Posted: May 7, 2010, 3 a.m. EST
Q: We have a 6-month-old orange tabby cat; she is orange and white, no black, pink pads, lips and eyelids, very sweet. Is there any truth to the notion that female orange tabbys are sterile? We would have her fixed anyway but if we don't need to put her through that and it would save us the expense, it would be nice. Any help would be appreciated.
A: You’re confusing orange female cats with male calico cats. Orange female cats are a little uncommon; only about 1 in 5 orange tabbies are female. But they’re not sterile at all. Male calico cats, however, are much rarer. Not just calicos. Torties, too.
Here's a litte feline genetics lesson: The reason is that black and orange hair can only occur together in the hair coat if that cat has two X chromosomes. Calico cats (white cats with patches of black and orange) and tortoiseshell cats (black and orange swirled together), therefore, have to have two X chromosomes, and two X’s means that you’re a girl.
In order to be a boy, you need a Y chromosome. Boys are XY; girls are XX. Very rarely, a mutation occurs that leads to a calico or tortie male. Genetically, these cats are XXY. The two X’s allows for the color; the Y allows for the maleness. The incidence is reported to be 1 in 3,000.
In other words, out of every 3,000 cats with black and orange together in the hair coat, on average, 2,999 will be girls, and only one will be a boy. The XXY mutation leads to sterility. They can’t reproduce. Your orange tabby girl is not sterile. Get her spayed.