You can distinguish a male dolphin from a female dolphin by examining its lower stomach. A male dolphin has two slits: One slit contains the penis and the other contains the anus. Female dolphins have only one slit, which contains the vagina as well as the anus. Both sexual organs are located internally on a dolphin. A female dolphin starts reproducing at age 8, while males begin a little later, around age 12.
Dolphins mate in the water, lying with their bellies facing one another. When the male dolphin is aroused, his muscles allow the penis to protrude from the slit in his skin. Then the male dolphin inserts his penis into the slit where the female dolphin's vagina is located. Intercourse lasts for several seconds. Dolphins mate all year long, usually in groups. Several females and several males will usually reproduce with one another. Dolphins do not mate for life.
Dolphins mate at all times of the year, but there are only certain times when female dolphins can become pregnant. A female dolphin becomes pregnant once every three years or so. It takes a year for the foetus to develop fully, and the baby grows inside the mother just as a human baby does. When a female dolphin is preparing for birth, she will rise to the surface of the water and swim back and forth until the baby is born. Labor lasts for about an hour. Dolphins have only one baby at a time.