Air Date: Week of June 6, 2003

Living on Earth’s Maggie Villiger reports on motion camouflage, pioneered by dragonflies to hide while they’re in flight.

Transcript

CURWOOD: Coming up: why forest fires, even big ones, may be for the good. First, this Note on Emerging Science from Maggie Villiger:

[EMERGING SCIENCE NOTE MUSIC]

VILLIGER: Most animals can hide pretty well if they’re standing still. But a new study shows that dragonflies can hide even while they’re flying. Researchers found this out by setting up two cameras at places where dragonflies do battle with each other so they could reconstruct in a lab how the dragonflies interacted in three dimensions. They found that 40 percent of the interactions involved a technique called motion camouflage. Here’s how it works.

Insects are good at picking out movement in the environment when something changes its position against the background. But when a predator is using motion camouflage, he moves in a way that makes him appear to be stationary. Imagine one straight line that connects a prey dragonfly, a predator dragonfly, and a fixed object like a tree far off to their right. As long as the predator mimics the motions of the moving prey and stays in line with the tree, he appears stationary too, even though he could be moving closer and closer to his prey along that line. But dragonflies don’t need to base their motion camouflage maneuvers on real fixed objects, like the tree in this example. They seem able to calculate how a stationary object could appear to the prey. The researchers imagine adapting dragonfly motion camouflage for use in unmanned aerial vehicles. That’s this week’s Note on Emerging Science. I’m Maggie Villiger.

CURWOOD: And you’re listening to Living on Earth.

[MUSIC: Michael Hedges “After the Gold Rush” Aerial Boundaries - Windham Hill (1984)]