Lemmings, the small burrowing rodents that live in the Arctic regions, are an odd bunch. They look a bit like hamsters, but they are notoriously fierce. (Case in point: a lemming attacking a sled dog.) Like many rodents, they are prodigious reproducers, but the Norway lemming and the brown lemming have particularly dramatic population booms. Their population can fluctuate so chaotically that, for centuries, people have been coming up with wild explanations for the overwhelming abundance of little lemmings, followed by a seemingly sudden disappearance.
Back in the 1530s, the geographer Zeigler of Strasbourg, tried to explain these variations in populations by saying that lemmings fell out of the sky in stormy weather, and then suffered mass extinctions with the sprouting of the grasses of spring.
The strangest myth—and the one that makes calling another person "lemming" an insult — is the idea that lemmings will mindlessly commit suicide by jumping off a cliff. It probably has a basis in reality: When "lemming years" happen, some areas will grow so densely populated that groups of lemmings will set off en masse to find better fields. While these migrations may have inspired the suicide myth, one person may be largely responsible for perpetuating it: Walt Disney.
In the 1958 academy award-winning Disney documentary called White Wilderness, dozens of lemmings are shown tumbling down a cliff, bouncing off rocks and landing in the sea, where they struggle against the waves.
But the footage was a farce, explains Nicholls:
For a start, White Wilderness – filmed in Canada rather than Scandinavia – depicts the wrong species. Although all lemmings experience population highs and lows, the accounts of mass movements were all based on observations of Norwegian lemmings, not the brown lemmings that Disney used. He paid Eskimos "$1 a live lemming," says [Nils Christian Stenseth of the University of Oslo in Norway].
But that's just the start. In an infamous sequence, the lemmings reach the edge of a precipitous cliff, and the voiceover tells us that "this is the last chance to turn back, yet over they go, casting themselves bodily out into space."
It certainly looks like suicide. "Only they didn't march to the sea," says Stenseth. "They were tipped into it from the truck."
The many dead lemmings found after a population boom do suggest catastrophe. But the mortality can be chalked up to overenthusiastic predators, competition for resources and fatalities from failed stream crossings.
There’s at least one more myth that deserves debunking. Lemmings do not explode when they get angry. Perhaps this myth came out of the out-of-proportion fierceness of these tiny animals, a misinterpretation of the idea that lemming populations explode, or eviscerated lemmings that have been pecked by birds and look like they’ve burst, as Nicholls supposes. Or maybe people are confusing the real animal with the video game "Lemmings." The green-haired, hapless critters in the classic PC game do explode on command.