Lemmings are key members of the North's food chain. In winter they build tunnels and burrows under the snow searching out food and bearing young. They are preyed upon by almost every meat eating animal in the Arctic.

There are two main species of lemmings, the collared lemming and the brown lemming. They are small, round and so thick-set they appear to have no neck or even legs. They have tiny black, beady eyes and almost no tail.

They live in colonies in a maze of tunnels and runways under leaf litter in summer and under insulating snow in winter. They are prolific breeders during their one year life span, breeding all year long and beginning as young as three weeks of age. Their numbers reach a critical high at which time breeding is less frequent and the breeding season becomes shorter with greater infant mortality. In this fashion lemming populations rise and fall every three to four years. The reason for this phenomenon is still not fully understood, although there are several theories.

Biologists have dismissed the theory of mass suicide which has been the most popular theory in recent years. In the fall, collared lemmings develop bifid "digging" claws, structures unique to the genus Dicrostonyx. Bifid claws form from the pads on the third and forth digits of the front paws which grow into compressed, cornified tissue separated from the normal claw by a groove and a deep notch at the tips. These claws enable collared lemmings to dig through wind-packed snow and ice. The soles of the feet are well-furred at all times.