Lemmings have a long-standing reputation as unintelligent animals. Video games and urban legends are based around these arctic rodents mindlessly jumping off cliffs and drowning for no apparent reason during migration.
The only lemmings that regularly migrate are Scandinavian species, and they only do so when absolutely necessary. The reason for these migrations has to do available food supplies for the population, which can run low quickly. The Norway lemming reaches sexual maturity at one month old and can produce a litter of six to eight young every three weeks year round if weather is good. This can lead to a larger lemming population than the area can support.