The cheeky trick butterflies use to confuse predators

New research by teams across two UK universities has discovered that butterflies use optical illusions to escape danger.

An optical illusion is something that affects the way the brain and eyes process information, meaning that they are tricked into believing they are seeing something else.

It's this tactic that butterflies use to confuse a predator's sense of speed and direction - which can mean a bird attacking a butterfly often ends up snapping its beak at thin air.

The research teams at the University of Essex and Exeter made the important discovery whilst studying a butterfly's flight and wing pattern.

Butterflies have striking patterns that make them stand out, but experts had wondered why remarkably few predators had been able in catching them during flight.

"Butterfly wings deform (change shape) as they fly so their stripes shift angle and point in different directions as they flap," said Dr. Jolyon Troscianko from the University of Exeter.

This is similar to the red-and-white striped pole outside barber shops, where the stripes appear to travel upward even though the pole is only spinning in place.

Butterflies and moths are also well known for using camouflage while resting, but movement breaks camouflage; so the study showed how, whilst highly visible in flight, butterflies evolved their patterns for a completely different defence tactic.

To test the theory the team used a high-speed camera to film real butterflies taking off, to see how their patterns behave in flight and to mimic how it would appear in eyes of a bird.

They then got 100 volunteers to act as "predators," trying to catch virtual butterflies on a touchscreen.

"Combined with their unpredictable flight paths, this patterning creates misleading motion illusions, causing a predator to miss entirely, or to strike a less vulnerable part of the wing, such as the hindwing or tail", Dr Troscianko added.

The new study has been published in the journal Nature.