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Why Cats Have Vertical Pupils
Cat’s eyes look really amazing, most of the time they have vertical slits surrounded by homogeneous color. Have you ever wondered why cats have those strange looking eye of Sauron instead of normal circular pupils like humans?
New research published August 7, 2015 in the journal Science Advances claims that there is a striking correlation between pupil shape and the way animals spend their day. Ambush predators, most often, have vertically elongated pupils, while species with horizontally elongated pupils are very likely to be a prey. However, not all predators have vertical pupils. These which haunt their prey from ambush like cat and fox have vertical slits, but these which are active predators like wolf and lion and need to chase their prey have circular pupils. How does the shape of pupils help? Ambush predators have to be very good at measuring distance to effectively hunt their prey out of hiding. “Vertically elongated pupils create astigmatic depth of field such that images of vertical contours nearer or farther than the distance to which the eye is focused are sharp, whereas images of horizontal contours at different distances are blurred”. On the other hand horizontal pupil of herbivorous prey minimizes distraction which comes from above and below and allows focusing better at what is in front and behind. Moreover, ambush predators have two more muscles which are responsible for compressing the pupil. That allows for a huge change of the amount of light coming into the eye. For example, they are capable of undergoing a 135-to-300-fold change in the area, whereas humans’ circular pupil changes by ~15-fold. That is why cats can hunt during the day and the night. |