By: New Scientist Female dragonflies use an extreme tactic to get rid of unwanted suitors: they drop out the sky and then pretend to be dead./
Rassim Khelifa from the University of Zurich, Switzerland, witnessed the behaviour for the first time in the moorland hawker dragonfly (Aeshna juncea). While collecting their larvae in the Swiss Alps, he watched a female crash-dive to the ground while being pursued by a male.
The female then lay motionless on her back. Her suitor soon flew away, and the female took off once the coast was clear.
“I was surprised,” says Khelifa, who had never previously seen this in 10 years of studying dragonflies.
Female moorland hawkers are vulnerable to harassment when they lay their eggs since, unlike some other dragonflies, they aren’t guarded by their male mates. A single sexual encounter with another male is enough to fertilise all eggs and copulating again could damage their reproductive tract.
Khelifa found that the females often retreat to dense vegetation near ponds at this time, probably to hide. And they often act dramatically when they emerge.
He observed 27 out of 31 females plummeting and playing dead to avoid males, with 21 of these ploys successful. Plunging at high speed is risky though, and according to Adolfo Cordero-Rivera at the University of Vigo in Spain, it may be a strategy that they use only in areas with lots of dragonflies. “Females may only behave in this way if male harassment is intense,” he says.
Few animals have been caught feigning death to trick suitors. The behavior has been seen in a species of spider (the males use it to improve their chances of mating), two species of robber fly and a type of mantis.
Playing dead to avoid predators, however, is more common and has been observed in dragonflies. “It’s likely that females expanded its use to overcome male coercion,” says Khelifa.
Khelifa is interested in finding out whether the behaviour is unique to species that lay eggs alone or whether it is more widespread. Using extreme tactics to resolve sexual conflict isn’t unique to moorland hawkers: in their damselfly relatives, for example, females eat their partner.
Journal reference: Ecology, DOI: 10.1002/ecy.1781