The Siberian flying squirrel (''Pteromys volans'') is an Old World flying squirrel ranging from the

Baltic Sea The Baltic Sea is an arm of the Atlantic Ocean that is enclosed by the countries of Denmark, Estonia, Finland, Germany, Latvia, Lithuania, Poland, Russia, Sweden, and the North European Plain, North and Central European Plain regions. It is the ...

in the west, throughout Northern Asia to the coast of the

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five Borders of the oceans, oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean, or, depending on the definition, to Antarctica in the south, and is ...

in the east. It is the only species of flying squirrel in

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

and is considered vulnerable in the

European Union The European Union (EU) is a supranational union, supranational political union, political and economic union of Member state of the European Union, member states that are Geography of the European Union, located primarily in Europe. The u ...

where it occurs only in

Estonia Estonia, officially the Republic of Estonia, is a country in Northern Europe. It is bordered to the north by the Gulf of Finland across from Finland, to the west by the Baltic Sea across from Sweden, to the south by Latvia, and to the east by Ru ...

and

Finland Finland, officially the Republic of Finland, is a Nordic country in Northern Europe. It borders Sweden to the northwest, Norway to the north, and Russia to the east, with the Gulf of Bothnia to the west and the Gulf of Finland to the south, ...

. In

Latvia Latvia, officially the Republic of Latvia, is a country in the Baltic region of Northern Europe. It is one of the three Baltic states, along with Estonia to the north and Lithuania to the south. It borders Russia to the east and Belarus to t ...

, it was last sighted in 2001 and has been considered to be locally extinct since 2013.

Description

A female Siberian flying squirrel weighs about 150

gram The gram (originally gramme; SI unit symbol g) is a Physical unit, unit of mass in the International System of Units (SI) equal to one thousandth of a kilogram. Originally defined in 1795 as "the absolute Mass versus weight, weight of a volume ...

s, 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 grey 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 The patagium (: patagia) is a membranous body part that assists an animal in obtaining lift when gliding or flying. The structure is found in extant and extinct groups of flying and gliding animals including bats, theropod dinosaurs (inclu ...

, 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 In aerodynamics, the lift-to-drag ratio (or L/D ratio) is the lift generated by an aerodynamic body such as an aerofoil or aircraft, divided by the aerodynamic drag caused by moving through air. It describes the aerodynamic efficiency under give ...

of 3.31, but is normally 1-1.5.

Behavior

Diet

Its diet consists of

leaves A leaf (: leaves) is a principal appendage of the stem of a vascular plant, usually borne laterally above ground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, stem, ...

seed In botany, a seed is a plant structure containing an embryo and stored nutrients in a protective coat called a ''testa''. More generally, the term "seed" means anything that can be Sowing, sown, which may include seed and husk or tuber. Seeds ...

cones In geometry, a cone is a three-dimensional figure that tapers smoothly from a flat base (typically a circle) to a point not contained in the base, called the ''apex'' or '' vertex''. A cone is formed by a set of line segments, half-lines, ...

bud In botany, a bud is an undeveloped or Plant embryogenesis, embryonic Shoot (botany), shoot and normally occurs in the axil of a leaf or at the tip of a Plant stem, stem. Once formed, a bud may remain for some time in a dormancy, dormant conditi ...

s, sprouts, nuts and

berries A berry is a small, pulpy, and often edible fruit. Typically, berries are juicy, rounded, brightly colored, sweet, sour or tart, and do not have a stone fruit, stone or pit (fruit), pit although many wikt:pip#Etymology 2, pips or seeds may be p ...

. Local hunters claim that they occasionally eat bird eggs and nestlings, however, there is no evidence of this behavior. When

alder Alders are trees of the genus ''Alnus'' in the birch family Betulaceae. The genus includes about 35 species of monoecious trees and shrubs, a few reaching a large size, distributed throughout the north temperate zone with a few species ex ...

and

birch A birch is a thin-leaved deciduous hardwood tree of the genus ''Betula'' (), in the family Betulaceae, which also includes alders, hazels, and hornbeams. It is closely related to the beech- oak family Fagaceae. The genus ''Betula'' contains 3 ...

catkin A catkin or ament is a slim, cylindrical flower cluster (a spike), with inconspicuous or no petals, usually wind- pollinated ( anemophilous) but sometimes insect-pollinated (as in '' Salix''). It contains many, usually unisexual flowers, arra ...

s are plentiful, the squirrel may store them for the winter in old

woodpecker Woodpeckers are part of the bird family (biology), family Picidae, which also includes the piculets, wrynecks and sapsuckers. Members of this family are found worldwide, except for Australia, New Guinea, New Zealand, Madagascar and the extreme ...

holes or similar nooks.

Reproduction

They mate early in the spring. In southern

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. They preferentially build their nest in holes made by woodpeckers, but they may also nest in

birdhouse A nest box, also spelled nestbox, is a man-made enclosure provided for animals to nest in. Nest boxes are most frequently utilized for birds, in which case they are also called birdhouses or a birdbox/bird box, but some mammals such as bats ma ...

s 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. They can live up to about five years.

Habitat

The nominate subspecies, ''P. v. volans'' is widespread across the Northern Palearctic (specifically from

Northern Europe The northern region of Europe has several definitions. A restrictive definition may describe northern Europe as being roughly north of the southern coast of the Baltic Sea, which is about 54th parallel north, 54°N, or may be based on other ge ...

