 Not all animals have circular pupils.Some have slits or ovals which may be oriented vertically, as in crocodiles, vipers, cats and foxes, or horizontally as in some rays, flying frogs, mongooses and artiodactyls such as sheep, elk, red deer, reindeer and hippopotamus, as well as the domestic horse.Goats, toads and octopus pupils tend to be horizontal and rectangular with rounded corners.