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Palearctic Collared Lemming

Dicrostonyx torquatus

French: Lemming a collier / German: Echter Halsbandlemming / Spanish: Lemming paleértico de collar

Other common names: Arctic Lemming, Collared Lemming

Taxonomy. Mus torquatus Pallas, 1779, mouth of River Ob, NW Siberia, Russia.

Dicrostonyx torquatus 1s in the subgenus Misothermus. In the past, it was treated as a Holarctic species, with five subspecies in Eurasia and 6-12 in North America. Evolutionary split between Palearctic and Nearctic species was first retrieved from chromosomal evidence and cross-breeding experiments and subsequently confirmed by molecular markers and morphometric data. Three subspecies recognized.

Subspecies and Distribution.

D.t.torquatusPallas,1779—NEEuropeanRussiaandW&CSiberia(WofYeniseiRiver).

D.t.chionopaesG.M..Allen,1914—ESiberia(EofYeniseiRiver),includingBolshevikIandNewSiberianIs,EtoChukchiandKamchatkapeninsulas.

D. t. ungulatus Baer, 1841 — Novaya Zemlya I (N Russia).

Descriptive notes. Head—body 88-140 mm, tail 11-21 mm; weight 63-155 g. Size of the Palearctic Collared Lemming is fairly stable across its entire distribution. It is similar to the Nearctic Collared Lemming ( D. groenlandicus) in size, body proportions, color, other peculiarities of external morphology, and craniodental makeup. Its spinalstripe tends to be more distinct and reddish tints more pronounced in the west. Vestigial angles on molars tend to be less well developed than on species in the subgenus Di-Crostonyx.

Habitat. Dry and well-drained uplands in high Arctic tundra and forest tundra along southern distributional border. Suitable habitat of the Palearctic Collared Lemming is rich in dicotyledons (avens, Geum, Rosaceae, and dwarf willows, Salix, Salicaceae); cottongrass ( Eriophorum) and other sedges ( Cyperaceae); grasses ( Poaceae); and mosses. Winter habitats are on steep slopes, in depressions, and in peat tundra with thick snow layers. They have been recorded up to elevations of ¢.1400 m in the Ural Mountains and 500-700 m in eastern Siberia.

Food and Feeding. Summer diet of the Palearctic Collared Lemming is diverse and includes forbs, monocotyledons (sedges and grasses), and dicotyledons (dwarf willows, avens, blueberries, Vaccinium, Ericaceae; rockfoils, Saxifraga, Saxifragaceae; and lousewort, Pedicularis, Orobanchaceae). Dicotyledons can comprise more than 75% of diets in summer and autumn. Monocotyledons become more important under snow. Winter diet is monotonous, frequently only 2-3 plant species. Lichens are not palatable. Reports on food caches for winter are contradictory.

Breeding. Breeding season of the Palearctic Collared Lemming starts under the snow in April-May and even February-March in some years. Gestation lasts 17-21 days, and females have 1-12 embryos. Mean numbers of embryos per female have been reported as 4-3-8-4. Overwintered females have largerlitters (mean numbers of embryos 5-5-5-7) than females of the year (4-3—4-8); spring litters are larger (8) than summerlitters (5-7). Females normally have 2-3 litters/season. Sex ratio is female-biased, which is a consequence of an unusual genetic system in the Palearctic Collared Lemming. Similarly to the Wood Lemming, the X-chromosome can be either orthodox (X) or with a mutation (X*) suppressing the Y-chromosome gene. X*Y females have eggs with either X* orY sex chromosomes and therefore produce twice as many females as males.

Activity patterns. Palearctic Collared Lemmings are active throughout the day and year. Entrances to underground tunnels are not connected by surface runways. During winter, they dig under snow. Nest chambers are 11-20 cm in diameter and lined with dry sedges, grasses, and mosses.

Movements, Home range and Social organization. Territoriality among Palearctic Collared Lemmings is pronounced in summer. Adult pair shares a burrow. Level of aggressive behavior is low.

Status and Conservation. Classified as Least Concern on The IUCN Red List. Insular subspecies ungulatus from Novaya Zemlya is classified as vulnerable in the Red Book of Russian Federation. The Palearctic Collared Lemming is in The Red Book of the Magadan Region due to its rarity along the Sea of Okhotsk.

Bibliography. Abramson & Tikhonova (2002), Chernjavskij (1984, 2016e), Dokuchaev (2008), Gromov & Erbajeva (1995), Krivosheev (1984), Shenbrot & Krasnov (2005), Tavrovskiy et al. (1971).