Birth, Coupling A special tube called the vagina or birth canal lets the animal go from the uterus to the outside of the animal during birth. This tube is important in mating also. The male mammal must put his sperm into the female's body to fertilise the egg or 'ova'. Male mammals have a tube-like organ called the 'penis'. The male mammal puts his penis into the female's vagina.
Special muscles squirt the sperm into the vagina.
In some mammals the penis reaches right into the uterus and sperm are placed there. This happens for the horse and probably for the members of the deer family. The act of putting the sperm into the female's body is called coupling, sexual intercourse, or copulation. During copulation, the penis becomes stiff like a rod. Many male mammals, such as wolves, deer, and rodents have a thin bone that stiffens the penis.