h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

TORTOISESHELL and CALICO:
Which is which? The two names are commonly mixed up. The generally accepted differentiation is that the tortoiseshell is a black cat with red and/or orange markings and some white, while the calico is a white cat with patches of red, orange, and black. More important, however, the tortoiseshell has a mottled coat coloring, not distinct patches like a calico.


WHY FEMALE?
Most tortoiseshell and calico cats are female. One male born for every 3000 females is the proper estimation according to Calico Cat Registry International. And yes, chromosomes are indeed the reason.

The occurrence of male calicos is theoretically impossible. Ordinarily, male cats have XY chromosomes, while females have XX. The X chromosomes carry the genes for coat colors. Therefore, female cats inherit their coat color from both their queens (XX) and their toms (XY). To create a calico (or tortoiseshell) pattern, one of the X chromosomes must carry the black gene and the other the orange gene. If a black male and an orange female mate, the result will be a half-black and half-orange female offspring, a calico. A black female and an orange male will also produce a calico female.

Usually, the male kitten (XY) inherits its coat color (X) from the queen alone, since the Y chromosome (from the tom) determines its sex but has nothing to do with its coat color. The male black cat mating with an orange female will produce an orange male; the male orange cat and a black female will produce a black male kitten.

Geneticists have discovered that only one of the two X chromosomes in females is functional, which explains why you usually can make a blanket prediction that any male offspring will be the color of the queen. But occasionally, chromosomes misdivide, and a male calico is born with an extra chromosome - two X chromosomes and one Y chromosome. If one of the X chromosomes carries the orange gene and the other the non-orange, a calico will result.

Note that the presence of the extra X chromosome doesn't in itself create the calico. If both chromosomes are coded for orange or black, the offspring will be that color rather than a combination.

Abnormal chromosome counts are unusual but not rare. Most cat cells contain nineteen pairs of chromosomes, but sometimes a mutation will yield one extra chromosome or double or triple the number.

Although male calicos are oddities, they are normally healthy and have excellent life expectancies. But, unlike their female counterparts, male calicos do tend to have a common problem - their sexual organs are often malformed, so they are usually sterile.

Can't remember how it works, but it works for dogs too.

I know a ginger female and shes's *weird* She was spayed, but from the look of her, I don't think she could have had kittens anyway...she's a bit of an odd shape.

The beautifully proportioned Ccat

There may be an offical difference between the two names tortoiseshell and calico, but there's an unoffical difference too - which is that "calico" certainly used to be unheard of outside America. I know that here in Ireland if I used the term "calico cat" people would either look blank or say "Oh, do you mean tortoiseshell?" (or else "You've been spending too much time on the Internet with all those Americans!")

Azara

Yes, when speaking in terms of common vernacular, tortoiseshell-with-white cats are sometimes called calicos in North America while elsewhere in the world no distinction is made - a tortoiseshell is simply a tortoiseshell.



As a matter for those interested, the distinction I made previously between the tortoiseshell and calico was distilled from the more complicated nomenclature used among cat breeders, exhibitors, show judges, veterinarians, and other ailurophiles throughout the world. The system goes like this:

If your cat is randomly patched with different colors, you probably have a tortie, patched tabby, or calico...

For cats without white markings:
-A "tortoiseshell" or "tortie" is randomly patched all over with red, black, and cream. The patches may be very mingled, or they may be more distinct.
-A "blue-cream" (also called "blue tortie" or "dilute tortie") is randomly patched all over with blue and cream. This is a soft, pastel color.
-A "brown patched tabby" looks almost like autumn leaves, with patches of brown tabby and patches of red tabby. This color is also known as "torbie" because it is a tabby tortie.
-A "blue patched tabby" is a soft color with patches of blue tabby and patches of cream tabby.

There is special terminology for tortoiseshells with white markings, depending on how much white they have:
-A "tortoiseshell and white" or "blue-cream and white" has only small white areas. The body has mingled colors.
-A "calico" has more white. As a rule, the more white there is on the cat, the larger and more distinct the red and black patches will be. You'll notice that the large black patches are solid black, and the large red patches are actually red tabby.
-A "dilute calico" has the same amount of white as a calico, but instead of red and black patches, it has blue and cream patches. The blue patches are solid blue, and the cream patches are cream tabby.
-A "patched tabby and white" or "torbie and white" may have any amount of white. A patched tabby with a lot of white, like a calico, has large distinct patches of color, and is sometimes called a "patterned calico," "calico tabby," or "caliby."

But then what colour is a moggie?

Azara

The book that mentioned why white cats are often deaf is back at the library I think.

"Moggy", or "moggie", is a good old British slang word for "cat", supposedly derived from "mongrel". Moggy is the feline equivalent of a canine mutt. Moggies do not conform to any standards - coming in a range of shapes and sizes, plus a riot of attractive coat colours and patterns. The term is one of common vernacular that can be applied to any non-purebred domestic cat, including tortoiseshells.

And you'll find the slang word "moggy" as rare in the United States as the slang word "calico" is outside of them.