Lemmings are small, stocky rodents uniquely adapted to the Arctic tundra. This habitat is defined by a layer of permafrost and low-lying vegetation, which limits the available food sources. The lemming’s diet is highly specialized, consisting almost exclusively of the sparse plant life that manages to survive the harsh conditions. Their feeding behavior is a primary factor influencing their famous population cycles and the broader tundra ecosystem.
Primary Tundra Food Sources
The majority of a lemming’s diet consists of the most common and accessible low-growing plants in the tundra: graminoids and mosses. Sedges and grasses, which are types of graminoids, form a substantial part of their intake, especially the tender, newly grown shoots. Lemmings possess specialized continuously growing incisors that allow them to effectively shear and process these fibrous materials.
Brown mosses are another significant dietary component, particularly for certain lemming species, though their importance varies by region and time of year. While primarily herbivores, lemmings also consume herbaceous plants, roots, and bulbs when accessible. Their digestive systems are adapted to extract maximum nutrition from these high-fiber, low-calorie plant materials, though they digest grasses and sedges less efficiently than some related voles.
Despite the abundance of some plants, lemmings often select their food disproportionately, favoring specific species that offer higher nutritional density. They actively seek out the basal parts of plants, which are often nutrient-rich storage organs. This selective foraging has a noticeable impact on the local plant community, sometimes leading to the removal of graminoids in areas of high lemming density.
Seasonal Dietary Shifts
The brief Arctic summer allows lemmings to feed on fresh, actively growing vegetation, which is generally more palatable and easier to digest. During this season, they consume the tender leaves, flowers, and new shoots of sedges and grasses. The abundance of this high-quality, green food supports the rapid reproduction that characterizes the growth phase of their population cycles.
However, the long winter necessitates a dramatic shift in foraging strategy and diet composition. Lemmings remain active throughout the winter, surviving in the subnivean layer, the insulated space between the ground and the snowpack. Here, they rely on stored food caches or forage for frozen, still-green plant material.
Their winter diet often includes the basal parts of plants, rhizomes, and roots accessed by tunneling through the soil or snow. They also consume the bark and terminal twigs of dwarf shrubs like willow and birch, and lichens found on the snow surface. Recent DNA analysis suggests that prostrate willows and graminoids can dominate the winter diet, revising the older idea that lemmings are primarily moss specialists during the cold months.
Water and Mineral Intake
Hydration in the tundra presents a unique challenge, as liquid water is often scarce or frozen for much of the year. Lemmings primarily obtain their water requirements directly from the vegetation they consume, as fresh shoots and leaves have a high moisture content during the summer. This provides a continuous source of hydration that minimizes the need to drink free water.
In the winter, when the vegetation is frozen and dry, lemmings rely on consuming snow and ice within the subnivean layer to meet their fluid needs. They have physiological adaptations that help them conserve water and manage the ingestion of cold material. Although their herbivorous diet supplies necessary minerals, lemmings occasionally supplement their intake from unusual sources.
They have been observed gnawing on shed deer antlers or abandoned eggshells, which provides them with calcium and other trace minerals. This behavior is a form of osteophagia, or bone-eating, used to acquire nutrients limited in their primary plant-based diet. Their ability to source both water and minerals from a variety of means demonstrates their resilience in the nutrient-poor Arctic environment.