:
John,
Scientists have figured out how to follow individual monarch butterflies as they make their epic migration across North America.
Tiny solar-powered radio tags let researchers watch a single butterfly travel from wintery Ontario all the way to colonies in the mountains of central Mexico.
It's an incredible feat of technology, one that underscores the miracle of the monarch migration ... as long as monarchs still have a chance to travel.
Each fall, monarchs born in the northern U.S. and Canada set out on an impressive journey of up to 3,000 miles. Eastern monarchs head for the fir forests of central Mexico, while Western monarchs gather in groves along California's coast.
The last generation of the year, the one to undergo the long trip south, is a special "super-generation" that can live up to nine months, far longer than a typical monarch lifespan.
When they arrive, millions of butterflies cluster together on tree trunks and branches. They pack together so densely that the combined weight of their little bodies can bend, and even break, tree limbs.
In spring, they migrate back north over the course of several generations, returning to northern meadows and gardens just in time for summer.[1]
The new tracking tags are letting scientists see this journey in more detail than ever.
Each tag weighs only a percentage of a monarch's body weight and can be detected by billions of Bluetooth-enabled devices, like your phone, as the butterfly passes overhead.[2]
This research is revealing a lot about how individual monarchs fly, where they travel, how they rest, and what habitats they depend on.
Some butterflies took the expected, straight route over the Midwest and Texas into Mexico. Others were less efficient, veering out east over the Bahamas before passing over Florida to complete their journey south.
While this information is both entertaining and crucial to better understand one of the longest migrations in the animal kingdom, it's also making clear just how many pressures these butterflies now face.
This 3,000 mile journey is hard enough already, with only about 1 in 4 of the butterflies surviving the trip, but recently, human activity is making it even deadlier.[3]
In the 1990s, hundreds of millions of Eastern monarchs spent the winter in Central Mexico's forests. In recent years, that number has fallen by up to 80%. Meanwhile, Western monarchs are faring even worse, with population declines estimated to be more than 95%.[4]
Much of this decline stems from habitat loss, as development and agriculture have erased the meadows, prairies and roadside spaces monarchs once relied on for nectar and rest.[5]
At the same time, heavy pesticide use has nearly eliminated milkweed -- the only plant monarch caterpillars eat -- leaving entire landscapes functionally useless for breeding.[6]
These pressures are compounded by the widespread use of pollinator-killing neonicotinoid (neonic) pesticides. Applied on millions of acres of farmland and gardens across the country, neonics have driven a 48-fold increase in the toxicity of America's fields toward insect life.[7]
These pressures are putting the future of this iconic migration at risk.
That's why our supporters, members and people like you have come together to protect monarchs and the habitats they call home.
Together, we've called on retailers to stop the sale of neonics, asked governors to plant more milkweed on state land and supported legislation to help these iconic butterflies survive and recover.
For generations, monarch butterflies have filled our yards, gardens and skies during their epic migrations, and the more we learn about their travels, the more impressive these butterflies seem to become.
Now these trips are at risk, but together, we can keep working to protect these butterflies, and their incredible journeys, for many years to come.
Thank you for standing with monarchs and other pollinators,
Ellen Montgomery
P.S. We're working to protect monarchs and native pollinators from pesticides, habitat loss and other threats. If you'd like to help support our work, please consider donating today.
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1. Andrew Rothman, "Where do butterflies go in the winter?," Environment America, October 30, 2025.
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2. Dan Fagin, Jonathan Corum "We can now track individual Monarch butterflies. It's a revelation," WLRN Public Media, November 20, 2025.
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3. Anderson Cooper, "Monarch butterfly super generation live up to 9 times longer than most monarchs, migrates thousands of miles," CBS News, April 20, 2025.
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4. Steve Blackledge, "Two Congress members have a plan to save the Western Monarch," Environment America, August 13, 2025.
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5. Steve Blackledge, "Two Congress members have a plan to save the Western Monarch," Environment America, August 13, 2025.
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6. Andrew Rothman, "Where do butterflies go in the winter?," Environment America, October 30, 2025.
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7. Steve Blackledge, "How just a single seed can kill 80,000 bees," Environment America, June 30, 2025.
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