Each September, the butterflies begin their 3,400-mile journey from the forests of eastern Canada and parts of the United States to the central Mexican mountains. The voyage is considered an aesthetic and scientific wonder. The butterflies return to the U.S. and Canada in late March, where they breed and cycle through up to five generations before heading back south. Scientists say they are genetically programmed to return to Mexico, where they settle into the same mountains their ancestors inhabited the year before. According to Brower, sometimes they even return to the exact same trees — probably because previous monarchs have marked the area through a mechanism scientists don't yet understand. The monarchs that spend the winter in Mexico do not reproduce until they return to the U.S. and have a much longer life span than those born in the spring and summer. Omar Vidal, director of the World Wildlife Fund's Mexico program, applauded Calderon's plan. "This is the longest migration of all insects, a unique phenomenon and a natural wonder and Mexico has the biggest responsibility to protect them because they come here to hibernate," he said. Brower said the monarch isn't at risk of extinction because it can be found in Mexico, Canada, the U.S., most of South America and even parts of Australia and New Zealand. But disappearing habitat could threaten a delicate migratory route that has existed for an estimated 10,000 years. "The whole migratory phenomenon which involves two continents and over a million square miles could just go down the drain," he said. |
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