Right whale dolphin

For the similarly named whale, see Right whale.

Right whale dolphins
Northern species, Lissodelphis borealis
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Artiodactyla
Infraorder:	Cetacea
Family:	Delphinidae
Subfamily:	Lissodelphininae
Genus:	Lissodelphis Gloger, 1841
Type species
Delphinus peronii Lacépède, 1804
Species
L. borealis Peale, 1848 L. peronii Lacépède, 1804
Northern and southern right whale dolphin ranges

Right whale dolphins are cetaceans belonging to the genus Lissodelphis. It contains the northern right whale dolphin (Lissodelphis borealis) and the southern right whale dolphin (Lissodelphis peronii). These cetaceans are predominantly black, white beneath, and some of the few without a dorsal fin or ridge. They are smaller members of the delphinid family, oceanic dolphins, and very slender. Despite scientists being long acquainted with the species (the Northern species was identified by Titian Peale in 1848 and the Southern by Bernard Germain de la Cépède in 1804), little is known about them in terms of life history and behaviour.

Physical description

Size comparison with a human (northern species)

Both species have slender bodies, small, pointed flippers and a small fluke. Conspicuously, neither species has a dorsal fin; nor do right whales and this may explain the dolphins' name. The northern right whale dolphin is the only dolphin in the Pacific with this property. Similarly, the Southern is the only finless dolphin in the southern hemisphere. The two species can be readily distinguished (apart from the geographical separation in their ranges) by the extent of the whiteness on the body. Both have white bellies; however, the area of white coloration on the Southern species covers much more of the body — including the flanks, flippers, beak and forehead.

Northern males are about 220 cm (87 in) long at sexual maturity. Females are 200 cm (79 in). Both sexes become mature at about 10 years. New-born right whale dolphins are about half the length of their parents. The southern species is typically larger (up to 250 cm (98 in)) and heavier (up to 100 kg (220 lb) compared with the Northern's maximum of 80–90 kg (180–200 lb)). The dolphins live for about 40 years.

Distribution

The northern right whale dolphin (L. borealis) is common in the waters of the temperate North Pacific, though its range does not extend north of the Aleutian Islands or reach as far south as Hawaii; generally, the northern species is found in a band of ocean between Kamchatka (Russian Far East) and Hokkaido and Honshu (Japan), in the west, east to the waters off of British Columbia. Its range down continues south along the West Coast of the US to the central coast of Mexico's Baja California Peninsula. It is not known with certainty if L. borealis follows a migratory pattern. However, individuals have been observed close to the California coast, following their main food source, cephalopods (such as the schools of Humboldt squid), in both winter and spring. Such sightings have not been recorded in summer; beyond these seasonal observations, the species is mainly pelagic. No global population estimates exist, though there are an estimated 14,000 individuals in waters off of the Pacific Northwest.

The southern right whale dolphin (L. peronii) has a much broader, circumpolar distribution, found across the Southern Hemisphere from about 40° to 55°. The southern species is typically found in waters off of Western Australia (south of the Kimberley), South Australia, Tasmania and Victoria, as well as New Zealand, southern Oceania, and the Tasman Sea. L. peronii is known from southern coastal Peru to the Chilean coast, southern Argentina, South Africa, and the southern Indian Ocean.

Behaviour

Right whale dolphins lack dorsal fins. Shown is the northern species, so the only white parts are the bellies, hidden from this angle.

Both species of right whale dolphin are highly gregarious, swimming in pods of several hundred individuals, sometimes into the thousands. The pods are as much a social and familial gathering as they are a defensive tactic against potential predators, primarily killer whales. Further bolstering their defenses, these large, traveling congregations may sometimes contain dusky dolphins and pilot whales, in the Southern Hemisphere, and Pacific white-sided dolphins in the north. The right whale dolphins are some of the fastest-swimming cetaceans, observed swimming in excess of 40 km/h. They can, in turns, become quite boisterous, breaching and tail-slapping, but also become very quiet, timid, and almost undetectable when trying to evade threats. At high speeds, they can leap upwards and out of the water, breaching up to seven metres across the water's surface, in a graceful bouncing motion.

The species will generally avoid boats, though bow-riding has been recorded, on occasion.

A single, rare stranding event was recorded for the northern species on 9 June 2018, when a 5.5-foot female was found deceased on Manzanita Beach on the Oregon Coast. There has been one recorded mass-stranding of 77 southern right whale dolphins, on Chatham Island.

Conservation

L. peronii is experiencing pressures from Peruvian whaling operations. L. borealis has never been commercially targeted; however, tens of thousands of the northern species were killed in the 1980s due to becoming caught in oceanic drift gillnets which were newly introduced, at that time. These nets were banned by the United Nations in 1993. Conservation campaigners work vigorously to try to ensure these bans are enforced.

Attempts to keep right whale dolphins in aquaria have all ended in failure and death. In all cases, but one, they have died within three weeks.

References

Other sources

• National Audubon Society Guide to Marine Mammals of the World (2006), Random House, ISBN 0-375-41141-0
• William F. Perrin (ed) (2008), Encyclopedia of Marine Mammals, Academic Press, ISBN 0-12-551340-2
• Mark Carwardine (2010), Whales, Dolphins and Porpoises, Dorling Kindersley, ISBN 0-7513-2781-6