42.

Hokkaido Red-backed Vole

Craseomys rex

French: Campagnol royal / German: Hokkaido-Graurotelmaus / Spanish: Topillo rojo de Hokkaido

Taxonomy. Clethrionomys rex Imaizumi, 1971, Kanrosen, Mt. Rishiri, Rishiri Island, Hokkaido, Japan.

Craseomys rex is in the subgenus Craseomys . In the past, it was reported as Clethrionomys stkotanensis, which is a junior synonym of Craseomys rufocanus . Until very recently, the specific name rex has been associated with generic names Clethrionomys or Mpyodes. Up to three subspecies have been recognized, but subspecific taxonomy is in need of revision. Monotypic.

Distribution. Endemic to several Pacific islands of Russian Far East and Japan: C & S Sakhalin, Hokkaido (including Rebun and Rishiri), and Kurils (Kunashir, Zelionyi, and Shikotan).

Descriptive notes. Head-body 112-149 mm, tail 44-68 mm; weight 33-76-7 g. Sexes of the Hokkaido Red-backed Vole are similarly sized. It is very similar to the Gray Redbacked Vole ( C. rufocanus) except for being on average larger and lacking contrasting rusty gray pelage. Back is brown, and flanks are less gray. Fur is short. Females have four pairs of mammary glands, two pairs of pectoral and two pairs of inguinal. Skull is robust and ridged. Enamel pattern of M? is complex, with three reentrant angles on lingual side. Molars develop roots in adults.

Habitat. Grasslands, abandoned fields, sparse bamboo stands, and mixed stands of birch ( Betula, Betulaceae) and bamboo on rocky substrate from sea level up to elevations of ¢.1900 m. The Hokkaido Red-backed Vole is sympatric with the Gray Redbacked Vole throughoutits distribution, and habitat selection reflects competitive interactions between the two closely related congeners. The Hokkaido Red-backed Vole avoids dense coniferous forests (except in high elevations on Hokkaido) and largely occupies a niche typical of species of Microtus .

Food and Feeding. The Hokkaido Red-backed Vole prefers seeds and berries but also eats insects. Barking of trees occurs in late autumn and during winter.

Breeding. The Hokkaido Red-backed Vole has 2-4 litters/season, with 4-11 young each. Litters usually have 8-9 young. Sexually maturity occurs in the year forllowing birth.

Activity patterns. Nests of Hokkaido Red-backed Voles are constructed of grasses, including bamboo. They measure 20-25 cm in diameter and have 1-3 entrances. On wet substrates, nests are located on the surface. On dry ground, burrows are simple, with a nest chamber that also serves as a cache.

Movements, Home range and Social organization. No information.

Status and Conservation. Classified as Least Concern on The IUCN Red List (as Myodes rex). Overall distribution of the Hokkaido Red-backed Vole is ¢.84,000 km?.

Bibliography. Abramson, Abramov & Baranova (2009), Krivosheev (1984), Nakata & Iwasa (2015), Shenbrot & Krasnov (2005).