Monarch Migration: Tiny Tech Reveals Butterfly Secrets
For generations, the annual migration of the monarch butterfly has been a source of wonder – and mystery. Now, a groundbreaking initiative is leveraging miniature technology and citizen science to unlock the secrets of these incredible insects, offering the most detailed look yet at their journey between Canada, the United States and Mexico.
A Grain-of-Rice Tracker
Researchers at the Monarch Butterfly Biosphere Reserve in Michoacán, Mexico, are attaching transmitters weighing just 60 milligrams – about the weight of a few grains of rice – to the thorax of monarch butterflies. These devices, powered by tiny solar panels, are allowing scientists to track the butterflies’ movements with unprecedented accuracy. Adriana Avelina Ruíz Márquez, deputy director of the reserve, spearheaded the effort, utilizing a delicate process involving fake eyelash glue, a toothpick, and a Q-Tip to secure the trackers.
Crowdsourced Tracking with Smartphones
What makes this tracking method truly innovative is its reliance on a network of “passive detectors” – smartphones. The transmitters emit a signal detectable by iPhones with Bluetooth and location services enabled. Anyone who downloads the Project Monarch app, or uses a handheld receiver, can contribute to charting the butterflies’ path. David La Puma, director of global market development with Cellular Tracking Technologies, the device’s developer, explains, “Literally, [monarchs] are flying over roads and people are driving down the road and it’s giving us a location. It’s a fantastic level of spatial detail that was never before possible.”
Unveiling Migration Mysteries
Previously, scientists relied on tags affixed to butterfly wings, providing only the points of tagging and eventual rediscovery. This new technology allows researchers to understand the nuances of the migration, including how monarchs move between colonies – a phenomenon previously only theorized. Ruíz Márquez believes the data will help solve lingering questions about the butterflies’ route, activity upon arrival, and departure times.
The Biosphere Reserve: A Vital Sanctuary
The vast majority of North America’s eastern monarch population overwinter in the El Rosario sanctuary, located within the Monarch Butterfly Biosphere Reserve in Mexico. This reserve, encompassing approximately 135 square kilometers, is crucial for the survival of the species. The reserve is protected by community patrols, like the one led by Horacio Cruz Guzmán, who work to prevent illegal logging and maintain the health of the oyamel fir forests that provide shelter for the monarchs.
Community-Based Conservation
The El Rosario ejido – land collectively held and managed by the community – plays a vital role in the reserve’s protection. The community has developed a thriving tourism industry around the monarch overwintering season, providing a crucial source of income. They also actively participate in reforestation efforts, planting oyamel seedlings to ensure the long-term health of the forest.
Looking Ahead: Expanding the Tracking Network
After successful pilot programs in 2023 and 2024, the transmitter technology was deployed as part of a continent-wide monarch tracking project, involving over 20 groups. In September 2025, 30 monarchs were tagged in Ontario, Canada, and a total of 400 monarchs were tagged from Canada to Cuba, with many successfully tracked as they entered the Mexican reserve in November. Cellular Tracking Technologies is also developing an upgrade to allow Android smartphones to function as passive detectors.
FAQ: Monarch Butterfly Tracking
- How small are the transmitters? The transmitters weigh approximately 60 milligrams and include a solar panel the size of a grain of rice.
- How does the tracking work? The transmitters emit a signal detectable by nearby smartphones with Bluetooth and location services enabled.
- Where do monarchs overwinter? The vast majority of eastern North American monarchs overwinter in the Monarch Butterfly Biosphere Reserve in Mexico.
- Who is involved in the tracking project? The project involves researchers, government agencies (like Environment and Climate Change Canada), and citizen scientists.
Pro Tip: You can contribute to monarch tracking by downloading the Project Monarch app and keeping Bluetooth and location services enabled on your smartphone while traveling!
Learn more about monarch conservation efforts at Butterfly Pavilion and the Monarch Butterfly Biosphere Reserve.
What questions do you have about the monarch migration? Share your thoughts in the comments below!
