118.

Middendortt’s Vole

Alexandromys middendorffii

French: Campagnol de Middendorff / German: Middendorff-Wiihlmaus / Spanish: Topillo de Middendorff

Other common names: Middendorf's Vole

Taxonomy. Arvicola middendorffii Poljakov, 1881, Dudypta River, Taymyr Peninsula, Krasnoyarskiy Krai, Russia.

According to B. S. Vinogradov in 1933, A. middendorffu and A. hyperboreus were considered separate species, but recent genetic and morphometric studies demonstrated their conspecifity. Alexandromys middendorffii is now in subgenus Alexandromys and mongolicus species group. Morphologically and genetically,it is sister species to A. gromovi. Three subspecies recognized.

Subspecies and Distribution.

A.m.middendorffiiPoljakov,1881—W&CSiberia,fromObandTazgulfsEtoKhatangaBay,andfromTaymyrPeninsulaStoEasternSayanMts(Russia).

A.m.hyperboreusVinogradov,1933—ESiberiaandRussianFarEast(Yakutia[=SakhaRepublic],ChukotkaAutonomousDistrict,NKhabarovskKrai,MagadanRegion,andNKamchatkaKrai).

A. m. ryphaeus Heptner, 1948 — shores of Barents and Kara seas from Kanin Peninsula E to Yamal Peninsula and Northern Ural Mts (Russia).

Descriptive notes. Head-body 99-150 mm, tail 21-42 mm, ear 10-15 mm, hindfoot 15-22 mm; weight 20-70 g. Male Middendorff’s Voles are larger than females. Fur color of head and upperparts varies from light reddish brown to dark brown, underparts are light or dark gray, and tail is distinctly bicolored. Sole of foot has five plantar pads. M® has 4-5 (usually four) inner and 3-5 (usually four) outer angles. Baculum is more than 4 mm long; its base is wide, with rightor obtuse-angle proximal edge. Median distal processes are medium-sized, and lateral is short. Chromosomal complement has 2n = 50 and FN = 58-60.

Habitat. Riparian habitats of coastal and mountain tundra, forest-tundra, and boreal coniferous forest zones. In tundra, Middendorff’s Vole prefers edges of bogs, lakes, and rivers. In forest-tundra and taiga, it occupies meadow bogs and edges of dry terraces in river valleys.

Food and Feeding. In summer and autumn, Middendorff’s Vole eats green parts of sedges and grasses. It stores food (sedge roots) for winter in caches inside a burrow; winter caches can be several kilograms per family group.

Breeding. Breeding of wild Middendorff’s Vole was recorded in May—August. Litters have 1-11 young (average 4-6-9), and intervals between pregnancies are 19-51 days (averages 32-9-34-4). Overwintering females can produce 3-5 litters/year. Gestation lasts 19-20 days. Females of the first and second generations can produce 1-2 litters during the first year; those born at the end of summer (third and fourth generations) reach reproductive maturity in the following spring.

Activity patterns. Middendorft’s Voles are active round-the-clock; in summer, they are often diurnal.

Movements, Home range and Social organization. Middendorf{f’s Vole lives in family colonies. Home range of a family group contains winter burrow, several summer nest burrows, aboveground nests, separate storage chambers, and shelter burrows. All nests, shelter burrows, and foraging sites within the colony are connected by pathways. Winter burrows are complex and have underground nest chambers and aboveground nests, and several storage chambers connected by tunnels; these burrows occupy c.l m* and have 10-20 entrances. Tunnels and underground nests are under the ground’s surface in the topsoil layer. Summer nest burrows are simple, consisting of nest chamber and 3-4 entrances. Nest chambers are 8-10 cm in diameter and up to 18 cm deep. Middendorff’s Voles communicate acoustically. Females emit quiet and sharp squeals; males emit songs when in contact with a female.

Status and Conservation. Classified as Least Concern on The [UCN Red List (as Microtus middendorffii).

Bibliography. Abramson & Lissovsky (2012), Bannikova et al. (2010), Bobretsov & Kupriyanova (2010), Gromov & Erbajeva (1995), Kostenko (1984), Lissovsky & Obolenskaya (2011), Lissovsky et al. (2010), Meyer et al. (1996), Rutovskaya (2015), Tavrovskiy et al. (1971), Vinogradov (1933).