Now that a calico cat has been defined as a cat with three colors, the question is: why are they nearly always female? The answer is in genetics. Coat color in cats is a sex-linked trait, a physical characteristic (coat color) related to gender. Female animals have two X chromosomes (XX), males have one X chromosome and one Y chromosome (XY). The genetic coding for displaying black or orange color is found on the X chromosome. The coding for white is a completely separate gene.
Since females have two X chromosomes, they are able to "display" two colors (orange and black, or variations thereof) and white; creating the 3-color calico mix. Since males have only one X chromosome, they can only be orange OR black. It is more complicated than simply having the color genes -- it is a complex process of dominant and non-dominate genes interacting on the X chromosomes, but that is the basis for coat color in calico cats. For those of you interested in the detailed coat color genetics, please see the "Related Reading" articles at the bottom of this FAQ.
Can a calico cat ever be male? Yes, in rare instances. In this situation, the cat has two X chromosomes and one Y chromosome (XXY). Cats with this chromosomal configuration are usually sterile (not able to breed). This is similar to a condition in humans called Klinefelter's syndrome, or XXY Syndrome.
Interesting calico cat fact: on October 1, 2001, the calico cat became the official cat of the state of Maryland in the United States.
Tortoiseshell And Tri-Colour Cats
Copyright 2002, 2005, Sarah Hartwell
Torties, Calicos and Tricolor Cats
Copyright Barbara French, Tarantara Cattery, Rochester, NY