Why do goats have rectangular pupils?

In this ‘I Wonder Why’ episode from World by Charlie, Casey Engelman wants to know why goats have rectangular pupils. Her brother and host Charlie Engelman didn’t know either, so they did some research.

Those horizontal rectangular pupils turn out to be a super useful shape that helps goats see more, which can help keep them safe. From NPR: Eye Shapes Of The Animal World Hint At Differences In Our Lifestyles…

Take a close look at a house cat’s eyes and you’ll see pupils that look like vertical slits. But a tiger has round pupils — like humans do. And the eyes of other animals, like goats and horses, have slits that are horizontal.

Scientists have now done the first comprehensive study of these three kinds of pupils. The shape of the animal’s pupil, it turns out, is closely related to the animal’s size and whether it’s a predator or prey.

…if you’re the kind of animal that gets hunted, “you’re very likely to have a horizontal pupil” and to have your eyes on the side of your head. That makes sense, [vision scientist Martin Banks] says, because it gives prey animals a panoramic view, so they can best scan all directions for danger.

Next: Ed Yong explores how animals sleep and see the world, TED-Ed explains how animals see in the dark, and Maddie Moate and Greg Foot ask, “why is it so hard to catch a fly?”

Plus: The Goat Brigade: Preventing Wildfires in Southern California