They will help provide the most detailed look to date at the first leg of the butterflies' migration north, said Eduardo Rendón Salinas, a biologist with WWF Mexico. WATCH | Swarms of monarch butterflies spend winter in this Mexican sanctuary: In Mexico's monarch empire | Duration 0:58 Millions of monarch butterflies spend the winter in the El Rosario butterfly sanctuary in Mexico's Michoacán state. WATCH | Monarch butterflies tracked on migration south: Tagged monarch butterflies tracked on migration to Mexico | Duration 0:37 Data from Project Monarch shows how tiny transmitters attached to select butterflies tracked their migration from southern Ontario to Mexico between September and November 2025. A monarch butterfly with tiny transmitter attached prepares to take flight from the hands of Adriana Avelina Ruíz Márquez, deputy director of the Monarch Butterfly Biosphere Reserve. "We feel fortunate to belong here, and to have this natural wonder that is the monarch butterfly."

Source: CBC News March 15, 2026 09:33 UTC