Solar-powered radio tags let scientists follow endangered monarchs along California coast

In a joint effort, the U.S. Fish & Wildlife Service’s Coastal Program and Althouse & Meade deployed solar-powered radio backpacks on migratory monarch butterflies at three overwintering locations on California’s central coast. The tiny transmitters, affixed with eyelash glue to individuals deemed sufficiently robust, broadcast geospatial signals that researchers can track alongside site-specific weather data. Tagging took place in early mornings when the cold limited the insects’ flight, and each butterfly was measured and sexed before deployment.

Data gathered will help clarify how monarchs use coastal groves and nearby nectar sources, informing future restoration strategies. The initiative also incorporates citizen scientists, who can view tagged butterflies on a map and submit observations through the Project Monarch mobile application.