The Monarch butterfly is simply an amazing creature that survives by migrating and hibernating each year. They are the only insect that survives by making a 2500 mile journey every year, in order to survive. This single journey is completed through four generations of offspring due to the 2-6 week life span of most adult Monarch butterflies.
Monarch butterflies are not able to survive in the harsh, cold temperatures that winter brings in the northern United States and Canada. To survive, the Monarchs east of the Rocky Mountains migrate south to the Michoacán Mountain Range every year and the Monarchs west of the Rocky Mountains migrate south to the Pacific Grove area of California. The Monarchs return to the exact same trees every year! The Monarch’s unique hibernation habitat is only found on twelve mountaintops on the planet. The migration south begins sometime between September and October, depending on how early the weather turns cold. They travel to California or Mexico’s warm climate and hibernate for several months before they begin the journey north again in search of their needed food source, which is only located in the north. So how is it that the Monarchs can travel so far and complete a yearly migration when their life span is only 2-6 weeks long as an adult?
Hibernating Monarchs awaken and become active in February and March of each year. They find a mate in order to quickly reproduce and they begin their flight northward. They stop in several southern states in the U.S. to lay hundreds of their eggs in milkweed plants. After surviving 4-5 months of hibernation, travel and reproduction, this generation finally dies. This is considered the fourth generation of Monarchs per year. The rotation is as follows and contains the needed time for a butterfly to begin as a baby caterpillar, grow to a full size caterpillar and finally transform out of its chrysalis into an adult Monarch butterfly.
Between March and April the eggs of the last generation hatch into baby caterpillars and transform to butterflies. This is now considered the first generation. They travel north to find the food they need to survive. Their lifespan after becoming adult butterflies is 2-6 weeks.
Between May and June, the second generation is born from the first and they also travel north to find food. Their lifespan after becoming adult butterflies is 2-6 weeks.
From July to August the third generation is born and they finish the journey north to the final destination and fill up on food. Their lifespan after becoming adult butterflies is 2-6 weeks. This group lays their eggs, which will become the final generation of the year.
From September to October the fourth generation is born and goes through the phases to become an adult butterfly. This is the only generation each year of Monarch butterflies who do not die after 2-6 weeks. They fill up on food and tens of millions of Monarchs head south to migrate to warmer weather. They will survive the entire trip and hibernate for roughly five months before starting the journey northward between March and April to lay their eggs.
These unique and amazing creatures always return to the same trees as the fourth generation before them without ever being there before. How is this possible? Many scientists speculate that they must have an internal map and compass that is innate. At the very least they are born with an instinct to complete the migration.
The Monarch butterfly uses the position of the sun as a compass. They migrate during the day, and the sun is the celestial cue that leads them south. The Monarchs have an internal clock that helps them orient themselves to head south depending on the position of the sun. It is also believed that the Monarchs instinctually recognize landmarks like mountain ranges that help them follow a southern route and funnel them into the right area. In addition, the Monarch butterfly has a magnetic compass that gives them a keen sense of direction. This magnetic compass helps direct them to the equator. Once they are far enough south, they use smell and social cues to help guide them to their exact wintering sites.
It is also theorized that Monarchs are born with an internal map based on the magnetic field of the Earth that guides them to all of their destinations. This is much like sea turtles. The creatures are born with an internal map that directs them to the places they need to go in order to survive.
Unfortunately, the Monarch butterfly is in danger because their favorite trees in their wintering sites are being cut down to build roads, houses and farms. These beautiful creatures cannot survive if their migration is compromised.
These creatures make an incredible journey every year and it is up to us to protect their habitat. The Monarch butterfly is an iconic symbol of beauty and peace, and it is imperative that we save their habitat and protect their migration in order for them to survive.
Written by Megan Frison
More information can be found at:
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