The cat's ear is yet another marvel of feline engineering. Like a sophisticated satellite dish turning to pick up a signal, the cat's external ear, or pinna, rotates up to 180 degrees to locate and identify even the faintest of squeaks, peeps or rustling noises.
While dogs are renowned for detecting high-pitched whistles far beyond human hearing, cats actually hear much higher frequencies than canines and are only slightly inferior at the low end of the frequency scale. They also can detect the tiniest variances in sound, distinguishing differences of as little as one-tenth of a tone, which helps them identify the type and size of the prey emitting the noise. This heightened sense of hearing is especially important in wildcats, which depend on hunting for survival. It also enables wild and domestic feline mothers to hear faint squeals of distress from their cubs or kittens when they stray too far away.
A cat up to 3 feet away from the origin of a sound can pinpoint its location to within a few inches in a mere six one-hundredths of a second. Cats also can hear sounds at great distances — four or five times farther away than humans.
The Organ of Balance
The ears also serve in another way that is vital to successful feline life. The vestibular apparatus, housed deep in the cat's inner ear, is responsible for the cat's remarkable sense of balance. This sense organ's tiny chambers and canals are lined with millions of sensitive hairs and filled with fluid and minute floating crystals.
When the cat moves suddenly, the delicate hairs detect the movement of the fluid and crystals and rapidly send messages to the brain, giving readings on the body's position.
This is similar in principle to the instrument in an airplane called the "artificial horizon" or "altitude indicator" that tells the pilot the position of the plane's wings in relation to the horizon. When a cat loses its balance and actually takes a spill, the vestibular apparatus kicks in. This helps the cat register which direction is up and triggers the "righting" reflex that cats rely on to turn themselves in midair, adjusting the orientation of the body so that they land squarely on all four feet.
This organ, together with the tail, which acts as a counterbalance, permits the cat to perform its remarkable signature acrobatics. The Manx, a tailless breed, is thought to have an especially sensitive vestibular apparatus to compensate.
Cats, like humans, can experience hearing problems or even total deafness due to disease, infections, outer-ear trauma, inner-ear damage (from excessively loud noises) or simply old age.
The cat's ability to detect high frequencies particularly declines as the eardrum thickens with age. This condition not only affects the cat's hunting skills; it also can compromise the feline's ability to heed noises signaling danger.
In domestic cats, however, deafness is most commonly hereditary. Although inherited deafness has not been genetically related to specific breeds, the dominant gene responsible for producing white hair is sometimes associated with inner-ear abnormalities that often lead to deafness.
Incidences are highest in white cats with blue eyes; white cats with eyes of different colors are often deaf only in the ear on the blue-eyed side.