Each and every year one of the most impressive and beautiful migration of a species undertakes, the journey often times expanding over 3,000 miles. As the only known migratory butterfly the majestic monarch (Danaus plexippus) is unique and special in many more ways than one. The explanation for why the monarch butterfly travels on a migratory path is due to the fact that it is the only specie unable to survive through the winter in the forms of larvae, pupae, or even adult butterflies in cold climates. Typically starting in October, the monarch migration is the most impressive annual exodus of animal populations in the world.
Categorized into two separate populations, the migration stems into two entirely different destinations, one site being the mountainous region and oyamel fir filled forests of Mexico, and the other located in several different congregational sites in the warm southern Pacific Grove of California. The determination of the final destination is based on the origin of the traveling monarch population. Monarch populations in different locations to the east of the Rocky Mountains will convene paths over Central Texas and then continue together as one large group toward the oyamel forests of Mexico. Populations to the west of the Rocky’s will settle in southern California in eucalyptus trees along the Pacific Grove. Monarchs roosting in the oyamel forests of Mexico during the winter season experience the ideal microclimate, here temperatures rarely drop below 0 degrees Celsius and never surpass 15 degrees Celsius. The high humidity of the forests ensures the conservation of the Monarch’s energy. To stay warm and conserve their fat reserves while traveling and roosting in their winter get-always, monarch cluster together in groups, in fact over tens of thousands of monarchs can reside in one tree while resting! Fortunately the oyamel and eucalyptus are strong enough to support the large congregations on their boughs. The monarchs overwintering in California experience similar microclimates than their cousins in Mexico. The warm and humid climate coupled with the monarch’s clustering technique successfully allows them to stay warm.
However the fun doesn’t stop here, monarchs actually make a two way migration after sticking out the cold winter in their tropical paradises and travel back. Biologists and lepidopterologist alike are still fascinated and study the monarch’s two-way trip. Contrary to popular belief the monarch that hatches from its egg, undergoes metamorphosis, and emerges as an adult in the early spring is not the same monarch that takes part of the migration. In fact it takes four entire generations to complete the two-way migration! The first generation lives in February and March, their primary role is to locate a mate and find a suitable site to lay their eggs. The second generation hatches from those laid eggs and live through March and April; they mate then lay their eggs on the leaves of milkweed plants. The third generation follows much the same destiny as its parents and grandparents, searching for a mate then laying its larvae living in May and June. Sadly the fourth generation is the only generation that actually migrates; their lifespan differs dramatically than the first three generations as they live for up to six to eight months after over wintering in the warmer environments while the others live hardly longer than 6 weeks. Perhaps the most astounding feat the fourth generation accomplishes is that they return to the same approximate location as where their great grandparents were hatched, starting the cycle all over again!
Devastatingly, the monarch migration is in danger. Due to steady inclines of deforestation in the oyamel forests regions in Mexico and the drastic shortage of milkweed plants throughout North America, the monarch’s vital food source, the Monarch is becoming less and less able to complete their annual migration. To see what you can do to help visit this website for more information. Unless action is taken the world may lose of its most stunning migrations ever witnessed, something we cannot allow to happen.