Today was so slow at work. I am on a construction site inspecting work and I have very little to do. It’s so slow, I sit there for 3 hours and do 20 minutes of work, then same thing over again at the next spot. Ugh. I had forgot just how slow this can be. It’s all hurry up and wait. It’s so annoying.
But today, as I sat on my stack of bricks that I found, I was watching all these Monarch butterflies as they migrated through the construction site. There must have been a couple hundred that flew by throughout the day. It was really pretty, yet kinda creepy at the same time.
The migration of the monarch butterfly begins in Canada and the
northernmost parts of the United States. The fall migration begins in late August ending in the months of November and December. The destination of the
butterflies lies in Central Mexico, in the Oyamel forests. Traveling in a southwesterly direction, the monarchs fly east of the Great Lakes and south-southwest in areas west of the Great Lakes. Those that reach the gulf of Mexico follow the coastline in a continuous stream. They continue in a southwest direction eventually reaching the overwintering site in the Transvolcanic Plateau of Mexico. As many as 300 million spend the winter there.During the migration, monarchs encounter many dangers. These dangers include such things as storms, predators, humans (more accurately, their cars), and simple fatigue. Many butterflies are the casualties of storms and are eaten by birds. Hundreds are crushed by cars crossing the
highways, and still many more can be seen limply trying to keep aflight, ready to collapse at any moment. Even after the monarchs arrive at their winter retreats, the danger of storms is still a major factor on the survival. The danger is greater, particularly in Mexico, where temperatures, strong winds, and snow kill thousands. As mentioned before, this migration takes up to three generations to complete! The exact migratory path is still being plotted today.
Scientists are tagging the butterflies, and recording their locations during the months of the fall migration.During the migration, the monarchs feed extensively on flowers to gain carbohydrates from nectars which fuel daily activities and contribute to the build up of the fat body in the abdomen. This fat supply gives energy to the monarchs on their long journey. Monarchs travel distances as great as 3,100 miles during their migration, traveling roughly 50 miles per day. Monarch flight speeds have been measured at 12 miles per hour. Once they have reached their roosting site, they cluster in large numbers in the branches and trunks of the oyamel trees. While clustering they remain quiescent (they stay relatively sill and maintain low metabolic rates).
In mid-February, the monarchs at the roost sites become more active and mating behavior begins. By the end of February, some of the monarchs begin moving northward, by mid-March the roost is usually depleted (Urquhart1987). This initiates the start of the spring migration. The spring migration starts out with only about half of the original roosting population. Forty to sixty percent of the monarchs die during their stay in Mexico. During the spring migration, the monarch butterflies return to their homes in Canada and the northern most parts of the United States. Along the way, they roost and reproduce, giving rise to new butterflies that will continue the spring flight back.
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