Gary: 1 in 3000

Meet Gary.  Gary is a male calico cat.  Calico refers to a color pattern of the fur and not to a breed.  Calico cats are almost always female.  How or why does this occur?

First a little lesson in genetics.  Mammals have two sex chromosomes: the X chromosome and the Y chromosome. A normal female has two X chromosomes and no Y chromosomes and normal males have one X chromosome and one Y chromosome. It is the chromosome that comes from the father which determines the sex of the mammal. The father will either contribute his X chromosome whereby the offspring will be female or his Y chromosome and the offspring will be male.


Calico cats are almost always female because the X chromosome determines the color of the cat and a female cat has two X chromosomes. A common male cat has one X and one Y chromosome. Since the Y chromosome does not have any color genes, there is no chance he could have both orange and non-orange together. One main exception to this is when, in rare cases, a male has XXY chromosomes, in which case the male could have tortoiseshell or calico markings. Most male calico or tortoiseshell cats are sterile due to the abnormality of carrying two X chromosomes.  In the case of a calico cat, the feline’s parents passed on different versions of X chromosomes genes related to coat color. The color of calico or tortoiseshell cats is determined by the X chromosome(s). Tortoiseshell and calico cats are almost always female because of X chromosome inactivation.

Wow!  That was scientific!  Now time for some nonsense.  Old wives tales:  Calico cats are believed to bring good luck.  Myth--Male calico cats are worth a lot of money.  Calico males are rare, but calico is a color and not a breed and are usually sterile, so cannot reproduce and pass on the color.  So they are not worth much monetarily.