57.

Strelzov’s Mountain Vole

Alticola strelzouvi

French: Campagnol de Streltzov / German: Flachkopf-Gebirgswiihimaus / Spanish: Topillo de montana de Strelzow

Other common names: Flat-headed Mountain Vole, Flat-headed Vole

Taxonomy. Microtus strelzovi Kastschenko, 1900, near Lake Teniga, Altai Mountains, Altai Krai, Russia.

In the past, A. strelzovi has been consist ently classified as the only member of the subgenus Platycranius. Phylogenetic reconstructions based on molecular markers showed that despite its unique cranial morphology, A. strelzovi nests among other mountain voles occupying Central Asia. At c.80° E, A. strelzouvi 1s subdivided into two phylogenetic lineages. Two subspecies recognized.

Subspecies and Distribution.

A.s.strelzoviKastschenko,1900—AltaiMtsinRussiaandNWMongoliaextendingintoSTuva.

A. s. desertorum Kastschenko, 1901 — E Kazakhstan, NW China (Xinjiang), and W Mongolia; possibly also in Russia S of Gorno-Altaysk.

Descriptive notes. Head-body 101-135 mm,tail 33-47 mm; weight 34-58 g. Females are on average heavier and have slightly longer head—body length than males. Strelzow’s Mountain Vole has large semi-circular ears and moderately long tail ¢.33% of head—body length, which gets longer with elevation. Pelage is long (c.13 mm) and dense (138 hairs/ mm?), grayish brown dorsally and whitish gray below. Young individuals are duller and start molting when they weigh 20-27 g. Shoulders and area around ears are frequently buff. Tail is white, shaded cream in some individuals, densely covered by stiff hairs, terminating into distinct pencil. Feet are whitish. Females have four pairs of nipples. Skull is extremely flat and further depressed in interorbital region. Viewed from dorsalside, interorbital region is flat and wide, and zygomatic arches are bowed. Mandible is elongated, relatively lower than in other species of Alticola . Molars show no peculiarities other than those seen in other species of Alticola . M” has three inner salient angles.

Habitat. Accumulations of rocks, isolated boulders, and talus slopes in steppes and semi-deserts at elevations of 400-3000 m. Strelzow’s Mountain Vole seeks shelter in cracks and fissures, frequently on steep slopes (5-70°). Deep horizontal fissures are preferred because vertical cracks shelter less effectively against rain that can decay caches. High humidity is limiting northern distribution, and frequent droughts define southern distribution.

Food and Feeding. Strelzow’s Mountain Vole predominantly eats green plants and seeds. Lichens can be important in diet in late winter and early spring. Diet is diverse, with ¢.200 species known to be eaten. Most commonly found in caches are various species of sagebrush ( Artemisia) and centaury ( Centaurea), both Asteraceae; field pennycress ( Thlaspi arvense, Brassicaceae); savin juniper ( Juniperus sabina, Cupressaceae); Siberian chives ( Allium nutans) and snowdrop onion ( Allium galanthum), both Amaryllidaceae; eastern pasqueflower ( Pulsatilla patens, Ranunculaceae); stonecrops ( Sedum) and dunce caps ( Orostachys spinosa), both Crassulaceae; currant (Ribes saxatile, Crossulariaceae); double flowering meadowsweet ( Filipendula hexapetala), cinquefoils ( Potentilla bifurca), prickly rose ( Rosa acicularis), bibernal rose (R. spinosissima), and various species of spirea ( Spiraea), all Rosaceae; yellow lucerne ( Medicago falcata) and bramble vetch ( Vicia tenuifolia), both Fabaceae; milkwort ( Polygala hybrida, Polygalaceae); woolly speedwell ( Veronica incana, Plantaginaceae); bedstraw (Gallium, Rubiaceae); and honeysuckle ( Lonicera microphylla, Caprifoliaceae). Usually 5-10 plant species make up the majority of a cache. Strelzow’s Mountain Voles start gathering plants for caches immediately in spring (e.g. early May in Ereymentau District Mountains, northern Kazakhstan) and continue into autumn. Between 40 and 68 species of plants have been identified in caches, depending on region. In summer, most dry plant material consist of leaves (50-60%), followed by stems (20-30%) and flowers and seeds (c.15%). Plants are gathered into small heaps that can be up to 40-50 m from a nest. There can be up to 43 heaps/m?. In Khakassia and Tuva, southern Russia, they collect plants up to 80-100 m from the nest in summer and 150-200 m in autumn. Dry plants are cached in rocky caverns that can be large; e.g. in Kazakhstan, a cavern measuring 200 x 100 x 50 cm contained 8 kg of plant matter. It is estimated that a colony has 3.5-6 kg (mean 4-5 kg) of cached plants. Caches contain also dry insects, mummified reptiles and small mammals, and bones of large mammals, all with clear signs of gnawing. Fungi are locally important, making up ¢.50% of caches. Caches can rot in rainy weather or be destroyed by insects. While feeding on caches, Strelzow’s Mountain Voles always stay under shelter.

