Northern Flying Squirrel

The Northern Flying Squirrel, “Glaucomys sabrinus yukonensis” is a gliding “volplaning” mammal that is unable to take true flight like birds and bats. There are around 25 subspecies across North America, with Interior Alaska being the northern and western limits of the species’ range.
The generic name, “Glaucomys” is from the Greek words “glaukos” (silver, gray) and mys (mouse). “Sabrinus” is derived from the Latin word “sabrina” (river-nymph) and refers to the squirrel’s habit of living near streams and rivers.
Adult flying squirrels’ average weight is about 139 g and 12 inches in total length. The tail is broad, flattened, and feather-like. Moreover, an exclusive feature of the body is the lateral skin folds (patagia) on each side that stretch between the front and hind legs and function as gliding membranes.
The Northern Flying Squirrel is nocturnal and has large eyes that are extremely resourceful on the darkest nights. The color of the eyeshine is a distinctive reddish-orange. The squirrel pelage is silky and thick, with the top of the body light brown to cinnamon, the sides grayish, and the belly whitish.


The Northern Flying Squirrels require a forest mosaic that includes acceptable denning and feeding areas. Den sites include tree cavities and witches’ brooms. Tree cavities are most frequent in old forests where wood rot, frost cracking, woodpeckers, and carpenter ants have created or enlarged cavities.
Witches’ brooms, clumps of abnormal branches caused by tree rust diseases. The most common denning sites of flying squirrels in Interior Alaska. In Nov or Dec, when temperatures start to drop sharply, flying squirrels move out of cavities and into brooms. During the coldest periods of the winter season, they form aggregations of two or more individuals in the brooms and sleep in torpor.

Northern Flying Squirrel Facts

The feeding areas normally preferred by flying squirrels contain fungi (mushrooms and truffles), berries, and tree lichens, maybe in either young or old forests. Also, dried fungi cached in limbs by red squirrels are sometimes stolen by flying squirrels.
Flying squirrels may get water from foods they eat and from rain, snow, and dew. Hence, the constant sources of free water are lakes, ponds, and watercourses, and they do not appear to be a stringent habitat requirement.
In a year’s time, a flying squirrel in Interior Alaska may use as many as 13 different den trees within 19.8 acres (8 ha). On a night foray, a squirrel may travel as far as 1.2 miles (2 km) in a circular route and be away from its den tree for up to 7 hours. It may change den trees at night and move to different ones more than 20 times over a year, staying in each for a varying number of days. Den trees with brooms are used more than twice as much as trees with cavities.
Fairly dense, old, closed-canopy forests with logs and corridors of trees (especially conifers) that are spaced close enough to glide between are needed for cover from predators. High-quality flying squirrel habitat can be a community mosaic of small stands of varying age classes in which there is a mix of tall conifers and hardwoods.
Moreover, part of the mosaic must be an old coniferous forest with den trees containing witches’ brooms, woodpecker cavities, and natural cavities for nesting sites. Riparian zones provide outstanding habitats in all coniferous forest associations.


In Alaska, flying squirrels breed anytime from March to late June, depending on the length and severity of the winter. The female squirrel may breed before 11 months of age and give birth at about 1 year of age. The gestation requires about 37 days, so the young are born from May to early July. One litter of two per year is probably the usual case for Alaska, but they are identified as having litters ranging from one to six in other parts of their range.
At birth, the young flying squirrel (nestling) is hairless, and its eyes and ears are closed. The nourishing process is slow in comparison with other mammals of similar size. Normally, eyes open at about 25 days, and they nurse for about 60 to 70 days.
At around 240 days, the young are fully grown and cannot be distinguished from adults by body measurements and fur characteristics. The mortality rate for northern flying squirrels is 1 and 2 years old, at around 50 percent, and few live past 4 years of age. Complete population turnover can occur by the third year.
Individual flying squirrels nest in tree cavities, witches’ brooms, and drays. In Interior Alaska, most brooms and cavity entrances have southerly exposures. Nests in cavities are usually located about 25 feet above the ground but may range between 5 and 45 feet. Flying squirrels excavate chambers in witches’ brooms and line them with nesting materials.
A dray nest is a ball-like mass of mosses, twigs, lichens, and leaves, with shredded bark and lichens forming the lining of the chamber. Flying squirrels build drays completely by themselves or adapt the nests of other species (e.g., bird nests, red squirrel nests). The dray is frequently positioned close to the trunk on a limb or whorl of branches, with its entrance next to the trunk. Most days in Alaska are probably coniferous.


The Northern Flying Squirrel is omnivorous, so very little is known about its diet. However, the food they consume in other parts of its range includes mushrooms, truffles, fruits, lichens, nuts, seeds, green vegetation, tree buds, insects, and meat (fresh, dried, or rotted).
The nesting birds and birds’ eggs may also be eaten. Those observed foraging in the wild in the Interior ate mushrooms (fresh and dried), truffles, berries, tree lichens, and the newly flushed growth tips on white spruce limbs.
In the spring and summer seasons, their diet consists mostly of fresh fungi. In winter, it’s mostly lichens. Flying squirrels are not known to cache fungi for winter in Alaska, but they are known to do so elsewhere in their range. Witches’ brooms and tree cavities would be likely places to find their caches.

Predators and Parasites

Hawks, owls, and carnivorous mammals prey on flying squirrels. However, the main predators are perhaps the great horned owl, goshawk, and marten due to their massive occurrence and widespread range in Alaska’s forests. The three different flea species may infest a single squirrel.
Normally, forest fragmentation is a real threat to the flying squirrel population due to its dependence on gliding locomotion in forests. Though gliding ability isn’t affected by weight or sex,. So, the forest gap should not exceed the distance traversable with a distance between forests and tree height at the forest edge.  These are the only gliding mammals that extend the wingtip by means of cartilage at the wrist

Economic and Ecological Value

Flying squirrels are important to forest regeneration and timber production because they disperse spores of ectomycorrhizal fungi like truffles. Truffles are fruiting bodies of a special type of fungus that matures underground. They are dependent upon animals to smell them out, dig them up, consume them, and disperse their spores in fecal material where the animal travels.
The animal serves to inoculate disturbed sites (e.g., clear cuts, burned areas) with mycorrhizae that join symbiotically with plant roots and enhance their ability to absorb nutrients and maintain health. The northern flying squirrel’s ecological role in forest ecosystems, consequently, gives it economic value.
Furthermore, they may be important prey for a variety of hawks, owls, small carnivores, and fur-bearers like marten, lynx, and red fox. Numerous Alaskans value flying squirrels just for their interesting habits and aesthetic qualities.
In view of management considerations, the logging for house logs, wood for fuel, and lumber can have devastating effects on flying squirrel populations if the clear cut size is too big or if some scattered tall conifers in large cuts are not retained as cover and for travel across the open spaces.
Management should include the retention of other squirrel species in shared habitats. Snags with woodpecker holes or other natural cavities and coniferous trees with witches’ brooms must also be maintained in managed forests in order to provide adequate habitat for flying squirrels.

Flying Squirrel Sound

The Northern Flying squirrels emit short, but high-pitched chirps to connect with one another. Normally, they are habitually making soft churning noise and chirping sounds. Flying squirrel are not dangerous to humans, but make their homes on your property and damage the wires, pipes, drywall, and insulation. 

Also Read:

The Northern Flying Squirrel is nocturnal and has large eyes that are extremely resourceful in the darkest nights.
The Northern Flying Squirrel is nocturnal and has large eyes that are extremely resourceful on the darkest nights.

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