The Truth About Norway Lemmings

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Norway lemmings (Lemmus lemmus) aren’t always easy to spot until the population booms. In some years, they race through grass, dart between rocks, and even appear in campsites across the Scandinavian mountains. In one peak year, 1974, researchers recorded 22 nesting snowy owls in a single area, each surrounded by piles of lemmings brought to feed their chicks. Hikers reported waves of lemmings rushing across the tundra, and campers described hearing them outside their tents at night.

They are not your average rodent. While most small mammals rely on freezing or fleeing, this species does the opposite. When threatened, it stands its ground, chatters loudly, and may even lunge or bite. Its coat has bold patches of orange, black, and white that stand out against the snow. Biologists believe this vivid coloring, combined with its sharp vocalizations, helps deter certain predators. Even birds like the long-tailed skua have been startled by the aggressive response of a lemming that refuses to back down. Among small rodents, this kind of defiance is rare.

Norway lemmings follow a boom-and-bust population cycle. For two or three years, their numbers remain low. Then, almost overnight, the population surges. In peak years, researchers have counted up to 330 lemmings in a single hectare, which is an area about the size of two and a half football fields. In low years, that number can drop to just three. Females can begin reproducing at only three weeks old and give birth to litters of six to eight pups every few weeks. Breeding continues through winter. When the snow is deep and stable, it insulates their nests and allows them to stay active and continue reproducing. By spring, when the snow melts, lemmings often appear in overwhelming numbers.

As their numbers grow, so does the tension. Norway lemmings are antisocial and don’t tolerate overcrowding. When food becomes scarce and space runs out, dominant individuals may push out weaker ones. These evicted lemmings then spread across the tundra in search of better conditions. In Norway and Sweden, people have witnessed these migrations firsthand, with waves of lemmings crossing fields, swimming rivers, and sometimes running into obstacles along the way.

For centuries, people have tried to explain the sudden appearances and disappearances of Norway lemmings. In the 1600s, some believed they fell from the sky during storms. Others claimed they could explode from rage. While they are certainly feisty, they do not burst like popcorn. The most enduring myth, however, is that they commit mass suicide by throwing themselves off cliffs. This idea was popularized by the 1958 Disney documentary White Wilderness, which staged scenes of lemmings being forced into water. Many viewers believed the footage was genuine, but the filmmakers later admitted to herding the animals off a ledge to create a dramatic scene.

The Truth Behind the “Suicides”

Lemmings do not intentionally kill themselves. When their population surges, many are forced to leave in search of food and space. They may swim across rivers or lakes, and although they are strong swimmers for their size, some drown or fall from steep terrain during these migrations. These deaths are accidental. Dispersing helps reduce competition and increases the chances that some individuals will find enough food and continue the population cycle.

The staged 1958 documentary clip was seen by millions and still resurfaces on social media today. But in reality, Norway lemmings are not giving up. They are adapting to their environment and doing their best to survive.

Feast and Famine

When lemmings are abundant, the entire food web responds. Birds of prey such as snowy owls and rough-legged buzzards gather in large numbers. A mother owl may lay more eggs than usual, confident her mate can bring enough lemmings to feed their growing brood. Smaller predators like weasels and Arctic foxes also shift almost entirely to eating lemmings. Arctic foxes are so closely tied to lemming cycles that they often skip breeding in low years. But during a boom, a single fox mother can raise up to 18 pups because of the reliable food supply.

Other species benefit indirectly. With hawks and foxes focused on lemmings, ground-nesting birds like ptarmigans and waders face less pressure from predators. Even the plants benefit. All those lemmings leave behind large amounts of droppings, which enrich the soil. New vegetation flourishes, supporting grazers like reindeer and Arctic hares.

The Norway lemming’s population cycles shape the balance of predators, prey, and plant life. When lemmings thrive, the entire Arctic ecosystem shifts with them.

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