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Physical Characteristics - General Feline Information
Sight: The tapetum lucidum reflecting green in the pupils of a cat. The reflective tapetum lucidum of a cat at dusk. Testing indicates that a cat's vision is superior at
night in comparison to humans, and inferior in daylight. Cats, like dogs and many other animals, have a tapetum lucidum that reflects extra light to the retina. While this enhances
the ability to see in low light, it appears to reduce net visual acuity, thus detracting when light is abundant. In very bright light, the slit-like iris closes very narrowly over
the eye, reducing the amount of light on the sensitive retina, and improving depth of field. 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 interaction of the flash with the tapetum.
Average cats have a visual field of view estimated at 200°, versus 180° in humans, with 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 apparently
differentiate among colors, especially at close range, but without appreciable subtlety.
Cats have a third 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, content cat this membrane is often visible. If a cat chronically shows the third eyelid, it should be taken to a veterinarian for evaluation.
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. Cat owners can often entice their pets to squint or even fully close their eyes just by talking to them in a soothing
or pleasing manner. Many cats will also squint in response to seeing their owners squint.
Cats have a wide variation in eye color, the most typical colors being golden, green and
orange. Blue eyes are usually associated with the Siamese breed, but they are also found in white cats. If a white cat has two blue eyes, it is often times deaf; however, orange eyes
usually indicate the cat is free of hearing problems. White cats having one blue and one other-colored eye are called "odd-eyed" and may be deaf on the same side as the blue eye. This
is the result of the yellow iris pigmentation rising to the surface of only one eye, as blue eyes are normal at birth before the adult pigmentation has had a chance to express itself
in the eye(s).
Hearing: Humans and cats have a similar range of hearing on the low end of the scale, but cats can hear much higher-pitched sounds, up to 70 kHz, which is 1.6 octaves above
the range of a human, and even 1 octave above the range of a dog. When listening for something, a cat's ears will swivel in that direction; a cat's ear flaps (pinnae) can
independently point backwards as well as forwards and sideways to pinpoint the source of the sound. Cats can judge within three inches (7.5 cm) the location of a sound being made
one yard (approximately one meter) away-this can be useful for localizing prey, etc.
Smell: A domestic cat's sense of smell is about fourteen times as strong as a human's. Cats have twice as many smell-sensitive cells in their noses as people do, which means
they can smell things we are not even aware of. Cats also have a scent organ in the roof of their mouths called the vomeronasal, or Jacobson's organ. When a cat wrinkles its muzzle,
lowers its chin, and lets its tongue hang a bit, it is opening the passage to the vomeronasal. This is called gaping, "sneering", or "flehming". Gaping is the equivalent of the
Flehmen response in other animals, such as dogs, horses and big cats.
Touch: A cat has about twenty-four movable vibrissae ("whiskers"), in four rows on each upper lip on each side of its nose (some cats may have more), in addition to a few
on each cheek, tufts over the eyes, bristles on the chin, the cat's inner "wrists", and at the back of the legs. The Sphynx (a nearly hairless breed) may have full length, short,
or no whiskers at all.
Vibrissae aid navigation and sensation. The upper two rows of whiskers can move independently from the lower two rows for even more precise measuring.
Whiskers are more than twice as thick as ordinary hairs, and their roots are set three times deeper than hairs in a cat's tissue. Richly supplied with nerve endings at their base,
whiskers give cats extraordinarily detailed information about air movements, air pressure and anything they touch. Vibrissae possess exquisite sensitivity to vibrations in air
currents. As air swirls and eddies around objects, whiskers vibrate too. Whiskers may detect very small shifts in air currents, enabling a cat to know it is near obstructions without
actually seeing them. Cats use messages in these vibrations to sense the presence, size, and shape of obstacles without seeing or touching them.
Whiskers are also good hunting tools. The structure of the brain region which receives information from the vibrissae is similar to that found in the visual cortex, suggesting
that the nature of the cat's perception through its whiskers is similar to that via its vision. Stop motion photography reveals that at the moment a cat's prey is so close to
its mouth to be too near for accurate vision, its whiskers move so as to form a basket shape around its muzzle in order to precisely detect the prey's location. A cat whose
whiskers have been damaged may bite the wrong part of a mouse it's attacking, indicating that signals from these delicate structures provide cats with vital information about
the shape and activity of its prey - interestingly, whiskers also help cats detect scents.
It is thought that a cat may choose to rely on the whiskers in dim light where
fully dilating the pupils would reduce its ability to focus on close objects. The whiskers also spread out roughly as wide as the cat's body making it able to judge if it can fit
through an opening.
Whiskers are also an indication of the cat's attitude. Whiskers point forward when the cat is inquisitive and friendly, and lie flat on the face when
the cat is being defensive or aggressive.
Whiskers can also be a bother to a cat, especially when the cat tries to eat food out of a bowl. The end of the whiskers touching
the side of the bowl transfer irritating sensations to its brain, making it hard for it to continue eating.
Taste: The cat family was shown in 2005 to lack the T1R2 protein, one of two required for function of the sweetness sensory receptor; a deletion in the relevant gene (Tas1r2)
causes a shift in the genetic reading frame, leading to transcription stopping early and no detectable mRNA or protein produced. The other protein, T1R3, is present and identical
to that of other animals, and the relevant taste buds are still present but inactive. Such a genetic marker found in the entire family and not other animals must be the result of
a mutation in an early ancestor; as a deletion mutation it could not revert, and thus would be inherited by all descendants, as the evolutionary tree branched out. Most scientists
now believe this is the root of the cat family's extremely specialized evolutionary niche as a hunter and carnivore. Their modified sense of taste would cause them to some degree
to ignore plants, a large part of whose taste appeal derives from their high sugar content, in favor of a high-protein carnivorous diet, which would still stimulate their remaining
taste receptors. |
