Dicrostonyx Groenlandicus Research Articles

Arctic ground squirrel predation on collared lemmings

We document the first recorded evidence of predation of collared lemmings (Dicrostonyx kilangmiutak) by arctic ground squirrels (Spermophilus parryii). During an intensive study of lemming populations at Pearce Point, Northwest Territories, using livetrapping and radiotelemetry, we found one and six lemmings predated by arctic ground squirrels in 1987 and 1988, respectively. Predation involved some or all of the following: digging lemmings out of burrows, carrying them to temporary ground squirrel burrows, and partial or complete consumption. The best evidence was obtained during 1988, when a minimum of 4.5% (6/132) of radiotagged lemmings were killed by squirrels.

Observations on the ecology of arctic foxes Alopex lagopus in Eqalummiut Nunaat, West Greenland

Information on diet, home range and activity of arctic foxes Alopex lagopus was collected by radio-tracking and faecal analysis in Eqalummiut Nunaat, West Greenland during spring and summer 1984. The study aimed to investigate the feeding ecology of foxes in an area where »traditional« prey such as lemmings Dicrostonyx groenlandicus and coastal food sources are absent.
 Foxes were found to be heavily dependent on abundant caribou Rangifer tarandus carrion, and invertebrates found in the layer of soil above the permafrost. Scat analysis and behavioural observations showed that foxes were quick to modify their foraging to exploit seasonal changes in food availability, and preyed heavily on nesting birds, mainly passerines, when these became available. Mean home range size of two radio-tagged female foxes was 11.7 km2. It was thought that fox density was unusually high due to the abundance of caribou carrion as a result of the exceptionally long preceding winter.
 The incidence of food caches was investigated and it was found that most were unearthed in June, after the thaw and just before passerine prey became abundant. White-fronted goose eggs and caribou carrion were the items most frequently found at unearthed caches.
 Observations and radio-tracking revealed that foxes predominated in lowland areas, generally avoiding plateau areas above 500 m, where passerines and caribou carrion were scarce. Foxes were found 10 be 50% more numerous on the study area in 1984 than in 1979, and this was felt to be related to differences in the availability of caribou carrion. Foxes were found to be major predators of the eggs of Greenland White-fronted geese.

Normal and blocked pregnancy in the collared lemming: morphometrical and histological changes

Normal and blocked pregnancy were studied in the collared lemming, Dicrostonyx groenlandicus, in the laboratory with individuals bred from wild stock caught at Eskimo Point, N.W.T. Morphometrical changes (corpora luteal area, ovarian weight, uterine weight, fetal crown–rump lengths, spleen and adrenal weights) during normal and blocked pregnancy were documented and found to be similar to those of other microtines. Mean maximum corpora luteal area, and ovarian and uterine weights increased continuously throughout gestation, as did the fetal crown–rump lengths. Spleen and paired adrenal weights increased similarly; however, they were not significantly different when corrected for body weight. Ovulation occurred between 9 and 12 h post coitum, as evidenced by the presence of ovulated follicles with stigmata, and luteinization was observed within 24 h. No identifiable differences were observed in the histology of corpora lutea and corpora albicantia of normal and blocked females although significant differences in size occurred. Accessory luteal structures (accessory corpora lutea and luteinized follicles) were found in very high numbers in this species compared with other microtines, peaking by day 4 post coitum and declining in number and size towards the end of gestation. It is concluded that the accessory luteal structures function in a supportive role to the corpora lutea of pregnancy during the early stages of gestation but undergo atrophy towards parturition, when the corpora lutea of pregnancy reach their full size and functional capacity. The presence of large numbers of accessory luteal structures and the similarity of histology between ovarian structures in normal and blocked pregnancy makes the identification of these conditions in the field impractical at present.

