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. Although the blue whale is the largest animal on the planet, the testes of the right whale are actually ten times the size of those of the blue whale. Weighing up to 525 kg (1157 lbs), they are by far the largest of any animal on Earth.
All three species are migratory, moving to certain areas to feed or give birth. The warm equatorial waters form a barrier that prevents mixing between the northern and southern groups. 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. Right whales feed mainly on zooplankton but will 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. Sperm competition appears to be important in mating. 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.
Whale (origin Old English hwæl from Proto-Germanic *hwalaz) is the common name for various marine mammals of the order Cetacea. The term whale sometimes refers to all cetaceans, but more often it excludes dolphins and porpoises, which belong to the suborder Odontoceti (toothed whales). This suborder also includes the sperm whale, killer whale, pilot whale, and beluga whale. The other Cetacean suborder, Mysticeti (baleen whales), comprises filter feeders that eat small organisms caught by straining seawater through a comblike structure found in the mouth called baleen. This suborder includes the blue whale, the humpback whale, the bowhead whale and the minke whale. All cetaceans have forelimbs modified as fins, a tail with horizontal flukes, and nasal openings (blowholes) on top of the head.
Whales range in size from the blue whale, the largest animal known to have ever existed at 30 m (98 ft) and 180 tonnes (180 long tons; 200 short tons), to various pygmy species, such as the pygmy sperm whale at 3.5 m (11 ft). Whales collectively inhabit all the world's oceans and number in the millions, with annual population growth rate estimates for various species ranging from 3% to 13%.