Lemmus lemmus
Norway lemming

Norway, Sweden, Finland, extreme north west Europe.

Alpine, tundra, steppe, temperate grasslands, scrub, open forest, rocks.

Gestation 16- 28 days. Reach sexual maturity early (females: 2-3 weeks old, males: 6-8 weeks old). Very fecund. Breed in summer and winter. Length of breeding season varies. Mated female may fail to conceive or may abort if exposed to a strange male. Litter size may vary from 1-12 or more litters per year. Some females genetically programmed to bear only female offspring.

Active day and night. Construct burrows in summer. Survive in snow by tunneling beneath it. Rely on smell, hearing. Territorial. Calls indicate social status (alarm calls, threat calls, courtship and mating calls). Female gives parental care to young. Solitary. Easily irritated. Spacing behavior- scent marks determine territory. Males form a hierarchy of dominance in which the subordinates may be excluded from breeding. Some males are monogamous. Winter communal nesting to reduce energy requirements.

Herbivorous, diet consisting largely of berries, leaves, grasses, bark, lichens, roots, green part of plants, bulbs, mosses, pine needles. Forage both day and night. Graze and dig for roots.

Social behavior studied by many.

Some harbor vectors of disease, such as plague.

Many live in areas of little agricultural importance to humans. Not pests. Not endangered. Highly varying population density (see "Other Comments"). Clearing of forests by humans has increased habitat.

So-called "Suicidal March to the Sea" about every 3-4 years. Populations "cycle," increasing greatly approximately every 3-4 years. When this happens, lemmings may migrate in large numbers from densely populated areas in the mountains down to birch forests, searching for food. Encountering natural obstacles, including bodies of water, causes panic and a "flight response." This behavior sometimes takes them into the sea, and large numbers may die. So, they may die in this individual quest for food, but they aren't committing suicide for the sake of the rest of the population.

Predators of the lemming include the snowy owl, grouse buzzard, ermine, and arctic fox.