Photoperiodic effects on post‐weaning growth and food consumption in the collared lemming Dicrostonyx groenlandicus

The effects of long ‘summer’ (22L:2D) and short ‘winter’ (2L:22D) photoperiod on post‐weaning growth and food consumption of the collared lemming were examined. Growth was described by Gompertz equations. After 10 weeks, lemmings maintained under short photoperiods developed white winter pelage and heavy bifid claws; body mass and estimated asymptotic mass were significantly greater than for lemmings reared under long photoperiod. Sexual dimorphism in body size was observed within treatments, males growing larger than females. There were no significant differences in the overall growth rate constant k as a result of either sex or photoperiod treatment. However, instantaneous growth rates (dW/dt) were significantly higher in ‘winter’ lemmings. Mass at weaning was a significant determinant of adult mass at 90 days.Cumulative food consumption at 90 days was not significantly different between photoperiod groups, even though ‘winter’ lemmings gained more than double the mass of their ‘summer’ counterparts over the post‐weaning period. Increased gut length observed for winter morphs may act as the physiological mechanism promoting greater gross energy efficiency.The present study suggests that the overwintering strategy of the collared lemming with respect to body mass changes and energy requirements differs considerably from that of other microtines.

Photoperiodic effects on body size and energetics of the collared lemming, Dicrostonyx groenlandicus

Resting metabolic rates of adult collared lemmings, Dicrostonyx groenlandicus, acclimated from weaning to either long, "summer" (22L:2D) or short, "winter" (2L:22D) photoperiod at 15 °C were examined as a function of ambient temperature. Winter morphs were significantly heavier than summer morphs (73.8 ± 7.7 (SD) and 54.5 ± 7.2 (SD) g, respectively). However, there were no differences in mass-specific metabolic rates between treatments at 15 and 20 °C. At low ambient temperatures (0 and −10 °C), metabolic rates of summer morphs were significantly higher than those of winter morphs, indicating a shift in the thermoneutral zone with photoperiod acclimation. There were no significant differences in core temperature between morphs at any ambient temperature. Thermal conductance of winter morphs was significantly lower (0.05 mL O2 (g∙h∙°C)−1) than that of summer morphs (0.09 mL O2 (g∙h∙°C)−1). Comparisons with other myomorph rodents do not support the contention that lemmings have unusually high metabolic rates. However, minimal thermal conductances of lemmings were much lower than expected on the basis of body size. These data suggest that although lemmings may differ in seasonal patterns of energetics from other microtines, there is little evidence to support the assertion that high rates of metabolism are characteristic of all microtines, or that observed basal rates represent a phylogenetic adaptation to cold.

Diet selection in Arctic lemmings (Lemmus sibiricus and Dicrostonyx groenlandicus): forage availability and natural diets

We describe forage availability and diets of the lemmings Lemmus sibiricus and Dicrostonyx groenlandicus at Igloolik Island, Northwest Territories. Summer and winter diets of Dicrostonyx were dominated by the evergreen shrub Dryas integrifolia and supplemented by the deciduous shrub Salix arctica. Lemmus ate mainly graminoids and some mosses in summer but the reverse in winter. In both species, winter diets were similar in different habitats. Comparison with diets of lemmings in Alaska show sufficient similarity to explain the synchrony of population fluctuations over wide geographical areas. Site-specific differences occur, however, and these are accounted for by an examination of the diet selection process in each species. These differences have important implications for the demography of lemmings at different sites.

Variations of skull-body regressions of the lemming (Dicrostonyx groenlandicus) under laboratory and field conditions

Collared lemmings, Dicrostonyx groenlandicus, maintained in the laboratory under short-day photoperiods (2 h light: 22 h dark) grew faster than their cohorts kept under long-day photoperiods (22 h light: 2 h dark). Significant differences in cranial, visceral and body components were found in both sexes. Linear regressions of skull-body parameters were compared to those of wild lemmings trapped at Eskimo Point, Northwest Territories, Canada, during three consecutive summers from 1973 to 1975. The data support the conclusion that variation in body size and skull development associated with changes in population density are, in part, due to photoperiod influences. The importance of this facultative response is discussed in relation to current theories on thermal regulation and variations in subnivial breeding success observed in this species.

