A vintage Disney documentary, White Wilderness, purports to show the “mass suicide” behavior that makes lemmings famous. Masses of lemmings scurry toward the sea, while the narrator describes the scene. “They’ve become victims of an obsession, a one-track thought: Move on, move on, keep moving on,” he says. Then, as the rodents approach the cliff’s edge, the narrator intones, “This is the last chance to turn back. Yet over they go, casting themselves bodily into space.” Dozens of lemmings hurtle over the cliff, splash into the water, swim a short distance, and drown.
This evocative imagery solidified the popular notion that lemmings commit mass suicide when their populations grow too large. In reality, however, the mass suicide of lemmings is a myth. These rodents have populations that fluctuate wildly, peaking every 3 to 4 years. As the population reaches its height, lemmings begin to disperse to new habitats. Sometimes, an obstacle such as a lake or river blocks their path. Lemmings can swim, but if the distance is too great, they will drown before reaching the shore.
From an evolutionary viewpoint, mass suicide makes no sense. How can a population inherit the desire to kill itself? Even if such a trait were to arise in some lemmings, the ones lacking the self-destructive desire would presumably have the greatest reproductive success. Over many generations, a genetic tendency toward mass suicide should gradually disappear.
And what of the White Wilderness footage? Researchers who investigated the history of the film discovered that the entire lemming sequence was faked. The filmmakers purchased the lemmings from schoolchildren in Manitoba and transported the animals to landlocked Alberta, Canada. The crew then forced the lemmings into the water to create footage of the supposed mass suicide.