Common dolphins are viviparous, as are all mammals except monotremes. Females normally give birth to one baby at a time, but have been found to carry twins or triplets. Gestation usually lasts 10 to 12 months. When the calf is born (tail first) it is 3 feet long and usually weighs 25 to 35 pounds.
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. After this playful courtship, these dolphins mate in the belly-to-belly position. The male enters the female with his hidden penis and gives a short series of pelvic thrusts. Females have also been observed thrusting. Other sexual activity includes beak-genital propulsion.
Common dolphins have an estimated life span of 35 to 40 years.
(Alpers, 1961; Baker, 1979; Cousteau, 1988; McIntyre, 1974; http://whales.ot.com/).
Range number of offspring: 1 to 3.
Range gestation period: 10 to 12 months.
Range age at sexual or reproductive maturity (female): 12 to 15 years.
Range age at sexual or reproductive maturity (male): 12 to 15 years.
Key Reproductive Features: iteroparous ; gonochoric/gonochoristic/dioecious (sexes separate); viviparous
Average birth mass: 7000 g.
Average number of offspring: 1.
Babies immediately become a part of the family group. The calf stays close to its mother and never wanders more than a few feet away. The calf feeds on milk from the teats of its mother. Unlike human babies, however, dolphins do not have the lips needed to suck the teats. Also they could not breathe under water if they were able to suck. To solve these problems, the mother squirts milk into her offspring's mouth by contracting muscles. The young dolphin then goes up to the surface to breathe and then comes down for more. 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.
Parental Investment: pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female); pre-independence (Protecting: Female); post-independence association with parents; extended period of juvenile learning