The monarch butterfly migration occurs annually during each fall, mainly across North America. The known to be “one of the most spectacular natural phenomena in the world”, these beautiful colourful insects migrate in mass towards the West Coast of California or mountainous sites in Central Mexico.
Thus, during the monarch butterfly migration, millions of monarch butterflies depart from their summer breeding grounds and travel around 3,000 miles to reach overwintering grounds in southwestern Mexico and never return.
What makes the monarchs so fascinating is the fact that usually, orientation is not well understood in insects, however, theses butterflies that embark on epic migrations always reach their destination. Do they rely on their instincts?
Researchers believe that monarchs use their instincts to know which route to take during migration. As the days get shorter and the temperatures drop off, monarchs begin to search of a safe place to spend the winter. Their instincts always lead them to the overwintering ground, on the branches of oyamel fir trees, in central Mexico.
“The tree canopy and ecosystem provide a blanket effect for the monarchs, so the temperatures don’t go too high or too low,” says López, a research scientist at the National Autonomous University of Mexico.
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Why is the Monarch Butterfly Migration necessary?
“Migration also allows monarchs to escape habitats where parasites have accumulated at the end of the summer,” says Sonia Altizer, an ecologist at the University of Georgia.
During lab tests, adult butterflies infected with a protozoan parasite called Ophryocystis elektroscirrha, or OE, can’t fly as well. It was concluded that they travel shorter distances in the wild.
“We think that migration weeds out the most heavily infected monarchs, removing them from the populations,” says Altizer.