I was fostering a pregnant feral calico. She was a great mother, but very protective of her babies so I had no idea about the sexes of the kittens until they were old enough for me to remove from her. Imagine my surprise to find that the little calico was in fact a male!
How was that possible? Here’s a basic explanation:
Mom’s babies carry a pair of sex chromosomes, XX or XY, which will make her offspring either a girl or a boy. Mom always passes an X to her babies and dad will pass either an X or Y. If baby gets a Y from dad, it will be a boy; his genetic composition will be XY. With cats, color and physical characteristics are specifically tied to X or Y genes, depending on the circumstances. For a kitten to be a calico it needs to have two X genes; one that carries the orange characteristic and one that carries the non-orange characteristic (which can vary, but is usually black). One X would need to be dominant, the other X recessive, for the calico pattern to actually occur. So if a kitten has the XX combination of genes it needs to be a calico, then it should be a female. Therefore, calico’s are always female, right?
Well, not quite.
Sometimes in nature a genetic anomaly can occur where the offspring end up with an extra sex chromosome, which results in XXY combination (this is known as Klinefelter’s Syndrome in humans). The XX part meets the requirements of producing calico colors and the Y part produces the male sex. They are usually sterile and can’t reproduce. However, they are still male and will still produce testosterone, so they should still be neutered as you would any other male cat.
According to the Missouri College of Veterinary Medicine, the odds of a male calico are about one in three thousand and the odds of a nonsterile male calico are about one in ten thousand.
The little male calico, “Paisley” is now part of my ever-growing feline family and we couldn’t be happier. He is so sweet; we wouldn’t trade him for the world!
—Becki Schiller, LVT