San Francisco State University
Department of Geography

Geography 316:  Biogeography

In progress 12/10/2001

The Biogeography of  Northern Flying Squirrel (Glaucomys sabrinus)

by  Alison Kyi,  student in Geography 316, Fall 2001


The Northern flying squirrel at home in the tree. (Klein, 1983)



Kingdom: Animalia    
Phylum: Chordata
Class: Mammalia
Order:  Rodentia
Family:  Scuridae
Genus:  Glaucomys
Species:  Glaucomys sabrinus

Description of Species:

         Glaucomys sabrinus, also known as the northern flying squirrel are small nocturnal creatures that spend most of their time in trees.  They have large black eyes, rounded ears, and long whiskers.  Their soft fur varies in shades of gray and brown, and their belly is mostly white but lead colored at the base.  The northern flying squirrel has a flight membrane called a patagium that extends from their hands to their feet.  Since their patagium is elastic and retractable, allowing them to be nimble when they are running or climbing. When they glide, they stretch out their limbs so their patagium looks like a sail, then they jump off the branch and use their body to maneuver themselves in the air.  So they don’t fly the way a bird does, but they can glide well over 100ft. or about 30m (Jameson and Peters, 1988).  The northern flying squirrel has a flattened tail that is 40 percent of their total body length. The fur on their tails is very short on the top and bottom and long and flattened on the sides.  Their tails acts like a stabilizer and a rudder when they are gliding but also helps them land.


A northern flying squirrel as it lands from a glide. (National Geographic Society 1979)

            Northern flying squirrels moult once a year in autumn.  They are clean animals and spend part of their day grooming.  Their active period is pretty short, just a couple of hours after sunset and the last hour or so before sunrise (Savage, 1981).  Adult squirrels measure from 25 to 37 cm in length and weigh anywhere from 110g to 230g (Wells-Gosling 1985).  They have a call that is typical for squirrels a “chuck chuck,” but sometimes they chirp notes like a bird.  Their main predator is the Great Horned Owl, but the marten, lynx, bobcat, weasel, fox, ermine, and fisher are also their predators (Woods, 1980).


             Northern flying squirrels are found mainly in coniferous forests, but can also be found in deciduous and mixed coniferous/ deciduous forests.  In a Western habitat, they may live in an open forest with spruce and cedar.  In the east they may live in a mixed forest of birch and hemlock.  The northern flying squirrels live in nests in the summer and interior dens in the winter and for the birth of their young.  Common nests for the squirrels are abandoned woodpecker nests or a hollow of a tree.  They may insulate their nests first with leaves, dried grass, and then add shredded vegetation, feathers, fur, dried grass, or lichen.  The squirrels may give birth in an interior den and may then move their young into the nests.  They tend to live in different homes throughout the year, depending on the season.  

A northern flying squirrel resting on a branch.  (Savage, 1981)


Natural History:

            The northern flying squirrel has a typical squirrel diet, which consists of a variety of foods such as seeds, nuts, berries, some leaves, buds, mushrooms, acorns, flowers, fruits, fungi, lichen, sap, insects and sometimes bird’s eggs.  Unlike regular squirrels, lichen and fungi are a large portion of the flying squirrels’ diet.  The squirrels like to eat meat, and are known to get killed in traps meant for fur bearing carnivores, a factor that may lead to the declining numbers of the squirrel population in the wild. So many of the creatures are caught that the trappers are usually the main source of information on their location. Northern flying squirrels have been known to hoard food for the winter months, although they do not hibernate. 

A pregnant northern flying squirrel having lunch. (Wells-Gosling, 1985)

The mating season starts at the end of March and the beginning of April. It is common for the male to be driven off by their mate before their young are born, but usually they stay near their family by having a nest close by.  The female northern flying squirrel is territorial, whereas the male is not (Mammath and Mulheisen, 1996).  At night the adults may feed and play together, but there is no evidence that the males ever get to be with their offspring. The squirrels give birth in late April to June, and one litter is born a year.  The average litter size is three, but the range is from as little as one to as many as six (Malamuth and Mulheisen 1996). The gestation period is 37-42 days, and the newborns are naked, deaf, blind, hairless and weigh about 5-6 grams.  In about a month they have grown some fur, and may weigh four times as much as when they were born.  At about nine weeks they are weaned and become more and more independent.  By the twelfth week they try gliding.  At four months they become good gliders and are able to take care of themselves.  The northern flying squirrels survival rate is less than thirty percent for juveniles and fifty percent for adults.  The average life span is about 3-4 years but some in captivity may live as long as 10 years (Woods, 1980).  There is little known about the squirrels’ social structure, courtship, mating and reproductive behavior since they are nocturnal and may be hard to spot.



