Internal fertilization with many vertebrates such as reptiles , some fish , and most birds occur via cloacal copulation see also hemipenis , while mammals copulate vaginally, and many basal vertebrates reproduce sexually with external fertilization. American Society of Plant Biologists. And yet I wanted a serious erotic connection this time in the package. Encyclopedia of rape 1st ed. Customers who bought this item also bought. It's called red light therapy! Those having an addiction to sexual intercourse have a higher response to visual sexual cues in the brain.