Flying Squirrel

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Northern flying squirrel
Glaucomys sabrinus
Scientific classification:
    Kingdom: Animalia
    Phylum: Chordata
    Subphylum: Vertebrata
    Class: Mammalia
    Order: Rodentia
    Family: Sciuridae
    Genus: Glaucomys
    Species: G. sabrinus
Southern flying squirrel
Glaucomys volans
Scientific classification:
    Kingdom: Animalia
    Phylum: Chordata
    Class: Mammalia
    Order: Rodentia
    Family: Sciuridae
    Tribe: Pteromyini
    Genus: Glaucomys
    Species: G. volans
Flying Squirrels are facinating little creatures. Seldom will you see them or their tracks. Here at Deer Trail we are very fortunate to have at least 3 living in the large Oak right next to the feeder on cam #3. But you will need to watch closely for them, people were reporting to us that they saw them 6 months before we ever did! They are perhaps a little smaller than a red squirrel, and very very fast! We read that they have a mild disposition, but not sure how they come up with that when there are no other squirrels to argue over food with.

There are two species of flying squirrels in Minnesota, the southern flying squirrel (Glaucomys volans), and the northern flying squirrel (Glaucomys sabrinus). The southern flying squirrel is about the size of a chipmunk, and the northern flying squirrel is slightly larger. The southern sub-species is about nine inches long, while the northern sub-species measures almost 11 inches, including the wide flattened tail which is nearly half as long as the flying squirrel. The southern and northern flying squirrels weigh two and three ounces, respectively. Southern flying squirrels are found mainly in southern Minnesota hardwood forests, while the northern sub-species occurs in northern Minnesota forests. (Deer Trail is in central Minnesota)!?! Flying squirrels are the only nocturnal squirrels in Minnesota.

Flying squirrels have dense glossy cinnamon brown and gray fur on top with darker flanks and are a cream color underneath. All the lower parts including the tail are white. Only the shrews and moles have fur that comes close in softness and silkiness to that of flying squirrels. They have large, dark eyes that take up a lot of their head and their ears are usually small and rounded. Along with long whiskers, common to nocturnal mammals and a broad, flattened tail, to help them glide from tree to tree instead of jumping. 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 and helps them land.

How the Flying Squirrel got it's name

Flying squirrels do not actually fly like a bird, but glide from one place to another, by spreading their front and back legs and letting skin folds out that acts like a parachute or hang glider. This skin folds back when they land so they can be surprisingly nimble and very fast when they aren’t in the air. Their "flight" is made possible by a furry membrane called a patagium which extends between the front and rear legs, which is used to glide through the air. When the legs are outstretched, the skin stretches out tautly to form a large planing surface which enables the squirrel to glide as far as 295 feet, though most glides are between 20 and 30 feet. The patagium is elastic and retractable, allowing them to be nimble when they are running or climbing.

Females glide about 5 meters less than males. The fight is under full control, and they can even change direction in mid-glide. The direction and speed of the animal in midair is varied by changing the positions of its front and back legs, largely controlled by small cartilaginous wrist/ankle type bones. This changes the tautness of the patagium, the broad flattened tail stabilizes the squirrel in flight and acts as an adjunct airfoil, working as an air brake before landing on a tree trunk. Glide angle has been measured at 26.8 degrees and glide ratio at 1.98., width is 4 ft. When the flying squirrel lands after a glide, it often will move sideways to the opposite side of the tree to escape potential predators that may be in pursuit. As the squirrel approaches its landing site, it pulls up, slowing its descent! When it is gliding, it uses its tail as a rudder to help it change direction. If a glide is too long glide the animal comes to rest near or on the ground and must climb up again.

Many people who think they see birds flying across highways at night actually are seeing flying squirrels. If you're camping this summer and you think you see something flying from tree to tree, keep watch, you may get a visit from a northern flying squirrel as they have been known to check out campfires and cabin lights. You also may hear one rummaging in the trees or on the ground for food. And let's not forget to mention the all time favorite cartoon of Rocky the flying squirrel and Bulwinkle which some state has taken on as a mascot or some such thing!

