Why are most calico cats female?


By Emily Bruer

Calico cats have arguably one of the most beautiful coats in all of cat-dom.

Many people believe that “Calico” is used to describe a breed, but it is actually a coat color that can be found in many different breeds. This coat pattern is entirely unique and you will never find two calicos with the exact same markings.

A common myth is that all calico cats are female. While the large majority of calicos are female, one in 3,000 are male. The reason for this is completely genetic: the orange/non-orange coat color is carried on the X chromosome. Each parent contributes one chromosome to the baby. Females have XX and males have XY. This means that the father of the kittens determines the gender.

However, to get a calico coat the kitten must have both an orange and a non-orange X chromosome, which one would assume means that all calicos are female. In some rare cases, however, faulty cell division can cause an extra X chromosome. This extra X would be reproduced in all the cells, and if one of the Xs has the orange gene and one has the non-orange, the resulting kitten could be a male calico.

The XXY gene sequence can cause health conditions such as weak muscles, slow growth, and hormone imbalances and is referred to as Klinefelter’s syndrome.

If you are one of the few people who ends up with a male calico, there are a few things you should know. The first is that almost all male calicos are sterile.

1 in 10,000 male calicos are able to reproduce, but their genetic materials can be problematic due to their extra chromosomes. For a male calico to be able to reproduce they would have to have two double cells XXYY, which, as you can imagine, is very rare.

Another way that a male cat can be a calico is through two fetuses merging in the mother’s womb. This is referred to a chimera: during the merge one of the DNA strands can determine the coat color, while the other determines the reproductive organs. This is extremely rare, but it has occurred.

When choosing your new cat, be sure to base your choice on more than coat color. Let the adoption staff know about your home, activity level, and other pets, as many staff members will know the cats in their care exceptionally well.

Keep in mind that the shelter is a terrifying place for most animals, and some may act completely shut down or aggressive in the shelter when they are amazingly sweet, affectionate and outgoing in a home. While the staff may not be able to tell you exactly how a cat will act in your home, they may be able to guide you toward a cat they think will be a great fit.

If you don’t currently have a cat, consider adopting a bonded pair of adult cats. Bonded pairs have a hard time getting adopted, but they have twice the amount of love to give. They can keep each other company as well as help each other stay fit and exercised.

The only thing better than one calico cat is two!


Looking for your new calico pal(s)?  Check out the listings on a national adoption databases like Petfinder or Adopt-a-pet, or through a local rescue or shelter. 


emily-bruer-pawedinEmily Bruer has been penning the adventures of her imagination since she was old enough to hold a pencil. Working at animal shelters for the last five years, she learned an incredible amount about animal care and behavior. She is currently employed at a vet clinic where she continues her animal education. Emily’s love of animals is evident when you step into her home, which she shares with six dogs and six cats, all of whom were rescues.



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