Black cats are apt to polarise people’s opinions strongly, with black cats historically being the subject of much distrust, something that sadly still spills over to the present day, with black cats being the hardest to rehome, the most commonly overlooked in rehoming shelters, and the most commonly abandoned and given up. This is highly unfortunate, as of course superstition is no basis upon which to make a decision about a pet, and black cats are usually the most friendly, outgoing and affectionate cats around, and once you have got to know one, you will become very susceptible to their charms in the future!
However, when it comes to the most defining and uniting element of black cat life-their coat colour- all is not as it seems, and not all black cats are created equal!
In this article, we will look at the genetics behind the black coat colouration in cats, the elements of true black coats, colour variations and what they mean, and also answer the intriguing question “when is a black cat not actually a black cat?” Read on to learn more.
The colour of any given cat’s coat comes down to their genetics, and the genes that make up coat colour are called alleles. The alleles that produce a true or black coat are known as “B” (big B) alleles, while variations on this black coat gene, known as “b” (small b) alleles will lead to related colour strains, such as a dark or chocolate brown coat. The big “B” allele is dominant to all other variants of the small “b” gene, and so if a cat inherits just one big B gene from one parent, this will over-ride any other small “b” genes, leading to a black coat.
This is why black is one of the most common cat coat colours, and why a seemingly disproportionate number of kittens from litters of black and mixed parentage will also be black, due to the big B gene dominance.
However, while this might all seem fairly clear and easy to understand, there is a loophole to this “big B is dominant rule”- the big B or true black gene’s dominance only applies to small b genes, or other recessive genes from the black colour grouping, but does not override other types of colour genes as well.
The most dominant cat coat colour gene overall, and the one that will override virtually all other coat colour variants is the agouti or tabby pattern, which is why there are usually more tabby or part-tabby cats in the UK than any other type!
This means that for a cat to be true black in colour rather than having a tabby colour pattern base to the black, they need to inherit the big B gene, but without the corresponding dominant gene for tabby or agouti, instead inheriting a recessive tabby gene or no tabby gene at all, otherwise they will exhibit a tabby pattern.
If all of the above seems a little complicated, that is entirely understandable! However, it is worth reading it over a couple of times until you are confident that it all makes sense, as understanding this basic principle will help you to understand the next stage in the colour and genetics process where the black coat is concerned: When is a black cat not a black cat?
The answer to this question is, “when the coat appears to be black, but actually has an underlying tabby or agouti pattern!” You may sometimes see the faint signs of a tabby pattern on black kittens, or in adult cats that spend a lot of time outside in the sun so that their fur lightens up in the summer.
This occurs if the cat in question possesses the dominant B gene for black colouration, but the corresponding tabby or agouti colour gene is not fully repressed, and so, produces the shadows of the tabby pattern under the black!
While the colour bases for a black cat are pure black with the big B gene or black tabby with a non-fully repressed agouti gene, genuinely black cats can also change colour over time!
Obviously many cats will begin to develop the odd grey hair as they age, with some having a tiny little patch on their chest or neck, or a couple of white hairs present from birth-but even if your cat starts life as pure raven black, they are apt to get more of a salt and pepper appearance and more and more grey hairs as they age!
Added to the addition of a little distinguished grey as they age, black cats that spend a lot of time sunbathing may begin to fade in the sun, much like many people get sun-bleached hair in the summer! On black cats, this will appear as a fading of the ends of the fur into a rusty or chestnut-brownish shade, which will naturally return to a genuine black during the colder months of the year.
However, a rust-shade to the coat can also occur due to a deficiency in an essential enzyme called tyrosine, which is an element in the creation of black pigmentation of the coat. This same enzyme is part of the reason behind albino colouring too, as it interferes with melanin production by the coat and skin as well.
If your cat is not naturally producing enough tyrosine, their coat may appear to fade or become a rust or chocolate brown colour instead of a true black, and if their coat does not return to a true black in the winter, this is worth getting this checked out by your vet. If your cat is suffering from an enzymatic imbalance, this can cause other problems as well as discolouration, but can often be corrected with the appropriate replacement supplements.