Expert: Jessica - 10/3/2009

Question
my friend fluffer nutter is considered a calico by the vet.  but he is black white and brown.  do calico cats have to have orange coloring or just 3 different colors?  also how weird is it that he is a male calico?

Answer
Hi there.  This is a great question!

“Calico” refers to a color pattern.  Calico cats are white with distinct patches of orange and distinct patches of black (some have less white than others).  There is also a dilute calico, which has gray and cream patches instead of black and orange.  There are other tri-colored cats called tortoiseshells and patched tabbies, which have a different pattern of colors but also must have black and orange, or gray and cream.

In order for a cat to be considered a calico, all three colors – white, black (or gray) and orange (or cream) must be present.  While males can have three colors of fur, say white with patches of brown tabby, this is not considered a calico.

The X (“female”) chromosome carries the gene for fur color.  It can carry the gene for red fur OR black fur (as well as other colors).  Since females receive two X chromosomes, they can receive a gene for each color.  However, since the male only receives one X chromosome, he may have either red OR black fur, but not both.  This means that calicos are virtually always female.

There is one exception.  While females receive two X chromosomes (XX) and males receive an X and a Y (XY), some “male” kittens are born with two X chromosomes and one Y chromosome (XXY).  The two X chromosomes allow the cat to have black and red fur (as well as white), and the Y chromosome causes the development of male genitalia.  Genetically, these cats are not actually male or female, and the cats are generally unable to reproduce.  But since they appear to be males externally, they are labeled as male calicos.

Fewer than 1 out of 10,000 cats has an XXY mutation, and not all will be calico.  In addition, many of them suffer other types of mutations that affect vital organs, and they don’t survive kittenhood.  So adult male calicos are quite rare.