The Siberian flying squirrel is an Old World flying squirrel found across Eurasia. Its coat is grey all over, the abdomen being slightly lighter than the back, with a black stripe between the neck and the forelimb. It has a flattened tail and eyes that are large and strikingly black. 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.
Siberian flying squirrels occur from the Baltic Sea in the west to the Pacific Coast in the east. They favor old forests with a mix of conifers and deciduous trees.
Siberian flying squirrels are social and mostly nocturnal, being most active late in the evening, although females with young may also feed during the day. They do not hibernate, but in the winter they may sometimes sleep continuously for several days. When active they spend most of their time gliding from tree to tree collecting food. When alder and birch catkins are plentiful, the squirrel may store them for the winter in old woodpecker holes or similar nooks. As shy and nocturnal animals, Siberian flying squirrels are seldom seen. 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 nest.
Siberian flying squirrels breed early in the spring. In southern Finland, the first mating season begins in late March, with a second mating season occurring in April. They prefer to build their nest in holes made by woodpeckers, but 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. After a gestation period of 5 weeks, the female gives birth to a litter of usually 2 or 3 young, each weighing about 5 grams (0.176 oz).
The main threats that contribute to the decrease in the Siberian flying squirrel population size include habitat fragmentation, climate, and habitat loss in places they reside like boreal forests and old-spruce-dominated forests.
The IUCN Red List and other sources don’t provide the number of the Siberian flying squirrel total population size. Currently, this species is classified as Least Concern (LC) on the IUCN Red List but its numbers today are decreasing.