Failure of strange females to cause pregnancy block in collared lemmings, Dicrostonyx groenlandicus

The effects of exposure to unfamiliar females on pregnancy success of recently mated females were examined in collared lemmings (Dicrostonyx groenlandicus). Four days after mating, females in their home cage were exposed to strange, female intruders that were either nonpregnant or 16 days pregnant. Other recently mated females were introduced to the home cage of 16-day-pregnant females. Pregnancy success of the recently mated females was not reduced in any of these treatments. In the paired encounters, there was no relationship between dominance status and pregnancy status, nor between dominance and pregnancy success. These results do not support the hypothesis that in species in which females are aggressive and readily commit infanticide, unfamiliar females should cause other females to terminate early-stage pregnancies.

Influence of photoperiod and photoperiod reversal on growth, mortality, and indicators of age of Dicrostonyx groenlandicus

After weaning, collared lemmings (Dicrostonyx groenlandicus) were exposed to 3 months of summer (S) photoperiod (18.5L:5.5D) or winter (W) photoperiod (6.5L: 17.5D) or to one of four 6-month photoperiod treatments (SS, SW, WW, or WS). Lemmings were weighed every 3 weeks, and at the end of treatment, eye lenses were weighed and 10 body and 22 skull measurements were taken. At the end of treatment, W, SW, and WW lemmings did not differ in weight, but were significantly heavier than S, SS, and WS lemmings. Animals in WS were significantly heavier than those in SS and both were significantly heavier than S lemmings. The marked contrast of the photoperiodically induced growth pattern of Dicrostonyx groenlandicus with that of other microtines may be due to a relatively larger investment in winter reproduction by collared lemmings. Lemmings that died during the experiment were significantly larger both in body weight and skull size than those that survived. Eye lens weights of S and W lemmings did not differ, but were significantly smaller than those of SS, SW, WW, and WS lemmings. Inequality of mean lens weights was evident among the 6-month treatments, but nevertheless, eye lens weight was the best univariate age criterion and performed approximately as well as linear combinations of body or skull measurements selected by stepwise discriminant analysis.

Social olfaction in male brown lemmings (Lemmus sibiricus?=?trimucronatus) and collared lemmings (Dicrostonyx groenlandicus): II. Discrimination of mated and unmated females.

When tested in a Y-maze olfactometer, male brown and collared lemmings (Lemmus sibiricus = trimucronatus and Dicrostonyx groenlandicus) preferred the odor of unmated receptive females to the odor of females with which they had just copulated. Similarly, sexually satiated males preferred the odor of an unmated receptive female to that of a strange female that had recently copulated with another male. Sexually experienced males without recent copulatory experience also demonstrated this preference, but sexually naive males did not. Sexually satiated collared lemmings preferred the odor of bedding from a novel estrous female to bedding from the female with which they had just copulated even when the bedding was collected before mating occurred. These results suggest that discrimination between prior mates and unmated females may be based on individual recognition as well as recognition of subclasses of females (i.e., mated vs. unmated, familiar vs. unfamiliar).

Social olfaction in male brown lemmings (Lemmus sibiricus?=?trimucronatus) and collared lemmings (Dicrostonyx groenlandicus): I. Discrimination of species, sex, and estrous condition.

When tested in a Y-maze olfactometer, sexually experienced and sexually naive brown and collared lemmings (Lemmus sibiricus = trimucronatus and Dicrostonyx groenlandicus) preferred the odor of conspecific females to the odor of females of another species. Both experienced and naive males also preferred the odor of conspecific females to that of conspecific males. Only sexually experienced males showed a significant preference for estrous over nonestrous conspecific females. Sexually experienced males also discriminated between estrous and nonestrous heterospecific females of a familiar (lemming) and unfamiliar (meadow vole, Microtus pennsylvanicus) species. In conjunction with the results of earlier studies of the development of species-specific olfactory preferences, these findings suggest that two olfactory cues mediate a male's attraction to receptive females: a species-specific odor that is learned during early development and a sexual attractant whose saliency is established as a result of adult experience with a receptive female.

Social olfaction in male brown lemmings (Lemmus sibiricus = trimucronatus) and collared lemmings (Dicrostonyx groenlandicus): II. Discrimination of mated and unmated females.