          Squirrels are rodents that belong to the order Rodentia of the class Mammalia (Gurnell, 1987).  The first rodents may have been squirrel-like animals that lived in the forest.  These creatures have shown up in the fossil record about 50 million years ago in North America and Eurasia. We know that squirrels are in the same order as rodents but their origin and distribution is still a mystery.  Northern flying squirrels are small tree dwelling creatures with fragile bones so there aren’t many remaining fossils. Since there are thirty-three species of flying squirrels in Asia, it is thought that this is the center of their evolution.  It is believed that the ancestors of the native squirrels migrated here when it was possible to walk or glide from tree to tree across the continents (Wells-Gosling, 1985).  Northern flying squirrels are thought to be closer in relation to the Asian species rather than the southern flying squirrel since the baculum, a bone in the squirrels’ penis, is more similar to Hypopetes, an Asian species. The missing fossil records has made it difficult to be certain about squirrels’ origin and how they have evolved.

Evolutionary history of Nearctic Scuridae.  (Gurnell, 1987)


            Since northern flying squirrels can easily adapt, they are found in diverse habitat types.  They have a climatic relic distribution, since the species was distributed by the separation of the continents.  The range is from the Pacific Coast to the Atlantic Coast.  They can be found in Canada, from central Alaska to the mouth of the Mackenzie River in the Northwest Territory of Canada. In the United States they can be found in the northern tier of states, from the Appalachian Mountains to as far as North Carolina and Tennessee. They can also be found on the Pacific Coast side in Alaska along the coastal mountain range into northern California in the Sierra Nevada.  In Southern California they have been seen in San Bernardino and San Jacinto Mountains.  They can even be found in the Rocky Mountains, southern Utah through Wyoming. 

 Map of Distribution:

Distribution of Northern flying squirrels in the United States (Wells-Gosling, 1985) Distribution of Northern flying squirrels in California (Jameson and Peters, 1997)

Other interesting issues:

A cute northern flying squirrel hiding in a shirt pocket (Wells-Gosling, 1985)

            The name Glaucomys is derived from Greek, with glaukos meaning silver or gray and mys meaning mouse.  The word translated into English would mean gray mouse.  The species name sabrinus comes from the Latin name of the Severn River in England, since the type specimen was first collected at the mouth of the Severn River in Ontario Hoffman, Jones, Jones Jr., and Armstrong, 1983).  The northern flying squirrel is the only nocturnal squirrel in California (Jameson and Peters, 1988).  The northern flying squirrel has become more rare in recent years yet the reason for the decline is not certain.  The U.S. Fish and Wildlife lists the squirrel as an endangered species in Virginia and West Virginia (Brown, 1997).


Brown, Larry N.  A Guide to the Mammals of Southeastern United States.  1997 University of Tennessee Press

Gurnell, John. The Natural History of Squirrels.  1987 Library of Congress Cataloging      

Howell, Arthur H.  U.S. Biological Survey: North American Fauna, no. 44, Revision of the American Flying Squirrels.  June 13,1918

Klein, Stanley.  The Encyclopedia of North American Wildlife.  1983 Stanley Klein

Malamuth, Eldad and Mulheisen, Michael. (Sept.19,1996) Glacoumys sabrinus [online] Available:                                                                $narrative.html  

National Geographic Society.  Wild Animals of North America.  1979 Washington D.C. National Geographic Society

Peters, Hans J. and Jameson Jr., E.W. California Mammals.  1988 The Regents of University of California Press

Savage, Arthur and Candace.  Wild Mammals of North America.  1981 Candace Savage Press, Modern Press

Wells-Gosling, Nancy.  Flying Squirrels, Gliders in the dark.  1985 Smithsonian Institute Press  

Whitaker, John O.  National Society Field Guide to North American Mammals. New York. 1996,1998 Chanticleer Press Inc.

Woods Jr., Shirley E., The Squirrels of Canada, National Museums of Canada 1980. Pages 187-192  

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