Here's why:
* Calico coloration is a sex-linked trait: The genes for calico fur are located on the X chromosome.
* Females have two X chromosomes: This means they can inherit the calico gene from either parent, resulting in the distinctive calico pattern.
* Males have one X and one Y chromosome: They only inherit one X chromosome, so they can't have the calico gene combination.
It's extremely rare for a male guinea pig to be calico. It could happen in very specific cases involving genetic mutations, but it's highly unlikely.