38.

Richardson’s Collared Lemming

Dicrostonyx richardsoni

French: Lemming de Richardson / German: Richardson-Halsbandlemming / Spanish: Lemming de collar de Richardson

Other common names: Richardson's Hoofed Lemming, Richardson's Varying Lemming

Taxonomy. Dicrostonyx richardson: Merriam, 1900, Fort Churchill, Manitoba, Canada.

Dicrostonyx richardsoni was formerly recognized as a subspecies of D. groenlandicus, but karyology and breeding studies have led to recognition of six species ( groenlandicus, hudsonius, nelsoni, nunatakensis, richardsoni, and unalascensis) of Dicrostonyx in North America. Additional systematic work is needed to fully understand species limits. Monotypic.

Distribution. SE Northwest Territories to NE Manitoba, Canada; limited to N by the Nearctic Collared Lemming ( D. groenlandicus), to W & S by forests, and to E by Hudson Bay.

Descriptive notes. Head—body 106-135 mm, tail 9-15 mm; weight 35-90 g. Richardson’s Collared Lemmings are stocky, have short limbs and tail, and have small eyes. Their seasonally dimorphic pelage is long and white in winter and shorter and reddish to grayish brown in summer. In winter, front feet have bifurcated digging claws. Belly is reddish to grayish, and there is usually a reddish chest band or collar.

Habitat. Open, dry tundra. Richardson’s Collared Lemmings are seldom seen in wooded or wet, marshy areas. They burrow in a variety of soils, preferring sandy or rocky substrates, and use burrows to rest or escape predation.

Food and Feeding. Richardson’s Collared Lemming eats green plants, flowers, berries, buds, roots, and willow ( Salix, Salicaceae) bark.

Breeding. Richardson’s Collared Lemmings can breed year-round, although breeding in autumn and winter is not common except during population increases, which can occur rapidly. Gestation has been reported to average 20-21 days. Litters have 1-8 young (average c.4). A captive held pair had 17 litters in rapid succession. Population fluctuations are well-known and estimated to take place every 2-8-4 years in studies near Churchill, Canada.

Activity patterns. Richardson’s Collared Lemmings can actively feed day or night, although there is less activity between midnight and 06:00 h in summer. They can remain active throughout the year.

Movements, Home range and Social organization. Polygynous male Richardson’s Collared Lemmings are non-territorial and have much larger home ranges than territorial females. Females raise litters near the outside border of their home ranges.

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

Bibliography. Bradley, Ammerman et al. (2014), Cassola (20160), Engstrom et al. (1993), Fedorov & Goropashnaya (1999), Musser & Carleton (2005), Rausch (1977), Rausch & Rausch (1972), Stenseth & Ims (1993), Wilson & Ruff (1999).