Flying Squirrles are active in all seasons, but they are rarely seen by humans because of their nocturnal habits. Their large, dark eyes are specially adapted for night vision so they see as well at night as humans can see during the day. Flying squirrels may not hibernate, but slow their body activity in winter and sometimes nest in groups to stay warm. Flying squirrels are frequent visitors at bird feeders. Lights at the feeders do not bother them and then one can watch the flying squirrel's antics at night. (So the big question now is: Were the Flying Squirrels living in the large oak when Deerfeeder put up the feeder, or did they move into the Oak because it was by the feeder?!?)


Flying squirrels can consume quite a variety of foodstuffs - some are staples in their diet, and some are not. Often, what they eat depends upon geographic availability of a given food source, seasonal availability of a given food source, and the animal's "hunger state".
Flying squirrels eat a variety of fruits and nuts, from trees such as red and white oak, hickory and beech. Along with berries, blossoms, insects, small birds, seeds, meat scraps, insects, buds, mushrooms, fungi, carrion, bird eggs, nestlings, tree sap, cherries, leaves and flowers. Nuts and seeds as hazelnuts, beechnuts and spruce, balsam and maple seeds. Fruits of pin cherry, juneberry, huckleberry, gooseberry, blueberry, raspberry and blackberry.
The northern flying squirrel is known to cache food to eat later when feed supplies are low. These caches can be in cavities in trees, as well as in the squirrels' nest. Acorns,lichens and seeds are commonly cached. They store food, especially for winter consumption, even though they do not hibernate.

Another food source for the squirrels are various species of truffles, an underground fleshy fungus whose fleshy edible fruiting body is highly valued as a delicacy, the squirrels are able to locate truffles by smell, as dogs are used to find truffles. Squirrels seem to use cues such as the presence of coarse woody debris, indicating a decaying log, and spatial memory of locations where truffles were found in the past.

The squirrels like to eat meat, and are known to get killed in traps meant for fur bearing carnivores. Trappers are usually the main source of information on their locations. In Minnesota Flying Squirrels have no meat or fur value and thus are not hunted or trapped. Some management occurs when old trees or "snags" with cavities are left in logging operations.

Exposure to Southern Flying Squirrels has been linked to cases of epidemic typhus in humans. Typhus spread by flying squirrels is known as "sylvatic typhus" and the Centers for Disease Control and Prevention has documented a total of 39 such cases in the U.S. from 1976 to 2001. The squirrel acts as host to the Rickettsia prowazekii bacteria and transmission to humans is believed to occur via lice or fleas.

Flying Squirrels disseminate spores of the ectomycorrhizal fungi that they eat, and these are essential to conifer and some deciduous trees.

Nests & Reproduction

Flying squirrels are found mainly in coniferous forests, but can also be found in deciduous and mixed coniferous/ deciduous forests, an open forest with spruce and cedar, moist forests with many fallen, large decaying and mossy logs and mixed forests 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. The squirrels may give birth in an interior den and may then move their young into the nests. Some tend to live in different homes throughout the year, depending on the season.

Although the squirrels will make outside leaf nests, especially in pine woods, they prefer to nest in holes in dead trees, snags or even attics. They readily use artificial nest boxes. They choose holes with smaller entrances than those used by other squirrels. Sometimes they use holes that have been made by woodpeckers. Home ranges are up to 40,000 square metres for females and 50 percent higher for males.

The Northern flying squirrel nests in holes in trees, preferring large-diameter trunks and dead trees, and will also build outside leaf nests called dreys. Suitable nest sites tend to be more abundant in old-growth forests, and so do the squirrels, though harvested forests can be managed in ways that are likely to increase squirrel numbers. Except when rearing young, the squirrels shift from nest to nest frequently. They often share nests. In one nest, over 50 individuals were found co-habitating, although usually nests contain 2-5 individuals. The sharing of nests by flying squirrels is important in maintaining body temperature in the winter. In the winter, northern flying squirrels tend to live in conifer areas of mixed woods, while in summer they are found in conifers and deciduous areas. This behaviour is associated with the belief that the canopy cover is important in protecting the squirrels from predation and colder temperatures. In all but the most severe weather conditions, the squirrels are active year-round.