Social olfaction in male brown lemmings (Lemmus sibiricus = trimucronatus) and collared lemmings (Dicrostonyx groenlandicus): II. Discrimination of mated and unmated females.

Nutritional Ecology of Microtine Rodents: Food Habits of Lemmings near Barrow, Alaska

Analyses of stomach contents and feces showed striking differences in the diets of the brown lemming (Lemmus sibiricus) and the collared lemming (Dicrostonyx groenlandicus) near Barrow, Alaska. Brown lemmings ate primarily grasses, sedges, and mosses, whereas collared lemmings ate primarily willow leaves and forbs. Brown lemming diets changed markedly with season and with habitat. Monocotyledons were always the most important food items; in winter and in drier habitats mosses became a more important component of the diet (up to 40%). Among the monocotyledons, brown lemmings consistently preferred tundra grass (Dupontia fisheri), consistently avoided a sedge (Carex aquatilis), and took a relatively constant amount of cottongrass sedge (Eriophorum spp.) no matter what its availability. Differing food habits of lemmings in different habitats may have important consequences for their growth, reproductive performance, and population dynamics.

Sterility of hybrids of two subspecies of the varying lemming Dicrostonyx groenlandicus bred in captivity

The progeny of crosses between individuals of two subspecies of Dicrostonyx groenlandicus, D. g. richardsoni, and D. g. groenlandicus were sterile, although both subspecies had previously been successfully bred in captivity. This laboratory experience may be of importance in the extreme changes in population of lemmings, in their classification as subspecies, and in procedures adopted when breeding in captivity.

Spatial distribution of lemming mats in the Canadian High Arctic

Spatial distributions of lemming mats on exposed beach ridges on Bathurst and Devon islands, N. W.T., in the Canadian High Arctic were recorded by triangulation. The collared lemming Dicrostonyx groenlandicus is the only microtine in this region, which eliminates interspecific influences. In addition, vegetation is sparse, making centres of activity easy to identify. Mats were relatively permanent structures with a mean diameter of 3.88 m and an average of 13.0 burrows. The mean nearest neighbour distance ranged from 40 to 45 m and the average mat polygon area (interpreted as territory or home range) was 0.34 ha. Individual mat polygons were contiguous with an average of 5.3 other polygons and the distribution of the mats over the environment was nonrandom. The data support the conclusion that lemming mats represent core areas within lemming territories or home ranges which are distributed regularly over the environment because of social processes which influence social interaction. The data are discussed as they apply to current theories on microtine demography and population dynamics.

Vitamin D and Winter Reproduction in the Collared Lemming, Dicrostonyx Groenlandicus

Collared lemmings Dicrostonyx groenlandicus Traill were maintained and bred on vitamin D replete and deplete diets. Vitamin D deficient female lemmings had reduced fertility and their young exhibited lower post-weaning body weight and mineral content of bone than had vitamin D replete females and their young. Weaned young of D replete females maintained on vitamin D replete and deplete diets were not significantly different with respect to body weight and bone mineral content. Thus, maternal vitamin D status is more important in influencing the pattern of post-weaning growth than the presence of vitamin D in the post-weaning diet. During the arctic summer when the sun is above the horizon 24 h a day, collared lemmings have nearly equal levels of vitamin D2 and D3 in plasma. Ultraviolet radiation is required for the manufacture of vitamin D3 in mammalian skin, and vitamin D2 in plants. In the absence of solar UV during the arctic winter, lemmings are unlikely to manufacture vitamin D3 in the skin. Considering that vitamin D is needed for reproduction, it is proposed that the collared lemming must utilize dietary vitamin D2 to support winter reproduction.

The effects of cross-fostering on the behaviour of two species of North American lemmings, Dicrostonyx groenlandicus and Lemmus trimucronatus: I. Olfactory preferences

To determine the role of the maternal environment in the development of adult olfactory preferences, the young of two species of North American lemmings ( Dicrostonyx groenlandicus and Lemmus trimucronatus) were reciprocally cross-fostered shortly after birth. In-fostered (reared by foster conspecific females) and non-fostered animals served as controls. When adult, subjects were tested for olfactory preferences in a free-choice Y-maze olfactometer. When compared to controls, cross-fostered animals showed increased preference for heterospecific odour. This effect was stronger for males than for females. These results suggest that adult species-specific odour preferences are learned during the neonatal period.

