In fact, during these years, they eat so much plant matter that the results are noticeable from space. During the summer months, lemmings eat nothing but living vegetation, and when lemming populations are at their peak, the rodents eat so much vegetation they have to travel across the tundra in great numbers in search of greener pastures. On the other hand, population spikes in lemmings can be pretty destructive. This smorgasbord ends up having an impact on the entire tundra ecosystem. However, when they do, all the predators on the tundra that depend on lemmings for food - arctic foxes, hawks and jaegers, for instance - eat very well that year. Since lemming populations spike every few years - usually every three to five years, although, according to Ims, most lemming species don't peak in clockwork patterns like some other population cycling species. These cycles can be driven by disease, food availability and predation. Population cycles happen in ecosystems all over the world, and rodents are a common group of animals to experience population cycles. In an ecosystem, populations of a specific species may fluctuate drastically over a predictable period of time. One way lemmings affect the ecosystems in the arctic has to do with a phenomenon called population cycling. 'Their cycles are necessary for the maintenance of arctic biodiversity through their role as prey and grazers of plants.' 'Lemmings - and there are several species - are very important to the functioning of arctic ecosystems,' says Ims. The lemming suicide myth was popularized in the 1958 Disney film ' White Wilderness' in which many lemmings were allegedly herded off a sea cliff so that the filmmakers could get dramatic footage of 'lemming suicide.' The footage convinced many people of the truth of lemming suicide, though the veracity of the footage was later called into question and the myth debunked. It's unclear what causes these migrations, but social stress, food shortage or predators are candidates. 'During the peak years of this species, a large number of individuals migrate out of their normal habitat and die in large numbers. 'This idea stems from the migrations observed in one lemming species: the Norwegian lemming,' says Rolf Anker Ims, a researcher in the Department of Arctic and Marine Biology at the Arctic University of Norway, in an email interview. So, why would these little creatures, interested in preserving life and limb to the point that they would fight a human or a weasel rather than be eaten, also commit suicide? The truth is, their reputation for jumping off sea cliffs en masse is a myth.

They've even been known to attack humans studying lemmings. They also have the reputation for being extremely aggressive - rather than running away from a predator, they charge their attacker. They migrate when food becomes scarce and can even swim across rivers and lakes when necessary. They are stocky, short-tailed voles that burrow under the snow in winter, providing food for Arctic foxes and snowy owls, and spend the summer mating and eating mosses and grasses that aren't available in the winter. Lemmings are not impressionable people, however - they are actually a group of several species of small rodents native to the Arctic regions of the globe.

You've probably heard of a lemming before, but maybe just in context of a metaphor for someone so stupid they would follow a bunch of other people into a bad situation rather than think critically about their position and act according to their best judgment. Arterra/Universal Images Group/Getty Images

A Norway lemming ( Lemmus lemmus) leaving burrow under rock on the tundra in Lapland, Sweden.

Youtube lemmings jumping off cliffs