Why dog stay together after sex?

The Tie: Once a male successfully penetrates the female there is a bulbous gland at the base of the penis that swells locking it into the vagina. To get more comfortable, the male will usually do a little dance step over the rump of the female and end up facing away from her...this is called the "tie" and naturally lasts about 3-20 minutes. Do not try to separate them as they will separate naturally on their own as the swelling goes down in the bulbous gland.