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Glaucomys sabrinusnorthern flying squirrel

By Eldad Malamuth and Michael Mulheisen

Geographic Range

Glaucomys sabrinus ranges from the treeline in Alaska and Canada southward in the west to northern California and Colorado, in the middle of the continent to central Michigan and Wisconsin, and in the east to northern North Carolina and Tennessee. Island populations exist in areas of high elevation in other parts of the United States, including the southern Appalachian Mountains, the Black Hills, and the Sierra Nevada.

Habitat

Most often found in areas dominated by conifers, northern flying squirrels can also be relatively abundant in deciduous and mixed coniferous/deciduous forests. Glaucomys sabrinus has been found in diverse areas including regions dominated by spruce, fir, and mixed hemlocks, in beech maple forests, and in areas dominated by white spruce and birch with interspersed aspen groves. The northern flying squirrel often nests in conifers 1 to 18 meters above the ground. The nests are made of twigs and bark, and they are softened with feathers, fur, leaves, and conifer needles.

Physical Description

Glaucomys sabrinus weighs between 75 and 140 grams, and ranges from 275 to 342 mm in length. It has silky grey and cinnamon brown fur, with white tipped and grey based belly hairs. Northern flying squirrels have a furred patagium (fleshy membrane) that extends from the wrist of the foreleg to the ankles of the hindleg. The tail is furred, flattened, rounded at the end, and long (80% of the length of the head and body). Glaucomys sabrinus has large black eyes, which it uses for nighttime activity. Southern flying squirrels, which appear similar to the northern flying squirrels, can be distinguished because they are smaller and the hairs on the belly are often white all the way to the base of the hair. The dental formula for Glaucomys sabrinus is 1/1, 0/0, 2/1, 3/3 = 12/10 = 22.

  • Sexual Dimorphism
  • sexes alike
  • Range mass
    75 to 140 g
    2.64 to 4.93 oz
  • Average mass
    132.17 g
    4.66 oz
  • Range length
    275 to 342 mm
    10.83 to 13.46 in

Reproduction

Little information is available on the mating system of northern flying squirrels. Individuals most likely have different mates each breeding season.

Courtship begins in March and may continue until late May. One litter is born per year, and the female raises the young without the help of the male. Copulation occurs in early spring and is followed by a gestation period of 37 to 42 days. Usually, 2 to 4 young are born, though litters as small as 1 and as large as 6 have been recorded. Newborns are poorly developed; they weigh 5 to 6 grams, and they have closed eyes and ears, fused toes, and a cylindrical tail. By the sixth day the toes are separated, and the eyes open after 31 days. Young leave the nest at 40 days and are totally weaned after two months, though they may remain with the mother another month. Flying squirrels breed in the first summer after their birth.

  • Breeding interval
    Flying squirrels breed once yearly.
  • Breeding season
    Mating occurs between March and May.
  • Range number of offspring
    1 to 6
  • Average number of offspring
    2-4
  • Average number of offspring
    3
    AnAge
  • Range gestation period
    37 to 42 days
  • Average weaning age
    2 months
  • Average time to independence
    3 months
  • Average age at sexual or reproductive maturity (female)
    1 years
  • Average age at sexual or reproductive maturity (female)
    Sex: female
    210 days
    AnAge
  • Average age at sexual or reproductive maturity (male)
    1 years

Young flying squirrels are born helpless and are nursed and cared for by their mothers until they reach independence.

  • Parental Investment
  • altricial
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female
  • pre-independence
    • provisioning
      • female
    • protecting
      • female

Lifespan/Longevity

Most northern flying squirrels live less than four years in the wild.

Behavior

Glaucomys sabrinus is clumsy on the ground, but can glide gracefully from tree to tree. Northern flying squirrels sometimes share nests and may live in groups of up to 8 adults and juveniles. Individual Glaucomys sabrinus aggregate into single-sex groups for warmth during the winter. Strictly nocturnal, northern flying squirrels are active for about two hours beginning an hour after sunset, and again for an hour and a half to two hours before sunrise.

  • Range territory size
    0.008 to 0.31 km^2

Home Range

Depending on the habitat, the home range of northern flying squirrels ranges from 0.8 hectares to 31 hectares. Female northern flying squirrels are territorial, but males are not. The population density can be as high as 10 squirrels per hectare in favorable conditions.

Communication and Perception

Northern flying squirrels emit a soft low chirp, and they cluck when distressed. They also use scent and touch to communicate with one another.

They have excellent senses of hearing, smell, vision, and touch.