If left undisturbed, the flying squirrel will stay in its nest during the day. The nest may be anywhere from the surface of the ground to 50-60 feet up. They may insulate their nests first with leaves, dried grass, and then add shredded vegetation, feathers, fur, dried grass, finely shredded bark and lichen. The nest is sometimes an abandoned bird nest; a clump of twigs, moss, and shredded bark placed in the crotch of a branch.
Southern Flying Squirrels show substantial homing abilities, and can return to their nests if artificially removed to distances of up to a kilometre. Their home ranges may be up to 40,000 square meters for females and double that for males, tending to be larger at the northern extreme of their range.

Southern flying squirrels may have two litters in summer, but this rarely occurs in northern flying squirrel females. Both species mate in early spring (March-May) and 37-42 days/five weeks later, give birth from two to seven, furless, tiny (5-6g) deaf & blind young. The female cares for the young. Their ears open at 2 to 6 days old. In about a month they have grown some fur, and may weigh four times as much as when they were born. Their eyes don't open until they are 24-30 days old. At about nine weeks they are weaned and become more and more independent. By the twelfth week they try gliding. At four months (120 days) they become good gliders and are able to take care of themselves.

It is common for the male to be driven out of the nest 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. At night the adults may feed and play together during nesting season and as seen on Deer Trail, spring 2010 one adult often came down the smaller tree on cam #1 and the other the larger oak on cam #2, there are branches that over lap between trees, and that is how the young raccoon that fell out of the tree got back to to the rest of the raccoons, even though it ran up the wrong tree! So next spring we will need to watch and see what the Flying squirrels do. The northern flying squirrels survival rate is less than thirty percent for juveniles. The average life span is about 3-4 years but some in captivity live as long as 10 years.


Some common predators that flying squirrels may encounter during their night forays are: Owls, hawks, fox, marten, Fisher, Raccoon, Coyote, House cats, Bobcat, Lynx, and Weasels. A flying squirrel is ever-alert to potential predators. If they are not, they are dead. It is as simple as that! It's a good thing that the ones on the Trail are very alert and very very quick!

Many flying squirrel predators locate their prey by a combination of sound and movement. A flying squirrels' fur coat is designed to allow it to blend in with its surroundings, and when a flying squirrel detects the presence of a predator, its first instinct is to remain stock-still and not make a sound. This behaviour will prevent a predator, hopefully, from "zeroing-in" on the location of the flyer in question, lose interest, and leave the area for "greener pastures". This period of immobility also serves to allow the flying squirrel some time to decide upon its method and/or route of escape, should the predator attack. Flying squirrels, with the exception of juveniles, know their home range like the back of their paws! Every single refuge is known to them, and all the best routes to get to each refuge as well. The most dangerous period in a flying squirrel's life is when it is a juvenile. Inexperience in dealing with predators of various species, combined with an un-honed locomotion skill-set, minimal knowledge of its surrounding area, and a propensity for risk-taking make young flyers an easy target. Make for high mortality rates in juvenile flying squirrels, far higher than that found any other age group.

A flying squirrels' visual acuity is likely limited to seeing only blurred movement at at great distances. Because it has eyes on the sides of its head, it cannot judge with impunity how far away a predator may be until it is too late. So you can see, life is a precious commodity for many prey animals. If a predator is not fooled by a flying squirrel remaining perfectly still, it will attack. This is a time when all a flying squirrels arboreal abilities come into play. Through a combination of running, jumping and gliding, the squirrel will attempt to escape before being attacked. When a flying squirrel is being being watched or followed by an owl while gliding, it will instinctlivey run to the other side of it's landing spot in order to avoid being taken. In fact, this instinctual behaviour is so well-ingrained, you can watch wild flyers perform this manoeuver as a precaution, even when no owls are in the vicinity.

Flying squirrels have "breakaway" tails, as do many other species of squirrel. This is a real advantage, as a predator may only end up with a mouthful of tail, while the squirrel itself scampers away to a safe haven, its ego the only casualty.

Here are a few more clues to see if we have Northern or Southern Flying squirrels: 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).

We have seen the ones on deer trail active all times of the night and have never noticed any sounds they make at night. Feel free to write us or post if you have an idea which species is on Deer Trail or gather any more clues. Thanks!

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