Answer:
Dolphin calves are born after long gestation periods inside their mothers that range between 11 and 17 months according to the species.
Mothers deliver calves with the aid of another female dolphin who makes the role of a midwife.
Calves stay with their mothers for several years until they can survive by themselves.
After approximately six years, a time which also varies according to the species, young dolphins can hunt and protect themselves, so they leave their mothers and start an independent life.
This independent life sometimes means moving to another pod, but this is not a rule in all species as in some cases, just the females move to another group.