At one of the events I participated in I met up with a crazy cat lady and got into a discussion about a cat’s sense of hearing. I know a little bit about it but there was a lot discussed that none of us knew for sure about. Memo to self: check with Prof. Google when you get a minute.
That opportunity came and I got a lot of interesting info, mainly from the petMD and Animal Planet web sites. The best way to share what I found out is to peel back the onion, so to speak, and look at the cat’s hearing hardware and software from the outside in.
The triangular ear flap, known as the pinna, and the ear canal make up the outer ear. Those little slit-like folds of skin at the base of each pinna are known as Henry’s pockets, but back on the block we just called ‘em cutaneous marginal pouches. No one, not even Prof. Google, knows why they’re there.
The pinnae can independently rotate 180 degrees, increasing the cat’s hearing capability by up to 20 per cent and enabling it to locate and identify even the faintest sound in as little as six one-hundredths of a second. I’ve seen that capability attributed to German shepherds, too.
The pinnae capture sounds, sending them through the ear canal to the middle ear, which is made up of the eardrum and ossicles, tiny bones that correspond to the hammer, stirrup and anvil in our own middle ears. OK, back on the block: malleus, incas and stapes
Sound waves cause the eardrum and ossicles to send vibrations to the inner ear, where those vibrations are converted to electrical impulses and transmitted to the brain via the auditory nerve. Cats can hear sounds at higher and lower frequencies than dogs and people.
The inner ear also contains the vestibular system, tiny chambers and canals lined with millions of sensitive hairs and filled with fluid and floating crystals. Most mammals are equipped with a vestibular system, but the feline edition is one step better than the others.
When a cat suffers a fall, it’s righting reflex enables the cat to reorient its body to an upright position in less than a second, thus landing on its feet virtually every time. And the tail helps, too. But, they’re not born that way; it takes about six weeks for the reflex to develop in kittens.
So how come white cats with blue eyes are often deaf? A genetic flaw in the gene that produces white hair and skin, causing it to suppress pigment cells, including those in the tissue of the inner ear. The tissue degenerates and the cells die, leading to deafness.
Deafness in domestic cats is most commonly hereditary, although disease, infections, outer-ear and/or inner-ear damage, and aging can be factors. White cats with eyes of different colors are often deaf only in the ear on the side with the blue eye.
And, as cats age, their ear drums thicken and compromises their high frequency hearing. That’s not particularly problematic for indoor cats, but outdoor cats that rely on their hunting skills for survival are affected. They often prey upon animals that squeak and chirp at high frequencies.