It’s not only birds that fly south for winter. Many of Europe’s death’s-head hawkmoths also head off to warmer climes in autumn. And new research reveals that they do so by means of a sophisticated navigation system comparable to that of our feathered friends.
“They’re not just getting blown about,” says Myles Menz, lead author of the research, published in Science. “They have a place to go and they’re getting there.”
Menz and his colleagues were able to track the insects as they crossed the Alps by fitting them with tiny, short-range transmitters that could be followed by scientists travelling in a light aircraft. This revealed that the moths routinely adjust their heading to compensate for wind direction, allowing them to maintain a consistently straight flight path.
They also seek out the most favourable winds by varying their altitude. “They can get up really high to use a tail-wind,” says Menz. “In cross-winds or head-winds, they sit down low and power through.” Their precise destination is not yet entirely clear.
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“They’re probably heading to the Mediterranean, North Africa and possibly sub-Saharan Africa,” says Menz, who undertook the research at Germany’s Max Planck Institute of Animal Behavior. In which case, they may be covering 4,000km on their migratory flights. It’s possible, though, that the sub-Saharan population of death’s-heads are not connected to those from Europe and that they remain there year-round, says Menz.
This raises the intriguing possibility that populations vary in their migratory strategies – again, much like birds. There is also the question of how they know which way to go. Unlike birds, which can learn a route by following more experienced flock-members and then hone their strategy over subsequent years, the moths, which only live for a few weeks as adults, make the trip only once.
“There’s really good evidence for various compass mechanisms in insects – sun compasses in day-flying insects and magnetic ones in night-flying moths, or navigating using landmarks. We can now try to uncover how they might be using these different cues to get where they want to go,” says Menz.
Main image: the death's-head hawkmoth (Acherontia atropos) is famous for the human skull on its thorax. The moth species features in horror film Silence of the Lambs and on the film cover art. © Robin Bush/Getty