153.

Siberian Flying Squirrel

Pteromys volans

French: Polatouche de Sibérie / German: Européisches Gleithérnchen / Spanish: Ardilla voladora de Siberia

Other common names: Russian Flying Squirrel

Taxonomy. Sciurus volans Linnaeus, 1758,

“Boreal Europe, Asia, and America.”

Restricted by O. Thomas in 1911 to Finland. Based mitochondrial cytochrome-b gene, Pteromys appears to be most closely related to Petaurista. Four subspecies recognized.

Subspecies and Distribution.

P.v.volansLinnaeus,1758—NEurope(SFinland,Estonia,Latvia,NBelarus,andWRussia)EtoRussianFarEast(Chukotka),NWChina(NXinjiang),andNMongolia.

P.v.atheneThomas,1907—SakhalinI.

P.v.buechner:Satunin,1903—NE&CChinaandtheKoreanPeninsula.

P.v. ori Kuroda, 1921 — Hokkaido I, Japan.

Descriptive notes. Head-body 120-228 mm, tail 90-149 mm; weight 95-200 g. The Siberian Flying Squirrel is somewhat smaller (10-20%) than its sister species, the Japanese Flying Squirrel (P. momonga). Dorsal pelage is gray or dark gray, and ventral pelage is white to yellowish white. Tail is more brownish and edged with dark-tipped hairs, and feet are pale below and dark above. Upper parts of nominate volans are uniform pale silvery gray. Eye ring is narrow black, and underparts are dull buffy white. Upper parts of athene are drab gray. Underparts are dull whitish. Sides are washed with reddish brown. Overall color of buechneri, especially on tail, is much darker than in the northern populations. Subspecies orii is similar to volans. Underparts are pure white. Cheeks are almost pure white. Tail is buffy on margin and blackish on median.

Habitat. Mature boreal closed-canopy forests and particularly dependent on primary trees. The Siberian Flying Squirrel is sensitive to logging and severe forest fragmentation. Various studies suggest, however, that maintenance of well-connected habitat patches that meetits requirements allow it to persist in a landscape managed for timber harvests. The Siberian Flying Squirrel prefers mixed continuous forests, with old conifers (e.g. Norway spruce, Picea abies, Pinaceae) and numerous deciduous trees such as European aspen (Populus tremula, Salicaceae); deciduous trees provide critical nest cavities. Preference for spruce over pine (Pinus, Pinaceae) is also reported. In Finland, it is dependent on mixed forests that are dominated by spruce. Probability of local extinction of the Siberian Flying Squirrel increases as spruce in its habitat declines. Increased forest fragmentation has also contributed to its decline; however,it can reside in fragmented systems and move reasonably well between forest fragments if adequate corridors of vegetation exist and suitable habitat components (e.g. spruce) are available in the matrix. Its use of habitat edges varies with type of edges, overall landscape structure, and spatial scale.

Food and Feeding. The Siberian Flying Squirrel feeds heavily on buds, pollen, leaves, fruit, catkins of alder and birch, twigs, lichen, and mesophyll of conifer needles;it is less partial to seeds. In particular, large quantities of needles and leaves are reported to be consumed daily, and it appears that individual squirrels have preferred feeding trees. Occasional consumption of animal material (e.g. eggs, juvenile birds, and small mammals) has been reported.

Breeding. Reproduction of Siberian Flying Squirrels occurs in late February-March and April-May. It is estimated that one-third of females in Finland breed twice annually, whereas those in other parts of the distribution (e.g. Russia) may only breed once annually, unless a female loses a litter. Gestation lasts 40-42 days; litters are typically 2-3 young (range 1-6). Young follow their mothers during foraging bouts.

Activity patterns. Siberian Flying Squirrels are generally nocturnal, but activity peaks vary with the light/dark cycle. It might be active periodically, for up to nine hours; it can also be active during the day when daylength is long, despite lacking color vision found in diurnal sciurids.

Movements, Home range and Social organization. Male home ranges vary with landscape structure (20-135 ha). Female home ranges are much smaller (c.8 ha). They nest in cavities, abandoned woodpecker holes, or nest boxes. The Siberian Flying Squirrel is unique in that it shows female-biased juvenile dispersal, which is best explained by competition between mothers and daughters for limited resources. Mortality ofjuveniles appears to be highest before dispersal. It is reported to glide slowly (5-7 m/sec) but exhibit considerable maneuverability because ofits low-wing loading.

Status and Conservation. Classified as Least Concern on The IUCN Red List. Current population trend ofthe Siberian Flying Squirrel is decreasing. It is listed on Appendix

IT of the Bern Convention and on Annex II and Annex IV of the EU Habitats and Species Directive, in parts of its distribution where these apply. It is considered vulnerable in Finland; the Finnish Ministry of Forestry and Agriculture and Ministry of the Environment have published detailed guidelines on how to manage flying squirrels in forestry. Specific recommendations include protecting known feeding and nesting sites with a 30m buffer of untouched habitat. The Siberian Flying Squirrel is listed as regionally extinct in Lithuania, an area formerly within its distribution. It is possibly extinct in Belarus but may persist in the extreme north of the country. It is listed as vulnerable on the Chinese Red List. It is listed as rare in Estonia and endangered in Korea. Threats include habitat fragmentation, modern intensive forestry, and logging. Habitat changes that limit connectivity are detrimental because of its unwillingness to travel on the ground and limited glide distance.

Bibliography. Airapetyants & Fokin (2003), Desrochers et al. (2003), Hanski & Selonen (2009), Haukisalmi & Hanski (2007), Hurme, Kurttila et al. (2007), Hurme, Ménkkonen, Nikula et al. (2005), Hurme, Monkkonen, Reunanen et al. (2008), Jackson (2012), Jackson & Thorington (2012), Johnson-Murray (1977), Moénkkoénen et al. (1997), Oshida, Abramov et al. (2005), Oshida, Hiraga et al. (2000), Painter et al. (2004), Rassi et al. (2001), Reunanen, Monkkénen & Nikula (2000, 2002), Reunanen, Ménkkonen et al. (2004), Reunanen, Nikula & Monkkonen (2002a), Reunanen, Nikula, Monkkoénen, Hurme & Nivala (2002), Ryu Shi-Hyun et al. (2013), Sato et al. (2007), Selonen & Hanski (2003, 2004, 2006), Selonen et al. (2001), Shar, Lkhagvasuren, Henttonen et al. (2008), Smith & Yan Xie (2008), Thomas (1911c¢), Thorington & Darrow (2000), Thorington, Darrow & Betts (1997), Thorington, Koprowski et al. (2012).