In the days prior to and immediately following a full moon, there is often enough light in the hours after sunset for a person to meander along a well established woodland trail without the aid of a flashlight. By walking slowly and quietly, one can occasionally detect a small gray squirrel rustling about the dead leaves on the forest floor, climbing up a large trunk, or moving along the limb of a tree. While most squirrels strongly prefer to be active during the light of day, the flying squirrel favors the darkness of night and is the most common nocturnal tree dwelling mammal within the Park.
The flying squirrel is characterized by a loose fold of skin, called a patagium that extends from it front and hind legs and connects to its sides. This thin, furry membrane acts as a wing or airfoil when the animal stretches its appendages outward and enables it to glide forward as it slowly descends after leaping from a tree. The wide and flat tail of this rodent provides additional lift and greatly helps an airborne individual alter its flight path so it can accurately land at a selected spot.
In the Adirondacks there are two species of flying squirrels, and because of their similar appearances, identification is always a challenge in poor light. The southern flying squirrel, (Glaucomys volans) is slightly smaller than a chipmunk and confines its activities to lower elevation forests, particularly around the periphery of the Park. The northern flying squirrel, (Glaucomys sabrinus) is slightly larger than a chipmunk, but smaller than a red squirrel and has a rusty-tan hue on its back, a subtle feature impossible to note when seen in moon light. As would be expected, the northern flying squirrel is more cold hardy and abounds in mixed forests throughout our region regardless of elevation. Consequently, should a small, drab gray colored squirrel be seen well after dusk near Heart Lake, or around a lean-to in the West Canada Lake wilderness, chances are that it is a northern flying squirrel.
Both species of flying squirrels prefer to inhabit mature woodlands, especially those close to a waterway or where the soil tends to be constantly moist. Stands of hemlock mixed with older sugar maple and beech trees harbor an abundance of these rodents particularly if the area is near the shore of a lake or has a sizeable stream meandering through that location.
Older forests tend to have a thicker canopy which limits the development of vegetation on the forest floor. While the patagium allows the flying squirrel to effectively travel through the air, it occasionally hinders its ability to move quickly on the ground. In places where the forest floor is relatively free of debris, the flying squirrel is capable of ambling along at a fairly good rate. However, if there is an abundance of tall sedges, leafy plants and twigs covering the ground, this unique membrane can limit its maneuverability and makes it more prone to attack.
Seed produced by both softwoods and hardwoods provide these critters with an important component of their diet. Unlike most other members of this family of rodents, the flying squirrel supplements the plant items that it eats with significant amounts of animal matter. The nests of songbirds are raided whenever these structures are located in the crown of a tree for either the eggs or nestlings which they contain. Bugs of all shapes and sizes are also routinely ingested by this omnivore throughout the warmer months of the year. The flying squirrel is also known to attack young mice, and in winter, carrion of any type is gnawed on should an animal carcass be located close by. The flying squirrel is also known for consuming substantial amounts of mushrooms and other types of fungi that grow in the rich soil of mature forests, and during rainy, overcast years when mushrooms are plentiful these spongy items may comprise a substantial portion of their diet.
The carpet of decaying organic matter covering the forest floor is an ideal setting for mushrooms as it tends to remain cool and moist throughout the growing season. Rain is beneficial to nearly all forms of life here in the Adirondacks, including fungus which, in turn, benefits our flying squirrels.
A night time stroll through a grove of hemlocks near the shore of a lake can be a great experience as long as you remember to bring a flashlight and refrain from letting your imagination run wild when the sound of rustling leaves are heard a short distance away. Despite the difficulty that humans experience at seeing what is around them while outdoors at night, many forms of wildlife are quite capable of functioning under such conditions, and the flying squirrel is among the best here in the Adirondacks.
Illustration courtesy NYS Department of Environmental Conservation.
A version of this story first appeared on the Adirondack Almanack in July, 2012. Read all about small mammals in the Adirondacks here.