Glaucomys volans

Geographic Range

Glaucomys volans , better known as the southern flying squirrel, is predominately found throughout the eastern half of the United States, as far west as the Great Plains. The southern flying squirrel is also found as far north as Quebec, Nova Scotia, and New Brunswick and as far south as Honduras. However, it is relatively uncommon to find this species inhabiting the Canadian provinces.

Four subspecies of Glaucomys volans , including G. v. volans , G. v.texensis , G. v. saturatus , and G. v. querceti inhabit North American forests north of Mexico. Although these four species are specific to different geographic ranges, G. v. querceti , G. v. saturatus , and G. v. texensis , from east to west, in the south and G. v. volans in the north, no evidence has shown that the four subspecies are distinctly geographically separated from one another. Six isolated subspecies have been found to inhabit mountainous regions of Mexico and Central America. The subspecies G. v. madrensis inhabit the Sierra Madre Occidenal in areas of western Chihuahua and eastern Sinaloa. The next subspecies, G. v. herreranus inhabit the Sierra Madre Oriental throughout regions north and east of Mexico City, as far south as Veracruz. The range of G. v. chontali is limited to a small area southwest of Oaxaca. Glaucomys volans oaxacensis is found throughout the Madre del Sur, as far south as Oaxaca and as far north as Guerrero. Areas throughout the Chiapan highlands are inhabitaed by G. v. goldmani . Inland areas of Guatemala, as far south as northwest Honduras, are occupied by the subspecies G. v. underwoodi .

• Biogeographic Regions
• nearctic nearctic
  • native native

Habitat

Southern flying squirrels are most commonly found in temperate to subtemperate deciduous and mixed forests. Due to the wide geographic range of this species, elevation has not been reported for the species as a whole. However, the subspecies found south of the United States tend to inhabit higher altitudes, such as mountain ranges. Although they are not restricted to any particular type of forest, southern flying squirrels are more commonly found in beech-maple, oak-hickory, and poplar forests. They tend to either nest inside tree cavities or in nests made of leaves. Nesting choice is influenced by both local availability of cavities and climate. Common nesting sites include abandoned woodpecker holes, bird and squirrel nests, and nest boxes. They also tend to nest more commonly in shelters within 100 meters of a body of water.

• Habitat Regions
• temperate temperate
• terrestrial terrestrial

• Terrestrial Biomes
• forest forest
• mountains mountains

Physical Description

Southern flying squirrels grow to a maximum length of 285 mm (range: 200-285 mm) and a maximum weight of 90 g (range: 38-90 g). According to Whitaker Jr. and Hamilton Jr. (1998), measurements taken from 64 individuals in Indiana averaged: total length 228 mm, tail 100 mm, hind foot 31 mm, and weight 63 grams. Another set of measurements, reported by Whitaker Jr. and Hamilton Jr. (1998), taken from 66 individuals in Florida averaged: total length 221 mm, tail 100 mm, hind foot 30 mm, and weight 52 grams. Their ears are pink and hairless on the inside, and are covered in greyish brown hair on the outside. Each ear measures between 15 and 25 mm in total length. Southern flying squirrels have large eyes in relation to their body size. Eyes are black and encircled by black hair. The hair on their underbellies and under their nose is an off white cream color throughout, while the hair on their dorsal side and above their nose is greyish brown at the tips and black at the base. Their front and rear feet are nearly the same size, but their rear feet contain five claws while their front feet only contain four. They have 22 teeth, and their dental formula is 1023/1013.

Newborn southern flying squirrels are 3 - 5 grams in total mass, and are completely hairless. Their eyes and ears are sealed shut until approximately three to four weeks after birth, and they are nursed until they are approximately five weeks old. After three weeks, they are covered in dense fur everywhere other than their underbellies, which are densely furred by the fourth week. Once young squirrels are six to eight weeks old, they can only be distinguished from adults on the basis of size. Differentiation between male and female southern flying squirrels can only be determined by identification of external sex organs. Males have a penis bone that is, on average, 19 millimeters long. Both sexes have four sets of nipples that extend the entire length of the belly.

Members of this species are characterized by a loose fold of haired skin, known as either the patagium or the gliding membrane, which is bordered by black hair. The patagium extends from the front wrists to the rear ankles, and allows for the animals to glide when both their front and hind legs are extended. Individuals have soft, dense hair.

The southern flying squirrel can be differentiated from the northern flying squirrel, Glaucomys sabrinus , on the basis of underbelly color. The fur on the underbellies of southern flying squirrels is a white to cream color, while that of northern flying squirrels is grey. Southern flying squirrels are also distinguished from northern flying squirrels on the basis of size. The total length of northern flying squirrels ranges between 250 - 300 mm and mass is 70 - 140 grams.

