their nocturnal vision, and ability to glide in the dark.  G.volans has a body length typically between 220mm-250mm, where as the tail lengths are typically between 80-120mm.  The mean weight is between 50 and 75 grams.

The southern flying squirrels are readily known for their ability to maneuver through a forest canopy. Their light weight and several membranes make them maneuverable and agile.  G.volans has a gliding membrane called the plagiopatagium which is between the forelimbs and hind limbs. When limbs are extended the membrane fans out, allowing an increase in surface area and more air resistance.  Another gliding membrane is the propatagium, which is located between the cheek and the wrist on the forelimb. When making glides, the tail serves as a rudder and stabilizer (Thorington et al. 1998).  Flying squirrels glide in a descending curve towards another tree.  At the end of its glide it will swing sharply upward and land heads up on the tree, and then it will climb near the top to take another glide to a neighboring tree.  The glides average from 6-9meters in length, however they can glide up to 30 meters (Jackson 1961).      

Distribution in Wisconsin:

G. volans are found bordering on  the southern two thirds of the state in suitable habitat, which is predominately deciduous forest (Hartley and Jackson 1961). Their home range varies depending on habitat structure, interactions among species, and behavior of the individual.  G. volans tend to stay away from clear-cut areas because they are slow and easily captured on the ground (Gates 1987).

Habitats and Ecology:

Reproduction-

Females form small same sex groups about 20 days before maturation, they then nest alone with shredded bark for bedding. Gestation period is 40 days; young are born blind, deaf, furless, and pink. Mean body weight at birth is between 3 and 5g (Dolan Dillford 1979).  Young are completely covered in fur at 2 weeks; and eyes are open at 4 weeks of age.  Birth to weaning typically takes 8 weeks, with a 60 day period of post natal care (Fridell and Litvaitis 1991).  Males do not assist in taking care of the young (Madden 1974).  The females will defend their home range against other flying squirrels when bearing young.

Food habits-

Southern flying squirrels are omnivores that eat a variety of foods.  Their main source of food is nuts from mast producing trees such as oaks and hickories. They also eat seeds, berries, leaf buds, bird eggs, nestlings, and smaller birds such as chickadees. Their main source of water seems to come from their diet, yet dew and water filled cavities in trees are also used. In autumn the decrease in photoperiod triggers the onset of intensive nut storage (Dolan and Carter 1977). Hoarding of nuts can typically last them through the winter and into the summer. In fall acorns are abundant yet they are a fleeting resource.  Acorns can be consumed quickly, where shagbark hickory nuts (Carya ovata) are taken to storage sites. Shagbark hickory nuts are high in protein and contain easily metabolized lipids. (Thomas and Weigl 1998).  G. Volans prefer shag bark hickory (Carya ovata) and red oak(Quercus rubra) over black walnut (Juglans Nigra).  This is due to the relative amount of protective tissue encasing the seed.  Shagbark hickory, and red oak are advantageous due to less handing time, which save on physical constraints (Swihart 2000).   G. volans  do not display torpidity when seed availability is at maximum.  Energy from seeds is allocated toward thermal regulation, and activity necessary for foraging (Merrit et al. 2001).

Nesting-

Tree cavities and snags are preferred for nesting, along with woodpecker holes.  Most nests are located in oaks, poplars, or maples and they tend to stay away from pines due to resin.   G. volans may kill cavity nesting birds to obtain possession of the nest site (Stapp and Garstone 1989). Feathers, moss, and shredded bark may be used for bedding. It is not uncommon to find one nesting a box or in a loft or attic (Bendel and Gates 1987).

Thermoregulation-

Large aggregations of flying squirrels form in late autumn through winter.  A large group will produce more heat, and protection for the cold than a single nestling.  8 to 15 animals are not unusual in such a wintering colony (Hartley and Jackson 1961). Large groups with 6 or more individuals rarely have nesting material (Fridell and Litvaitis 1991). G. Volans posses non-shivering thermogenesis (NST), brown adipose tissue represents the primary site.  NST is controlled by the sympathetic nervous system which converts chemical energy to heat.  No muscle contractions are involved in this process.  This method can be activated in a short period of time (Merrit et al. 2001).

Parasites-

External parasites known to be carried G. volans and include 3 lice, 8 kinds of fleas, and 1 chigger.  Internal parasites include 3 protozoans and 4 round worms (Hartley and Jackson 1961).

Predators-

Due to being nocturnal and arboreal G. volans has few natural predators.  The domestic cat is thought to be the main mammalian enemy.  The great horned owl (Bubo virginianus) is another main predator.  However, man is the most likely threat to survival due to the clearing of dead or dying trees and in turn destroys nesting sites (Hartley and Jackson 1961).

Literature Cited:

Bendel, P.R. and J.E. Gates.  Home range and Microhabitat partitioning of the southern flying squirrel.  Journal of Mammalogy 68(2): 647-652.

Dolan, P.G. and D.C. Carter.  1977.  Glaucomys volans.  Mammalian Species 78:(1-6).

Fridell, F.A. and J.A. Litvaitis.  1991.  Influence of Resource Distribution and Abundance On Home-range Characteristics of the Southern Flying squirrel.  Canadian Journal of Zoology 69(10): 2548-25555.

Hartley, H.T., and Jackson.  1961.  Mammals of Wisconsin:  Flying Squirrels: 175-180.  Published University of Wisconsin-Madison Press.

Ivan, J.S. and R.K. Swihart.  2000.  Selection of mast by granivorous rodents of the central hardwood forest region.  Journal of Mammalogy 81(2): 549-562.

Merrit, J.F., D.A. Zegers, L.R. Rose.  Seasonal thermogenesis of southern flying squirrels.  Journal of Mammalogy 82(1): 51-64.

Stabb, M.A., M.E. Gartshore, P.L. Aird.  Interactions of southern flying squirrel, and cavity nesting birds.  Canadian Field Naturalist 103(3):401-403.

Thomas, R.B. and P.D. Weigl.  1998.  Dynamic foraging behavior in the southern flying squirrel (Glaucomys volans): test of a model.  American Midland Naturalist 140(2): 264-270.

Thorington, R.W., K. Darrow, and G. Anderson.  Wing Tip Anatomy and aerodynamics in flying squirrels.  Journal of Mammalogy 79(1):245-250.

Reference written by Brad Miller , Biology 378 student.  Edited by Christopher Yahnke.
Page last updated 4-23-04.