High-arctic lemmings, Dicrostonyx groenlandicus. II. Demography

Abstract

Captures of Dicrostonyx groenlandicus on northeastern Devon Island peaked in 1969 and 1973, were higher than expected in 1971, and were minimal (< 5 per 1000 trap-nights) in 1970 and 1972. Captures declined from July to August in at least five of seven summers and may have declined in a 6th year (1973). No change was detected in 1972. Body size was maximal in 1973 for mature and immature males and females and for all pelage (=age?) classes. Sexual maturity was delayed, at least in males, in 1973. Wintering females conceive under the snow in May and the litter is weaned at the normal time of snowmelt. Two other summer cohorts are produced by surviving old females and early maturing females of the first litters. None of the late summer cohort matures before the onset of winter. No female examined bore more than two summer litters. Mean summer litter size was 5.7 with no significant variation between years. Mean sex ratio was 50.3% male. It is suggested that density-related effects ought to occur in winter, rather than summer, but evidence on this point is equivocal. Arctic adaptations of D. groenlandicus are discussed.

Lemming winter habitat choice: a snow-fencing experiment

“…Regarding the spatial dimension of winter habitat, our experimental results strongly support and amplify the observations from past field studies that lemmings tend to place their winter nests in areas of deepest winter snow, usually areas associated with topographic breaks providing lee slopes for deposition of wind-blown snow (Fuller et al 1975a;Reid and Krebs 1996;Duchesne et al 2011b). Tussock or hummocky vegetation and heaths with prostrate shrubs are typical arctic lemming habitats.…”

“…All species live in insulative burrows in the ground or in vegetation (e.g., Eriophorum tussocks) as long as access is not blocked by ice. Under a cover of snow, they frequently build nests of sedge, grass and other vegetation at ground level or slightly up in the snow column, and these nests provide essential insulation against below-freezing temperatures for resting individuals (MacLean et al 1974;Fuller et al 1975a;Casey 1981). Remaining active all winter, these rodents can reproduce under the snow with litters raised in winter nests (Krebs 1964;Fuller et al 1975b;Krebs et al 1995;Duchesne et al 2011a).…”

“…This insulation increases with snow depth and decreases with the square of density (Pomeroy and Brun 2001), so small rodents should experience a warmer sub-nivean thermal regime under deeper snow and snow that is relatively uncompacted by wind re-distribution and melting. Many lemming researchers have noted an association of lemming and vole winter nests with areas of greatest winter snow accumulation, which on the tundra tend to be in the lee of topographic breaks providing shelter for the deposition of wind-blown snow in drifts (Fuller et al 1975a;Reid and Krebs 1996). Duchesne et al (2011b) investigated this relationship on Bylot Island and found that the probability of occurrence of brown and collared lemming winter nests increased with snow depth to about 60 cm and was fairly constant at depths from 60 to 120 cm.…”

A contrasted pattern of chromosome evolution in two genera of lemmings, Lemmus and Dicrostonyx (Mammalia, Rodentia)

“…Secondly, Lemmus and Dicrostonyx exhibit an identical population cycle. The cycle has a rather steady period (3-4 years) and comprises a phase of low density, a phase of gradual increase and a peak of abundance (Fuller et al, 1975;Chernyavsky, 1978). Strong inbreeding within microdemes seems inevitable, especially at low density and increase phases (Maynard Smith & Stenseth, 1978;.…”

Alteration of testicular response to long photoperiod by transient exposure to short photoperiod in collared lemmings (Dicrostonyx groenlandicus)

“…SD-6 and SD-10 did not differ from each other (P= 0.66 (Chapin et al, 1975). Also, the melting of snow during June floods the lemmings' habitat (Fuller et al, 1975) and interrupts breeding (Banfield, 1974).…”