175.

Common Vole

Microtus arvalis

French: Campagnol des champs / German: Feldmaus / Spanish: Topillo campesino

Other common names: Guernsey Vole (Guernsey |), Orkney Vole (Orkney |)

Taxonomy. Mus arvalis Pallas, 1779, “Per omnen [= throughout] Europam & Russiam.” Based on neotype selection, restrict ed by V. M. Malygin and V. N. Yatsenko in 1986 to Pushkin, Leningrad (= St. Petersburg) Oblast, Russia.

Microtus arvalis is in subgenus Microtus and arvalis species group. Species now in the subgenus Microtus (i.e. mystacinus, transcaspicus, and ilaeus) and few species in subgenus Alexandromys (e.g. mongolicus) were synonymized with arvalis . Microtus obscurus is most closely related to M. arvalis . The two species share identical diploid number (2n = 46) but differ in morphology of chromosomes: M. obscurus has ten pairs of acrocentric chromosomes and M. arvalis has four pairs. Their distributionsslightly overlap, and they hybridize in a narrow parapatric zone that is up to 10 km wide. Most individuals from this zone show intermediate chromosomal complements and contain arvalis mitochondrial markers, therefore implying asymmetrical introgression. Number of subspecies previously recognized under M. arvalis is large, without much consensus among authorities on actual number and distributions. As a result, usefulness of formal recognition of infraspecific entities was frequently questioned. Phylogeographic studies demonstrated several allopatric evolutionary lineages: Western, Central, Italian, Eastern, and Balkan. Western lineage (western Germany, Low Countries, Switzerland, France, and Spain) is further substructured into northern and southern sublineages. Currently regarded as monotypic but in need of further assessment.

Distribution. From N Iberian Peninsula throughout most of Europe N & W to Denmark, SE Finland, and W European Russia, and SE to Macedonia and Bulgaria; also isolated populations on Is off the Atlantic coast of France (Noirmoutier, Yeu, and Oléron), Orkney Is in the N coast of Great Britain, Guernsey in the ChannelIs, several Is in the Wadden Sea off the NW coast of Germany, and Is off the W coast of Estonia.

Descriptive notes. Head-body 95-120 mm (males) and 93-120 mm (females), tail 27-37 mm (males) and 24-38 mm (females); weight 18-40 g (males) and 18-32 g (females). Sizes of Common Voles vary geographically, and some marginal populations, notably insular ones, can be significantly larger. Data for populations on Orkney Islands are: head-body 98-134 mm (males) and 97-128 mm (females), tail 28-44 mm (males) and 27-41 mm (females); weight 29-67 g (males) and 22-55 g (females). Females are, on average, smaller than males. In external and craniodental morphology, the Common Vole is very similar to the East European Vole ( M. mystacinus). Tail is ¢.33% of head-body length. Hindfoot has six plantar pads, and females have four pairs of mammary glands. Fur is soft and dense, with 5900 hairs/cm?® on posterior side of back. Dorsal side is usually buffy brown, flanks are more yellow, and belly is gray, washed white or buff. Wide range of color variants has been reported, including albino, black, chinchilla, ivory, and silver. Black individuals occur sporadically on Orkney. Adult skull shows expanded zygomatic arches, narrow interorbital constriction, and prominentsagittal crest. Dental formulaisI 1/1, C0/0,P 0/0, M 3/3 = 16. Upperincisors are orthodont. Enamel pattern is indistinguishable from that of the East European Vole.

Habitat. Well-drained open landscapes, typically grasslands and pastures within forest zone and alpine meadows above tree line up to elevations of ¢.3000 m. This Common Vole can be abundantin grain and alfalfa fields and is regarded as an agricultural pest. It is occasionally found in forest plantations with herbaceous or grassy understory, marshes, bogs, and moorland. In short-grass habitat, it is exposed to avian predation, and therefore it seeks protection by digging underground galleries.

