The tiny transmitter tracking monarch butterflies' migration, Canada to Mexico

Tiny solar-powered transmitters are giving conservationists an unprecedented view of monarch butterflies’ 4,000-kilometre migration from Canada and the United States to Mexico. The BlūMorpho device weighs about 60 milligrams and is attached to a butterfly’s thorax with eyelash glue. It sends a signal that nearby phones and wildlife receivers can detect, allowing Project Monarch’s app to map individual journeys. In Winnipeg, 29 butterflies were tagged this fall as part of a larger effort involving more than 1,300 monarchs. One, nicknamed Eddie, travelled 1,258 kilometres to Kansas before its signal went quiet; another reached Mexico in 40 days. Five of Winnipeg’s tagged butterflies had made it to Mexico by late October.

The migration data can reveal where monarchs find enough nectar to refuel and where habitat gaps may strand or kill them. This matters because the long-lived “super generation” must reach Mexican forests to overwinter, while milkweed - the caterpillars’ main food - is being lost to herbicides, climate change and urban growth. Project Monarch brings together 82 organizations across three countries to turn tracking information into conservation action. Communities are using it to establish “monarch waystations” planted with native milkweed and nectar-rich flowers, aiming to create a chain of feeding sites across the continent. The project combines lightweight technology and public participation to identify priority areas and help sustain the species’ life cycle.