Rectangle or Round?

The animal kingdom is full of incredible variety, thanks to evolution, but one thing most animals have in common is that they use a set of eyes to navigate the world around them. But even the pupil of the eyeball, the biological aperture responsible for how much light enters the eyes, is nearly as diverse as the types of birds that soar the skies or fish that swim the seas.

For mammals, one big factor determining the shape of a pupil is whether the creature is predator or prey. For example, a goat is a grazing prey animal that would be a pretty easy target for coyotes, bears, and other predators with sharp teeth. Yet evolution gave the goat a few tools to defend itself.

The horns certainly help, but the biggest advantage is a goat’s horizontal rectangular pupils.  These long, horizontal pupils create a panoramic view that lets the animal see more of the landscape, which makes it harder to sneak up on them. The pupils also enhance the image quality of objects (read: threats) all around the goats, and they cut down on glare from the sky by capturing less light from above and more from below.

Cats and snakes, on the other hand, are ambush predators, whose vertical pupils help them hunt in the night and judge the distance between themselves and their next meal. But according to scientists, vertical pupils are reserved only for animals whose eyes are close to the ground. That’s why other cats that are higher up, like lions and tigers, have round pupils rather than vertical ones.

Who knew?!

Keep your eyes open!