Goats Have Rectangular Pupils

If you’ve ever found yourself trapped in a staring contest with a goat you might have noticed something fairly unusual. Goats have horizontal, rectangular pupils. They’re not alone, either. Sheep, deer, horses, and many other grazing animals share this oblong eye shape — and for good reason. Horizontal pupils give herbivores a panoramic view of the world, allowing them to scan for predators without lifting their heads from the ground while they graze. Their pupils even rotate as they tilt their heads, helping keep the horizon in focus. 

Predators, by contrast, often have vertical slit pupils that improve depth perception and help them judge the distance to their prey. Humans fall somewhere in between, with round pupils that provide balanced, even vision and accurate depth perception — much more suitable for a species that relies on hands rather than hooves.