Once impregnated, the female dragonfly has no use for additional mates but turns her focus to tending to her eggs. If however, she does find herself approached by unwanted advances, she gets of it easily, by “playing dead”, new research has discovered.
This odd, but quite understandable, behavior was observed coincidentally by PhD student Rassim Khelifa, from the University of Zurich, while he was out collecting samples of the moorland hawker dragonfly in the Swiss Alps. Khelifa intended to gather the larvae of the insect to test them in his lab in order to study the effects of climate change by conducting heat experiments. However, he got more than he bargained for as he started to notice the females’ specific behavior every time a male approached them.
The student discovered that the females begin by picking a well-hidden area to lay their eggs, to avoid being detected. However, they can still be badgered by males looking for some action while they fly to and from the nesting area. It is in this case that they resort to plummeting to the ground and pretending to be dead.
The majority of females Khelifa observed employed this strategy, with most being successful in fending off the unwanted attention. Male dragonflies usually scope out their mates by detecting motion and colour, hence they failed to notice the ones lying motionless on the ground, especially when these opted for thick grass and flowers to conceal themselves further. After successfully tricking their predators, the females quickly re-emerged from their corpse position and took flight again.
It seems that this behavior is quite common in other animals too but in the Aeshna juncea dragonfly, it also acts a means for the female to protect herself from harm to her reproductive organs that may be caused by having numerous mates; “When a male copulates with a female, it first extracts the sperm of the previous male. This can damage the reproductive tract of the female. So, multiple mating is not advantageous,” explained Khelifa.
The findings were published last week in the scientific journal Ecology.