The tortoiseshell is not an individual or specific breed of cat but is a color point and marking. The color point can be part of a wide range of cat breeds. It is lighter than a traditional tortoiseshell due to the blue coloring, and because the color is available as part of a range of breeds, a blue tortoiseshell cat can have any type of personality.
A blue tortoiseshell cat has the same markings as a tortoiseshell. These actually more accurately match the marking of a turtle than a tortoise, as tortoises tend to have shells with a single color. The pater can contain any two colors and may include white as well.
The markings vary according to genetics and the breed of cat. Because it is a color mutation and not a specific breed, the blue tortoiseshell marking does not determine factors like personality or temperament in the cat.
1. Genetic Mutation
The blue tortoiseshell pattern is actually a genetic mutation of the tortoiseshell coloring. All cat colors are made up of a combination of just two color pigments: eumelanin and pheomelanin, or black and red. However, cats may also carry other genes, in this case, the dilute gene. This dilutes or lightens the black and red colors.
For a blue tortoiseshell, both the black and the red genes are diluted. Lightened black gives the cat a gray color, which is referred to as blue. The diluted red appears cream
Beyond this, the blue tortoiseshell can have any combination of blue and cream colorings, and these can appear in different shades, as well as with white hairs and white patches. Ultimately, though, a blue tortoiseshell cat gets their color from mutated pigments.
2. Most Torties Are Female
The X chromosome determines whether the cat will have black in their coat, while another X chromosome dictates the existence of red color pigments. A tortoiseshell, whether blue or standard, has both black and red in their coat, which means that they must have two X chromosomes, making them female.
If one of the chromosomes is a Y chromosome, which is required for the cat to be male, they will only have red or black in their coat.
3. Males Are Usually Sterile
Cats usually have two chromosomes. Those with two X chromosomes are female, and those with one X and one Y chromosome are male. In rare cases, a male cat can be born with two X’s and one Y chromosome. This means they have the two X chromosomes required to give the tortie coat and the XY chromosome mix that makes them male. However, this XXY combination leaves the cat with serious health issues. They will usually have a shortened lifespan, and the vast majority of the very small number of male tortoiseshells are sterile.
4. Many Breeds Can Be Blue Tortoiseshell
Mixed breeds can be born tortoiseshell, while purebreds like the American and British Shorthair, the Persian, Cornish Rex, and Ragamuffin can also be born with this unique coloring.
5. Coat Length Can Vary
A tortoiseshell may have short or long hair. There are several mutations within a single gene that determine this. It is not related to the X or Y chromosome.
Generally speaking, a cat with hair that is 2 inches or longer is considered a long-haired cat. This isn’t always obvious in kittens, but if your kitten has tufts around their ears, this is usually a good indication that they will mature to be a long-haired cat.
6. They Can Have White Patches
Tortoiseshells can have some white in their coat. White is another mutation and actually represents a total lack of pigmentation in the coat. Some cats are born without pigmentation in some areas, and some develop it as they age, typically because of a condition called vitiligo.
The white color cannot be muted, which means that it appears in both the tortoiseshell and the blue tortoiseshell coats.
That said, male blue torties tend to get seriously ill, rarely make it to adulthood, and are almost always sterile, but these cats are rare and not usually sold by breeders.
7. They Do Not Have Any Specific Health Conditions
A blue tortoiseshell cat’s weight, temperament, and lifespan can vary according to their breed. The color mutation that leads to the blue tortoiseshell markings does not impact the cat, so there are no illnesses or conditions that can arise as a result of the tortie markings.
8. They Are Rare
For a cat to be born a tortoiseshell, they must have two X chromosomes, and these must have the right combination of B, b, and bl genes to have black markings and O and o genes to have red markings. To be a blue tortoiseshell, the cat must also have diluted gene mutations.
Blue Tortoiseshell Cats
Blue tortoiseshell cats are rare, almost always female. They are not a specific breed but have markings that can be present in any of several breeds of cats. They do not have any specific genetic conditions (unless they’re male), although some owners are convinced that tortoiseshells are especially sweet and loving cats.
Featured Image Credit: Shutterstock, Nils Jacobi