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Cat senses are adaptations that allow cats to be highly efficient predators. Cats have acute sight, hearing and smell, and their sense of touch is enhanced by long whiskers that protrude from their heads and bodies. These senses allow cats to hunt effectively in dim light or at night. ==Sight== Cats, like dogs and many other animals, have a ''tapetum lucidum'', which is a reflective layer behind the retina that sends light that passes through the retina back into the eye. While this improves the ability to see in darkness, it appears to reduce net visual acuity, thus detracting when light is abundant. In very bright light, the slit-like pupil closes very narrowly over the eye, reducing the amount of light on the sensitive retina, and improving depth of field. Big cats have pupils that contract to a round point. The tapetum and other mechanisms give the cat a minimum light detection threshold up to seven times lower than that of humans. Variation in color of cats' eyes in flash photographs is largely due to the reflection of the flash by the tapetum. Cats have a visual field of view of about 200°, compared to 180° in humans, but a binocular field (overlap in the images from each eye) narrower than that of humans. As with most predators, their eyes face forward, affording depth perception at the expense of field of view. Field of view is largely dependent upon the placement of the eyes, but may also be related to the eye's construction. Instead of the fovea, which gives humans sharp central vision, cats have a central band known as the visual streak. Cats can see some colors, and can tell the difference between red, blue and yellow lights, as well as between red and green lights. Cats are able to distinguish between blues and violets better than between colors near the red end of the spectrum.〔http://www.kittyshow.com/cat_color_vision.html Cat Vision and How Cats See〕 Cats have a second eyelid, the nictitating membrane, which is a thin cover that closes from the side and appears when the cat's eyelid opens. This membrane partially closes if the cat is sick, although in a sleepy state this membrane is often visible. Cats often sleep during the day so they can "hunt" at night. Unlike humans, cats do not need to blink their eyes on a regular basis to keep their eyes lubricated (with tears). Unblinking eyes are probably an advantage when hunting. Cats will, however, "squint" their eyes, usually as a form of communication expressing affection and ease around another cat or human. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Cat senses」の詳細全文を読む スポンサード リンク
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