Bottlenose Dolphin Newborn Baby Calf dolphin showing foetal marks just after birth (Tursiops truncatus), Foetal marks will disappear after one or two days, Part of a sequence of imagesDolphin gestation pregnancy lasts approx, 12 months, the birth can take between half an hour to 3 4 hours depending on the experience of the mother, Weaned after 9 18 months, Young stay closely with mothers for up to 6 years