The Great Monarch Migration

Each autumn, tiny orange-and-black monarch butterflies begin one of the longest journeys in the animal world. From Canada and the northern United States, they fly south, sometimes traveling more than three thousand miles. Their destination is a small ring of fir forests high in the mountains of central Mexico.

How can a butterfly weighing less than a paperclip find its way? Scientists believe monarchs use the sun as a compass. Special cells in their tiny brains help them adjust the sun's position throughout the day, so they always head in the right direction.

When they arrive in Mexico, millions of monarchs cluster together on tree branches. Their orange wings turn the forest into a living tapestry. In spring, they wake up, mate, and begin the return trip north — but no single butterfly finishes the whole journey. It takes several generations to complete the round trip.