Food and Feeding. Diet consists of leaves, stems, and roots of various herbs and grasses. More than 80 plants have been identified in its diet. Preferred dicotyledons are daisies (Asteracea) and legumes ( Fabaceae). Depending on season, they also eat fungi, lichens, berries, nuts, seeds, bulbs, tubers, and bark. In alpine meadows, Common Voles eat alpine thimothy ( Phleum alpinum), alpine bluegrass ( Poa alpina), tufted hair grass ( Deschampsia cespitosa), and fescue ( Festuca), all Poaceae; woodrush ( Luzula alpinopilosa) and rush ( Juncus), both Juncaceae; buttercups ( Ranunculus montanus and R. alpestris, Ranunculaceae); alpine bistort ( Polygonum viviparum, Polygonaceae), clovers ( Trifolium pratense and 1. pallescens, Fabaceae); cinquefoil ( Potentilla, Rosaceae), unbranched lovage ( Ligusticum mutellinoides, Apiaceae); snowbed willow ( Salix herbacea) and blunt-leaved willow (S. retusa), both Salicaceae; gentian ( Gentiana, Gentianaceae), sedges ( Carex, Cyperaceae), and mountain tassel ( Soldanella pusilla, Primulaceae). Insects are not common in diets, but Common Voles can be carnivorous and prey on eggs and nestlings of ground-nesting passerines. Food is stored, and cached vegetation can weigh up to 3 kg. Daily consumption is c.3-6 g of dry matter.

Breeding. Breeding season of the Common Vole is in March-November. Ovulation is spontaneous. Gestation in the laboratory lasts 16-25 days (19-21 days in 60% of females). There is postpartum estrus, and captive females have litters monthly. In the wild, females usually have 2-3 litters/year. Numbers of embryos are 1-13/female (3-8 in 93% of females). Mean number varies among regions (e.g. 5-8 in Czech Republic and 6-3 in Lower Saxony, Germany) and months (4-4 in October and 6-8 in July). Laboratory litters are 4-2 on mainland and 2-8 on Orkney. Rate of prenatal mortality correlates positively with parity. At birth, young weigh 2-1 g and are nude, blind, and deaf. Eyes open at nine days old. Young are weaned at 12-21 days old. After leaving nests, young feed for several days with their mothers and then disperse. During lactation, which lasts ¢.15-20 days, females increase energy consumption by up to 2-5 times. Both parents spend much time grooming young in nests. Females reach sexual maturity at a mean age of 27-4 days, although precocious breeding can occur at 13-14 days of age. Increased photoperiod accelerates puberty. Common Voles usually reproduce in their second year and then die. Autumn population mainly consists of individuals born in the same year. Survivalis low, and life expectancy is 2-4 months for those born in spring compared to 7-9 months for those from autumn litters.

Activity patterns. Common Voles are active year-round and do not hibernate. Surface activity is crepuscular and diurnal, depending on season and density. In winter, they are more active during day . Conditioned captive individuals show 1-7-2-8hour cycles of resting and foraging. Most of the time, the Common Vole moves slowly with belly almost in contact with the ground. It can swim but is a poor climber and hardly prone ofjumping. Aboveground network of runways through ground vegetation connects burrows and covers the entire home range. Common Voles are rarely seen outside of runways, which make orientation easier and enable fast locomotion. Burrows are usually short (100-150 cm long and 35 cm deep) and terminate in nest chamber and caches. Nests (8=15 cm in diameter) are woven of dry grass and are 5-15 cm below the ground’s surface; they usually have 2-3 exits. In winter, nests of dry grass are built just below the snow. Stores are of two types: autumn ones that contain seeds and grains and winter ones of bulbs, tubercles, and roots.

Movements, Home range and Social organization. Common Voles are sedentary; they rarely move more than 10-20 m. Seasonal migrations or unusual movements are over longer distances (e.g. to and from arable land and after natural disasters such as flooding). Home ranges are usually 200-400 m? for females and 1200-1500 m?* for males, although much lower median values have been reported (e.g. 125 m* for males and 30 m? for females). Home ranges are larger at low densities than high densities; mean values for male Common Voles on Orkney are 836 m* at low densities and 619 m? at high densities. Breeding females defend home ranges around their burrows but tolerate strange males when they are in estrus. Males are solitary and wander across their larger home ranges from one female to another to mate. Females with juveniles live in groups in large burrows. They can share and defend a communal nest. A female territorial system changes to group home ranges in winter, and the last 2-3 litters of the season overwinter in mothers’ home ranges. In spring, young females settle around their maternal home ranges while young males disperse. They are mainly silent, rarely emitting high monosyllabic calls.

Status and Conservation. Classified as Least Concern on The IUCN Red List (together with the Altai Vole, Microtus obscurus). The Common Vole is one of the most common rodents in Europe; therefore, recent taxonomic separation of the Altai Vole from the Common Vole probably did not change its current conservation status.

Bibliography. Bauer (2001a), Briner et al. (2005), Bure$ (1997), Gorman & Reynolds (2008), Haynes et al. (2003), Lavrenchenko et al. (2009), Malygin & Yatsenko (1986), Meyer et al. (1996), Meylan (1995), Niethammer & Krapp (1982b), Prescott-Allen (1981), Tougard et al. (2013), Tkadlec & Zejda (1995).