41.

Gray Red-backed Vole

Craseomys rufocanus

French: Campagnol de Sundevall / German: Graurételmaus / Spanish: Topillo rojo gris

Other common names: Gray-sided Vole

Taxonomy. Hypudaeus rufocanus Sundevall, 1846, Lappmark, Sweden.

Craseomys rufocanus 1s in the subgenus Craseomys . In the past, it was referred to as Clethrionomys rufocanus or Myodes rufocanus . Majority of genetic variability is allocated in the south-eastern part of the distribution, and distinct phylogenetic lineages occupy the lower Amur region, Hokkaido and adjacent islands, and Sakhalin. Most of the distribution from Fennoscandia to Kamchatka is populated by a single lineage. Five subspecies have been recognized, but a revision is needed. Monotypic.

Distribution. Fennoscandia in N Europe E through Siberia to Pacific coast and Kamchatka Peninsula, S as far as Southern Ural, upper reaches of Ob River, N China (Xinjang, Inner Mongolia [= Nei Mongol], Heilongjiang,Jilin, and Liaoning), Mongolia, N Korea, and Pacific Is of Sakhalin, Hokkaido, Kurils, Shantar, and small Is around Hokkaido and in the Sea of Okhotsk.

Descriptive notes. Head-body 100-142 mm, tail 27-63 mm; weight 27-52 g. The Gray Red-backed Vole has large ears and eyes and relatively short tail of ¢.40% of head-body length. Females have two pairs of pectoral and two pairs of inguinal mammary glands. Fur is shaggy in summer and long and soft in winter. Coat color is characteristic, with narrow reddish dorsal mantle that is sharply defined against gray sides. Belly is gray, shaded buff and dulled by slate underfur. Tail is sharply bicolored, brownish above and dirty white below. There is considerable seasonal and geographical variation in color. Back of summer pelage is more reddish, and flanks are more buff in the east; island populations on Sakhalin and Hokkaido show less contrast between back and flanks. Juveniles are grayish, with back scarcely tinted red. Skull is massive and angular, with square-like braincase and moderately expanded zygomatic arches. Appearance of molar roots is postponed compared with the Bank Vole ( Myodes glareolus). M” is simple, with two reentrant angles on lingual side—a pattern that is remarkably stable.

Habitat. Coniferous forests (taiga) and rocky places. The Gray Red-backed Vole is a generalist and can also occupy meadows, scrubland, forest plantations, mixed forests, and high-elevation tundra up to ¢.3000 m. Presence in meadows is frequently due to absence of competing species of Microtus . In forests, the Gray Red-backed Vole prefers mesic oligotrophic sites with dense ground vegetation of dwarf shrubs, particularly of berries ( Vaccinium, Ericaceae).

Food and Feeding. The Gray Red-backed Vole eats a wide variety of food but is mainly herbivorous. It is more folivorous than sympatric species of Myodes . Green plants usually form more than 50% of diets. During summer, they mainly eat forbs and grasses; staple winter diets consist of leaves and lichens. Bamboo shoots are important in winter diets on Hokkaido Island. Buds are eaten in spring; mushrooms, acorns, and berries in autumn; and tree bark in winter. Insects are rare in diets. In Fennoscandia, the Gray Red-backed Vole specialized on bilberry ( Vaccinium myrtilus), with stems forming most of winter diets and leaves dominating summer diets. At low temperatures, food intake increases, and internal organs (heart, kidneys, small intestine) can become hypertrophied.

Breeding. The Gray Red-backed Vole is promiscuous; litters are sired by multiple males. Proportion of multiple paternity correlates positively with local density of males. At high density, dominant male is unable to deter subordinates from access to mates. Breeding period lasts 5-5-5 months from spring (March-April) to autumn (October— November); it is shorter at northern latitudes and high elevations. At 69° N in Finland, breeding season lasts 90-150 days. Depending on length, breeding season of the Gray Red-backed Vole has two peaks (spring and autumn) or a single peak in mid-summer. Pregnancy rate is higher in spring when postpartum estrus is also frequent. Winter reproduction was reported but probably has no major effect on population size. Reproduction period is shorter during high density and frequently has a single peak. Breeding females have 2—4 litters/breeding season, fewer at high densities. Individuals from spring litters normally mature in summer and have 1-2 litters in the same year. Maturity is postponed until the next season in young born in late summer and autumn. Gestation under captive conditions lasts 18-19 days and can extend to 20 days in the wild. Litters have 1-13 young, most frequently 3-8. Overwintered females have largerlitters (mean number of embryos in northern European Russia is 6-5) than young ones (mean of 5-2). Neonates are naked, are blind, and weigh 1-9-2-1 g. Eyes open at day 12-13. Young are weaned at 17 days old and attain sexual maturity at 30 days at weights of c.16 g for females and c.24 g for males. Life expectancy is 16 months in the wild. Individuals born in spring grow faster than those from latter litters. At the end of reproductive season, a population consists mainly of individuals born in the same year and can be up to ten-fold larger than in spring.

Activity patterns. Activity of the Gray Red-backed Vole is polyphasic and mainly nocturnal, butit is mainly crepuscular in summer. Nests are 15-20 cm in diameter and are constructed from leaves of trees and shrubs and grass steams. They are usually 10-25 cm deep and have two entrances. Caches are located close to entrances. In damp habitats, nests made of grass are on the ground’s surface, concealed in dense vegetation. Winter nests are also constructed on the surface under snow.

Movements, Home range and Social organization. Home ranges of breeding male Gray Red-backed Voles are 400-1300 m? female home ranges are 200-600 m*. A single male covers breeding home ranges of several females. Ranges of breeding males overlap, but females have exclusive ranges and are territorial. Homeless females or those with overlapping ranges are inhibited in their sexual maturation. Territoriality is relaxed outside the breeding season when individuals share communal nests and spend winterin kin-based groups. Females are philopatric, and dispersal is male-biased. Average dispersal distance is 35-2 m for females and 65-9 m for males.

Status and Conservation. Classified as Least Concerned on The IUCN Red List (as Myodes rufocanus). Overall distribution of the Gray Red-backed Vole is ¢.13,000,000 km?.

Bibliography. Abramson et al. (2012), Anufriev & Bobrecov (1994), Gromov & Erbajeva (1995), Kaneko et al. (1998), Krivosheev (1984), Nakata et al. (2015), Shenbrot & Krasnov (2005).