If you have a cat, you may have noticed the vertically shaped pupils and wondered why their eyes don't look like yours. Vertical and slit-like eyes turned out to be common among nocturnal predators such as cats and snakes. Some studies have found that this eye shape likely provides cats and other lurking predators with the sharpest way to measure distances to leap onto their prey.
Other benefits of vertical slit eyes are their ability to allow for a greater change of field in the cat eye. They may do this because of the two extra side muscles that open or close their eyes more forcefully. In addition, vertical slit pupils have a 135-fold change between constricted and dilated states, while round pupils in the human eye only allow for a 15-fold change. This gives cats a more dynamic range, allowing them to adapt more precisely to lighting conditions. While cats can see in extremely dim light, they can adjust their eyes to prevent them from being blinded by bright light.
WHY DO CATS HAVE VERTICAL EYE DOUBLES?
Humans and animals have two ways of measuring depth, and cats' eyes are designed for both. In the first, called stereopsis, the brain compares images from each eye to tell how close the visible objects are. To measure depth using vertical lines, it turned out to be easier to distinguish the distance between two images than horizontal lines. This means that vertical pupils tend to provide the best views for stereopsis.
CAT'S IUDIES ALLOW ME TO MEASURE DEPTH WITH HIGH ACCURACY
The second way depth can be determined by the eyes is by using the blur of distant objects. Cats and other slit-pupil predators likely use blur to determine depth at horizontal distances. To maximize the effect of blur, the eyes need to be able to open wide from top to bottom. The ideal shape for this is a pupil that is narrow horizontally and wide vertically. This perfectly defines the vertical slit eye shape of cat eyes.
Cat eyes are the ideal shape for both ways of determining the depth needed for hunting. Cats are lurking hunters, meaning they sneak up and pounce on their prey. Being able to accurately assess depth is an important part of ambushing prey and staying on target. Cats are extremely sensitive to this, thanks to the shape of their pupils.
OTHER ANIMALS' EYES HAVE THEIR OWN FUNCTIONS.
Vertical slit eyes in ambush predators are not the only type of eyes that serve a specific function. In the studies, the research team also examined the oblong pupil shape of herbivorous predators such as goats, sheep, horses and some toads. It turned out that 36 out of 42 of these animals have an oblong eye shape.
The horizontal shape of herbivorous predators helps to minimize entry from above and below while maximizing front and rear entry. This creates a panoramic image that allows the animal to see all parts of its body more easily. The horizontal shape helps prevent them from being blinded by sunlight without sacrificing the rest of the field of view. The horizontal shape also helps minimize blurring of horizontal contours. This creates a sharper image of the ground; It is an ideal feature in predators that may need to flee whenever a predator appears at any time.
While this research has found causes for vertical slits and horizontal pupils, the reason behind other pupil shapes, such as the round shape of human pupils, is less clear. Future research will need to be done to determine whether there is an evolutionary advantage to the human pupil in the way that ambush predators and herbivorous prey have evolved.
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