Mating occurs in temperate, low-latitude seas during the winter, followed by an 11- to 12-month gestation period. A newborn weans from its mother at 6 or 7 months of age when it is in length, and the accompanies the mother to the summer feeding ground. Females reproduce every 2 or 3 years, with as many as six fetuses being reported, but single births are far more common. Females reach sexual maturity between 6 and 12 years of age at lengths of in the Northern Hemisphere and in the Southern Hemisphere. Calves remain with their mothers for about one year.