Breeding. Female Strelzow’s Mountain Voles deliver two litters with 2-11 young annually. Mean numbers of embryos per female are 5-9-7-3 and vary among localities. Firstlitter is larger (4-9 young, mean 7-1) than second litter (4-7, 5-1). Resorption of embryos was not observed in Kazakhstan. Pregnant females can share the same nest.

Activity patterns. Strelzow’s Mountain Vole is active day and night and throughout the year. It avoids leaving the nest in heavy wind and rain. Nest is constructed of grass, with diameters of 10-25 cm, and is hidden under a stone or in a fissure. These places buffer against climatic extremes of the surrounding environment; e.g. when daily temperature outside the nest is 18°C,it is only 4°C in the shelter. Horizontal rocky shelters can be further protected against adverse environmental conditions by a stony wall constructed by its occupants. Strelzow’s Mountain Voles use incisors to carry 1-36 g stones, corresponding to as much as one-third of their body weights. Mean weights of stones are 6-6-12-5 g, depending on the wall. Stones are mixed with excrements and urine to consolidate materials. Walls are usually 3-4 m long, ¢.30 cm high, and 30 cm wide at the base, but much larger walls have been reported measuring up 8-10 m long, I m high, and up to 1 m wide at their bases.

Movements, Home range and Social organization. Strelzow’s Mountain Vole moves around by walking, running, and jumping. It can jump a distance of 50 cm and up to 40 cm high. It is agile climber over steep (60-70) rocks and on plants. It is able to climb up a stalk not more than 6-7 mm wide and can climb trees up to 10 m high. It is also good swimmer and was observed swimming across a river 10m wide. Distances between nest chamber and feeding ground can be 100-170 m. Strelzow’s Mountain Voles live in groups and share one or more communal shelters. Shelters vary in size. Normally, there is enough of room for nest and cache, but sometimes shelters are so small they can hardly accommodate nests. Two shelters of the same group can be up to 25 m apart. Family groups are dispersed due to the mosaic nature of rocky environments. In Ereymentau and Chingiz-Tau Mountains (Kazakhstan), family groups can be up to 150-800 m apart, and in Kazakh highlands, there were 1-12 groups/ha. In Khakassia and Tuva, groups occupied 40-450 m*. Groups have 3-6 individuals (mean 4-2) in spring and 5-11 individuals (8-1) in summer. Tails play roles in communication among individuals. While moving around,tails are elevated at angles of 25-40". Tail flips are visible from various distances, even in dark underground situations.

Status and Conservation. Classified as Least Concern on The IUCN Red List (as A. strelzown).

Bibliography. Chertilina et al. (2012), Gromov & Erbajeva (1995), Shenbrot & Krasnov (2005), Sludskiy et al. (1978), Yudin et al. (1979).