The bottlenose dolphin reproduces through sexual copulation. The gestation period is 12 months. While twins do occur in bottlenose dolphin births, single calves are the most common. A calf remains with its mother from 18 months to 8 years following its birth.
Females give birth to calves in shallow water. The birthing process is often assisted by what marine biologists label as a "midwife" dolphin. The dolphin that performs this supportive role is in the majority of instances another female, although males have also been documented performing this function. Immediately after birth, the calf is brought to the water's surface to breathe fresh air. Right after this, the first nursing takes place. Nursing occurs from the mother's mammary glands. Bottlenose dolphins have two nipples that are covered by protective slits on her underbelly. The calf must insert its snout into these slits to attach to a nipple for nursing. Weaning is usually prompted by the mother getting pregnant during a subsequent breeding season.
The age of sexual maturity for bottlenose dolphins is between 5 and 12 years for females. For males it is 10 to 13 years. Dolphins have multiple sexual partners during a mating season. Care and rearing of the calves is done exclusively by the mother.