Lemming

Lemming, Arctic rodent, about 3–6 in (7–15 cm) in length, closely related to the vole. Genera include Lemmus and Dicrostonyx. Like many small mammals of simple ecological systems, lemmings show periodic fluctuations in numbers. These 3- to 4-year fluctuations result in spectacular mass migrations in search of food. One species, L. lemmus, is particularly noted for migrations that lead many members to accidental drowning in the ocean.