Adriana Avelina Ruíz Márquez carefully attaches a small transmitter to the thorax of a monarch butterfly using fake eyelash glue just behind its head. Despite weighing only half a gram, the butterfly effortlessly carries the 60-milligram device, which includes a tiny solar panel. After the delicate procedure, which involves a toothpick and a Q-Tip, Ruíz Márquez releases the butterfly, and it swiftly takes flight.
This innovative tracking device, introduced for the first time in Mexico to tag monarch butterflies before their migration back to the U.S. and southern Canada, aims to unravel some mysteries about these insects. Ruíz Márquez expressed her belief that utilizing people’s smartphones will help track the movements of the butterflies and shed light on their migration patterns.
Nestled in the mountainous El Rosario butterfly sanctuary in Mexico, where butterflies flutter around like mosquitos in Canadian marshlands at dusk, the majority of North America’s monarchs east of the Rocky Mountains spend the winter. This sanctuary is part of the Monarch Butterfly Biosphere Reserve, spanning Michoacán and the State of Mexico.
Teams from the federal Commission for National Natural Protected Areas and World Wildlife Fund (WWF) Mexico have tagged a total of 160 monarchs across the reserve, with 40 in El Rosario, using the new transmitters. This initiative, led by biologist Eduardo Rendón Salinas, will provide unparalleled insight into the initial phase of the butterflies’ migration northward.
The super generation of monarchs, which embarks on the journey south in one continuous flight from the Prairies to the Maritimes, down through the U.S. Northeast and Midwest, plays a crucial role in the migration process. Subsequent generations lay eggs on their route back north after mating in sanctuaries such as El Rosario.
The microchipped transmitter emits a signal detectable by nearby iPhones, allowing crowd-sourced tracking of the butterflies’ path if Bluetooth and location services are enabled. The Project Monarch app or a handheld receiver can help map the butterflies’ trajectory accurately, offering a level of detail previously unattainable.
Previously, scientists relied on wing tags to track monarchs, but these only provided limited information on the butterflies’ movements. Cellular Tracking Technologies is enhancing the transmitter to enable passive detection by Android smartphones, enhancing tracking capabilities further.
Following successful trials in 2023 and 2024, the transmitters were deployed in a continent-wide monarch tracking project, involving over 20 groups across Canada, the U.S., and beyond. The data collected will contribute to a comprehensive understanding of the monarchs’ migratory patterns and behaviors.
During the winter months, the Monarch Butterfly Biosphere Reserve in Mexico becomes a haven for the butterflies, swarming and clustering on the oyamel branches. The community patrols, led by individuals like Horacio Cruz Guzmán, protect the sanctuary from illegal activities, ensuring the butterflies’ safety and preservation of their habitat.
The community of El Rosario has developed a sustainable tourism industry during the monarchs’ winter stay, providing essential income. They also cultivate oyamel seedlings to maintain the forest’s health, showcasing their dedication to preserving this natural wonder.
This collaborative effort between researchers, conservationists, and local communities underscores the importance of protecting the monarch butterflies and their habitats for future generations.