Solar Tags Track Monarchs on 3,000-Mile Migration
Scientists have fitted nearly 1,750 monarch butterflies with solar-powered radio tags to map their routes across North America.
Updated on Nov. 3, 2026 in Environmental
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Researchers attached solar-powered radio tags to nearly 1,750 monarchs this year, with tracking that began last year. The data revealed the first evidence of a butterfly reaching Utah, west of the Rockies, joining eastern monarchs in central Mexico.
Why it matters
Monarch populations have fallen sharply, with eastern numbers down more than 80% and western numbers down about 95% since the mid-1990s. Tracking migration routes helps scientists understand where and why these butterflies are declining.
The tags cost $200 each and weigh about as much as a drop of water, allowing trackers to log nightly roost sites and daily flight distances. Monarchs migrate some 3,000 miles from as far as southern Canada to central Mexico, but the full extent of their routes remains under study.
The players
Cellular Tracking Technologies
A company that developed the solar-powered radio tags used to track the monarch butterflies.
Trump administration
The U.S. presidential administration of President Donald Trump, which delayed a federal decision on monarch protections last year.
The details
Scientists attach tiny solar-powered radio tags to hundreds of butterflies to record where they roost each night and how far they fly each day. Some monarchs migrated down the Eastern Seaboard to Florida, jumped the Gulf of Mexico, and are tracking across Mexico, while the tags were developed by Cellular Tracking Technologies.
Timeline
Mid-1990s: Eastern and western monarch populations began their steep declines.
Last year: Tracking began, and the Trump administration delayed a decision on federal monarch protections.
This year: Solar-powered radio tags were attached to nearly 1,750 monarchs.
2030: A court-ordered deadline for the government's final decision on monarch protections.
Big Picture
A court has ordered the federal government to make a final decision on monarch protections by 2030, after the Trump administration delayed that decision last year. The new tracking data on migration routes arrives as that review proceeds.
Monarchs migrate some 3,000 miles, so readers who plant milkweed and nectar flowers along migration routes can support the butterflies on their journey. Protection decisions made by federal agencies will affect the habitats these butterflies rely on.
The takeaway
Monarchs use temperature and other environmental cues to begin migrating, and human-caused climate change keeps northern areas too hot for too long, which can disrupt those cues. Tracking their routes helps show where conservation efforts matter most.
What happens next
A court has ordered the government to make a final decision on federal monarch protections by 2030.
Further reading
Explore more on Environmental to see how species migration and habitat loss are being studied.
Source note: This article includes information reported by Irish Examiner.
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