Lemmings are small rodents inhabiting the cold, expansive landscapes of the Northern Hemisphere. They are often associated with the Arctic and subarctic regions, where they navigate some of the planet’s most challenging environments. They represent a diverse group of species, each uniquely adapted to survive the extreme conditions of their northern homes.
Appearance and Arctic Home
Lemmings typically measure between 8 to 18 centimeters (3 to 7 inches) in body length, with a short tail that adds only 1 to 2 centimeters (0.4 to 0.8 inches). Their compact, rounded bodies, short legs, and small ears help them conserve heat in frigid temperatures. They are covered in dense, soft fur, which can be brown, gray, or sandy yellow, providing insulation against the cold. Some species, like the collared lemming, even change their fur to white in winter for camouflage against the snow.
These rodents primarily inhabit the Arctic tundra and subarctic regions across North America, Eurasia, and Greenland. They are well-adapted to their harsh environment, possessing specialized flattened claws on their front feet that aid in digging through snow and frozen ground. Their ability to construct intricate tunnel systems beneath the snow is an important adaptation, offering refuge from both predators and the severe cold.
Daily Life and Habits
Lemmings are herbivores, with their diet consisting mainly of mosses, grasses, and sedges. They also forage for berries, leaves, shoots, roots, and lichens, even beneath the snow cover during winter. Unlike many other animals in cold climates, lemmings do not hibernate; they remain active throughout the year.
They create extensive networks of tunnels and nests under the snow, which act as insulated living spaces. These burrow systems protect them from the elements and many predators. While generally solitary, lemmings may gather in larger groups during breeding seasons or when dispersing in search of new territories.
Lemmings have a high reproductive capacity. Females can mature and begin breeding as early as a few weeks old, capable of producing multiple litters annually. Each litter typically contains an average of four to five young, though this can range from two to eight. Breeding can occur year-round, including under the snow during winter, which supports population growth.
The Truth About Lemming Population Cycles
Lemmings are known for their population fluctuations, often referred to as boom-and-bust cycles, which typically occur every three to five years. During peak years, populations can increase by hundreds or even a thousand times, leading to a high density of individuals.
The common misconception that lemmings commit mass suicide by intentionally jumping off cliffs is inaccurate. What appears as mass suicide is actually a dispersal event driven by overpopulation and the search for new food sources and suitable habitats. During these movements, many lemmings may accidentally fall from cliffs or drown while attempting to cross bodies of water, not due to intentional self-destruction, but as a consequence of sheer numbers and disorientation.
Several factors contribute to these cyclical patterns, including predator populations, food availability, and disease. Predator numbers, such as those of arctic foxes, snowy owls, and stoats, often lag behind lemming populations. When lemming numbers are high, predators thrive and reproduce successfully, which in turn intensifies predation pressure, eventually causing lemming populations to decline. Winter conditions also play a role, as stable and deep snowpack is important for successful winter breeding and survival, affecting the population cycle.
Their Role in the Ecosystem
Lemmings hold an important position in the Arctic food web, serving as a primary food source for a wide array of predators. They are considered a keystone species, meaning their presence and population dynamics have a disproportionate impact on the entire ecosystem.
Their predators include specialist hunters like snowy owls, which often nest only when lemmings are abundant, and stoats and ermines. Generalist predators, such as arctic foxes, also depend heavily on lemmings but can switch to other prey when lemming numbers are low. Fluctuations in lemming populations directly influence the breeding success and survival rates of these predator species. When lemming populations crash, it can lead to declines in predator numbers and impact other prey species as predators seek alternative food sources.