Why do some animals pretend to have eyes?

BioGalleries

Eye To Eye

Article and Photographs by David Denning

Imagine you are a butterfly flying from flower to flower in search of nectar. Although you can fly to avoid many predators, you are not really very fast or agile, and whenever you land on a flower you are suddenly a very vulnerable meal for a hungry bird. So, what can you do to prevent predation? Shock tactics!

Butterfly Eyespot

A survival adaptation that evolved in many lines of butterflies and moths is the presence of false eyespots on the wings. These "eyespots" probably serve to shock or scare predators. When the butterfly opens its wings to an approaching predator, the eyespots suddenly come into view. This may simulate the large and menacing face of an animal dangerous to the would-be predator. Some species of hawk-moths can puff themselves and display their false eyes to appear remarkable like a snake, complete with hissing noise.

False eyespots are not limited to butterflies and moths. Caterpillars with false eyes can tuck in their heads and look convincingly like a menacing face with eyes. The False-eyed frog of South America has two large eyespots on his tail end. When threatened this frog will bury its head in the sand and stick its large rump in the air displaying a fierce false face to the oncoming danger.

Most predators key visually on eyes of their prey, making an effort to approach the prey from a direction where they won't be seen. There is a distinct advantage to any prey that can fool the predator into approaching from the wrong end — the one with real eyes that will see the predator and trigger a timely escape. Many fish have a conspicuous false eyespot on or near their tail fins. When a predator approaches from the "rear", the prey fish is fully aware of the danger, and it escapes in the exact opposite direction to that expected! Some insects will go so far as have entire false head with conspicuous false eyes at their tail end, to utterly confuse an approaching predator.

The presence of false eyespots in some species is related more to success at creating offspring than to success at fooling and escaping from predators. This is a factor of sexual selection, where a male that appear more conspicuous and attractive to a female will father more offspring and thus pass on more of the genes for the conspicuous display. An outstanding example of this the peacock, where they male's inordinately large tale feather display is adorned with conspicuous eye-like patterns. Scientists think that the abundance of conspicuous false eyespots in some groups of tropical fish, is related both to sexual selection and natural selection.