Dolphin milk has 6 times more protein and is much more fattening than human milk. It allows the baby dolphin to increase its weight 2 to 3 times faster than a human baby does during the first six months. Suckling goes on for about a year and a half. After six months, the baby occasionally takes solid food. Common dolphins reach sexual maturity after 12 to 15 years.
Courtship occurs in the spring and fall.
Males and females court by stroking each other with their flippers, by vigorously rubbing their bodies together, and by swimming along side each other. The male often rushes towards the female as if he is about to bump into her before moving away. The female often swims away from the male's pursuits. The male enters the female with his hidden penis and gives a short series of pelvic thrusts. Females have also been observed thrusting.