Why Animals Have Such Different Pupils in Their Eyes

The pupils in our eyes adjust in size to let in more or less light to maximize our vision. That's a pretty handy ability to have, and it's automatic. Most animal species have eyes with adjustable pupils, too, but they vary an awful lot. House cats have vertical slits for pupils, while big cats like lions and tigers have round pupils. It's not just a matter of size, though, since bobcats have vertical slits and a Pallas's cat has round pupils, and they are about the same size. Strangely, some foxes also have vertical slits while dogs do not. The animal kingdom has developed a bunch of different pupil shapes, from the goat's horizontal boxes to the cuttlefish's "W" shaped pupils. All these shapes are there for a reason that has to do with the lifestyle of the animal. Except praying mantises. Their pupils are there just to freak us out. -via the Awesomer