Why are male calico cats sterile?

Answer 1

The orange and black colours found on calicos are both located on the two X chromosomes of a female cat; since male cats should have a set of XY chromosomes, they should only be able to have either the black chromosome or the orange chromosome.

However, as with every part of the body, mutations are possible. A cat may have a XXY s*x chromosome layout; called Klinefelter's Syndrome, the extra X chromosome almost certainly will lead to the sterility of the animal that has it, whether human or feline.