32.

Siberian Brown Lemming

Lemmus sibiricus

French: Lemming de Sibérie / German: Sibirischer Lemming / Spanish: Lemming de Siberia

Other common names: Black-footed Lemming, Brown Lemming, Ob Lemming, Siberian Lemming

Taxonomy. Mus lemmus sibiricus Kerr, 1792, between Polar Ural Mountains and lower course of Ob River, Yamalo-Nenetskaya Nats. Okr., Russia.

Lemmus sibiricus is closely related to L. lemmus and L. amurensis, and in captivity, they hybridize freely. Nevertheless, L. sibiricus consists of several deeply divergent evolutionary lineages. Genetic distances between the most divergent lineages (particularly between west-Siberian and eastSiberian) exceed divergence between west-Siberian lineage of sibiricus and L. lemmus . The idea that all these species are actually conspecific has a long history. The form portenkoi was classified as a separate species until very recently. Molecular assessments placed portenkoi and novosibiricus in the east-Siberian lineage, close to subspecies bungei. Lemmus sibiricus was reported as L. obensis in the past. Four subspecies recognized.

Subspecies and Distribution.

L.s.sibiricusKerr,1792—NEEuropeanRussia,NovayaZemlya,andW&CSiberiaasfarEasLenaRiver.

L.s.bunge:Vinogradov,1925—ESiberiabetweenLenaandKolymarivers.

L.s.novosibiricusVinogradov,1925—NewSiberianIs(NERussia).

L. s. portenkoi Tschernyavsky, 1967 — Wrangel I (NE Russia).

Descriptive notes. Head—body 99-160 mm, tail 8-17-6 mm; weight 49-120 g. Size is highly variable among and within populations of Siberian Brown Lemmings. They tend to be larger at high latitudes and smaller in taiga. They are very similar to Norway Brown Lemmings ( L. lemmus) in external morphology and craniodental architecture, but their pelage is monochromatic. Back of the Siberian Brown Lemming is yellowish brown or rusty brown, and belly is whitish gray, with variable amount of buff tint. Black spinal stripe extends from neck to mid-back but is frequently interrupted or faint.

Habitat. Flat moist Arctic tundra, with mires and bogs in lowlands and uplands up to elevations of ¢.800 m. Summer habitats of Siberian Brown Lemmings are frequently in river valleys, along creeks, and around lakes. Habitat is small-scale mosaics of wet spots, with fresh plants and drier patches (peat heaps and bogs) for burrowing. Winter is spent under deep snow cover (1-5-2 m in Yakutia [= Sakha Republic], Russian Far East) in mossy areas with dwarf birch ( Betula nana, Betulaceae). Siberian Brown Lemmings frequently congregate under thick snow accumulated by wind. In spring, melting snow forces them to summer habitats. In lowlands along the Kolyma River (Russian Far East), they live in coniferous forests of the taiga type.

Food and Feeding. Fifty-three species of plants were identified in the diet of the Siberian Brown Lemming on Wrangel Island, and 20 were preferred: two species of mosses (Tomentypnum nitens and Philonotisfontana); common horsetail ( Equisetum arvense, Equisetaceae); alpine meadow-foxtail ( Alopecurus alpinus), hairgrass ( Deschampsia cespitosa), spike trisetum ( Trisetum spicatum), two species of bluegrass ( Poa arctica and P. glauca), tundragrass ( Dupontia fischeri), all Poaceae; three species of cottongrass ( Eriophorum angustifolium, E. triste, and E. vaginatum), three species of sedge ( Carex lugents, C. saxatilis, and C. stans), all Cyperaceae; mountain sorrel ( Oxyria digyna, Polygonaceae); two rockfoils ( Saxifraga hirculus and S. flagellaris, both Saxifragaceae); capitate lousewort ( Pedicularis capitata, Scrophulariaceae), and ragwort ( Senecio arcticus, Asteraceae). Diets can be less diverse elsewhere, e.g. only twelve species were recovered in Yakutia. Monocotyledonous plants (grasses, sedges, and cottongrass) are staples in summer and winter diets. Mosses start becoming important in autumn and constitute ¢.50% of diets in winter. Lichens are not palatable to Siberian Brown Lemmings. Data on daily consumption vary among sources, e.g. 50-80 g of green plants/lactating female, or 110-130 g by an individual weighting 52 g. Annual consumption is estimated to be 40-50 kg/lemming. In peak years, Siberian Brown Lemmings destroy up to 70% of plant biomass and 90-94% of preferred plant species.

Breeding. Breeding starts in early April (June on the Yamal Peninsula) and peaks in July. Winter reproduction has been recorded. Female Siberian Brown Lemmings have 2-4 litters/year. Mean litter sizes are 5-6-7-4 embryos. Melting snow can heavily increase mortality of young from winter litters. Females sexually mature at ¢.2 months. Populations oscillate widely, with peaks every 2-5 years. Mean periodicity of oscillations varies between regions: 2-8 years in north-western Yakutia, 3-2 years in Kolyma, and 3-4-3-8 years on WrangelIsland.

Activity patterns. Siberian Brown Lemmings spend most of their life under snow. On Wrangel Island, most activity is under 0-5-1 m of snow. They construct globular nests with grasses and sedges.

Movements, Home range and Social organization. Siberian Brown Lemmings migrate only short distances, e.g. during spring snow melt, distances up to 1 km. Females with litters are territorial; mature males and subadults prefer nomadism. There is no evidence of antagonistic behavior, even in winter habitats with considerable aggregations of individuals.

Status and Conservation. Classified as Least Concern on The IUCN Red List. Lemmus portenkoi was classified as Data Deficient on The IUCN Red List as a separate species; here,it is considered a subspecies of the Siberian Brown Lemming. It has a small distribution (Wrangel Island is 7600 km?) that might be fragmented. Although no conservation threats have been identified for the Siberian Brown Lemming, oscillations toward low densities might pose an intrinsic threat.

Bibliography. Abramson et al. (2008), Chernjavskij (2016c¢), Kiryuschenko & Kiryuschenko (1979), Krivosheev (1984), Pokrovski et al. (1984), Shenbrot & Krasnov (2005), Tavrovskiy et al. (1971).