Snow lemmings are small rodents inhabiting the Arctic tundra, persisting in one of the planet’s most extreme environments. The collared lemming (Dicrostonyx genus) is known for its year-round activity. These small mammals survive prolonged cold and extensive snow cover, demonstrating remarkable adaptation to challenging climates.
Remarkable Adaptations for Arctic Life
Snow lemmings possess distinct adaptations for harsh Arctic winters. The collared lemming, for instance, exhibits a seasonal coat change, molting from grayish or brownish summer fur to a pure white winter coat. This transformation provides camouflage against the snowy landscape, helping them evade predators like snowy owls and Arctic foxes. The coat also offers enhanced insulation against extreme cold.
Beyond their fur, lemmings develop specialized digging claws on their front feet during winter. These enlarged claws, often called “snow shovels,” enable them to efficiently tunnel through dense snow and ice. This modification allows them to access food and create insulated pathways beneath the snowpack, supporting their survival and activity without hibernation. This adaptation is exclusive to the Dicrostonyx genus among rodents.
Arctic Habitat and Daily Life
Snow lemmings primarily inhabit the treeless Arctic tundra, a landscape characterized by permafrost and open grasslands. They are herbivorous, consuming various plant matter. Their diet includes tender grass shoots, herbs, sedges, mosses, and lichens, shifting to frozen green plants, moss shoots, bark, willow twigs, and dwarf birch during winter.
Snow lemmings construct extensive tunnel systems beneath the snow. These subnivean tunnels provide insulation from extreme cold, with temperatures within nests typically warmer than the outside air, averaging around -15.8°C compared to ambient temperatures of -23.4°C. These networks also offer protection from predators and facilitate year-round foraging beneath the snowpack. Lemmings spend approximately six hours daily foraging among mosses and lichens.
Population Fluctuations and Common Misconceptions
Snow lemming populations exhibit fluctuations, often following a three-to-five-year cycle where numbers increase before declining. These “boom and bust” cycles are a natural phenomenon in Arctic ecosystems. During high population density, lemmings may undertake mass movements, which are actually dispersals in search of new food sources or territory.
This dispersal behavior has led to the widespread misconception of “mass suicide.” This myth was popularized by a 1958 documentary that falsely depicted lemmings intentionally leaping off cliffs. In reality, when lemmings encounter bodies of water during dispersals, they may attempt to swim across, sometimes resulting in accidental drownings, but this is not intentional self-destruction.
Snow Lemmings in a Warming World
Climate change poses a significant challenge to snow lemmings, primarily through its impact on snow cover. Warmer winters can lead to less consistent or altered snowpack, affecting the lemmings’ insulated subnivean habitat. Increased rain-on-snow events, for example, can create hard, icy layers difficult for lemmings to penetrate, hindering food access and increasing digging energy expenditure.
Reduced snow depth or changes in snow quality can also compromise the protective cover snow provides against predators, making lemmings more vulnerable. These environmental shifts can negatively impact their ability to forage and reproduce throughout the long Arctic winter. Such disruptions may lead to declines in lemming populations, with cascading effects on the Arctic food web, as many predators rely on lemmings as a primary food source.