Are all calico cats female?

No, not all calico cats are female, but the majority are. The calico coat pattern is linked to the X chromosome, and the combination of black and orange colors requires two X chromosomes. Since females have two X chromosomes (XX), they can express both colors, creating the calico pattern. However, male cats have one X and one Y chromosome (XY), so having only one X chromosome limits their ability to display the calico pattern.