Anne Kumchy, age 12, of Ottawa, Ontario, Canada, for her question:

Why do lemmings march to their destruction?

Generations of human observers have watched the lemmings march in millions to their doom. Every few years, armies of the small furry creatures left their burrows and swarmed on and on, crossing land and streams. The journey ended at the sea, when countless lemmings plunged in and perished in the tossing surf. For a long ties, many observers thought that the tragic event was some sort of mass suicide. Now that we know more about animal behavior, this theory must be rejected.

Nowadays, the most widely accepted theory suggests that the lemmings are trying to cope with a population explosion. They multiply very fast, and in a few years there is not enough food to support the local population. Then swarms of hungry lemmings depart, seeking new homes in other grassy meadows. They are good swimmers, and along the way they cross many streams successfully. Disaster befalls them when they mistake the sea for just another stream. Based on what we know of lemmings and their behavior, this explanation seems most likely.