Name: Vibrissae; also known as tactile hairs or whiskers.
Description: They differ from the cat's normal body hair in that they are long, tapering, stiff yet flexible hairs. They are double and even three times the thickness of a normal cat hair and many times the length; they can grow to be extremely long.
The most obvious will be found in horizontal rows on the puffy area known as the whisker pad on the cheeks of a cats face, mainly in the area between the corner of a cat's mouth and the outer corner of the nose. Yet there are many more all around the face, in the area of the chin, and the eyebrows, also on the body especially around the front-, the hind legs and feet, although they are sometimes shorter.
Each whisker is rooted deeply in a follicle, surrounded by a highly developed sheath of muscle tissue, rich in nerves and sensory cells, sealed by a capsule of blood, called a blood sinus. The muscle is used to move the whisker in any direction to optimise use. The nerves connect the whisker to a large section of the brain of the cat especially reserved to processing the nerve impulses coming from the whiskers. Touching the whisker, causes it to move, the blood in the sinus is compressed to the opposite side. The blood amplifies the movement, thus allowing the sensor cells to detect the most miniscule of movement. All this: because the whiskers are one of the cat's main survival tools.
Their function:
Measurement
When a cat's facial whiskers are "put up" and alert, they are roughly equal to the width of the body. If you observe a cat testing an opening, it will stick its head in and out of the opening and then only proceed. What has happened is it was measuring the size of the hole compared to its body size and width. The cat has learnt with experience how much pressure on the sensor cells in the hair follicle equals a safe passage.
Navigation
A cat has excellent sight many times that of man, but still it cannot see when it is completely dark, here its whiskers aid the cat to feel its way around. A very dark night or an enclosed area (man made like a tunnel or natural for example a cave) and there is no or very little light the cat will rely on air currents to navigate. Its whiskers can detect the slightest movement of air, air moves in distinct ways around barriers, the cat has learnt to read these signals.
Mood indication
Whiskers are a good indication of a cat's state of mind.
* Whiskers pulled back towards its body: - defensive, aggressive, angry.
* Whiskers pushed forward: - very happy, curious.
* "Put-up"-extended to their full in a circle around the face: - alert, interested, curious.
* Forward pointed: - excited, animated.
* Relaxed: - resting, content.
A few more facts:
* Similar to normal hair they do fall out naturally and re-grow.
* Cats whiskers are like human finger prints, the individual aligning is unique to each cat.
* The breed of cat called the "Sphinx", often have no whiskers.
Why you shouldn't cut or trim a cat's whiskers
* Clipping, cutting or otherwise removing the cat's whiskers is cruel; it is likened to removing one of our senses, e.g. Sight (to be blinded), smell (to lose your sense of smell), touch (to not be able to feel), taste (not to be able to taste anything) or hear (to be deaf), in a cats case they have the special sense of detection; the work of the whiskers.
* You will be depriving the animal of one of his means of communication (see mood indication above).
* You will be putting the animals life in danger, it will not be able to discern openings accurately and runs the danger of getting stuck, with possible fatal consequences.