The southern right whale (Eubalaena australis) is a large baleen whale and one of three species of right whale belonging to the genus Eubalaena. Found throughout the Southern Hemisphere, it inhabits oceans between the latitudes of 20° and 60° south. Like its northern relatives, the southern right whale is noted by its broad back without a dorsal fin, a long, arching mouth, and white growths on its head known as callosities. Previously hunted for hundreds of years, almost to extinction, the species is now protected and its global population was estimated to be around 13,600 (2009).
Each year, the southern right whale migrates. During the summer months, it feeds on zooplankton and krill in the cold waters of the Southern Ocean, often near Antarctica. In the winter, it travels northward to the warmer coastal waters off Argentina, Australia, Brazil, South Africa, and New Zealand to breed and calve. The whales are known for their active behavior at the surface, which includes breaching and a unique practice called "tail sailing," where they use their flukes to catch the wind.
Historically, southern right whales were the primary target for whalers (thus the "right" whale to hunt), who killed tens of thousands from the 18th to the 20th century, decimating the population. International protection was established in 1937, though illegal whaling by the Soviet Union continued into the 1970s. Since cessation of industrialized whale slaughtering, the population has seen a steady increase, growing an estimated 7% per year. Today, the species is a focus for whale watching, though it continues to face threats from ship strikes, entanglement in fishing gear, and pollution.
Taxonomy Right whales were first classified in the genus Balaena in 1758 by Carl Linnaeus, who at the time considered all right whales (including the bowhead) to be a single species. In the 19th and 20th centuries the family Balaenidae was the subject of great taxonometric debate. Authorities have repeatedly recategorised the three populations of right whale plus the bowhead whale, as one, two, three or four species, either in a single genus or in two separate genera. In the early whaling days, they were all thought to be a single species, Balaena mysticetus.
The southern right whale was initially described as Balaena australis by Desmoulins in 1822. Eventually, it was recognised that bowheads and right whales were different, and John Edward Gray proposed the genus Eubalaena for the right whale in 1864. Later, morphological factors such as differences in the skull shape of northern and southern right whales indicated at least two species of right whale—one in the Northern Hemisphere, the other in the Southern Ocean. As recently as 1998, Rice, in his comprehensive and otherwise authoritative classification, Marine mammals of the world: systematics and distribution, listed just two species: Balaena glacialis (all of the right whales) and Balaena mysticetus (the bowheads).
In 2000, Rosenbaum et al. disagreed, based on data from their genetic study of DNA samples from each of the whale populations. Genetic evidence now shows that the northern and southern populations of right whale have not interbred for between 3 million and 12 million years, confirming the southern right whale as a distinct species. The northern Pacific and Atlantic populations are also distinct, with the North Pacific right whale being more closely related to the southern right whale than to the North Atlantic right whale. Genetic differences between E. japonica (North Pacific) and E. australis (South Pacific) are much smaller than other baleen whales represent among different ocean basins.
It is believed that the right whale populations first split because of the joining of North and South America when the Panama isthmus formed. The rising temperatures at the equator then created a second split, into the northern and southern groups, preventing them from interbreeding.Palaeobiology and Biodiversity Research Group , University of Bristol
In 2002, the Scientific Committee of the International Whaling Commission (IWC) accepted Rosenbaum's findings, and recommended that the Eubalaena nomenclature be retained for this genus.
The cladogram is a tool for visualising and comparing the evolutionary relationships between taxa. The point where a node branches off is analogous to an evolutionary branching – the diagram can be read left-to-right, much like a timeline. The following cladogram of the family Balaenidae serves to illustrate the current scientific consensus as to the relationships between the southern right whale and the other members of its family.
Other junior synonyms for E. australis have included B. antarctica (Lesson, 1828), B. antipodarum (Gray, 1843), Hunterus temminckii (Gray, 1864), and E. glacialis australis (Tomilin, 1962) (see side panel for more synonyms).
Description
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 than North Atlantic and more on its lower lips than the two northern species. The biological functions of callosities are unclear, with proposed purposes including protection, identification, and use in mating.
