14 DAY TRIAL // The rules governing long-distance travel may be simpler and more ancient than was once thought: scientists have now discovered that migrating dragonflies exhibit many of the same behaviors as songbirds.
The team of researchers from Princeton University, led by the evolutionary biologist Martin Wikelski, placed radio transmitters weighing only 300 milligrams - about a third as much as a paper clip - on 14 green darner dragonflies. There are around 5200 species of dragonflies over the world, but only 25 to 50 species are thought to be migratory. Green darners are one of them.
Once the tracking devices were in place scientists started a major dragonfly tracking operation. They tracked the insects for 10 days from both aircraft and handheld devices on the ground. The result was totally unexpected: dragonflies' flight patterns showed many similarities to those of birds that migrate over the same regions of coastal New Jersey.
"The dragonflies' routes have showed distinct stopover and migration days, just as the birds' did," said Wikelski. "Additionally, groups of both birds and dragonflies did not migrate on very windy days and only moved after two successive nights of falling temperatures. We saw other similarities as well, which makes us wonder just how far back in Earth's history the rules for migration were established in its animals."
According to fossil records, dragonflies predated the first birds by about 140 million years - the first dragonflies appeared about 285 million years ago. Of course, birds did not evolve from insects, so this discovery shows that there aren't really that many ways in which an animal could migrate - the environment places strict limits that allow only a small number of viable migrating strategies.
The study is also groundbreaking in its technique of tracking small animals over great distances. The authors point out that their tracking technique could have all sorts of useful applications in agriculture and ecological management.
"These small transmitters could enable us to track animals from space all around the globe if satellites were available," Wikelski said. "Though nearly everyone has heard of animal migration, we actually know very little about how animals move. It could tell us a lot about the way species respond to climate change and other disturbances. Because the economies of many nations are still largely agrarian, a better understanding of how, say, locust swarms travel could assist us with managing both local agriculture and the world economy that hinges upon it."
Photo credit: Alessandro Marzio