53.

Silver Mountain Vole

Alticola argentatus

French: Campagnol argenté / German: Silberfell-Gebirgswiihimaus / Spanish: Topillo de montana plateado

Taxonomy. Arvicola argentata [sic] Severtzov, 1879, Alichur, Murgab District, Pamir Mountains, Tajikistan.

In the past, A. argentatus was synonymized with A. roylei . It is paraphyletic with respect to A. albicauda and is most probably an artificial assemblage. Some authors regard blanfordi as a distinct species. Eight subspecies recognized.

Subspecies and Distribution.

A.a.argentatusSevertzov,1879—PamirMtsinEUzbekistan,Tajikistan,WChina,andNAfghanistan.

A.a.blanfordiScully,1880—KashmirinNPakistanandNWIndia.

A.a.parvidensSchlitter&Setzer,1973—KhyberPakhtunkhwaProvinceinNPakistan.

A.a.phasmaG.S.Miller,1912—EKarakoruminSWChina(Xizang).

A.a.severtzoviTichomirov&Korchagin,1889—TianShanMtsinKazakhstanandKyrgyzstan.

A.a.subluteusThomas,1914—TianShanMtsinEKazakhstan,Kyrgyzstan,andNWChina(Xinjiang).

A.a.tarasoviRossolimo&Pavlinov,1992—TianShanMtsinKyrgyzstanandNWChina(Xinjiang).

A. a. worthingtoni G. S. Miller, 1906 — Basin of Tekes, Tian Shan Mts, Xinjiang, NW China.

Subspecies range limits poorly resolved and not all populations have subspecific names, including some mountain ranges in S & E Kazkhstan, E Uzbekistan, and NW China (Karatau, Nuratau, Dzungarian Alatau, Tarbagatai, and Saur Mts).

Descriptive notes. Head-body 87-119 mm, tail 36-64 mm; weight 20-8-54-6 g. The Silver Mountain Vole is highly variable in all aspects of its morphology. Size is small to medium, and tail is moderately long, accounting for 32-51% of head-body length. Tail is sparsely haired, lightly penciled, and uniformly whitish or bicolored. Females have four pairs of nipples. Among Silver Mountain Voles from the Osh region in southwestern Kyrgyzstan, ¢.28% of individuals had cheek pouches (length 35-9 mm, width 4-9-14-7 mm) that extended back to shoulders; individuals from the rest of Kyrgyzstan and Kazakhstan lacked such pouches. Vibrissae are up to 37 mm long. Fur is soft (length up to 10 mm) and variable in color, sandy brown to brown above and pure white to light gray on belly. Demarcation along flanks is faint or distinct. Feet are white. Juveniles are dull gray and start molting into adult pelage at weights of 18-20 g and finish at 26-27 g. Color differences may relate to aridity. Skull is lightly built, with long braincase and short orbit. Molars are small and light, hypsodont, and rootless; they have long drawn-out appearance of grinding surfaces, thin enamel, squeezed dental fields, and wide reentrant folds with little cement.

Habitat. Rocky areas, talus slopes, and accumulations of boulders at elevations of 500-4300 m. Silver Mountain Voles avoid dense vegetation, and southern exposures are preferred.

Food and Feeding. Silver Mountain Voles eat primarily roots and seeds in winter and green plants for the rest of the year. Invertebrates, flowers, fruits, bark, mosses, and lichens form smaller portions of diets. In Kazakhstan, the following plants are most important: knotweed ( Polygonum, Polygonaceae); locoweeds ( Oxytropis), white clover ( Trifolium repens), alpine milkvetch ( Astragalus alpinus), bramble vetch ( Vicia tenuifolia), and false lupin ( Thermopsis), all Fabaceae; lousewort ( Pedicularis, Orobanchaceae); spurge ( Euphorbia, Euphorbiaceae); white nettle ( Lamium album, LLamiaceae); cinquefoils ( Potentilla, Rosaceae); cranesbills ( Geranium, Geraniaceae); wild thyme ( Thymus serpyllum, Lamiaceae) and edelweiss ( Leontopodium alpinum, Asteraceae). When vegetation starts growing, plants are collected, dried, and cached for winter. Silver Mountain Voles regularly turn over these piles to expedite drying. Caches consist of up to 29-40 different species of plants, depending on location. They weight 2-42 g, rarely up to 700 g, but caches of 270-1500 g were recorded on Trans-Ili Alatau (northern Tian Shan) in October. In autumn, dried plants are stored in well ventilated fissures and under stones. Various items found locally (e.g. bones and excrement) are mixed with caches and overmarked with urine and feces by owners. They do not cache in mesic habitats where plants remain lush throughout the growing season and where they are covered by snow. Seeds are transported in cheek pouches that can contain 0-2-5 g of food.

Breeding. Pregnant Silver Mountain Voles have been recorded in February-December, but main breeding season is in March—October and May-September at high elevations. Winter reproduction has been recorded at lower elevations. Females have 2-3 litters/year, and numbers of embryos per female is 2-9. Average numbers of embryos are higher at mid-elevations in forest and subalpine zones (4-8 embryos/female) and lower in lowlands (3-5) and alpine zone (3-8). At high elevations of Kazakhstan where breeding season is curtailed to 2-5-3 months, females have an average of 6 embryos, but 6-8 embryos/female were reported from Kyrgyzstan. Winter litters are small, with averages of 3-3-8 embryos/female. Young females become sexually mature and have 1-2 litters during theirfirst year oflife.

Activity patterns. Silver Mountain Voles are diurnal, with peaks in activity at 05:00-07:00 h and 18:00-20:00 h. They are active throughout the year. In winter, they stay under snow, only rarely emerging on the surface. They move around by walking and running, and they are good climbers, skillfully moving also across steep and hanging rocky walls. They occasionally climb in bushes. They do not dig burrows but seek shelter in fissures and cracks. They only exceptionally use burrows under roots of trees and shrubs around rocky outcrops. Rocky shelters can be protected against adverse environmental conditions by walls constructed of stones, excrement, and urine. A shelter found in Kazakhstan was 1 m long and 10-18 cm high. Spherical nests are constructed from plant debris and are divided into a resting part and brooding chamber. Nest chamber is lined with grass. Nests are 13-40 cm long, 8-44 cm width, and 11-60 cm deep.

Movements, Home range and Social organization. Silver Mountain Voles can move up to 500 m away from their nests. They live in kin groups of 7-9 individuals. Feces are deposited in certain places.

Status and Conservation. Classified as Least Concern on The IUCN Red List.

Bibliography. Davydov (1988), Gromov & Erbajeva (1995), Litvinov et al. (2015), Nadachowski & Mead (1999), Rossolimo & Pavlinov (1992), Shenbrot & Krasnov (2005), Sludskiy et al. (1978), Tarasovskaya (1993).