Siberia Siberia ( ; , ) is an extensive geographical region comprising all of North Asia, from the Ural Mountains in the west to the Pacific Ocean in the east. It has formed a part of the sovereign territory of Russia and its predecessor states ...

and

East Asia East Asia is a geocultural region of Asia. It includes China, Japan, Mongolia, North Korea, South Korea, and Taiwan, plus two special administrative regions of China, Hong Kong and Macau. The economies of Economy of China, China, Economy of Ja ...

), while other subspecies have limited distribution, with ''P. v. athene'' known from

Sakhalin Sakhalin ( rus, Сахали́н, p=səxɐˈlʲin) is an island in Northeast Asia. Its north coast lies off the southeastern coast of Khabarovsk Krai in Russia, while its southern tip lies north of the Japanese island of Hokkaido. An islan ...

, ''P. v. buechneri'' known from

China China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...

and '' P. v. orii'' known from

Hokkaido is the list of islands of Japan by area, second-largest island of Japan and comprises the largest and northernmost prefectures of Japan, prefecture, making up its own list of regions of Japan, region. The Tsugaru Strait separates Hokkaidō fr ...

. They favor old forests with a mix of

conifer Conifers () are a group of conifer cone, cone-bearing Spermatophyte, seed plants, a subset of gymnosperms. Scientifically, they make up the phylum, division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a sin ...

s and deciduous trees. They are mostly

nocturnal Nocturnality is a ethology, behavior in some non-human animals characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnality, diurnal meaning the opposite. Nocturnal creatur ...

, being most active late in the evening, although females with young may also feed during the day. They do not

hibernate Hibernation is a state of minimal activity and metabolic reduction entered by some animal species. Hibernation is a seasonal heterothermy characterized by low body-temperature, slow breathing and heart-rate, and low metabolic rate. It is most ...

, but in the winter they may sometimes sleep continuously for several days. As shy and nocturnal animals, they 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.

Predators

The squirrels are preyed upon by

martens A marten is a weasel-like mammal in the genus ''Martes'' within the subfamily Guloninae, in the family (biology), family Mustelidae. They have bushy tails and large paws with partially retractile claws. The fur varies from yellowish to dark bro ...

hawk Hawks are birds of prey of the family Accipitridae. They are very widely distributed and are found on all continents, except Antarctica. The subfamily Accipitrinae includes goshawks, sparrowhawks, sharp-shinned hawks, and others. This ...

owl Owls are birds from the order Strigiformes (), which includes over 200 species of mostly solitary and nocturnal birds of prey typified by an upright stance, a large, broad head, binocular vision, binaural hearing, sharp talons, and feathers a ...

dog The dog (''Canis familiaris'' or ''Canis lupus familiaris'') is a domesticated descendant of the gray wolf. Also called the domestic dog, it was selectively bred from a population of wolves during the Late Pleistocene by hunter-gatherers. ...

s and

cat The cat (''Felis catus''), also referred to as the domestic cat or house cat, is a small domesticated carnivorous mammal. It is the only domesticated species of the family Felidae. Advances in archaeology and genetics have shown that the ...

In human culture

It is the emblem of

Nuuksio National Park Nuuksio National Park (, ) is one of Finland's 40 national parks. Established in 1994, the park spreads over an area of forests and lakes in Espoo, Kirkkonummi and Vihti. North-west from Helsinki, it is the second-closest national park to the ca ...

Espoo Espoo (, ; ) is a city in Finland. It is located to the west of the capital, Helsinki, in southern Uusimaa. The population is approximately . It is the most populous Municipalities of Finland, municipality in Finland. Espoo is part of the Helsi ...

municipality of

due to the density of the population in this region. In Estonia, the Siberian flying squirrel is depicted on the logo of the Estonian Nature Fund.

Threats

In Finland and especially the Baltic states, the Siberian flying squirrel has been at risk potentially becoming an endangered species. ''P. volans'' is already

extirpated Local extinction, also extirpation, is the termination of a species (or other taxon) in a chosen geographic area of study, though it still exists elsewhere. Local extinctions are contrasted with global extinctions. Local extinctions mark a chan ...

from

Lithuania Lithuania, officially the Republic of Lithuania, is a country in the Baltic region of Europe. It is one of three Baltic states and lies on the eastern shore of the Baltic Sea, bordered by Latvia to the north, Belarus to the east and south, P ...

. Since 1996, it was also considered extinct in

Belarus Belarus, officially the Republic of Belarus, is a landlocked country in Eastern Europe. It is bordered by Russia to the east and northeast, Ukraine to the south, Poland to the west, and Lithuania and Latvia to the northwest. Belarus spans an a ...

, until being spotted again in 2017, with more than 80 habitats subsequently discovered in far northern regions of the country in 2019. Acts that are believed to be contributors to the decrease in the population size are

habitat fragmentation Habitat fragmentation describes the emergence of discontinuities (fragmentation) in an organism's preferred environment (habitat), causing population fragmentation and ecosystem decay. Causes of habitat fragmentation include geological proces ...

, climate, and habitat loss in places they reside like boreal forests and old-spruce-dominated forests. Because Finland is a member of the European Union, the squirrel is under the protection of the EU's 1992 Habitats Directive. The EU, Finland and Estonia have responded with a six-year, 8.9 million euro project to help protect the squirrel.

References

External links

Pteromys volans
at Animal Diversity Web.

and text in Swedish about Pteromys volans. {{Taxonbar, from=Q243339 Pteromys Rodents of Asia Rodents of Europe Fauna of Siberia Mammals described in 1758 Taxa named by Carl Linnaeus Habitats Directive species