Today's Radio Solution from 4BC

29 January 2008

Today on 4BC we had a great question from Hayley from Mt Alvernia College at Kedron.

Hayley asked why her white cat has two different coloured eyes?

It is actually a feline form of heterochromia and believe it or not, it does occur in humans as well as some animals. Some famous humans who have this condition are Alexandra The Great, Dan Akryod, Jane Seymour and Christopher Walken. On further research it seems that whilst David Bowie's eyes may appear to be different colours, it is because he has a permanently dilated (enlarged) pupil which makes his blue eye look green or brown depending on the light, and not heterochromia.

Now back to white cats. In cats, the odd-eyed colouring is caused by one of two genes:

1. The dominant white gene, which actually has the ability to mask any other colour genes and turns a cat completely white, or
2. The white spotting gene, which is the gene responsible for bicolour cats - white being one of the colours.

The white or white spotting gene has the ability to prevent pigment granules from reaching one eye during development, resulting in a cat with one blue eye and one green, orange or yellow eye. This rare eye colouring is most commonly found in white cats, although it can be found in any coloured cat in which the white spotting gene is present.

As all cats are blue-eyed as kittens, the differences in an odd-eyed kitten's eye colour might not be noticeable other than they have a different shade of blue in one eye, which can only be picked up on very close inspection. The colour of the odd eye changes over a period of months, for example, from blue to green to yellow, until it reaches its final, adult colour.

There is a common misconception out there that all odd-eyed white cats are born deaf in one ear. This is not true, as about 60%–70% of odd-eyed white cats can hear. White cats with one or two blue eyes do, however, have a higher incidence of genetic deafness, with the white gene occasionally causing the degeneration of the cochlea, beginning a few days after birth.