The body of the young are some what paler, darkening in adults to black with white patches where skin has sloughed off. There are 225 to 250 baleen plates up to 2.2 metres long in each side of the upper jaw. Size of calves are five to six metres long at birth an average of fifteen metres at maturity. Individuals up to 17.7 metres have been recorded. Calves are born in winter after a twelve month gestation period and are suckled until they reach about 8.5 metres in length.
Sexual maturity is reached at fifteen metres in males and sixteen metres in females.
There appears to be a three year calving interval. Southern Rights are slow swimmers that do not normally expose large amounts of body and breaching or leaping out of the water is infrequent in adults but can sometimes be seen as long sequences in the playful juveniles and young. It was some time before experts realised that nearly all the animals close to shorelines were in fact pregnant females, and mostly mothers with calves. Whalers in their day had no compunction in killing the calves to make it easier to attack the mother, and the combination of these two moralities along with catches on the high seas proved somewhat devastating in depletion of stock. Diet - A selective feeder on small planktonic crustaceans, mainly copepods and krill.