The Flight of the Monarch Butterfly
Every November, millions of Monarch butterflies migrate to the Sierra Madre Mountains in central Mexico, where they hibernate through the winter. Or, at least that’s what’s supposed to happen.
The Monarch butterfly is tougher than it looks.The Monarch possesses an incredible skill: it inherently knows how, when and where to migrate across the US and eventually back into Mexico …and it takes four generations to make the yearlong trek. The Monarch butterfly begins its migration in spring with the first generation coming into the world in March and April. These butterflies travel north on a generational journey that can total up to 2,500 miles. That’s quite the feat for a small insect with a 3-4 inch wingspan! The first generation usually doesn’t live longer than two months, spending a large part of their lives eating, metamorphosing and laying eggs.
Not all Monarchs reach their destination in the US, but those that don’t will lay eggs along the way. The eggs laid by this first generation hatch into baby caterpillars after about four days, typically entering the world in the warm months of May and June. The next two weeks ares pent eating and growing until they’re ready to attach themselves to stems or leaves and transform into a chrysalis. Ten days later, stunning butterflies emerge and fly away, continuing the course and stopping on the way to feed on milkweed.Monarchs cannot survive without milkweed;their caterpillars only eat milkweed plants and monarch butterflies need milkweed to lay their eggs. These butterflies lay eggs for the next generation,which is born in July and August. Like the first, both the second and third generations have only two to six weeks to complete their journey. It’s the fourth generation, born in September and October that leadsthe longest and most productive life. Thesebutterflies don’t die after two to six weeks, there’s too much to do. Instead, they live upward of eight months, spending their extra time traveling to ensure their species’ survival. With cold weather approaching, the butterflies instinctually know it’s time to head south. These Monarchs sometimes rack up about 80 miles a day, spreading out their journey over two months.
The Monarch is in trouble. In recent years, scientists have noticed a disturbing trend. The number of Monarchs migrating to Mexico has been dropping sharply. In 2012, a record low of just 60 million Monarchs arrived at their Mexican habitats. And fresh data from WorldWildlife Fund (WWF) suggests that the more recent winter’s numbers are even lower. The yearly Monarch count in Mexico shows a 90 percent decline over the past 20 years. Data indicate that the butterflies are missing a whole generation this year. And reports coming in from across the US from the Rockies all the way to Virginia and Maine, show there are very few butterflies breeding anywhere.
So Why Are The Monarchs Vanishing?
Scientists have cited three reasons:
1) Severe weather (drought and cold) along their migration path for the last two years;
2) The deterioration of their habitat in Mexico due to illegal deforestation;
3) The use of herbicides on Midwest farms. Herbicide resistant crops are planted in the farm fields of the US, where the Monarchs do most of their breeding. And normally in that area there would be milkweed growing in the edges of the fields and the sides of roads. The whole Monarch migration evolved in relation to this milkweed flora. The use of these herbicides kills the milkweed seedlings and all the budding plants. The common milkweed once found with abundance in crop fields is vital to the survival of Monarchs.
But there is hope. The Center for Biological Diversity petitioned the U.S. Fish and Wildlife Service to rule the Monarch butterfly threatened and give it Endangered Species Act protection. The process can often take years,but if the Monarch is ruled threatened, it can get special protection and restrictions from activities that have proved to diminish its population.
