Scientists use tiny trackers and an airplane to track moving moths
NEW YORK (AP) — Billions of insects migrate across the world each year, but little is known about their journeys. So, to search for clues, German scientists took to the skies, placing tiny trackers on the backs of giant moths and following them by plane.
To the researchers’ surprise, the butterflies seemed to have a definite idea of where they were going. Even when the winds changed, the insects stayed on a straight path, the scientists reported in a study published Thursday in the journal Science.
Their flight paths suggest these death’s-head hawk-moths have complex navigational skills, the authors said, challenging previous ideas that insects are just vagrants.
“For many, many years it was thought that insect migration was mainly driven by the winds and that they blew,” said lead author Myles Menz, now a zoologist at James Cook University in Australia.
It’s been difficult for scientists to look closely at how insects move, in part because of their small size, Menz said. The types of radio beacons used to track birds may be too heavy for small flyers.
But the transmitters have become smaller. And it helps that the death’s-head hawk-moth is huge compared to other insects, with a wingspan of up to 5 inches (127 millimeters).
The iconic species – dark in color with yellow wings and skull-like markings – was able to fly just fine with the tiny tracker taped to its back, said Martin Wikelski, study co-author and migration researcher at the Max Planck Institute for Animal Behavior in Germany.
The butterflies are thought to migrate thousands of miles between Europe and Africa in the fall, flying at night.
For the study, the researchers released tagged moths in Germany in the hope that they would start flying on their migration path to the Alps.
Wikelski, the study pilot, took off in his plane, circling the area and waiting for moving moths. If he picked up a signal from a little traveler, he would follow his radio blips for hours on end.
“The little butterfly guides you,” he says.
The researchers tracked the flight paths of 14 moths, with their longest track around 56 miles (90 kilometers).
Not only did the moths fly in a straight line, but they also seemed to circumvent wind conditions, Menz said, flying low to the ground when the winds were against them, or rising up to catch a useful tailwind.
Although the number of tracked moths is quite small, it’s important to take a close look at insect migration, said Ryan Norris, an insect and bird migration researcher at the University of Guelph in Canada, who did not participate in the study.
“I was surprised how far they could follow them,” Norris said. “And it’s certainly surprising that individual moths stay on this straight path.”