- Lemmings are small rodents, found in the northern parts of Europe, Asia and America. They weigh between 40 and 110g and can measure up to 15cm in length. They have long, soft fur, and short legs and tail.
- The black and yellow-brown Norwegian lemming (Lemmus lemmus), common in northern Scandinavia, is also the biggest animal in the lemming genus.
- Lemmings do not hibernate in winter, but hide from the cold in shallow burrows in the snow.
- Females can have litters of up to 12 young (although 3-9 is more common). They breed throughout the year and gestation is only 21-23 days. Breeding is more prevalent in summer and young born at this time are weaned within two weeks.
- Contrary to popular belief, lemmings do not commit mass suicide. But their population can rocket. When this happens, lemmings head for new pastures in search of food. They can swim and will cross bodies of water, occasionally drowning in their quest.
- The study of lemmings since 1970 showed the last population boom was in 1994, ending a pattern of peaks every 3-5 years. This is believed to be a result of global warming.