Your Phone Can Already Detect Migrating Monarch Butterflies, but This App Lets You See Them

Birds aren’t the only migrators: Dozens of North American insect species also undertake long-distance journeys seasonally, including beetles, moths, and grasshoppers. Best known, and beloved across their range, are monarch butterflies, which traverse from central Mexico to southern Canada in a cycle that spans four generations. Scientists and volunteers have tracked their journey for decades with sticker tags and point counts, but tiny, cutting-edge tracking devices are now giving researchers a much clearer picture of their travels. You and your mobile phone can help—and may be already. 

The new trackers are small and light enough that monarchs have no problem flying with them; they weigh about as much as a grain of rice, attached to the butterflies with a dab of eyelash glue: “Apparently it’s great for clubbing—and migrating all the way to Mexico,” says David La Pluma, vice president of global market development for Cellular Tracking Technologies, which developed the transmitters. 

But the real innovation is a coding tweak that enables cell phones to detect butterflies’ trackers as they flutter past. Piloted in 2024 and expanded last fall with nearly 500 monarchs tagged, the new tech allows researchers to watch the movement of each monarch in real time—a precision earlier scientists could only dream of. “All these questions that you could never really ask before when you just had the start and the end of their journey, now you can fill in all the details,” says Sean Burcher, director of science at the Cape May Point Arts and Science Center, which leads the Project Monarch tracking initiative. 

A tracker small enough for a butterfly was researchers’ dream for at least a decade, says La Pluma. Cellular Tracking Technologies initially manufactured transmitters for Golden Eagles—one of the largest birds in North America—and has worked its way down to smaller and smaller devices. “It’s a total game changer,” says Ray Moranz, pollinator conservation specialist at the Xerces Society for Invertebrate Conservation, a project partner. “I’ve been placing paper sticker tags on monarchs to track their movements on and off for the last 10 years,” Moranz says, “Those are cool. But the Bluetooth transmitters are so much more efficient and effective in giving us data.” In addition to mobile devices, Motus towers can also detect the butterfly trackers. Moranz tips his hat to the ornithologists who originally developed the transmitter technology: “I have to give a shout out to the bird people.”

You may already be aiding the effort to track monarchs in stunning new detail: As long as your cell phone is turned on, with location tracking enabled and Bluetooth on, it will detect any tagged butterflies nearby—within about 100 meters—and anonymously share the data with researchers. But if you download the Project Monarch app, by Cellular Tracking Technologies, your phone will capture and report richer data for the project—and you will have your own window into monarch migration, with a dashboard that tallies how many monarchs your phone has detected and even allows you to track the travels of individual butterflies. 

Your participation provides much-needed help because, despite decades of conservation work, monarchs are declining across their range. Project Monarch researchers will use the new trackers to pinpoint and protect the habitat that matters most to the butterflies along their journeys. You can help with that, too, by planting native milkweed and nectar-rich plants in your yard or community green space. “A little bit of effort can make a big difference in a single monarch’s life,” says Brett Ewald, director of New Jersey Audubon’s Cape May Bird Observatory, a Project Monarch partner. And when a whole lot of people make that effort, they can shape the future of the species. 

This story originally ran in the Summer 2026 issue as “Hold the Phone.” To receive our print magazine, become a member by making a donation today.