Monarch Migration Research

Posted on July 26, 2010  Comments (3)

Monarch Butterfly

Monarch butterflies – renowned for their lengthy annual migration to and from Mexico – complete an even more spectacular journey home than previously thought.

New research from the University of Guelph reveals that some North American monarchs born in the Midwest and Great Lakes fly directly east over the Appalachians and settle along the eastern seaboard. Previously, scientists believed the majority of monarchs migrated north directly from the Gulf Coast.

Unfortunately the press release doesn’t provide a link to the study – maybe it is not open science. Often organization focused on closed science don’t do well providing web links (though even open science organizations fall down on this more than they should).

“It solves the long-standing mystery of why monarchs always show up later on the east coast compared to the interior,” he said. “Importantly, it means that the viability of east coast populations is highly dependent upon productivity on the other side of the mountains.”

Monarchs travel thousands of kilometres each year from wintering sites in central Mexico back to North America’s eastern coast, a journey that requires multiple generations (in the same year) produced at various breeding regions.

Biologists had suspected that monarchs fly back from Mexico west-to-east over the Appalachians, but no evidence existed to support the theory. “Ours is the first proof of longitudinal migration,” Miller said.

For the study, the researchers collected 90 monarch samples from 17 sites between Maine and Virginia in June and July of 2009. They also collected 180 samples of milkweed (the only plant monarch larvae can eat) from 36 sites along the eastern coast between May and July of that year.

They then used hydrogen and carbon isotope measurements to determine when and where the monarchs were born. Isotope values in milkweed vary longitudinally and can be measured in monarch wings, Miller said. The researchers discovered that 88 per cent of the monarchs sampled originated in the Midwest and Great Lakes regions.

“This means that the recolonization of the east coast is by second-generation monarchs that hatched around the Great Lakes and then migrated eastward over the Appalachians,” Miller said. “We must target the Great Lakes region to conserve the east coast monarch populations.”

Full press release

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3 Responses to “Monarch Migration Research”

  1. TessaM
    July 28th, 2010 @ 12:44 am

    I love the beautiful monarchs. We have a species of milkweed we call “Butterfly Weed” that blooms with an orange spray of flowers we encourage to bloom in our yards and pastures. We have several lovely butterflies here, but the Monarch is a favorite. One year the Memphis Zoo had a butterfly habitat where we could walk through and see the life stages with hundreds of butterflies fluttering freely through the enclosure. I have never forgotten how quietly beautiful it was.

  2. Keith
    July 31st, 2010 @ 10:48 am

    Growing up in NE Wisconsin I saw countless monarch butterflies. My children hardly ever see a monarch. This beautiful summer friend is all but gone here. It is sad. This summer I have seen only one monarch. I think hybrid corn may be killing monarchs here. I hope they can be preserved.

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