So, for the females they have two X chromosomes (XX), males have one X and one Y chromosome (XY). The answer is in their genetics. Coat colour in cats is a sex-linked trait, a physical characteristic (coat colour) related to gender. The occasional and very rare male tortoiseshell cat is the result of a genetic mutation. Tortoiseshell and calico coats are the results of the interaction between genetic and developmental factors. Tortoiseshell cats are almost exclusively female as well.

Torties with this lighter colouring are called dilute Torties. Sometimes, these colours present in lighter versions such as lilac or cream. The size of the patches varies from a fine speckled or brindle to large patches of colour. The term “tortoiseshell” is used for cats with brindled coats that have few or no white markings. They also have a distinctive combination of bi colours of either black, amber, red, cinnamon or chocolate. So, if you see a Calico cat, you can almost be assured that it will be a female cat.Ī similar cat to Calico’s is the Tortoiseshell or Torties for short. Another interesting fact is that approximately one calico in 3,000 is male. But did you know, that the Calico is not a breed of cat, but the colour pattern of it’s fur? To be called “calico”, three colours must be present: black, white and orange. I often hear people describe their cat as a “Calico cat” like one would say I have a Siamese cat.

Cat tortoiseshell calico