• Other Physical Features
• endothermic endothermic
• homoiothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• sexes alike

Reproduction

Southern flying squirrels breed twice a year, once in early spring (February to March) and again during the summer (May to July). The testes of male southern flying squirrels are abdominal from August to November, but become scrotal in mid-January, prior to the spring breeding season. Although males are capable of mating at this time, females are not fertile until the membrane that covers the opening of their vagina disappears shortly after males' testes become scrotal. These processes are triggered by the increasing photoperiod length, and may vary slightly in areas of differing climates.

Once a female southern flying squirrel becomes fertile, males gather around the female in order to compete for her attention. Males compete for the female's attention through both kicks and rapid back and forth movements of their hind quarters. On most occurrences, the female will mate with the dominant male. However, the female will often allow a subordinate male to compete with the dominant male prior to making her final decision. The dominant male is usually successful, but nonetheless this process is important because it often leads to greater genetic diversity among populations of southern flying squirrels.

Southern flying squirrels are polygynandrous, but mating between a specific male and female may occur on multiple occasions throughout their lives. After mating occurs, male southern flying squirrels depart, and contribute no further parental care. Females are capable of reproducing during both the spring and summer breeding season. However, the percent of females that successfully deliver two litters each year is unknown.

• Mating System
• polygynandrous (promiscuous) polygynandrous (promiscuous)

Breeding between male and female southern flying squirrels occurs biannually, with peaks from February to March (spring breeding season) and May through July (summer breeding season). A study conducted in New Hampshire, by Stapp and Mautz (1991), showed that the spring breeding season took place between February 11 and March 26, while the summer breeding season occurred between June 19 and July 8, assuming a gestational period of 40 days. Although the early breeding season peaks between February and March, it can begin as early as January in areas of warmer climate, and can be vary based on yearly weather and food production. If only a small amount of cached food is available for the spring breeding season, then the breeding season can be delayed. Therefore, winter severity and mast production affect the commencement of the spring breeding season.

The offspring produced during the spring mating period, in most cases, are born between early March and mid-April, while those conceived during the summer breeding season are generally born between July and August. Female offspring born during the summer breeding season reach sexual maturity and begin breeding by the following spring breeding season. One study, conducted by Sonenshine et al. (1979), showed that 94.2% of female southern flying squirrels became pregnant within six to eight months after birth. Female offspring born during the spring breeding season generally reproduce during the following spring season.

Female southern flying squirrels continue to reproduce during each breeding season until they reach approximately three years of age, after which they are no longer fertile. The oldest recorded female to give birth was three years and eight months old. Little research has been conducted on the reproductive details of male southern flying squirrels. However, it has been noted that males begin mating approximately 11 months after birth, and reach reproductive conditions prior to females. Therefore, it is suggested that the breeding seasons are dictated by female reproductive conditions.

Three studies have been published that reported both the mass at birth and litter size of southern flying squirrels, all of which found contradictory results pertaining to seasonal mass differences. To date, it is undetermined whether the mass at birth differs from the spring breeding season to the summer breeding season. However, average mass at birth was between 2.5 and 3.5 grams (range: 2 - 6 grams) in each study. No conclusive studies have shown a difference in average litter size between the two mating seasons, but spring litters generally contain two or three young, while summer litters are more likely to contain four to five young. The litter size, across both breeding seasons, can range from one to seven pups.

Female southern flying squirrels have an average gestation period of 40 days, after which the female takes care of her litter for approximately eight weeks. The mother nurses her young, on average, for the first six weeks of their lives (range 5-8 weeks), after which gradual weaning begins. Generally, by eight weeks old the young are able to take care of themselves. However, the mother and her young may stay together until the mother has her next litter.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• fertilization fertilization
• viviparous viviparous

Although it is not uncommon to see pairs of southern flying squirrels, males leave females prior to the birth of the offspring, and females solely take care of their offspring. Before birthing, females build a new nest for their young inside of a tree cavity. Females become extremely territorial of this new nest, as parturition nears, and do not tolerate any other adults that are within the immediate vicinity of their nest.

Female southern flying squirrels give birth to hairless, helpless young that are extremely uncoordinated and incapable of rolling over. During the first few days of their lives, the young continuously squirm while emitting faint squeaks. The newly born squirrels are nursed and cared for by their mother, on average, for the first six weeks of their lives, after which they are slowly weaned to independence. By eight weeks of age, juvenile southern flying squirrels are no longer nursed, resemble adult southern flying squirrels, and are capable of living independently. However, young southern flying squirrels tend to stay with their mother until she produces her next litter.

• Parental Investment
• female parental care female parental care
• pre-hatching/birth
  • provisioning
    • female
  • protecting
    • female
• pre-weaning/fledging
  • provisioning
    • female
  • protecting
    • female
• pre-independence
  • provisioning
    • female
  • protecting
    • female
• post-independence association with parents

Lifespan/Longevity

Southern flying squirrels have an average lifespan of three to five years in the wild. Their average lifespan increases when they are in captivity to 10 years, with a maximum of 19 years.