An adult female is Branch, G.M., Branch, M.L, Griffiths, C.L. and Beckley, L.E. 2010. Two Oceans: a guide to the marine life of southern Africa and can weigh up to , with the larger records of in length and up to in weight,Department of Sustainability and Environment. 1998. Southern Right Whale – Eubalaena australis . Action Statement-Flora and Fauna Guarantee Act 1988. No.94. Retrieved on 31 October. 2014 making them slightly smaller than other right whales in the Northern Hemisphere.Whale and Dolphin Conservation. Endangered Species – Southern Right Whale Eubalaena australis. Retrieved on 31 October. 2014 On each side of the upper jaw are 200–270 baleen plates. These are narrow and approximately long, and are covered in very thin hairs. The pectoral fin is long. The testicles of right whales are likely to be the largest of any animal, each weighing around . This suggests that sperm competition is important in the mating process. The penis can reach in length.
The proportion and numbers of molten-coloured individuals are notable in this species compared with the other species in the Northern Hemisphere. Some whales remain white even after growing up.
The oldest living southern right whale was 70 years old. However, a 2024 study found that the median lifespan is around 73, with some individuals surviving to over 130.
Behaviour
Like other right whales, they are rather active on the water surface and curious towards human vessels. Southern rights appear to be more active and tend to interact with humans more than the other two northern species. One behaviour unique to the southern right whale, known as tail sailing, is that of using their elevated flukes to catch the wind, remaining in the same position for a considerable amount of time. It appears to be a form of play and is most commonly seen off the coast of Argentina and South Africa. Some other species such as humpback whales are also known to display. Right whales are often seen interacting with other cetaceans, especially humpback whales and dolphins. There have been records of southern rights and humpbacks thought to be involved in mating activities off Mozambique, and along Bahia, Brazil.
A female southern right whale was spotted off the coast of Western Australia accompanying a lone humpback whale calf, although the actual relationship of this pair is unclear.
Reproduction Southern right whales display strong maternal fidelity to their calving grounds. Calving females are known to return to calving grounds at 3-year intervals. The most commonly observed calving interval is 3 years, but intervals can range from 2 to 21 years. Calving takes place between June and November in calving grounds between 20 and 30° S.
In Australia, southern right whales have shown a preference for calving grounds along coastlines with high wave energy, such as the Head of the Bight. Here, the sound of breaking waves may mask the sound of the whales' presence, and so protect infants and calving cows from predators such as killer whales. Deep waters alongside shallower calving grounds may serve as training grounds for calves to build up their stamina ahead of migration.
The age of sexual maturity for southern right whales is between 3 and 6 years. Females give birth to their first calf when they are between eight and ten years old. A single calf is born after a gestation period of one year, about in weight and in length. The calf usually remains with its mother during the first year of its life, during which time it will double in length. A southern right whale with sex chromosome aneuploidy (XXY) has been reported.
Southern right whales have been observed nursing unrelated orphans on occasions. Southern right whales have been observed to have male to male penetration, with the behaviour being attributed to different possibilities: socialization, play, and reducing tension between males.
Predation The only known predator of the southern right whale is the killer whale, There have been cases of adult killer whales hunting a southern right whale calf in Golfo San Jose, Argentina in 1986, and of killer whales hunting a newborn southern right whale in Balneario Quintão, off the northern coast of Rio Grande do Sul, Brazil, in July 2008.
Feeding Like right whales in other oceans, southern right whales feed almost exclusively on zooplankton, particularly krill. They feed just beneath the water's surface, holding their mouths partly open and skimming water continuously while swimming. They strain the water out through their long baleen plates to capture their prey. A southern right whale's baleen can measure up to long, and is made up of 220–260 baleen plates.
Population and distribution The global population of southern right whales was estimated at 13,611 in 2009. An estimate published by National Geographic in October 2008 put the southern whale population at 10,000. A population estimate of 7,000 followed a March 1998 IWC workshop. Researchers used population data from three surveys of adult females in the 1990s (Argentina, South Africa and Australia). They extrapolated to include the population of unsurveyed areas, and used known male-to-female and adult-to-calf ratios to estimate and include numbers of males and calves. Recovery of the overall population size of the species is predicted to be at less than 50% of its pre-whaling state by 2100 due to heavier impacts of whaling and slower recovery rates.CSIRO. 2017. Post-whaling recovery of Southern Hemisphere. Phys.org. Retrieved on 22 August 2017 Since hunting ceased, the population is estimated to have grown by 7% a year.