North America spans three countries where monarch butterflies complete their annual odyssey, journeying thousands of miles from summer breeding grounds to winter refuges.[1][2]
A Journey That Defies Imagination
Monarch butterflies cover up to 3,000 miles in a multi-generational relay that starts in southern Canada and the northern United States.[3] The eastern population heads to oyamel fir forests in Mexico’s Transvolcanic Belt, while western ones seek coastal California groves. Scientists long puzzled over the precise routes, stopovers, and survival rates during this perilous flight. Harsh weather, habitat loss, and pesticides threatened the travelers, whose numbers plummeted in recent decades. Researchers estimated that only 20 percent or fewer completed the trek successfully. Now, innovative tools offer clarity on these fragile navigators.
The migration’s scale astounds: insects lighter than a paperclip traverse lakes, cities, and oceans. Tagged individuals revealed crossings over Lake Erie and detours through urban Ohio.[4] Such details emerged from fall 2025 efforts, highlighting vulnerabilities at every turn.
Breakthrough in Tracking Technology
Cellular Tracking Technologies developed BlūMorpho transmitters weighing just 60 milligrams – about a tenth of a monarch’s body weight.[2] Solar panels the size of rice grains power the devices, which broadcast at Bluetooth frequencies for detection by smartphones and wildlife receivers. Each tag costs around $200 and attaches gently to the butterfly’s thorax after chilling it briefly. Volunteers slip protective envelopes over wings during application to safeguard delicate scales. The MOTUS network and Project Monarch app crowdsource detections, yielding hundreds per tag.
Prior tags proved too heavy for full migrations. This leap, refined since 2017 prototypes, enabled continent-spanning surveillance.[4] Western monarch studies in Santa Cruz used similar tags to monitor coastal movements.[5]
Project Monarch’s Collaborative Triumph
Over 20 organizations united in the Project Monarch Collaboration, deploying more than 400 tags across Canada, the U.S., and beyond in fall 2025.[4] Partners included Monarch Watch, which tagged 30 in Kansas; Birds Canada at Long Point, Ontario; and Xerces Society in California. Monarch Watch reported 30 percent of its butterflies reaching Mexico and 70 percent detected in Oklahoma. Data flows through the Blū+ Portal and app for real-time analysis.
- Cape May Point Arts and Science Center funded initial efforts.
- James Madison University confirmed tags posed no survival risk.
- WWF Mexico and CONANP aided overwintering site monitoring.
- Monarch Joint Venture coordinated eastern population tracks.
- Xerces Society focused on western declines over 99 percent since the 1980s.
Insights Lighting the Path Forward
First tagged monarchs arrived at Mexico’s El Rosario sanctuary on November 9, 2025 – JMU004 and MW026 among them.[6] Others took coastal routes through Florida or veered offshore to the Bahamas before heading west. “There’s nothing that’s not amazing about this,” said Cheryl Schultz, a butterfly expert at Washington State University. The data exposed weather responses and urban flyovers, challenging old assumptions.[2]
Plans call for spring 2026 tagging to trace northward returns. Such precision aids habitat restoration and policy amid ongoing declines.
Key Takeaways
- Over 400 tags provided first individual tracks to Mexico overwintering sites.
- Solar-powered tech weighs 60mg, detectable by everyday phones.
- Reveals higher survival and diverse paths than previously known.
These revelations promise to bolster monarch recovery across borders. What paths have surprised you most? Share in the comments.
