An article from the BBC clarifies the popular notion about lemmings.
On the back of the animated classic Bambi, Disney undertook a series of ground-breaking, feature-length nature documentaries known as The True-Life Adventures. In one of these, White Wilderness, he dramatized the lemming mass suicide. … 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."