The Northern Flying Squirrel, Glaucomys sabrinus, is frequently a night time visitor to local bird feeders in winter. Compared to the busy, chattering Red squirrel, which is active in the day, the flying squirrel is quiet and gentle and strictly nocturnal. We rarely see these little squirrels, however, they are fairly common in the Denali woodlands. Because these squirrels are nocturnal, they have large eyes and their silky, cinnamon brown fur is soft and silent in flight, like the night-flying owls.
The furred “wing” membranes on each side of the body are attached to the full length of the fore and hind legs which when extended laterally, the squirrel becomes a glider. By adjusting its legs, a flying squirrel controls the shape and angle of the patagium, the skin stretched along both sides of its body from wrist to ankle. Their flying carries them from the top of one tree to the base of another and with an upward swing and accompanying stall, they slow down to alight with a soft thud, (heard on the roof of many cabins over the course of a winter night). When they land on the base of a tree they almost instantaneously run around to the other side of the trunk to avoid an owl that may be in pursuit. If trees are spaced far apart, the squirrel may make a five-point landing in the snow, (in winter) with its broad furry tail used as a rudder and gliding surface, and to some extent as a landing ski.
They nest in old woodpecker holes or in chambers excavated in a witches’ broom, and they also make ball-like nests of moss, lichen, twigs, and leaves. One squirrel may use up to twenty different dens in a year. They do not hibernate, however, in particularly cold weather they will huddle together in groups in a state of light, transitory hibernation known as torpor.
Mushrooms are the flying squirrel’s favorite food. The mushroom spores dispersed in squirrel droppings are an important component of healthy forests.
A wonderful winter night activity is to watch the flying squirrels gliding overhead silhouetted against the starlit, moonlit sky.