Local Scientists Utilize Bluetooth Tech to Track Monarch Migration

At Natural Bridges State Beach in Santa Cruz, California, local enthusiasts are harnessing Bluetooth technology to track the migratory patterns of monarch butterflies. This year, citizen scientists, including Sasha Hernandez, a second-year neuroscience student at UC Santa Cruz, are participating in a groundbreaking project that aims to understand the monarchs’ journey from their breeding grounds to their winter colonies in Mexico.

Through the Project Monarch app, launched with the help of the Xerces Society, individuals can contribute to this research by using their smartphones to detect butterflies fitted with advanced Blu+ tags. These tags utilize Bluetooth technology to communicate with nearby devices, allowing users to record data when a tagged butterfly comes within a 100-yard range. This citizen science initiative marks a significant advancement in the study of monarch migration, which has faced numerous challenges over the years.

Innovative Tracking Technology

This initiative represents a shift from traditional tracking methods, which often involved writing numbers on butterfly wings and using spotting scopes to identify them. The Blu+ tags, developed by Cellular Tracking Technologies and the Cape May Point Arts & Science Center in New Jersey, weigh just two-thousandths of an ounce and are about the size of a grain of rice. Ashley Fisher of the Xerces Society emphasized that these tags are so light they can be used on monarchs, akin to a human carrying a 22-pound backpack.

The tags are powered by miniature solar panels and emit radio signals every three seconds, transmitting key information such as location and battery status. This data can be captured not only by stationary receivers but also by smartphones using the Project Monarch app. For Hernandez, this technology bridges her academic studies with real-world applications, making science more accessible.

As of July 2025, the project reported nearly 360,000 detections during eastern monarch migrations, showcasing the potential for extensive data collection. The tags are set to be activated on the West Coast by mid-December, allowing for comprehensive tracking of western monarchs, which have experienced a dramatic decline of approximately 95 percent in recent decades.

Community Engagement and Conservation Efforts

The need for community involvement in tracking western monarchs is critical due to their fragmented migration route. Unlike their eastern counterparts, these butterflies migrate from inland valleys and mountain ranges to the coastal regions of California, where they find refuge in eucalyptus groves. This more localized migration makes them particularly vulnerable to habitat changes, emphasizing the importance of citizen scientists in monitoring their populations.

According to Charis van der Heide, a senior biologist at Althouse and Meade, every small contribution from volunteers is significant. Each migration season, volunteers count butterflies along California’s coast from October to January. This year, the Xerces Society encourages volunteers to run the Project Monarch app in the background while they tally butterflies. Van der Heide likens the data collection process to a treasure hunt, enhancing the overall experience for participants.

The data gathered may help researchers identify better overwintering sites for monarchs, beyond known factors such as proximity to the coast and diverse nectar sources. Understanding the locations where monarchs linger versus those they abandon could significantly influence future conservation strategies.

For Hernandez and many others, this project fosters a deeper connection with these iconic insects. “When I see a monarch fly away, the first thing I think is: Where did it go?” she reflected. This new technology not only empowers citizen scientists but also plays a crucial role in conserving a species that has captured the interest and admiration of many.