Yes, they will have a "period" and they will bleed. I take newborn diapers and custom cut a hole for Chiquita's tail and she wears those while she is bleeding, it really helps to protect your furniture and flooring.
Before my sister's dog was spayed, my sister used to cut a hole in some panties for the tail and put them on Sugar. They worked really good and Sugar looked so cute in Mickey Mouse! :wink: Sugar is a pitbull so they have very noticeable blood.