Food Habits

Glaucomys sabrinus has a characteristic squirrel diet. They eat nuts, acorns, fungi, and lichens, supplemented by fruits, buds, sap and the occasional insect and bird egg. Northern flying squirrels diverge from many squirrels in that lichens and fungi are a large portion of the diet and are not just supplements. It is thought that northern flying squirrels hoard food for the winter, though this has not been confirmed.

  • Animal Foods
  • birds
  • eggs
  • insects
  • Plant Foods
  • seeds, grains, and nuts
  • fruit
  • sap or other plant fluids
  • lichens
  • Other Foods
  • fungus

Predation

The main predators of northern flying squirrels are owls, hawks, martens, weasels, coyotes, and the domestic cat. They avoid predation mainly by being active at night and through their vigilance and agility in the trees.

Ecosystem Roles

Glaucomys sabrinus may be important in the dispersal of spores of mycorrhizal fungi. Northern flying squirrels may also be important in the dispersal of conifer cones, though some wonder if their activity actually impedes forest reproduction through their predation on seeds.

  • Ecosystem Impact
  • disperses seeds

Economic Importance for Humans: Positive

There are no known direct positive effects of northern flying squirrels on humans. Because they are may disperse seeds and spores and are prey to a variety of predators, they help maintain a thriving ecosystem.

Economic Importance for Humans: Negative

Northern flying squirrels sometimes select den sites in houses and barns, which is undesireable due to the noisy activity at night and the litter from nests and seed caches. Northern flying squirrels can also cause problems for professional trappers in the winter, as the squirrels enter traps set for martens and minks.

  • Negative Impacts
  • household pest

Conservation Status

The subspecies Glaucomys sabrinus coloratus and G. s. fuscus are threatened populations in the Appalachians. Glaucomys sabrinus coloratus, North Carolina flying squirrels were designated as endangered in 1985. Between the 1880's and the 1920's, 500,000 acres of forest supporting the two subspecies were reduced by timbering to 200 acres. Conservationists are concerned that further habitat destruction, fragmentation, and pollution will eliminate the small and vulnerable islands of high elevation habitats. The plan being implemented through the U.S. Fish and Wildlife office is the following: 1) determine the exact distribution of the two subspecies 2) protect areas with suitable habitat 3) explore the ecology of the two subspecies 4) test the response to various habitat modifications, concentrating on enhancement measures and compatible timber harvest methods. Some argue that many other populations of subspecies are also endangered, but none have been listed as of yet.

Other Comments

The wing-loading coefficient of northern flying squirrels is about 50 Newtons/square meter, 2-3 times that of most bats. An average 'flight' of G. sabrinus is 20 meters, though flights as long as 90 meters have been recorded. Northern flying squirrels have also been seen making full semi-circles in a single flight.

Contributors

Tanya Dewey (editor), University of Michigan-Ann Arbor, George Hammond (editor), Animal Diversity Web Staff.

Allison Poor (editor), University of Michigan-Ann Arbor.

Eldad Malamuth (author), University of Michigan-Ann Arbor, Michael Mulheisen (author), University of Michigan-Ann Arbor.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

acoustic

uses sound to communicate

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

arboreal

Referring to an animal that lives in trees; tree-climbing.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

fertilization

union of egg and spermatozoan

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

granivore

an animal that mainly eats seeds

herbivore

An animal that eats mainly plants or parts of plants.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

motile

having the capacity to move from one place to another.

mountains

This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.

mycophage

an animal that mainly eats fungus

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

social

associates with others of its species; forms social groups.

solitary

lives alone

stores or caches food

places a food item in a special place to be eaten later. Also called "hoarding"

tactile

uses touch to communicate

taiga

Coniferous or boreal forest, located in a band across northern North America, Europe, and Asia. This terrestrial biome also occurs at high elevations. Long, cold winters and short, wet summers. Few species of trees are present; these are primarily conifers that grow in dense stands with little undergrowth. Some deciduous trees also may be present.

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

visual

uses sight to communicate

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

References

Kurta, Allen. 1985. Mammals of the Great Lake Region. University of Michigan Press, Ann Arbor, pg 131-134

Annapolis field office of the U.S. Fish and Wildlife Office and the Northern Flying Squirrel Recovery Team. 1990. Appalachian Northern Flying Squirrels Recovery Plan. Annapolis, U.S.A.

Baker, Rollin H. 1983. Michigan Mammals. Michigan State University Press, East Lansing, pg 236-243.

Wells-Gosling, Nancy. 1985. Flying Squirrels. Smithsonian Institution Press. Washington, D.C.

Wells-Gosling, Nancy, and Heaney, Lawrence R. 1984. Glaucomys sabrinus. Mammalian Species No. 229. American Society of Mammalogists. North Hampton, Ma.

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