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Montane Water Vole

Arvicola monticola

French: Campagnol monticole / German: Bergschermaus / Spanish: Rata de agua de montana

Taxonomy. Arvicola monticola de Sélys-Longchamps, 1838, Saint-Bertrand-de-Comminges, Hautes-Pyrénées, France.

Independent taxonomic status of fossorial water voles in Switzerland was demonstrated in late 1990s based on molecular markers. Swiss water voles were subsequently merged with fossorial water voles from various mountainous parts of Europe, including the Carpathian Mountains, and taxonomically recognized as A. scherman. This name, however, is a synonym of A. amphibius . Phylogenetic reconstructions showed that fossorial water voles belong to two distinct species and one of these is monticola . Subspecific taxonomy requires reassessment.

Distribution. Cantabrian ranges from Los Ancares and Sierra Segundera in NW Spain and Montesinho Natural Park in extreme NE Portugal, E to Pyrenees (France, Spain, and Andorra), and Alps (Switzerland and France); range limits poorly resolved.

Descriptive notes. Head—body 132-175 mm,tail 54-80 mm; weight 55-150 g. Only a fossorial morphotype of the Montane Water Vole is known. It is small, with tail 42-50% of head-body length. Fur is soft, yellowish brown to ocherous buff dorsally, faintly darkened on head but shaded buff along flanks. Belly is whitish gray, and tail is graybrown. Color varies seasonally and between regions. In Swiss Jura Mountains, ¢.4% of individuals are partial albinos. Skull is small and deep, with widely bowed zygomatic arches, shallow rostrum, long diastema, inclined occiput, and low sagittal crest. Mandible is surprisingly slender for fossorial species. Incisors are proodont and conspicuously protruding from mouth.

Habitat. Meadows on firm soil from close to sea level up to elevations of ¢.2000 m.

Food and Feeding. The Montane Water Vole eats bulbs, roots, tubers, and green plants such as common dandelion ( Taraxacum officinale, Asteraceae) and spring crocus (Crocus albiflorus, Iridaceae). It also eats bark. The Montane Water Vole feeds mainly inside galleries. Food is cached in stores of up to 1 kg of vegetative matter, mainly bulbs, rhizomes, and fleshy roots.

Breeding. In Spain, breeding season of the Montane Water Vole is from March to October—-November, exceptionally in winter. During one reproductive cycle, a female can deliver up to six litters, with a total of 31 young. Litters normally contain 2-8 young; four is the most common. Young suckle for c.2 weeks and are sexually mature at ¢.5 weeks. Gestation is 22 days, and lactation lasts 15 days. Life span is believed to be up to 24 months.

Activity patterns. Activity of Montane Water Voles is polyphasic, with six peaks during the day . Regularity of peaks is obvious in winter, less so in summer. They stay mainly inside burrows, but they also move aboveground. In winter, they are active between soil surface and snow, which provides thermal insulation and protection from predators. Extensive system of branching tunnels with multiple entrances and several chambers is excavated. One chamber contains a breeding nest that is woven from grass and lined with finely shredded plant material. Total lengths of tunnels are 4-8-199-3 m (mean 40-2 m). The Montane Water Vole uses proodont incisors and skull as powerful drill and shovel to loosen soil that is pushed behind body with foreand hindlimbs and later transported to the soil surface and deposited in hummocks. It is estimated that the amount of unearthed soil in the Pyrenees equals 54-124 tons/ha/year, but this could be overestimated.

Movements, Home range and Social organization. Home ranges of Montane Water Voles are 43-200 m* and do not differ between males and females. Dispersal movements are frequent, with 30% of individuals leaving their burrow at least once in their life to settle elsewhere. Distances moved are short (30-60 m). Males move more often and further than females. System of tunnels is occupied by an adult couple and their offspring from 1-2 generations. The Montane Water Vole is monogamous, but this can be disrupted at high densities when each male controls home ranges of several females. Home ranges are marked using flank glands, which are significantly larger in females than in males. Size of glands and amount of secretion increase during breeding.

Status and Conservation. Classified as Least Concern on The IUCN Red List (as A. scherman). Although distribution of the Montane Water Vole is disjunct and less than distributions of all fossorial water voles in Europe, its conservation status will probably remain unaltered. In some areas, Montane Water Voles are agricultural pests.

Bibliography. KrysStufek, Koren et al. (2015), Meylan & Saucy (1995), Saucy (1988), Taberlet et al. (1998), Ventura (2002a), Ventura & Gosalbez (1989).