A biology student traveled 20,000 kilometers collecting milkweed, creating isotope analysis of monarch butterflies’ annual migration journey, hoping to identify factors behind this threatened insect’s decline.

Milkweed is the host plant to the monarch butterfly and Megan wanted to compile a diverse sampling of it to run an isotope ratio analysis that would build a map to show how the isotopes vary over landscape. This would help her pinpoint where her monarch samples had hatched and, perhaps, better understand the migratory routes of this endangered insect.

Megan’s trip took 74 days, traveling 20,000 kilometres over 22 states to collect samples with the help of teachers, state and federal biologists, city employees, campground owners, and farmers. She has now published a research paper demonstrating how mapping strontium isotopes can greatly improve the ability to track these important insects.

«As animals feed on the landscape, they gather and preserve the local isotopic signature in inert tissues, and with monarchs it’s in their wings. These tissues preserve the isotopic signature of the individual’s natal origin,» says Megan, a PhD student in the Faculty of Science.

«In this study, we show that strontium isotopes, particularly when combined with hydrogen isotopes, can help researchers pinpoint where a monarch butterfly hatched to a more precise area. We then used the new tool by applying it to a sample of monarchs to see where they originated.»

Tracking monarchs: A tough task

Tracking monarch butterflies, which are small-bodied and traverse thousands of miles over international borders, is an expensive and difficult task. Recovering tagged monarchs is rare.

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