Monarch butterflies head to Mexico as scientists unlock new way to track their journey
Each fall, millions of monarchs from Canada and the U.S. travel thousands of miles to reach their winter home in the mountain forests of central Mexico.
Eastern monarch butterfly population less than half of last year
Eastern monarch butterflies overwinter in Central Mexico. Each year, surveyors estimate how many millions of butterflies are crowded on trees across the area. This winter's count came out 59% lower than last year's.
THE TAKEAWAY
- Millions of Monarch butterflies from Canada and the U.S. travel to Mexico each fall.
- Some monarchs travel as far as 3,000 miles.
- This year, scientists are using lightweight, solar-powered tracking devices to follow their migration.
- Scientists hope the technology will reveal how monarchs find their migration routes.
Monarch butterflies are nearing the end of their annual fall migration to Mexico, with the journey continuing through late October.
Each fall, millions of monarchs from Canada and the U.S. travel thousands of miles to reach their winter home in the mountain forests of central Mexico.
Their migration begins in regions across North America, including Minnesota, California, Indiana and Iowa.
Overview of the fall migration pattern. (FOX Weather / FOX Weather)
The journey typically begins in late summer and early fall, when a special generation of monarchs emerges from its pupae, or chrysalides.
According to Monarch Watch, these butterflies are biologically and behaviorally different from those that emerge in the summer, allowing them to survive the long journey south.
As they migrate, monarchs stop to feed on nectar and actually gain weight along the way. Some researchers believe the butterflies conserve energy during flight by gliding on air currents as they travel south.
Monarch butterflies at nesting grounds in Mexico. (Sylvain CORDIER / Gamma-Rapho / Getty Images)
Experts consider the migration one of the most remarkable journeys in the insect world, with some monarchs traveling as far as 3,000 miles.
But this year's migration comes with a new scientific tool that could offer researchers an unprecedented look at the butterflies' movements.
Fast facts about monarch butterflies
Learn more about migratory monarch butterflies -- the iconic orange-and-black insects that signal spring and summer.
According to Monarch Joint Venture, lightweight, solar-powered tracking devices have allowed scientists to follow individual monarchs in near-real time for the first time.
The tiny transmitters use solar power and can be detected by smartphones and other receivers as the butterflies travel.
The resulting data helps researchers map individual migration routes and better understand how monarchs navigate their long journey south.
Migratory monarch butterfly resting on milkweed. (Joe Schelling / IUCN / FOX Weather)
Scientists hope the technology will reveal how monarchs find their way to the same wintering grounds year after year.
It could also help researchers identify critical habitats and potential obstacles along migration routes, providing valuable information for conservation efforts.
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The migration pattern for the end of October. (FOX Weather )
As of Oct. 6, more than 1,800 monarchs had been tagged using the technology across North America in 2026.
In early October, three tagged monarchs originating in Manitoba, MN and Ontario crossed into Mexico, marking a milestone for the tracking effort.
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Monarch butterflies at nesting grounds in Mexico. (Sylvain CORDIER / Gamma-Rapho / Getty Images)
The technology could prove especially valuable as monarchs face numerous threats, including habitat loss, pesticide exposure and climate-related changes that affect the availability of milkweed and nectar-producing plants.
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Although some tracked butterflies have already reached Mexico, the broader fall migration is still underway. The monarchs will remain in Mexico through the winter before beginning their northward journey in the spring.