When do you guys sort your rats? Ive been trying to sort threw our babies and keep males and females separeted because I would like to keep the females and raise them to be breeders but im feeding off the males once they get large enough. But im having alot of trouble sexing them. I look for nipples but I just dont see them until they start to get to large sizes. Is there any sure fire easy way to tell if they are males or females?