Lemmings are small rodents, usually found in or near the Arctic.
Together with the voles and muskrats, they make up the subfamily Arvicolinae (also known as Microtinae), which forms part of the largest mammal radiation by far, the superfamily Muroidea, which also includes the rats, mice, hamsters, and gerbils.
Lemmings mostly weigh 30 to 112 grams (1–4 oz) and are about 7 to 15 centimetres (2.75 – 6 in) long.
They usually have long, soft fur and very short tails.
They are herbivorous, feeding mostly on leaves and shoots, grasses, and sedges in particular, but also roots and bulbs in some cases.
Like many rodents' teeth, their incisors grow continuously, allowing them to exist on much tougher forage than would otherwise be possible.
While many people believe that lemmings commit mass suicide when they migrate, this is not actually the case.
Lemmings will often migrate in large groups and as a result some lemmings will occasionally be pushed off cliffs or drowned in bodies of water simply by the press of their compatriots but such deaths are unintentional and incidental.