Northern flying squirrels are found throughout most of the forested areas of Canada. They 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; they see as well at night as humans can see during the day.

A furry membrane unites the front and back legs. When stretched, it acts like a parachute, enabling the squirrel to glide from higher branches to lower ones. Northern flying squirrels can glide from 3 to 50 m (10 to 164 ft.) and they can change direction mid-glide. This species averages about 30 cm (12 in.) long, including about 14 cm (5.5 in.) of tail.

Individuals and families will occupy several nests during the year. They usually nest in hollow trees or stumps lined with shredded tree bark, leaves, lichens and mosses. Males and females frequently occupy separate nests in the summer. In the winter months they often live together in groups of 2 to 10 for warmth. Northern flying squirrels are sociable animals with strong maternal instincts; they have one brood per year, averaging 2 to 4 young per litter.

Their varied, omnivorous diet includes berries, nuts, lichens, fungi, seeds, tree buds, blossoms, insects, carrion and bird eggs. Their fondness for maple sap has often led to their tumbling into sap buckets in spring and drowning. An important prey animal, its principal enemies are owls, martens, fishers, weasels, raccoons, bobcats and domestic cats.