Have you ever wondered how different animals see?
The differences in the shapes of eyes in the animal kingdom are astounding. Eyes have evolved in different ways to suit each animal’s needs.
An eagle files almost a kilometer above the ground, so it should be able to see small prey down on the ground.
Predators like the cheetah should be able to spot prey hidden behind bushes.
Cats should be able to see in the dark, fish should e able to see underwater, amphibians should be able to see both in water and on land.
All these creatures have eyes that suit their lifestyles.
Predators that need to spot their prey quickly have eyes on the front of their faces. They also have powerful eye muscles that help the eyes to focus quickly. Animals which move fast generally have large eyes. When it comes to eyes, there is no one-size-fits-all!
Some animals are able to see in color, like humans; some are able to see more colors than humans, like the mantis shrimp; while some can only see to colors, like the horse.
The iris in human eyes is circular, but its shape varies in different animals. Goats have rectangular irises. Snakes like pythons and vipers have vertical slit, as do cats and foxes.
The vision of an animal depends not only on how powerful its eye is, but also on the location of the eye.
For example, having eyes fixed on the front of our heads restricts what we see. Imagine what it would be like to have eyes on antennae on our heads-we would be able to see all around us!
Some insects can do this, because they have eyes on stalks on their heads. The stalk –eyed flies, for example, sometimes have stalks that are even longer than their entire body. These tiny insects are up to a centimeter long and live in moist undergrowth, wriggling among leaves and dirt, feeding on microbes from decaying vegetation. In this dark and cluttered environment, it is good to have eyes on stalks, as they are able to see a larger area.
Every night, the stalk –eyed insects come together in groups at a particular place, and fight! The males of equal size line up facing each other `eyeball to eyeball’ with their stalk eyes looking into each other, trying to knock the other off. The winner of fight gets control of the place where the female insects gather together.
The story of these eyes gets event stranger. It seems that female insects prefer widely-spaced eye stalks to ones that are closer together. The greater the distance between the eyes, the more attractive the male insect is to a female. It is not known why females prefer this-whether it’s cosmetic or whether they have other benefits as well.