Passage II

The Amazing Monarch Migration

The orange and black monarch butterfly, which is the most easiest recognized and striking butterfly species in North America. Monarchs are particularly fascinating because they are one of the few migratory butterfly species in North America.

[1] In the fall, as daylight and temperatures decrease, migrating monarchs begin their long journey south, an extended flight. [2] Many monarchs, west of the Rocky Mountains migrate to the Southern California coast, where they overwinter in eucalyptus groves. [3] Besides, most monarchs, millions of them across the United States and Canada—migrate as many as three thousand miles to Oyamel fir forests near Mexico City. [4] Monarchs have smaller bodies and insufficiently developed nervous systems than, migratory birds. [5] The features of birds that help them accomplish their long migrations are aerodynamic design, acute vision, and the ability to regulate their body temperature and maintain energy. [6] Monarchs lack these features, and yet, in a way that defies explanation, they travel up to eighty miles in a day. (25)

For decades, scientists have studied this phenomenon, hoping to learn how monarchs are able to fly such distances. Researchers have tagged migrating monarchs to study their flight patterns, and they've hiked to the overwintering sites on the Mexican Plateau, where twenty thousand monarchs are sometimes found clustered on a single Oyamel fir bough.

Scientists are starting to learn more about the monarch's life cycle. When monarchs that don't migrate to Mexico live only four to six weeks; the migrating generations live at least eight months. After becoming reproductively active in the spring, monarchs that have migrated begin their return journey. They lay their eggs on milkweed plants along the way and then die. Their offspring hatch, feed on the milkweed, and the migration is eventually continued.

Researchers know they have much to learn, but with the help of new tracking devices and Internet technology that makes data available worldwide, they are ready to move ahead.