Dragonflies, they’re just like us!
The life of a dragonfly seems like a pretty good deal. The lazy summer afternoons, the flitting about the ponds, the flowers upon which to rest, the feeling of the sun warming one’s wings. It’s all fine and dandy – but for moorland hawker dragonfly (Aeshna juncea) females, at least, there’s one particularly vexing problem: The men.
Male moorland hawkers, like males of most species, are hot to mate. And who can blame them? “Each sex adopts reproductive strategies that best serve its own survival and reproductive success,” says Rassim Khelifa, a zoologist from the University of Zurich, who studies dragonflies.
For females of the species, however, untimely mating can shorten their lives and lead to fewer offspring. And thus, they have devised perhaps the best evasion tactic of any creature out there. They plummet from the sky, crash to the ground and play dead. Because who wants to mate with a dead dragonfly? After the pursuant suitor moves on, she pops back up and likely hightails it back to bushes.
Khelifa, who just published a new study about the before-unseen behavior, describes the Oscar-worthy antics:
While I was waiting at a pond near Arosa, at about 2,000 meter elevation, I witnessed a dragonﬂy dive to the ground while being pursued by another dragonﬂy... the individual that crashed was a female, and that she was lying motionless and upside down on the ground.
Upside down is an atypical posture for a dragonﬂy. The male hovered above the female for a couple seconds and then left. 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. The question arose: Did she just trick that male? Did she fake death to avoid male harassment? If so, this would be the ﬁrst record of sexual death feigning in odonates.
To ensure that this was indeed the case – and not some kind of one-off fit of dragonfly narcolepsy (I’m not sure that could really be possible, but it does make for a good children’s film premise), Khelifa began looking for more of it. In the end he observed that in 86 percent of cases in which males went on the chase, females dive-bombed and played dead; those that kept flying “were all intercepted by a male.” Out of 27 stage deaths he observed, it worked 21 times as the males moved on.
While a creature faking its own death is unusual, it’s not unheard of. Khelifa notes that two species of robber fly do it, as does the European mantis. The spider species Pisaura mirabilis does it too, but with a delicious switch of the gender roles – the males fake death in order to avoid being eaten by the females after mating.
The study, Faking death to avoid male coercion: extreme sexual conflict resolution in a dragonfly, was published in the journal Ecology.
Via New Scientist