Dragonflies already are known to be swift hunters, but new research shows that they aren’t turning and diving in reaction to their prey’s movements – they’re predicting those movements before they occur.
A study published in Nature reveals the insects’ internal complexity: A system of constant neurological calculations that help the winged bugs keep a perfect fix on their future meal. And it’s possible that the brain mechanisms that help dragonflies orchestrate this elaborate dance could help researchers figure out the ones humans use to accomplish similar tasks.
Before this study, it was generally assumed that dragonflies – and many other predators – use very basic reflexive movements to follow their prey.
“The idea is that you see something in the world, and that stimulus slowly but surely drives responses from your muscles, and something happens,” said Anthony Leonardo, lead author and Howard Hughes Medical Institute’s Janelia Research Campus group leader.
A basic example of this is the escape response: When something moved toward a fly, they see that movement and jump away.
We know that humans and other primates can’t always rely on these reflexes. Reaching for a morning cup of coffee – or catching a ball – requires incredibly sophisticated calculation. One must have an internal image of their own body in space, calculating both the movement of the body toward an object and any movement of the object itself. That’s why running to catch a flying football is no easy task.
Hunting dragonflies are performing moves just as smooth as a pro athlete’s, but scientists assumed their movements followed a reflexive mechanism. In other words, the dragonfly would twist its body in 90-degree angles in reaction to its prey’s movement. After all, the insects have fairly simple nervous systems.
But by testing dragonflies with real prey and fake targets (the flight patterns of which could be controlled by the research team) and tracking their movements, Leonardo and his colleagues found the bugs to be much more coordinated than we’ve ever given them credit for.
Instead of watching its prey for cues, a dragonfly on the prowl will move its body on a path that allows it to approach the prey from below, decreasing the risk of detection. But as it turns its body, the dragonfly manages to keep the most sensitive part of its eye fixed directly on the prey.
Think that sounds easy?
Imagine staring out a window at a bird as it flies from branch to branch. Instead of moving your eyes to follow it, try to predict its movements so that your eyes move in tandem with it – always keeping the bird fixed just at the center of your eyeball.
Yeah, it makes my head hurt, too.
But for dragonflies, Leonardo said, “the predictions are nearly perfect.”
“Clearly, somewhere there are interconnected neurons encoding this info,” he said, “and when a signal from the brain goes down to the wings saying ‘steer this way,’ it’s also able to say, ‘given that I’m steering this way, my body will rotate this way – and given that the prey is over there, that will make the prey rotate this way, and I should turn my head thusly to keep an eye on it.”
Leonardo and his team are hoping to track down the exact neurological mechanism that gives dragonflies this ESP-like hunting skill. And figuring out the secrets of this fairly simple – but clearly fascinating – nervous system may help scientists understand our own.
“Algorithmically, it’s exactly the same kind of process a human is going through,” Leonardo said. “When you reach to pick up coffee, you’re solving the same problem as the dragonfly.” So the underlying neurological circuitry will probably have something in common. “The hope is that studying this system will help us learn a lot about humans.”
On the net
How a dragonfly captures its prey: http://wapo.st/1yyZbRS
How a dragonfly predicts the movements of its prey: http://wapo.st/1yyZcFq
