I managed to bang one of my toes in a cat related incident today so I am a little bit distracted from my normal post. So I’ll do a trial version of those Q & A posts.
The gracious littlemiao asks:
So, I read in my cat calendar (not exactly a highly reliable source) that most black cats are actually brown. Where on earth would they get this from? Kemi seems black to me, not brown, and his undercoat is greyish.
Like a lot of popular sources, the calendar is taking a grain of truth and expanding it into a preposterous conclusion. Cat coats have exactly two pigment colors that are used to produce all the colors and shades we see. Leaving aside the big technical names, one is “black” and the other is “orange”. So in reality, there is no brown pigment on any cat.
In some sources, the gene that controls the black pigment is called the ‘browning gene’. If this is what the calendar meant, then it would have said that all black cats are brown. So they must mean something different.
At full intensity, the darkest black hairs are fully black. However, if something decreases the tint, the color ‘fades’ to a more brown color. This can happen in a number of ways – one is that the black gene can take different states besides full black – chocolate and cinnamon. In these, the black pigment grains are less round than black, making them appear lighter and browner.
Similarly, the colorpoint gene ‘fades’ the black grains to a degree depending on the temperature. Calpurnia has this gene, so over most of her body the black hairs are faded into dark browns (called seal) and lighter creme shades. Genetically, however, she is still a black cat.
What the article probably means is that exposure to light and weather can also fade the pigment on a black hair, resulting in a brown color. I believe that competition cats use special hair treatment to avoid the loss of points for not having an entirely black coat. Hopefully it is less harsh than black dye.
And as littlemiao notes, the pigment is not laid out uniformly on a cat hair. It tends to fade near the base. Some genes change how this happens pretty radically from the norm, and produce some striking cats as a result.
Just to confuse things even more, the term “Brown Tabby” is a totally different matter, not referring to the black stripes at all, or even the black pigment This brown is actually the result of the other pigment, Orange, laid out on the Agouti hairs. I have read this pigment is laid out ‘shredded’ which results in the hair not appearing fully orange. Some cats have enough to make the overall background appear brownish rather than grey.
Genetically, it would be more accurate to say all cats are black – they all have a gene locus to express a type of black pigment that can be inherited. Other genes can modify, or even block the expression of this gene on the cat’s coat, but the genetic information is still there waiting for its chance.