Behavior

Although squirrels are often thought to be confined to trees, southern flying squirrels travel along the ground and on top of logs while they forage. Southern flying squirrels are strictly nocturnal, and are extremely active at all times of the night during the summer months. However, during colder months their activity is limited to shortly after dusk and shortly prior to dawn. During periods of extreme cold, southern flying squirrels will stay in their nests for a few days at a time.

Southern flying squirrels are extremely sociable animals that congregate in one nest during winter months and communicate with one another throughout the night. Although these animals emerge from their nests at sunset, communication between squirrels is not made until astronomical twilight. Communication is made through both ultrasonic frequencies and a variety of squeaky notes that sound similar to that of a bird. During winter months, southern flying squirrels nest together in high numbers, sometimes as many as 20 will nest together for warmth. During warmer months, this number decreases to an average of five squirrels per nest. These nests are always very clean, and each southern flying squirrel keeps itself carefully groomed.

Contradictory of their name, southern flying squirrels do not actually fly, but rather glide between trees using their patagium. Prior to gliding, southern flying squirrels move their head from side to side in order to determine the distance to the targeted landing site. Once the distance has been appraised, they launch themselves into the air and simultaneously spread their arms and legs apart in order to draw the gliding membrane taut. The spread gliding membrane creates air resistance, which allows the squirrels to successfully glide distances up to 28 meters, although most glides are between 6 and 9 meters in length. Slack can be created in either the left or right membrane in order for the squirrel to control angle, speed, and course of the glide. Southern flying squirrels use their tails to steer through the various branches that are present between trees. By flipping their tail upward, southern flying squirrels are able to raise the front part of their body and easily control the landing process.

• Key Behaviors
• arboreal arboreal
• scansorial
• glides
• nocturnal nocturnal
• motile motile
• nomadic nomadic
• territorial territorial
• social social

Home Range

Female southern flying squirrels are territorial, and will defend both the tree containing their nest and the surrounding 4050 square meters of home range. Home ranges of female southern flying squirrels do not overlap with one another. If a female southern flying squirrel enters another's home range, the female squirrel occupying that home range will respond aggressively by staring, stamping her feet, lunging, jumping on, or even smacking the other female in the face. Females become even more territorial during both the mating seasons and when young are present. Although females are territorial, males do not defend any set territory, and occupy a home range of approximately 6000 square meters that overlaps that of other males.

Communication and Perception

Southern flying squirrels are nocturnal animals that rely heavily on their visual and auditory senses when foraging and communicating at night. Because they are nocturnal, southern flying squirrels have rather large eyes in relation to their body size, which allow them to see better at night. Little research has been conducted on the communication patterns of Glaucomys volans because nearly all communication occurs at night. However, research conducted by Gilley (2013) showed that at least one population of southern flying squirrels, located in North Carolina, communicate through three distinct calls, which have been characterized as either arc-whistles, trills, or crows. Of these three calls, trills occur the most often (45.1%), followed by arc-whistles (33%) and crows (21.9%). Certain individuals emit high frequency sounds, while gliding, that are believed to serve a purpose in echolocation. Young squirrels generate a variety of high-pitched squeaks, and may even communicate to others through ultrasonic notes.

• Communication Channels
• visual visual
• acoustic acoustic

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• ultrasound ultrasound
• echolocation echolocation
• chemical chemical

Food Habits

Southern flying squirrels are omnivores, but display feeding habits that make them among the most carnivorous members of the Sciuridae family. The primary diet of southern flying squirrels includes insects, nuts, bird eggs, berries, carrion, and seeds. However, they have been known to opportunistically consume nestlings, blossoms, buds, fungi, lichen, and bark. Insects consumed by southern flying squirrels include various species of wood-boring beetles. When foraging, individuals tend to stay within 160 meters of their nest, and consume what is readily available.

Southern flying squirrels forage nearly year round during the nighttime, excluding occasions of severe cold, during which they will enter a period of torpor. Beginning in November, they collect and cache food for the winter within cracks and cavities of their nests, and sometimes even in partially completed woodpecker holes. Food stored by southern flying squirrels include various types of nuts, such as hickory nuts and acorns.

