Other crustaceans, certain mollusks and worms, and small fish are also eaten. It usually migrates alone or in groups of 2-3, though sometimes up to 16 travel together. Moreover, there is segregation by age and sex during migrations. Generally females precede males and adults precede immature animals. Individuals have been observed to aid others that are injured or giving birth by pushing them to the surface so they can breathe.
Females are reportedly very protective of their young, even to the point of attacking whaling boats.
Females have a 2-year reproductive cycle. Most enter estrus and mate during a 3-week period in late November and early December, while still migrating south, but some do not mate until in the wintering lagoons or even on the northward migration. Births occur mainly from late December to early February. Gestation lasts about 13 months, lactation lasts about 7 months, and there are then 3-4 months of anestrus. The single newborn averages about 490 cm in length and 500 kg in weight.