Tortoiseshell cats aren’t a separate breed, and the word refers, instead, to a particular kind of coat pattern that is prevalent in mainly female cats and that appears across many breeds.
The tortie pattern isn’t the result of deliberate crossbreeding either but has gradually developed over the centuries into the well known pattern it is today.
The distinctive tortoiseshell pattern, of which the orange and black combination is, perhaps, the most well known, is linked to the gene for orange fur (O).
Should a female cat inherit two of these dominant O genes, she will be an orange tabby, but, should she inherit one, she will be a tortoiseshell.
The rare male cats that inherit the XXY chromosome combination will also born a tortoiseshell, but they won’t be able to breed as they’re born sterile.
The coats of the orange tabby and black tortoiseshells can be either patched (patches of the different fur colors) or woven/brindled (where the two colors are evenly mixed throughout the coat).
They aren’t limited to orange tabby and black either, and diluted color combinations, like creams and blues/browns/greys are also found.
There is also the “torbie” variation, which is a tortoiseshell whose color combination is orange tabby and grey/blue/brown tabby instead of orange tabby and black.
As with the mainstream torties, the torbies’ coats can also be either brindled/woven or patched.
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Some tortoiseshells also have the white spotted gene, which results in a white/orange tabby/black combination. In the US, these cats are called calicoes while, in the UK, they’re known as tortoiseshell and whites.
Again, as with the pure tortie, the non-white areas of the cats’ coats can either be patched or woven/brindled, and, if the white spots are extremely large, the cat is called a caliby.
There is also another way to categorize these cats: if their black and orange fur is patched, and these patches are mixed with the white spots, they’re calicoes, but, if the black and orange is woven/brindled between spots of white, they’re tortoiseshell and whites.
And just to add to the confusion, there are also torbie tortoiseshell and whites as well as torbie calicoes – the orange tabby/blue or grey or brown tabby/white mix – as well as both colorpoint torties and torbies, which are known as tortie points and torbie points respectively.
All of these coat pattern types can come in either the bright tortie colors (orange tabby and black) or the diluted ones (the creams and blues/grays/browns).
Tortoiseshell is a formally recognized coat pattern across many breeds, including natural breeds like the Persian, the American Shorthair and the Abyssinian.
It’s not limited to natural breeds, though, and it’s also seen in hybrid breeds like the Tonkinese and the Exotic Shorthair and also in mutation breeds like the Cornish Rex, the Somali and even the hairless Sphynx.
Last but not least, special mention must be made of the attitude that tortoiseshells are supposed to have: tortitude! These cats are personable and spunky, have large personalities and are, in a word, unforgettable.