Swarms may not mean population boom: expert
More data needed to determine whether population actually rising, expert says
Take a walk in the river valley this week and chances are good you’ll see swarms of dragonflies hovering back and forth, looking for smaller bugs to feed on.
While it may seem like dragonflies are swarming the city en masse, a local bug scientist says we shouldn’t jump to conclusions about any trends.
“It might not necessarily represent a huge population increase overall in the area,” said Robert Hinchliffe, an aquatic invertebrate taxonomist at the Royal Alberta Museum.
“We have to be careful when we say, ‘It looks like there’s way more dragonflies this year than there’s ever been.’ The question is, is that a perception based on something someone has observed? Or are we going on hard data?”
Right now, there’s no numbers available for this summer’s dragonfly populations, making it tough to evaluate how these critters fit into larger trends.
Regardless, it’s not difficult to find large groups of dragonflies in Edmonton right now, especially near the water.
“Dragonflies do tend to congregate at certain times. When you see that, you tend to see a high density of dragonflies in a certain area,” Hinchliffe said.
“The dragonflies may be there because they just emerged from the pond and haven’t yet dispersed to other areas.”
Dragonflies also congregate to mark their territory, as well as to prey on swarms of other bugs, like mosquitoes.
One of the main roles dragonflies play in Alberta’s ecosystem is acting as population control for smaller pest insects.
If dragonfly populations increased this year, it would likely be because of a confluence of weather conditions over the last four years, as that’s the amount of time that the larva of some dragonflies can live in water.
“For dragonflies, if we do see population changes, they’re going to be more drawn out. There’s so many factors affecting the population that you can’t just say, ‘It’s been a hot, dry summer, so that’s why we’re seeing more dragonflies,’” Hinchliffe said.
“In reality, the factors that affect the population are protracted over that four-year period.”