Northern Flying Squirrel

The **northern flying squirrel** (*Glaucomys sabrinus*) is one of three species of the genus *Glaucomys* and one of the two flying squirrel species found in North America.

## Characteristics

The northern flying squirrel is a small squirrel. It is about ten inches long from the tip of its nose to the tip of its tail. It has very large, round black eyes that help it see at night and a long, flattened tail. It has soft cinnamon brown and gray fur above and creamy white fur below. It has a loose fold of skin between its front and rear feet. When it stretches out its legs, this skin forms a kind of parachute that lets the squirrel glide from branch to branch. As it 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.

## Range

The northern flying squirrel can be found in Canada and the northern United States including Alaska, Washington, Oregon, California, North Dakota, South Dakota, Idaho, Montana, Utah, Wyoming, Minnesota, Michigan, and Wisconsin. It is also found in the Appalachian mountains from New England through North Carolina.

## Habitat

The northern flying squirrel lives in dense conifer or mixed conifer and deciduous forests.

## Diet

The northern flying squirrel eats nuts, acorns, fungi and lichens. It may also eat fruits, buds, sap, bird eggs, small nestling birds and insects.

## Life Cycle

Breeding season runs from March to May. The female gives birth to two to five young after a gestation period of about 40 days. The nest can be an abandoned bird nest; a clump of twigs, moss, and shredded bark placed in the crotch of a branch; or an abandoned woodpecker hole or tree cavity. The female cares for the young, who are weaned when they are about two months old. They learn to glide when they are about three months old. The female has one litter a year.

## Gliding

   Flying squirrels do not actually fly, they glide using a patagium created by a fold of skin. From atop trees, flying squirrels can initiate glides from a running start or from a stationary position by bringing their limbs under the body, retracting their heads, and then propelling themselves off the tree. It is believed that they use triangulation to estimate the distance of the landing as they often lean out and pivot from side to side before jumping. Once in the air, they form an "X" with their limbs, causing their membrane to stretch into a square-like shape and glide down at angles of 30 to 40 degrees. They maneuver with great efficiency in the air, making 90 degree turns around obstacles if needed. Just before reaching a tree, they raise their flattened tails, which abruptly changes their trajectory upwards, and point all of their limbs forward to create a parachute effect with the membrane to reduce the shock of landing. The limbs absorb the remainder of the impact, and the squirrels immediately run to the other side of the trunk or to the top of the tree to avoid any potential predators. Although graceful in flight, they are very clumsy walkers and if they happen to be on the ground in the presence of danger, they will prefer to hide rather than attempt to escape.

## Behavior

Northern flying squirrels generally nest in holes in trees, preferring large-diameter trunks and dead trees, and will also build outside leaf nests called dreys and will also nest underground. Tree cavities created by woodpeckers as 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 during winter months, forming aggregations. Usually, aggregate nests contain 4 to 10 individuals. The sharing of nests in winter by northern flying squirrels is important in maintaining body temperature (biothermal regulation), as northern flying squirrels do not hibernate, nor do they enter torpor states.

Northern flying squirrels gliding distances tend to be between 5 and 25 metres, though glides of up to 45 m and longer have been observed. Average glides are about 5 m less for females than for males. Glide angle has been measured at 26.8 degrees and glide ratio at 1.98.

Since first documented by Shaw in 1801, the general understanding was that northern flying squirrels bred but once per year. Recently, in southern Ontario, Canada, polyestrus behaviour (two litters per year) has been documented for the first time. This observation has since been confirmed by a second research team in New Brunswick, Canada. In southern Ontario, Canada, genetic evidence has recently shown hybridization with the rapid northward expansion and increased sympatry of southern flying squirrels.

## Predatation

Northern flying squirrels, along with pine squirrels, are an important prey species for the spotted owl (*Strix occidentalis*) and eastern screech owl (*Megascops asio*). Other predators include various other large birds, especially the great horned owl, hawks, the American marten, the Canada lynx, the red fox, and the domestic cat.