Scientists have long tried to understand where and how monarch butterflies migrate across North America. The population has plummeted and more data is needed to improve conservation.
But tracking monarchs has been tricky without harming the delicate creatures or hitting technical obstacles.
The monarchs’ annual trek is one of the largest insect migrations in the world, spanning up to 3,000 miles. The individual butterflies that participate are uniquely adapted for the feat, a so-called “super generation” that live up to eight months, eight times longer than their parents or grandparents.
This fall, a massive international effort called Project Monarch used new technology to track hundreds of monarchs from Canada to Cuba, providing the most comprehensive look yet at the famous journey.
Researchers in Virginia helped make it happen.
Butterfly expert Lee Brown, an assistant biology professor at James Madison University, had already been studying the impact of different tracking devices on monarchs’ ability to fly.
At the time, the smallest available tracker weighed only slightly less than a monarch, which averages about half a gram.
She looked at scientific papers on monarchs using such a tag and saw comments that some butterflies had trouble flying afterward.
Brown’s team tested how monarchs move under three scenarios: the traditional, heavier tag; a smaller new transmitter called the BluMorpho; and no tracker.
That required a lot of fieldwork – literally. Researchers would tag a monarch and track its trajectory visually, running after it to mark its path by throwing flags on the ground every 15 seconds.
The idea was also to get information about how butterflies move through different types of landscapes, Brown said. They often fly more quickly through a forest, for example, versus making lots of rest stops in a flower-filled meadow.
“You get the move lengths, the angles they're turning at and the time it takes them to make moves,” Brown said. But “we would lose quite a few, because they move pretty fast.”
Brown’s pilot data showed that butterflies using the new trackers fared pretty much the same as those that were untagged, while the heavier ones had a noticeable impact.
Her team also experimented with various glues for the trackers and settled on non-toxic eyelash glue as the best bet.
Their findings helped validate the method used in the recent international collaboration.
Officials laid the groundwork for Project Monarch about a decade ago, when a naturalist at the Cape May Point Arts and Science Center in New Jersey pitched the “moonshot” goal of building a transmitter light enough for a monarch.
"At the time, it seemed nearly impossible," Mike Lanzone, president and CEO of Cellular Tracking Technologies, which makes the BluMorpho devices, said in a recent news release.
The project ultimately led to the development of the new transmitters, which cost $200 each. They ping off a large network of radio towers and are Bluetooth-enabled, tapping into the phones of people who download the Project Monarch app.
The transmitter is powered by the sun instead of a battery, serving as the “smallest possible solar panel,” Project Monarch states on its website.
Last November was a milestone. A butterfly named Lionel was released in Cape May and provided the first-ever high-resolution track of monarch migration, ending in St. Augustine, Florida.
Starting this September, more than 20 partners across four countries tagged and tracked more than 400 butterflies.
The monarch species in the U.S. is separated into eastern and western populations, generally divided by the Rocky Mountains.
Brown said the migration of the easternmost population has been less understood.
“The Midwest monarchs, it's believed they definitely are going down to Mexico,” she said. “But east of the Appalachians, the question was are they just getting lost in the Southeast and integrating with the resident population that doesn’t migrate? Or do they end up going to Mexico?”
Her team tagged and released 20 butterflies in Harrisonburg and another participant sent five out of Virginia Beach. At least four from JMU made it to central Mexico by last week.
Other stragglers last pinged in spots along the way, such as New Orleans and Houston. Some took the snowbird route, heading south to Florida.
Out of the 400-plus contestants, it was a JMU-tagged butterfly that won “the metaphorical gold medal,” becoming the first detected at a reserve west of Mexico City, according to the New York Times.
Recent research shows that butterflies, overall, have rapidly declined nationwide since the start of this century.
Eastern migratory monarchs, specifically, are estimated to have declined by about 80% since the 1990s, with a high probability of extinction by 2080, according to the U.S. Fish and Wildlife Service, which has proposed protecting monarchs under the Endangered Species Act.
Butterflies face threats from pesticides, habitat loss and climate change.
“When you have hotter temperatures, you might have fewer of the caterpillars that survive, and loss of the overwintering habitat,” Brown said.
People who want to support monarchs can plant milkweed, avoid herbicides and stop mowing grass where possible.
Brown hopes that knowing more about where and how monarchs move could help officials protect those areas.
