Many people hear a lot about white cats being deaf. Indeed many people assume that if a cat is white, then it will not be able to hear. However, this is not the case. White coat colour and deafness are related, but the link is rather complicated. It is not a straightforward genetic link, ie it is not the case that a cat has a gene for white coat colour which also causes deafness. But a lot of people think that this is the case. I have even heard of a pedigree cat breeder, who should know better, say that her cats do not carry the gene for deafness. This may be a way of reassuring her kitten buyers, but it is actually nonsense. For deafness in white cats is not carried by a specific gene; the reasons for it are genetic, but are very different from simply being caused by one gene. Additionally, not all white cats are deaf, and although deafness is more common in white cats with blue eyes, not even all blue-eyed white cats are deaf. Here is a brief explanation of all of this, and of what causes some white cats to be unable to hear.
To start with, there is no actual gene for 'whiteness' in cats. It is not a gene which makes cats appear white. Instead, the apparent white colour is caused by a 'masking' gene; that is, a gene which prevents the underlying colour from showing itself. So apparently white cats actually have the gene for some other colour, but the masking gene prevents it from showing itself. This happens because the masking gene prevents melanin from developing, and it is melanin which causes the cat's fur colour to develop. This last point is very important...
Melanin affects the coat colour in cats, but it also has an effect on the cochlea in the inner ear. If the masking gene prevents melanin developing, this may mean that the cochlea degenerates shortly after birth and the cat is permanently deaf. This masking gene is also sometimes responsible for blue eyes in white cats. So if the cat has blue eyes, it is more likely to be deaf, and if it has only one blue eye, it maybe deaf on only that side, and the cochlea in the ear on the other side will have developed normally.
However, things are not quite that simple and clear cut. There are other reasons for cats being white, and also other genes which can affect eye colour. For instance, Siamese cats usually have blue eyes, but in this instance the white colour is caused by a different gene. So if a cat happens to have Siamese in its ancestry, it may appear white and have blue eyes, but if the blue eyes are caused by the Siamese gene, the cat may have perfect hearing. And even in pedigree cats, a cat's complete ancestry is rarely known for certain, and few breeders can guarantee that a cat has no Siamese in it's make-up.
To further complicate matters, there is also another gene for blue eyes in cats, which is inherited entirely separately from coat colour.
So to summarise, only some blue-eyed white cats are deaf, but by no means all.
To make things yet more complex, cats may be white for other reasons than the presence of the masking gene. There may be the complete absence of any pigmentation, which would make the cat an albino. It is usually easy to tell the difference between albino cats and other white cats, as albino cats generally have pink eyes which are very sensitive to light. But not all albino cats appear to be different from white blue-eyed cats with the masking gene. And albino cats are not deaf, as the cochlea will have developed normally.
Added to all this, some cats aren't actually white in the sense of having the masking gene. However, they have a white spotting gene, which normally is responsible for white spots or patches on the cat. Occasionally the white 'spot' will cover the whole cat, which then appears as white...but is of course genetically different. However, if such cats have blue eyes, they may still be deaf, for reasons which are not entirely clear.
Of course, a potential owner will want to know the chances of her white cat being deaf. Well, opinions vary, and so do research conclusions. However, in white cats with two blue eyes, roughly 60-80% are likely to be deaf. In those with only one blue eye, 30-40% will be deaf, so the majority will have normal hearing. In those cats with eyes of another colour, only 10-20% are likely to be deaf. And of course some cats of any colour may be deaf for a completely unrelated reason.
If you suspect that your white cat, or indeed any cat of any colour, is deaf, it is probably a good idea to get it tested to find out for certain. A simple test called a BAER test is used to test for deafness in cats, and there are various places where this can be carried out; just ask your vet. Breeders of white cats will usually test all of their kittens to determine whether they can hear normally, or they should do so. You can also try clapping or whistling loudly to see if your cat can hear you. However, it can be hard to tell if a cat is actually deaf, or has just decided not to respond.
If your white cat is deaf, do not despair. Deaf cats can lead a perfectly normal life. However, they should probably be kept indoors, since they will not hear traffic or other dangers. And of course they will not come when their owner calls them, but that is the case for many cats anyway! But a deaf cat can still be a healthy, happy cat.