The Siberian Flying Squirrel (Pteromys volans) is an Old World flying squirrel with a range from the Baltic Sea in the west to the Pacific coast in the east. It is the only species of flying squirrel found in Europe. It is considered vulnerable within the European Union where it is found only in Finland and Estonia.

A female Siberian Flying Squirrel weighs about 150 grams, the males being slightly smaller on average. The body is 13–20 cm long, with a 9–14 cm long flattened tail. The eyes are large and strikingly black. The coat is gray all over, the abdomen being slightly lighter than the back, with a black stripe between the neck and the forelimb. A distinctive feature of flying squirrels is the furry glide membrane or patagium, a flap of skin that stretches between the front and rear legs. By spreading this membrane the flying squirrel may glide from tree to tree across distances of over a hundred meters, and have been known to record a glide ratio of 3.31, but is normally 1-1.5.^[2]

The diet of a Siberian Flying Squirrel consists of leaves, seeds, cones, buds, sprouts, nuts, berries and occasionally bird eggs and nestlings. When alder and birch catkins are plentiful, the squirrel may store them for the winter in old woodpecker holes or similar nooks.

The squirrels are preyed upon by martens, owls, and cats.

Siberian Flying Squirrels mate early in the spring. In southern Finland the first mating season begins in late March, with a second mating season occurring in April. After a gestation period of five weeks, the female gives birth to a litter of usually two or three young, each weighing about 5 grams. Siberian Flying Squirrels preferentially build their nest in holes made by woodpeckers, but they may also nest in birdhouses if the size of the entrance is appropriate. The nest consists of a pile of soft materials (preferably soft beard lichen) into which the squirrel burrows. A Siberian Flying Squirrel can live up to about five years.

Siberian Flying Squirrels favor old forests with a mix of conifers and deciduous trees. They are mostly nocturnal, being most active late in the evening, although females with young may also feed during the day. Siberian Flying Squirrels do not hibernate, but in the winter they may sometimes sleep continuously for several days. As shy and nocturnal animals, Siberian Flying Squirrels are seldom seen. The most common sign of their presence are their droppings, which resemble orange-yellow rice grains and are often found beneath or on top of their nest.

The Siberian Flying Squirrel is the emblem of the Nuuksio National Park in Espoo municipality of Finland. It is owed to the density of these squirrel population in this region.^[3]

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