They do look like cute little pets, but they are not defenseless and can use their impressive incisors not only to bite their favorite food, such as moss, grass and shrubs. The Norway Lemming (Lemmus lemmus) is the only vertebrate that is endemic to Scandinavia. Other members of the genus Lemmus, however, can be found in e.g. Siberia and North America.
This rodent has a very short gestation period of 2 to 3 weeks. In an underground burrow the female gives birth to on average 7 young, which themselves are sexually mature after 2 weeks. About 8 litters can be produced per season. Through these parameters lemmings are capable of producing a stunning explosion of population size from time to time when the conditions are favorable. Extremely high densities of Norway Lemmings , as they can be observed at irregular intervals of several years or decades, lead to high stress levels, aggressive behavior and mass migrations, but not to the often quoted mass suicides, which are a myth. Fact is that during the mass migration lemmings do jump into waters, but not to drown but to cross them, and they are killed in thousands, but not in a collective suicide but e.g. because they are run over by cars or get stuck in manmade structures.
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