By closely following individual moths during migration, the world-first study unlocked a century-old mystery.
Insects Use Sophisticated Navigation Systems For Long-Distance Migration
Insects use “sophisticated” navigation systems for long-distance migration, reveals groundbreaking new research.
Tiny trackers show that nocturnally migrating hawkmoths continually adjust their flight headings in response to winds and the landscape to keep their straight course.
Researchers say their study, which achieved the longest continuous tracking of migrating insects, indicates that the species use a sophisticated internal map or compass mechanisms for navigation during their voyages.
Every year trillions of migrating insects – including butterflies, locusts, and moths – navigate vast distances across the globe on journeys that span continents, mountain ranges, seas, and a wide range of environmental conditions.
The death’s head hawkmoth travels as far as 2,500 miles between Europe and sub-Saharan Africa.
The new study, by scientists from the University of Exeter as well as the Max Planck Institute of Animal Behavior (MPI-AB) and the University of Konstanz in Germany, shows that they can maintain perfectly straight flightpaths even in unfavorable wind conditions.
The research team radio-tracked migrating hawkmoths for up to 50 miles – the longest distance that any insect has been continuously monitored in the wild.
By closely following individual moths during migration, the world-first study unlocked a century-old mystery of what insects do over their long-range journeys.
The study, published in the journal Science, confirms that hawkmoths can accurately maintain straight trajectories over long distances.
The findings reveal that insects are capable of accurate navigation, confirming that an internal compass guides them on their long journeys.
Even though insect migrants far outnumber better-known migrants, such as birds or mammals, their migration is the least understood form of long-range animal movement.
Study first author Dr. Myles Menz, who conducted the research at MPI-AB, said: “Studying insects on the move is a formidable challenge.
“They’re usually too numerous to mark and find again, and too small to carry tracking devices.”
He said much of what we know about insect migration has come from studies that sample insects at a single moment in time, such as through radar or direct observation, which has left vast knowledge gaps
Dr. Menz, who is now a lecturer at James Cook University in Australia, said: “Understanding what insects do during migration, and how they respond to weather, is a last frontier in migration science.”
The study, which followed radio-tagged moths in a light aircraft, is the first to continuously study nocturnal migrating insects in the wild.
The team focused on the death’s-head hawkmoth which, like many insects, is a multi-generational migrant, meaning that no individual knows the entire route.
The researchers reared caterpillars until adulthood in a lab to ensure that individuals were naive.
When moths emerged as adults, they were fixed with radio tags weighing 0.2 grams – less than 15 percent of an adults’ body weight.
Dr. Menz said: “The moths would probably eat more weight than that in a night, so these tags are extremely light for the insects.”
The researchers released the tagged moths and waited for flight to begin, after which they chose a single individual to follow at a time.
The team followed 14 moths each for up to 50 miles or 4 hours – a stretch long enough to be considered migratory flight – using antennas mounted on a Cessna airplane to detect precise locations every five to 15 minutes.
Insects were followed in the south-south-west direction from Konstanz into the Alps, which follows the route taken by hawkmoths towards the Mediterranean and northwest Africa.
Due to practical constraints of flying in an aircraft, the scientists tracked moths continuously until the insects stopped on route.
Senior author Professor Martin Wikelski, who piloted the plane during the study, said: “When you’re in an aeroplane, it becomes extremely difficult to wait for the insects to begin migrating again because you would have to be in the air when this happens, which could be any time in the night.”
The results show that moths maintained perfectly straight trajectories for long distances during flight.
The researchers said that was not because they waited for favorable tailwinds; rather, they employed a range of flight strategies to buffer against prevailing winds, allowing them to hold their course throughout the night.
When winds were favorable, they flew high and slow, allowing the air to carry them. But during harsh headwinds or crosswinds, they flew low to the ground and increased speed to keep control of their path.
Dr. Menz said: “For years it was assumed that insect migration was mostly about getting blown around.
“But we show that insects are capable of being great navigators, on par with birds, and are far less vulnerable to wind conditions than we thought.
“By showing that it is technically possible to continuously monitor individual insects over migration, and to observe their flight behavior in detail, we hope to inspire more studies to answer many more big questions in this area.”
He says the next step is to answer the question of how moths are able to maintain such straight lines.
Dr. Menz added:“Based on past lab work, it’s possible that the insects are using internal compasses, both visual and magnetic, to chart their way around the world.”
Produced in association with SWNS.