If you think you can outpace a dragonfly, think again. Researchers from the University of Guelph used radio transmitters to track the migratory flights of monarch butterflies and green darner dragonflies. They found that while, on average, the dragonflies flew about sixteen kilometres per hour, the fastest was clocked at a groundspeed of seventy-seven kilometres per hour (with tailwind assistance). Monarch butterflies flew at an average speed of twelve kilometres per hour, with the top monarch moving at thirty-one kilometres per hour with tailwind assistance. The study also estimated how far the insects travelled in a day and found that higher temperatures and wind assistance resulted in faster travel times. The results from this research study, the first of its kind, show how innovations in radio-tracking technology can help researchers understand the movement of insects across the globe.
Researchers caught the monarch butterflies and green darner dragonflies on the Bruce Peninsula in the fall of 2015 and 2016 and tagged the insects with radio transmitters weighing about 200 mg. Once the researchers had geared up the dragonflies and monarchs with a transmitter, which looked like a small oval casing with a long antennae sticking out to one side, the insects were free to continue their migrations. Their movements were tracked by a series of telemetry towers across southern Ontario and the northern United States.
“Being able to track insects individually really opens up the door to answer a lot of questions about habitat use and where they go in the winter,” says study co-author Dr. Ryan Norris of the Department of Integrative Biology at the University of Guelph. “For a lot of species, we don’t even know where they go after they’re done reproducing up in Ontario, or what they do when they leave.” Dr. Norris says that you can think of these insects as little transporters, moving nutrients from one part of the globe to another. “There’s quite a few insects flying over our heads that we’re not aware of, and those number in the billions. They’re important parts of our ecosystem.”
The weight and limited battery life of radio transmitters restricts the kinds of insects that can be tracked and for how long. But the technology behind radio telemetry is rapidly improving, opening up new avenues of research. “Certainly when transmitters get lighter and they last longer, there’s nothing to stop us from imagining being able to track individuals right down to their wintering grounds, even a monarch down to Mexico” says Dr. Norris. And the possibilities don’t end there. Improvements in radio transmitters could allow researchers to track insects from space stations. “Imagine being able to track dragonflies from space. I think that’s ten to fifteen years down the road. Once we’re able to do that, the possibilities open up for us being able to understand life cycles and migration routes of insects and the type of habitats they rely upon for successful migration.”