Sitting alone in the cockpit of a small biplane, Martin Wikelski listens to the beeps of a machine next to him. Sonic beacons help the ecologist to stalk death’s head moths (acherontia atropos) fluttering through the dark skies over Konstanz, Germany, about 80 kilometers north of the Swiss Alps.
The moths, nicknamed for the skull-and-crossbones pattern on their backs, migrate thousands of miles between North Africa and the Alps during the spring and fall. Many migratory insects go where the wind takes them, says Ring Carde, an entomologist at the University of California, Riverside, who is not a member of Wikelski’s team. Death’s-head hawk moths appear to be anything but typical.
“When I follow them with a plane, I use very little gasoline,” says Wikelski, of the Max Planck Institute for Animal Behavior in Munich. “That shows me that they are supposedly picking directions or areas that are probably supported by a bit of an updraft.”
A new analysis of data collected from 14 death’s-head hawk moths suggests that these insects are in fact piloting themselves, possibly relying in part on an internal compass tuned to Earth’s magnetic field. moths not only fly on a straight paththey also stay on course even when the wind changes, Wikelski and colleagues report August 11 in Sciences.
The findings could help predict how the moths’ flight paths might change as the globe continues to warm, Wikelski says. Like many animals, death’s-head moths will likely move north in search of cooler temperatures, she suspects.
To control the moths, Wikelski’s team attached radio transmitters to their backs, which is easier to do than you might expect. “Death’s-head hawk moths are totally cool,” says Wikelski. They are also huge. Weighing the equivalent of three jelly beans, the moths are the largest in Europe. That makes affixing the tiny labels a piece of cake, although moths don’t like it very much. “They talk to you, they yell at you a little bit,” he says.
Once the researchers released the newly marked and slightly upset moths, Wikelski set out after them on a plane. As the insects flew south toward the Alps, an onboard device beeped the transmitters at a frequency related to the moths’ distance from the plane.
While detailed tracking of eight of the moths allowed him to follow the insects for about 63 kilometers on average, he chased one for just under 90 kilometers. That’s the longest distance an insect has been continuously tracked, he says. “It’s outrageously crazy work,” he says of low-altitude night flights. “It’s also a bit dangerous and it’s just showing that it’s possible.”