Adriana Avelina Ruíz Márquez employs false eyelash adhesive to affix a small transmitter to the thorax, just behind the monarch butterfly’s head. Weighing around half a gram, the butterfly effortlessly carries the 60-milligram device, equipped with a tiny solar panel. Following the delicate procedure, which involves a toothpick and a Q-Tip, Ruíz Márquez releases the butterfly, allowing it to take flight. This innovative tracking device, a first in Mexico for tagging monarchs before their migration to the U.S. and southern Canada, aims to unravel mysteries surrounding the insects’ behaviors using smartphones for tracking.
The El Rosario butterfly sanctuary, located in Michoacán state about 180 kilometers west of Mexico City, serves as a wintering site for the majority of North America’s monarchs east of the Rocky Mountains. This sanctuary, part of the Monarch Butterfly Biosphere Reserve, comprises six sanctuaries across Michoacán and the State of Mexico, with a protected core area of approximately 135 square kilometers. 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 transmitter.
Eduardo Rendón Salinas, a biologist with WWF Mexico, highlighted the significance of tracking monarchs during their migration north, offering insights into their hibernation in Mexico. The tracking will also enable monitoring of monarch movements between colonies, a previously theoretical concept. Monarchs undertake a multi-generational journey spanning up to 5,000 kilometers north, with a unique super generation making the round trip from the Prairies to the Maritimes and back, before laying eggs for the next generation.
The microchipped transmitter emits signals detectable by nearby iPhones, enabling crowd-sourced monitoring of the butterflies’ flight path if Bluetooth and location features are activated. The Project Monarch app or a handheld receiver can be utilized to trace their movements in real-time, providing unprecedented spatial detail previously unattainable. David La Puma of Cellular Tracking Technologies, the developer of the device, mentioned plans for an upgrade allowing Android smartphones to function as passive detectors.
Prior to the introduction of the new transmitters, scientists relied on wing tags for monitoring monarchs, which offered limited movement details during migration. La Puma emphasized the enhanced tracking precision achieved with the new technology. Following successful trials in 2023 and 2024, the transmitters were integrated into a continent-wide tracking initiative involving over 20 groups. By October, 400 monarchs were tagged from Canada to Cuba, with tracking data showing their entry into Mexico’s Monarch Butterfly Biosphere Reserve in November.
During the monarchs’ winter stay in the El Rosario sanctuary, the area becomes a haven for the butterflies, forming massive clusters on oyamel branches. The community, including a patrol group led by Horacio Cruz Guzmán, safeguards the sanctuary from illegal logging activities. The sanctuary’s unique ecosystem sees various animals fleeing upon the monarchs’ arrival, while certain species like hummingbirds and orioles remain, adapted to the toxins present in monarchs due to their diet of milkweed in North America.
El Rosario’s community, as custodians of the land, has nurtured a thriving tourism sector during the monarchs’ wintering period, ensuring sustainable income. Additionally, they cultivate oyamel seedlings to maintain a healthy forest ecosystem. Cruz Guzmán expressed gratitude for being part of the community, cherishing the natural wonder that is the monarch butterfly.