Sensor Fastened to Monarchs Butterflies Will Reveal Their Migratory Patterns

Each fall, millions of monarch butterflies migrate to a particular group of mountain peaks located in central Mexico. How precisely they steer to their winter destination, and the way they select their route, is a subject of immense interest to researchers — particularly as climate change redirects their selected path.

Inhee Lee, assistant professor of electrical and computer engineering at the University of Pittsburgh, is part of a team designing a tracking platform that could be fastened to monarch butterflies to convey data about their location during their three-month migration south.

Recently, a paper describing these results was awarded the Best Paper Award at the MobiCom 2021 Conference.

Tracking animal migration is a critical ecosystem indicator. Migrators travel long distances across entire continents, and it can give us unprecedented insight into their migratory paths, how the environment around them is changing, and how species interactions are impacted by changing movements and distributions.

Inhee Lee, Assistant Professor of Electrical and Computer Engineering, University of Pittsburgh

Earlier, only larger animal migrators could be followed for substantial periods of their migration. Insect migrators, however, constitute a huge portion of the overall migrators worldwide. To monitor them, the scientists have developed a new wireless sensing system termed mSAIL, specially built for monarch migration.

The minute, 62 mg, 8×8×2.6 mm chip is fastened to the butterfly’s back and can instantaneously measure temperature and light intensity, wirelessly conveying that data back to the scientists once the butterflies arrive at their destination. The platform will apply a deep learning-based localization algorithm to rebuild the butterfly’s migration route after it has completed the journey.

To check the potential of mSAIL, the scientists fastened the unit to a real-life monarch butterfly in a botanical garden. The chip was fastened to the butterfly; it had no problem opening and closing its wings, flying or carrying out any other regular butterfly actions with the chip in place.

mSAIL is an extension of previous work that Lee undertook while an assistant research scientist at the University of Michigan. mSAIL combines formerly created integrated circuits within a three-dimensional (3D)-stacked form factor and shows, for the first time, the practicality of individual butterfly localization and monitoring using the unique embedded platform.

The study's next step is to mass manufacture more than 100 mSAIL sensors that can consistently work during the three-month monarch migration phase. The scientists will free the mSAIL-fitted butterflies at different locations in the United States and will track the sensors at the butterflies’ well-known resting spots — such as in the western Lake Erie archipelago — and at the final winter home in central Mexico.

Ultimately, the team hopes to incorporate an air pressure sensor into the mSAIL, which will enable it to establish altitude and more accurately evaluate the butterflies’ route.

The study titled “mSAIL: Milligram-Scale Multi-Modal Sensor Platform for Monarch Butterfly Migration Tracking” was headed by Lee and Roger Hsiao, who was an undergraduate student at the University of Michigan and is presently a graduate student at UC Berkeley. Other co-authors are from the University of Pittsburgh, the University of Nebraska, the University of Michigan, and the University of Delaware.

Video Credit: University of Pittsburgh