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Female Dragonflies Fake Death To Avoid Sexual Harassment

30 April 2017, 8:35 pm EDT By Luan Chan Tech Times
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A zoologist made a surprising discovery while observing odonates in the Swiss Alps. Female dragonflies pretend to die when harassed by males that wish to mate.  ( Marc Pascual | Pixabay )

We are already aware that dragonflies can do some incredible things for the survival of its species, like long-distance flying and anticipating a prey's movements for a swift kill. The colorful fliers also exhibit some unusual behavior but it is not until now that a zoologist has been able to discern the peculiar behavior exhibited by females of the Aeshna juncea species.

A study published on April 24 reveals that female common hawkers, also called moorland hawkers or sedge darners, have the tendency to fake a crash-and-die scenario in order to prevent males from harassing them to mate.

The Peculiar Discovery

Rassim Khelifa, a zoologist from the University of Zurich, had been out in the Swiss Alps to conduct an experiment on odonate eggs to see how temperature affects the larvae. As he conducted the experiment, Khelifa witnessed a dragonfly being chased by another near a pond. The one being chased suddenly crashed to the ground and lay motionless on its back. The chaser hovered above the body of the other dragonfly for a few moments before flying away.

He noted that the crash "victim" was a female A. juncea while the pursuer was a male.

"Upside down is an atypical posture for a dragonfly ... I expected that the female could be unconscious or even dead after her crash landing, but she surprised me by flying away quickly as I approached," Khelifa recounted.

Surprised at what he observed, Khelifa wondered if the crash-and-death scenario was an orchestrated trickery to avoid getting coerced into mating. To comprehend what he saw, the zoologist observed more moorland hawkers in the months that followed.

Crash, Die, Fly Away

Months of observing the dragonflies made Khelifa realize that the peculiar scenario he witnessed was actually quite common among females of the A. juncea species. In order to understand why the female dragonflies would resort to faking their own deaths, the zoologist looked into the species' reproductive behavior.

What Khelifa found was that male moorland hawkers usually just wait around to coerce females into mating then fly away afterward, leaving the females vulnerable as they lay eggs. This is unlike other dragonfly species whose males would stand guard to protect the females as they lay eggs.

He also found that the more male dragonflies patrol the area to wait for a mate, the more likely it is for females to play dead. The female dragonflies that do not resort to trickery are all intercepted by males and coerced into mating. Playing dead, however, is not always successful.

"Of the 27 motionless females, 21 (77.7 percent) were successful in deceiving the coercive male," the zoologist noted.

The study titled "Faking death to avoid male coercion: extreme sexual conflict resolution in a dragonfly" was published in the journal Ecology.

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