Tundra vole | Alexandromys oeconomus

Tracks

The main sign is the runway system in tall vegetation. Unlike the Common Vole, which lives in short grass, the Tundra Vole lays its paths under reed, sedge and rush: swept runways three to four centimetres wide through the litter, often over floating sedge or bog-moss cushions and to just above the water. The burrow entrances are round holes about three centimetres across, usually at the base of a tussock; in the wettest ground there is hardly any digging, and instead ball-shaped nests of finely cut grass and sedge leaves are built, above ground in a tussock or in winter under the snow. Along the runways lie cut stems of reed, sedge and grass in obliquely bitten pieces a few centimetres long, and droppings of four to seven millimetres, cylindrical with blunt ends, grass-green when fresh and brown later, in small latrines on a raised spot. For the winter stores of roots and rhizomes are laid down in underground chambers, up to a few kilograms per burrow. None of these signs can be distinguished from those of the Field Vole. The species is demonstrated through owl pellets: Barn Owl, Long-eared Owl and Short-eared Owl take it, and in teased-out pellets the flat molars, folded into zigzag prisms, can be identified to species. In the relict areas pellet analysis is therefore the standard method for establishing whether the species is still present, alongside live trapping, which requires a licence.

Identification

A fairly large, robust vole with a broad head, small ears hidden in the fur and small dark eyes. The back is dark brown to blackish brown, with a coat that is usually coarser and shaggier than in the Common Vole; the belly is dark grey; paler animals occur. The tail is long for a vole, about forty per cent of head-body length, and clearly bicoloured. A good character is on the feet: they are dark and the claws are white, which is immediately visible in an animal in the hand. In the Netherlands this is the largest of the three grassland voles. Elsewhere in Europe and in Asia the species is more variable and often paler; it is most numerous on the tundra.

Similar species

Common Vole, Field Vole and Tundra Vole cannot be separated with certainty in the field; a vole running through grass can only be recorded as 'vole'. With an animal in the hand more is possible: the Tundra Vole is larger, darker and longer-tailed than the other two and has white claws; the Field Vole is shaggy and dark, with ears hairy on the inside; the Common Vole is yellowish grey and shorter-tailed. In the relict areas, as in the Netherlands, locality is the main aid: in genuinely wet ground (quaking fen, reedbed, wet unimproved grassland, brackish creek banks) the Tundra Vole occurs and the other two are absent. Certainty requires the teeth, in practice through owl pellet analysis. The Bank Vole is smaller, reddish brown and lives in scrub; the Wood Mouse has large ears, bulging eyes and a tail as long as the body; the Water Vole is two to three times as heavy.

Habitat

Wet, tall and dense grassland and marsh: reedbed and sedge fen, quaking fen and bog-moss reedland, wet unimproved hay meadows, the swamp zone around lakes and peat cuttings, banks of creeks and inlets, and periodically flooded ground. In the Netherlands also brackish shores and marshy inner dune margins; in the north of the range the habitat continues into wet tundra and the damp parts of the taiga. The species persists where the soil is too wet for Common Vole and Field Vole; on drier ground it is displaced by those two. In the Asian mountains it occurs up to 2,500–2,900 m.

Distribution

A large range from central Europe and Fennoscandia east through Siberia to Alaska and north-western Canada, with a series of isolated relict populations in the west: the Netherlands, Germany, Austria, Hungary, Slovakia and the Neusiedler See area (Seewinkel). In the Netherlands the species lives in five separate areas: Texel, Friesland (the Frisian lakes and fen marshes), North Holland, the Utrecht–Holland peat meadow area and the Delta of South Holland and Zeeland; all these animals belong to the subspecies arenicola, a relict of the last ice age. In Flanders the species has disappeared. The nearest other populations are in north-western Germany and around the Neusiedler See. The species does not occur in the British Isles, on the Iberian Peninsula or in the rest of south-western Europe.

• Native
• dark = core range, pale = thinly spread

Way of life

Active in short, alternating bouts spread over day and night, with the emphasis on dusk and early morning; in the northern summer also by day. The species swims well and uses water as an escape route; a vole that dives into the water in a reedbed is often this species. The diet is vegetable: in summer green parts of reed, rushes, sedges and grasses, in winter roots, rhizomes, seeds and bark, supplemented with the occasional insect; the food is coarser and tougher than that of the Common Vole. The breeding season runs from April to October, with three to four litters a year and on average three to seven young after a gestation of about twenty-one days; in the north breeding may continue into winter in good years. Adult males are clearly larger than females. There is no hibernation; the winter is spent under the snow and in the litter layer. Barn Owl, Long-eared Owl, Short-eared Owl, Marsh Harrier, Stoat, Weasel, Polecat and Red Fox feed partly on this species.

Where and when to look

Search in a reedbed or quaking fen, for example in the Dutch peat meadow area, the Zeeland inlets or the Austrian Seewinkel, in the early morning or the last hour of the day. Walk along the edge of the reed rather than into it, and look at the base of the tussocks: there lie the swept runways and the small heaps of obliquely cut stems. A vole sitting on a floating sedge tussock and then entering the water is in this landscape almost certainly this species, but this cannot be established with certainty from a photograph. A reliable picture of the species present is obtained by collecting pellets under a Long-eared Owl or Barn Owl roost in autumn. Live trapping is only permitted under licence.

Conservation status

Globally Least Concern (2016); over its whole range this is one of the most numerous mammals of the north. That assessment, however, says nothing about the western relict populations, which are declining. In the Netherlands the Tundra Vole is listed as Vulnerable on the Red List and the subspecies arenicola is listed as a priority species under the Habitats Directive (Annexes II and IV); outside the Netherlands this applies only to the Pannonian subspecies mehelyi, not to the species as a whole. The decline has been caused by drainage, fragmentation, more intensive mowing and grazing of marsh edges and the loss of gradual transitions between land and water. There is also a specific threat: where the ground becomes drier, or where a dyke or dam forms a connection with higher ground, Common Vole and Field Vole invade the area and displace the Tundra Vole. Management is therefore aimed mainly at keeping the habitat wet. Because the Dutch animals belong to a subspecies that occurs nowhere else, the survival of this form depends almost entirely on management in the Netherlands.

Scientific name

Alexandromys oeconomus | (Pallas, 1776) (GBIF: Microtus oeconomus)

Pallas described the species in 1776 as Mus oeconomus; because it was later moved to another genus, the author and year stand in brackets. Alexandromys ends in Greek mys, 'mouse'; the first element is the personal name Alexander, but Ognev never said whom he meant by it. oeconomus is Greek oikonomos, 'householder, steward', after the stores of roots and seeds the animal lays up for the winter. The specimen the first description was based on came from Russia, Tyumen'.