Southern right whale

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.

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.

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.