BIOLOGY • SOLAR POWER • CONSERVATION
Solar Tags Track Monarch Migration
Miniature electronics offer a closer look at individual butterflies on the move.
ADDED OCTOBER 20, 2026 • CONSERVATION TECHNOLOGY
Evidence status: deployed technology, developing research
Researchers are using miniature solar-powered radio tags to follow individual monarch butterflies. The technology is operating in the field; interpreting the resulting movements and their conservation significance remains ongoing work.
A tiny transmitter on a remarkable traveler
Project Monarch brings together Cellular Tracking Technologies, the Cape May Point Arts & Science Center and research partners. Its approximately 60-milligram solar-powered tags transmit at 2.4 GHz, enabling detections by compatible receivers and smartphones. Nearby detections build a record of an individual butterfly's movements. Project collaborator interview [1]
From radio signals to migration maps
This is receiver-based tracking, rather than a continuous satellite-position feed from the butterfly. A route map is assembled from detections. As a practical inference, the line connecting two records should not be treated as proof of the exact path flown between them. Gaps can reflect detection coverage, illumination, tag performance or other causes; a missing signal alone does not establish that a butterfly died.
What the 2026 project reports
In its October 16 update, Monarch Joint Venture reported that more than 1,800 monarchs had been tagged across North America as of October 6. Three individuals tagged in Manitoba, Minnesota and Ontario had crossed into Mexico in early October. These are project-reported observations, not a complete census of monarch migration. 2026 update [1]
Can carrying a tag affect a butterfly?
Yes, that possibility requires testing. Helen St. John's 2026 master's thesis at James Madison University compared adhesives and two tag weights. The heavier 0.13-gram tags reduced movement lengths and increased resting probability. For the lighter 0.06-gram CTT tags, movement results varied by life-cycle stage, with marginally negative effects reported for migrants. Adhesive choice also affected survival in the study. This thesis abstract supports careful validation, rather than a blanket claim that tagging is harmless. Research abstract [2]
Why conservationists care
More detailed movement records can help researchers investigate stopovers and connections between habitats. A useful next question is whether protecting a particular location improves migration outcomes. Maps can guide such investigations, but mapping alone does not prove that a conservation intervention works. Receiver coverage and tagging effects must be considered when interpreting the records.
A classroom connection
Students can compare two recorded positions, estimate straight-line distance and ask what happened between detections. Have them separate observations from inferences: “detected at this location” is an observation; “flew straight to the next location” is an assumption. The activity connects biology, geography, measurement and engineering.
Explore the project
View the Project Monarch web app and the participating organizations' guidance. Observing project maps is a useful way to participate without handling wildlife.
Sources & further reading
- Monarch Joint Venture: interview with David La Puma, October 16, 2026. Firsthand project account of the technology, deployment and research questions.
- Helen St. John, Impacts of radio telemetry tags on monarch butterfly movement, behavior, and survival, James Madison University MS thesis, May 2026. This entry uses its publicly available abstract.
- Washington State University: new monarch tracking technology, April 6, 2026.