The effects of cross-fostering on the behaviour of two species of North American lemmings, dicrostonyx groenlandicus and lemmus trimucronatus: II. Sexual behaviour

The role of the maternal environment in development of sexual behaviour was investigated by reciprocally cross-fostering two species of lemmings ( Dicrostonyx groenlandicus and Lemmus trimucronatus). Non-fostered and within-species-fostered animals served as controls. When adult, cross-fostered (CF) animals engaged in more contact social and sexual behaviours with the foster species than did controls. Lemmings reared by conspecific dams directed sexual behaviour exclusively toward conspecifics. Since CF animals also mated with conspecifics, cross-fostering appears to have resulted in a broadening of ‘species identity’ to include the foster species. These results suggest that neonatal learning of the species characteristics of the mother is important in the ontogeny of premating sexual isolation in these species.

Development of Pelodera strongyloides (Schneider, 1860) Schneider, 1866 (Nematoda: Rhabditidae) in culture.

Dauerlarvae of Pelodera strongyloides, recovered from two species of lemmings, Dicrostonyx groenlandicus (Traill) and Lemmus trimucronatus (Richardson) trapped at Eskimo Point, N.W.T, were cultured on agar medium with E. coli. Development from egg to adult stage was followed. Eggs hatched between 22 and 26 hours at 22 degrees C. The first moult occurred 24 to 28 hours after the eggs hatched, the second at 40 to 48 hours, the third at 60 to 64 hours and the fourth at 84 to 88 hours at 22 degrees C. Adults lived approximately 5 to 6 days and females oviposited for 2 to 3 days during this time. All stages were measured and described. The effect of temperature on development was examined. Dauerlarvae survived freezing temperatures, short periods of desiccation and prolonged periods without food.

Site Variation in Summer Foods of Arctic Fox, Prince of Wales Island, Northwest Territories

Analysis of 840 arctic fox (Alopex lagopus) feces (scats) from Prince of Wales Island, indicate that collared lemming (Dicrostonyx groenlandicus) are the most frequent food item. Caribou (Rangifer), arctic hare (Lepus arcticus) and ermine Mustela erminea) were less important. Bird remains were not prevalent in the arctic fox scats. A marked difference was found between prey items at a den site and those recovered in scats from general searches. Caribou remains were more prevalent in scats from a den site because adult foxes were scavenging nearby wolf kills. Arctic fox scats were collected on Prince of Wales Island, Northwest Territories during July and August 1977 at a den site (n=375) and on general searches (n=465) surrounding the den. The Russell River den site (73 41' N, 97 41' W) is situated 100 m from an unnamed river, approximately 5.0 km from the northeast coast of the island. The den site is a low ( area in the northeastern region of the island between Bellot Cliff (73 32' N, 97 41' W) and Back Bay. These areas completely surround the den site and were an adequate scat sample for other arctic foxes travelling the general vicinity of the den site. All scats were collected separately and labelled with location. Winter scats were easily discerned from summer scats by their leeched appearance and by the apparent age of the scat deposition site. Only scats considered to be from the summer of 1977 were used in the analysis. Adult and whelp scats were separated following the criteria presented by Speller (1972). On general searches, scats were collected at a distance from the den to avoid overlap between den scats and those found elsewhere. Analysis of the scats was done on the basis of the microstructure of the hair or feathers recovered. After the scats were washed through 2 sieves (mesh size 75 and 200pm), the hair remains were mounted on acetate strips and examined microscopically (Williamson, 1951). A reference collection of known hair samples of all possible prey species available to arctic fox on Prince of Wales was used to identify hair. Feather remains were identified to taxonomic order after the methods outlined by Day (1966). All species identified from the scats were listed and these data were analysed by frequency of occurrence of items in the total numbers of scats. A Chi-square test of independence was used to find the significance of the variation in food items from each site.