Sorex tundrensis Merriam 1900

23. Tundra Shrew Sorex tundrensis French: Musaraigne de la toundra / German: Tundra-Rotzahnspitzmaus / Spanish: Musarafia de tundra Other common names: Holarctic Shrew Taxonomy. Sorex tundrensis Merriam, 1900, “ St. Michaels, Alaska,” USA. Sorex tundrensis is currently included in the subgenus Sorex and is closely related to S. asper, which is close to the araneus group based on karyotype and mtDNA and nDNA sequencing. Ten subspecies recognized. Subspecies and Distribution. S.t.tundrensisMerriam,1900—Alaskaincluding S.t. Lawrence and Kodiak Is (USA) and N & W Yukon, extreme NE British Columbia, and N Northwest Territories (NW Canada). S.t.baikalensisOgnev,1913—TransbaikaliaandtheadjacentstepperegionofNMongolia(KhentiiMts);thissubspeciesmayalsooccurintheforest-steppeofNMongoliatoLakeKhuvsgul. S.t.borealisKastschenko,1905—ESiberiantundrafromYeniseiGulfEtoChukchiPeninsula(ERussia). S.t.buxtoniJ.A.Allen,1903—ESiberiantaigafromVilyuyRiverBasinEtoOkhotskSeacoast(ERussia). S.t.parvicaudatusOkhotina,1976—MoneronI,CSeaofJapan. S.t.petschoraeOgnev,1921—UralMtsandWSiberiaEtoYeniseiRiver(CRussia). S.t.schnitnikoviOgnev,1921—C&SAltaiandmountainsofEKazakhstan(Tarbagatai,Saur,andDzungarianAlatau)andNWChina(Xinjiang). S.t.sibiriensisOgnev,1921—W&CSiberia,KuznetskAlatau,NEAltai,SayanMts,andTuva(SCRussia). S.t.stroganoviYudin,1979—PrimorskyKrai(SRussianFarEast);thissubspeciesmayalsooccurinNEChinaandAmurRegion(ERussia). S. t. transrypheus S.t., 1956 — W Siberia (C Russia) and N Kazakhstan. Subspecific distribution in various parts of the range is uncertain. Descriptive notes. Head-body 61-86 mm (immatures 52-70 mm), tail 20-38 mm (immatures 34-44 mm), ear 7-8 mm, hindfoot 13-15 mm; weight 8-11-5 g (immatures 4-8-7-5 g). The Tundra Shrew is medium-sized, with striking color. Pelage is generally bicolored in the Palearctic (deep brown to nearly black on back and whitish on sides and venter). Pelage is generally more noticeably tricolored during the summer and more bicolored during the winter. Summer pelage is dark brown to nearly black dorsally, lighter brown along the sides, and whitish ventrally, while winter pelage is more uniformly colored deep reddish brown to brown dorsally and whitish ventrally. Feet are dark; ears are short and barely extend past fur. Tail is ¢.50% of head-body length and sharply bicolored, dark brown above and lighter below. Tooth ridges (except for on unicuspids as in other species in the Sorex subgenus) are pigmented dark red, and there are five unicuspids that get smaller from first to fifth, with first two being significantly larger than last three, while last three gradually get smaller until the diminutive fifth. Chromosomal complementis extremely variable: 2n = 31-41 and FN = 56-60 in Siberia, 2n = 32 or 33 and FN = 58 in the Yukon; and 2n = 32 or 33 and FN = 62 in Alaska. This variation results from Robertsonian translocations effecting five autosomal chromosomes. Trivalent of sex chromosomes consists of large metacentric X-chromosome, small acrocentric Y-chromosome, and medium-sized acrocentric Y,chromosome. Habitat. Large variety of alpine, subalpine, and arctic habitats, shrublands, and meadows, often dominated by small trees and shrubs such as willow and birch, generally preferring open bush habitats. The Tundra Shrew is more efficient at colonizing tundra and steppe habitats than other species of shrews. It prefers to live in floodplain regions throughout taiga, avoiding forests, and in open areas between forests. Food and Feeding. Because Tundra Shrews live in various habitats, food items differ greatly among different geographical regions. For example, earthworms account for substantial proportions of diets in tundra, spiders and insects (commonly beetles) in taiga, and grasshoppers in steppe regions. Plant items are often included in diets, especially in winter; berries are eaten in southern regions of the distribution in Kazakhstan and pore fungi (Favolaschia, Mycenaceae) on Chukchi Peninsula. Breeding. Breeding of the Tundra Shrew generally occurs from late winter until early summer. Breeding season usually starts in May, and firstjuveniles appear by mid-June. Reproduction lasts until late August, and lactating females can be captured in early September. Up to 100% of female young-of-the-year reproduce in northern populations in someyears, and this distinguishes Tundra Shrew from other species of Sorex. A female has up to three litters in a breeding season. Reproductive rate can be extremely high in northern populations: 15 embryos were observed in single females in Yenisei forest-tundra, and mean number of embryos/female was 10-7 on Chukchi Peninsula. In southern regions, mean number of embryos/female is far lower: 5-7 in the Dzungarian Alatau and five in central Yeniseitaiga. Litters have 1-3 young on the Moneron Island where most females have only one litter in a breeding season. Activity patterns. Tundra Shrews are active day and night and are primarily terrestrial. Movements, Home range and Social organization. The Tundra Shrew is probably most similar to the Common Shrew (S. araneus) in its general ecology. It is solitary except when breeding and rearing young. Status and Conservation. Classified as Least Concern on The IUCN Red List. The Tundra Shrew is wide ranging and found in many different habitat types, although it might be threatened by effects of global climate change because it is found at higher latitudes. Tundra Shrews often dominate shrew communities in forest-steppe and forest-tundra regions and are sometimes the only shrew in the community of small mammals. It is on the Red Lists of Magadan and Sakhalin regions. In the latter case, this pertains to the subspecies parvicaudatus that lives only on Moneron Island. Bibliography. Andreev et al. (2006), Bannikova et al. (2010), Bekenov et al. (1985), Bobretsov et al. (2008), Churchfield & Sheftel (1994), George (1988), Hope et al. (2011), Jackson (1928), Junge & Hoffmann (1981), Junge et al. (1983), Lukéadova et al. (1996), Moraleva (1987), Nesterenko (1999), Okhotina (1984), Sheftel (1983), Volpert & Shadrina (2002), Volobouev (1989), Volpert & Shadrina (2002), Yudin (1989), Zaitsev et al. (2014).

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