Scientists have clever ways of doing tests to know how their vision works and know they are different from how human eyes see. All animals have different features about them, A cat only see's in blue black and red,A bull can't actualy see the colour red as red but as a bright colour white. Cats only see black white and blue. Pigs can smell 20'000 times better than a human and an Owl's eyes can see the small print of a news paper from a mile away as clear as if we was reading it normal. A crow can comunicate across 60miles to another crow by sending a high pitch tone that many birds each mile will copy until the other crow as far as 60miles away gets the message! just watch the animal programs on discovery!