Pteromys volans (Linnaeus, 1758)

Sexual Size Dimorphism

On average, female Siberian flying squirrels (Pteromys volans) weigh about 150 grams, while males are slightly smaller.

Body Length Measurements

Their bodies measure 13–20 cm in length, and they have a flattened tail that is 9–14 cm long.

Facial Features

They have large, strikingly black eyes.

Coat Coloration

Their coat is uniformly grey, with a slightly lighter abdomen and a black stripe running between the neck and forelimb.

Glide Membrane Structure

All flying squirrels share a distinctive feature: a furry glide membrane called a patagium, which is a flap of skin stretching between the front and rear legs.

Gliding Capability

By spreading this membrane, Siberian flying squirrels can glide from tree to tree over distances of over one hundred meters.

Glide Ratio

The maximum recorded glide ratio for this species is 3.31, but the normal glide ratio is between 1 and 1.5.

Nominate Subspecies Distribution

The nominate subspecies P. v. volans is widespread across the Northern Palearctic, specifically ranging from Northern Europe through Siberia to East Asia.

Other Subspecies Ranges

Other subspecies have limited ranges: P. v. athene is found on Sakhalin, P. v. buechneri is found in China, and P. v. orii is found in Hokkaido.

Preferred Habitat

Siberian flying squirrels favor old mixed forests that contain both conifers and deciduous trees.

Activity Period

They are mostly nocturnal, and are most active late in the evening.

Daytime Activity Exception

An exception is females with young, which may also feed during the day.

Winter Inactivity Pattern

They do not hibernate, but in winter they may sometimes sleep continuously for several days.

Observability

As they are shy and nocturnal, they are seldom seen.

Presence Indicator

The most common sign of their presence is their droppings, which resemble orange-yellow rice grains and are often found beneath or on top of their nests.

Mating Timing

They mate early in spring.

Finland Mating Seasons

In southern Finland, the first mating season begins in late March, and a second mating season occurs in April.

Gestation and Litter Size

After a gestation period of five weeks, the female gives birth to a litter that usually contains two or three young.

Newborn Weight

Each newborn weighs about 5 grams.

Nest Site Selection

The species preferentially builds nests in holes made by woodpeckers, but they will also nest in birdhouses if the entrance is the appropriate size.

Nest Construction

Their nest is a pile of soft materials, with soft beard lichen being preferred, that the squirrel burrows into.

Lifespan

Siberian flying squirrels can live up to about five years.