103.

Sikkim Mountain Vole

Neodon sikimensis

French: Campagnol du Sikkim / German: Sikkim-Felswihimaus / Spanish: Topillo de montana de Sikkim

Other common names: Sikkim Vole

Taxonomy. Neodon sikimensis Horsfield, 1851, Sikkim, India.

Neodon sikimensis was formerly placed in Pitymys by J. R. Ellerman and T. C. S. Morrison-Scott in 1951 or in Microtus by Ellerman in 1961, and it was sometimes united with N. irene . According to G. G. Musser and M. D. Carleton in 2005 and Liu Shaoying and colleagues in 2012, the two species can be separated by morphology and genetics. There is much debate about author and date of type description according to Y. Kaneko and C. Smeenk in 1996. This needsclarification. Although currently regarded as monotypic, the population north of the Himalayas may be a distinct, still unnamed species.

Distribution. Disjunct distribution in E Himalayas from C & E Nepal through Sikkim and extreme N West Bengal (NE India) to Bhutan and S Tibetan Plateau (S China).

Descriptive notes. Head-body 97-121 mm, tail 30-52 mm, ear 11-16 mm, hindfoot 17-22 mm; weight 27-49 g. The Sikkim Mountain Vole is dark brown dorsally and dark gray on underparts, and it has ocher-brown stripe between upperand underparts. Surfaces of forelimbs and hindlimbs are brownish white. Tail is ¢.39% of head-body length, bicolored, brown above, and white below. Females have six mammae (two pectoral and four abdominal) according to U. F. Gruber in 1969, but Neodon was noted to have eight mammae by D. P. Lunde in 2008. The Sikkim Mountain Vole is very similar to Irene Mountain Vole (N. irene) but distinguished by teeth and penis morphology, longer tail, larger body, and greater, broader skull. Skull has distinct temporal ridges. M, has three closed triangles. Karyotype is 2n = 48 and FN = 56 (Nepal).

Habitat. Alpine meadows and dense vegetation at edges of coniferous and Rhododendron (Ericaceae) forest at elevations of 2100-4000 m. The Sikkim Mountain Vole lives under rocks, bushes, or leaf litter. It prefers open dry areas to forest and never uses agricultural land.

Food and Feeding. Sikkim Mountain Voles eat green vegetation (herbs and mosses) and seeds to a lesser extent.

Breeding. Sikkim Mountain Voles breed in hollows of decayed trees or among roots, making nests of soft moss and grass. Females were reported with 2-4 embryos. In Nepal, 2-3 young/female were found in June.

Activity patterns. Sikkim Mountain Voles are nocturnal and diurnal, mostly active about noon and late afternoon. They are typically found in tunnels, rarely above the ground layer. They do not burrow and never dig “mole-hills.”

Movements, Home range and Social organization. Sikkim Mountain Voles live in groups up to 20 individuals.

Status and Conservation. Classified as Least Concern on The IUCN Red List. The Sikkim Mountain Vole occurs in several protected areas such as Langtang National Park. [tis threatened by loss of suitable habitat, invasive species, and predation by domestic dogs and cats.

Bibliography. Abe (1971), Agrawal (2000), Ellerman (1961), Ellerman & Morrison-Scott (1951), Gruber (1969), Kaneko & Smeenk (1996), Liu Shaoying, Sun Zhiyu et al. (2012), Lunde (2008), Mekada et al. (2002), Molur (2016d), Musser & Carleton (2005).