How Do You Track A Butterfly?

Imagine going on a trip that’s thousands of miles long and flying the entire way! That’s what monarch butterflies do every year in one of the animal kingdom’s most epic journeys. But how exactly do these delicate insects navigate that distance, and what dangers do they face along the way? For a long time, scientists could only track monarchs by placing tiny sticker tags on their wings and hoping someone would find them. Now, solar-powered radio tags small enough to glue onto a butterfly’s back are helping scientists uncover the secrets of this amazing voyage. Join journalist Dan Fagin and Science Friday Host Ira Flatow to learn what this groundbreaking technology is teaching us—and why understanding monarch migration has never been more urgent.

Each year, monarchs make a long two-way mass migration. Unlike other butterflies that become dormant or hibernate through winter, usually in their larval or pupal phase, monarchs can’t survive the cold. When the days get shorter in the fall, they fly up to three thousand miles south to the Californian coasts or the mountains of Mexico. At night, they gather in trees to stay safe and warm, clustering together in roosts of tens of thousands of butterflies. In the spring, they begin the journey north to breed and lay eggs. It can take several generations of monarchs to complete the return trip. This migration behavior is essential to the monarch’s survival — without it, the species couldn’t complete its multi-generational life cycle.

Along the way, monarchs depend on critical resources. During migration, they need nectar from flowers to fuel their flight and safe places to rest when severe storms or strong winds blow them off course. Even when the weather blows them off course, tagging has shown that many butterflies can get back on track and keep heading south. After migrating, they overwinter in cool, moist places, resting to conserve energy. They need water to stay hydrated and shelter to avoid predators like birds and mice.

However, scientists have observed a drastic decline in monarch populations. Climate change is altering weather patterns, making severe storms and droughts more common and disrupting the environmental cues monarchs rely on to know when to migrate. Rising temperatures, widespread herbicide use, and habitat loss mean less food along their migratory paths and less milkweed, the only food monarch caterpillars can eat, too. These changes to the ecosystem can ripple outward, affecting the entire monarch population.

But tagging and tracking projects like Monarch Watch and Journey North are helping researchers better understand monarch migration so that these amazing insects can continue their journey each year.

After you’ve listened to the podcast about monarch migration tracking, think about the following questions:

1. What information can scientists gather from the new tracking technology that they couldn’t learn with the old sticker method?
2. What evidence shows that monarch migration is in serious trouble?
3. How can changes along the migration route affect monarch populations?

• LS1.B: Growth and Development of Organisms – MS-LS1-4 – Use argument based on empirical evidence and scientific reasoning to support an explanation for how characteristic animal behaviors and specialized plant structures affect the probability of successful reproduction of animals and plants, respectively.
• LS2.A: Interdependent Relationships in Ecosystems – MS-LS2-1 – Analyze and interpret data to provide evidence for the effects of resource availability on organisms and populations of organisms in an ecosystem.
• LS2.C: Ecosystem Dynamics, Functioning, and Resilience – MS-LS2-4 – Construct an argument supported by empirical evidence that changes to physical or biological components of an ecosystem affect populations.

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Credits:
Lesson by Sandy Roberts
Digital production by Sandy Roberts
Original audio production by Charles Bergquist
Host Ira Flatow