• Primary Diet
• carnivore carnivore
  • eats eggs
  • insectivore insectivore
  • scavenger scavenger
• herbivore herbivore
  • frugivore frugivore
  • granivore granivore
• omnivore omnivore

• Animal Foods
• birds
• eggs
• carrion carrion
• insects

• Plant Foods
• wood, bark, or stems
• seeds, grains, and nuts
• fruit
• flowers
• lichens

• Other Foods
• fungus

• Foraging Behavior
• stores or caches food stores or caches food

Predation

Southern flying squirrels avoid many predators by foraging at night, gliding between trees, and scurrying across the ground. Predators of the southern flying squirrel include owls, hawks, snakes, bobcats ( Lynx rufus ), raccoons ( Procyon lotor ), weasels, and domestic cats ( Felis catus ). Although multiple species of snakes will opportunistically consume southern flying squirrels, black rat snakes ( Pantherophis ) are among the most common predators of the southern flying squirrel. In suburban areas, domestic cats have shown to take a large toll on the population numbers of southern flying squirrels.

Southern flying squirrels have greyish brown fur, which allows them to be very well camouflaged when against a tree. These animals are highly social and communicate information, such as the presence of a predator, to one another through a variety of high pitched signals. Some communication between members of the species occurs at ultrasonic frequencies, which may be above the hearing range of many predators. Gliding between trees allows these squirrels to escape many terrestrial predators. However, some terrestrial predators will occasionally capture and consume a southern flying squirrel as it scurries across the ground.

• Anti-predator Adaptations
• cryptic cryptic

Ecosystem Roles

Southern flying squirrels play several key roles that positively affect the environment(s) that they inhabit, which include the dispersal of seeds, nuts, and fungi. Because members of this species often bury seeds and nuts, they contribute to the continuation of forests. Southern flying squirrels consume the fruiting bodies of various types of fungi, and as a result, spores are spread via the feces these animals. The dispersal of these spores leads to the emergence of new fungi. Southern flying squirrels also feed on tree buds and wood-burrowing insects, which can stimulate tree growth. In areas where both southern and northern flying squirrels are present, the smaller southern flying squirrels often outcompete and displace the larger, endangered, northern flying squirrels.

Southern flying squirrels are arboreal animals that tend to nest in large numbers within tree cavities, which increases the chance of parasites spreading from one individual to another. Parasites that affect southern flying squirrels include mites, lice, fleas, protozoans, acanthocephalans, cestodes, and nematodes. Species of mites include: Psorergates glaucomys , Euhaemogamasus ambulans , Trombicula microti , and Haemolaelaps megaventralis . Species of lice include: Haploplura trispinosa , Neohaematopinus sciuropteri , Enderleinellus replicatus . Species of fleas include: Opisodasys pseudarctomys , Epitedia faceta , Orchopeas howardii , Peromyscopsylla catatina , Conorhinopsylla stanfordi , and Leptopsylla segnis . Species of protozoans include Eimeria parasciurorum , Eimeria glaucomydis , and Trypanosoma denysi . Species of nematodes include: Capillaria americana , Citellinema bifurcatum , Enterobius sciuri , Syphacia thompsoni , and Strongyloides robustus . Southern flying squirrels are hosts to only one species in Acanthocephala, Moniliformis clarki , and one species in Cestoda, Raillietina bakeri .

• Ecosystem Impact
• disperses seeds

Economic Importance for Humans: Positive

Southern flying squirrels are sometimes kept as pets, and are traded internationally.

• Positive Impacts
• pet trade pet trade

Economic Importance for Humans: Negative

Southern flying squirrels are sometime kept as pets, which assists the transmission of disease causing bacteria from squirrels to humans. However, most cases of human-related diseases are caused by wild southern flying squirrels and their nests. Southern flying squirrels have been associated with several cases of typhus fever from the bacterium, Rickettsia prowazekii . Other than lice and humans, southern flying squirrels are the only animals known to be carriers of this harmful bacteria. Between 1976 and 2001, there were 39 reported cases of typhus fever in humans that had no previous contact with lice. A majority of these cases occurred within the geographic range of southern flying squirrels. Approximately one-third of these 39 individuals who were diagnosed with typhus had previously came in contact with either a southern flying squirrel or southern flying squirrel nests.

• Negative Impacts
• injures humans
  • causes disease in humans causes disease in humans
  • carries human disease

Conservation Status

Southern flying squirrels are listed as a species of "Least Concern" by the IUCN Red List, and have no special status on any of the government lists in the United States or internationally (CITES). This species is not considered to be threatened because it can be abundant in areas across its wide geographic range. Although there are no major threats to southern flying squirrels, minor threats include the losses of habitat, cavity bearing trees, and mast producing trees. In areas that experience deforestation, resource depletion has shown to displace southern flying squirrels.

Additional Links

Encyclopedia of Life

Contributors

Alex Atwood (author), Radford University, Cari Mcgregor (editor), Radford University, Zeb Pike (editor), Radford University, Karen Powers (editor), Radford University, April Tingle (editor), Radford University, Jacob Vaught (editor), Radford University, Tanya Dewey (editor), University of Michigan-Ann Arbor.

References

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