The southern right whale (Eubalaena australis) is a baleen whale, one of three species classified as right whales belonging to the genus Eubalaena. Like other right whales, the southern right whale is readily distinguished from others by the callosities on its head, a broad back without a dorsal fin, and a long arching mouth that begins above the eye. Its skin is very dark grey or black, occasionally with some white patches on the belly. The right whale's callosities appear white due to large colonies of cyamids (whale lice). It is almost indistinguishable from the closely related North Atlantic and the North Pacific right whales, displaying only minor skull differences. It may have fewer callosities on its head and more on its lower lips than the two northern species. Approximately 10,000 southern right whales are spread throughout the southern part of the Southern Hemisphere.
The maximum size of an adult female is 15 m (49 ft) and can weigh up to 47 tonnes (46 long tons; 52 short tons). The testicles of right whales are likely to be the largest of any animal, each weighing around 500 kg (1,100 lb). This suggests that sperm competition is important in the mating process. Right whales cannot cross the warm equatorial waters to connect with the other (sub)species and (inter)breed: their thick layers of insulating blubber make it impossible for them to dissipate their internal body heat in tropical waters.
Right whales are three species of large baleen whales of the genus Eubalaena: the North Atlantic right whale (E. glacialis), the North Pacific right whale (E. japonica) and the southern right whale (E. australis). They are classified in the family Balaenidae with the bowhead whale. Right whales have rotund bodies with arching rostrums, V-shaped blowholes and dark gray or black skin. The most distinguishing feature of a right whale is the rough patches of skin on its head which appear white due to parasitism by whale lice. Right whales can grow up to 18 m (59 ft) long and weigh up to 100 short tons (91 t; 89 long tons), significantly larger than humpbacks or grays, but smaller than blues.
All three species are migratory, moving seasonally to feed or give birth. The warm equatorial waters form a barrier that isolates the northern and southern species from one anther. In the Northern Hemisphere, Right whales tend to avoid open waters and stay close to peninsulas and bays and on continental shelves, as these areas offer greater shelter and an abundance of their preferred foods. In the Southern Hemisphere, right whales feed far offshore in summer, but a large portion of the population occur in near shore waters in winter.Right whales feed mainly on copepods but also consume krill and pteropods. They may forage the surface, underwater or even on the ocean bottom. During courtship, males gather into large groups to compete for a single female, suggesting that sperm competition appears to be an important factor in mating behavior. Although the blue whale is the largest animal on the planet, the testes of the right whale are actually ten times larger than those of the blue whale – with each weighing up to 525 kilograms (1,160 lb), they are by far the largest of any animal on Earth. Gestation tends to last a year, and calves are born at 1 short ton (0.91 t; 0.89 long ton) in weight and 4–6 m (13–20 ft) in length. Weaning occurs after eight months.