Why do monarchs migrate?

By Daphné Laurier Montpetit
Coordinator of the Mission monarch project

 

If my first experience running a half marathon taught me something, it’s that 21 kilometers is long! Imagine the 4000 km that monarchs must travel to reach their wintering grounds. As the first champions are crossing the finish line of the state of Michoacán, Mexico, one wonders why these butterflies are going through so much trouble. Why do monarchs migrate?

The monarch, a great traveler

The monarch is, originally, a tropical butterfly. Populations of the species are found all over the world (the Americas, Pacific Islands, Oceania …), and some of these populations do not migrate. Indeed, under favorable conditions, generations can succeed each other on an ongoing basis, as is the case for monarchs in Mexico and South America.

Why then are others moving away from the tropics, year after year? It is probably in order to avoid strong competition for food within their environment. Milkweed, a plant necessary for the growth of monarch caterpillars, abounds in summer in northern regions. For the monarch, it is an all-you-can-eat buffet! By expanding its territory, it has access to more resources for the development of caterpillars.

The challenges of winter

There is, however, a price to be paid for this abundance: the arrival of winter! Insects living in temperate environments have developed different strategies to survive the cold season. Some species hide or bury themselves while others take advantage of the protection of snow to stay active. The monarch, for his part, has developed a formidable ability to move over long distances and an outstanding ability to navigate to specific wintering sites.

These wintering sites are not chosen at random. Oyamel fir forests, in central Mexico, offer the perfect conditions to spend the winter. The temperature is cool enough to allow the butterflies to adopt a metabolism that limits the energy expenditure, the trees offer protection against the wind and the moisture is adequate. In a few words, these sites are worth the trip!

Migration at the heart of the Mission

The formidable migration of monarchs is an unparalleled show. It stimulates scientific curiosity, cultural attachment and human passion. It is because of the rich and hospitable habitats that we can observe this magnificent butterfly in Canada, every summer.

To preserve this unique phenomenon, we must preserve the habitats that are necessary for the reproduction of the monarch. Understanding the habits of the butterfly and knowing which environments are most favorable to it will allow us to protect the species. And that is the purpose of Mission Monarch!

Let us ensure that our winged visitors always find the milkweeds they came to seek in Canada!

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