Baby dolphins, or calves, are born after gestation periods of up to 12 months in the mother's womb. Calves begin swimming in the mother's womb as early as 9 weeks into the pregnancy. When baby dolphins are born, they come out of the mother's womb tail first and immediately swim to the surface to breath air.
Calves are between 3 to 5 feet in length at birth, and weigh between 22 and 44 pounds. Baby dolphins are born with hair on their upper jaws, which falls out shortly after birth. Their dorsal fins and tail flukes are flexible for a few days after birth, but these structures gradually stiffen. Fetal folding lines, markings that look like stripes on baby dolphins, disappear after 6 months.
Like other mammals, dolphin calves nurse their mother's milk for about 12 to 18 months. After calves are weaned, the mother teaches her young how to hunt for food. Mothers care for their young for between 3 and 6 years.
Calves are born at any time of year, depending upon the location of dolphins in warm waters. Dolphins along the coast of Florida are born in late spring, early summer and early autumn. Along the coast of southern California, dolphins are born in the fall.