The southern right whale dolphin (Lissodelphis peronii) is a small and slender species of cetacean, found in cool waters of the Southern Hemisphere. It is one of two species of right whale dolphin (genus Lissodelphis). This genus is characterized by the lack of a dorsal fin. The other species, the northern right whale dolphin (Lissodelphis borealis), is found in deep oceans of the Northern Hemisphere and has a different pigmentation pattern than the southern right whale dolphin.
Taxonomy The species was first published by Bernard Germain de Lacépède in 1804. The southern right whale dolphins together with the northern right whale dolphins are the only members of the genus Lissodelphis, which name is derived from the Greek, with lisso meaning smooth, and delphis meaning dolphin. Recent classifications have placed Lissodelphis within the Delphinidae, the oceanic dolphin family of cetaceans. The specific epithet peronii commemorates François Péron, a French naturalist who saw the species near Tasmania during an expedition in 1802. Although some doubts remain on the validity of these two species, most authors currently retain them as separate species.
Both species in the genus are referred to by the name "right whale dolphin", a name derived from the right whales (Eubalaena) which also lack a dorsal fin. Other common names for the southern right whale dolphin include: whitebellied right whale dolphin, southern right whale porpoise, mealy-mouthed porpoise, (Spanish), (Spanish), (Japanese), (French), (Russian), (German), and (Dutch).
Description Southern right whale dolphins can be easily distinguished from other cetacean species within their range as they are the only dolphins without dorsal fins in the Southern Hemisphere. They have streamlined and graceful bodies, a single blowhole and a short and defined beak, possessing between 39 and 50 teeth per row.
A sharp dividing line separates the black dorsal part from the white ventral part of the body, running from the tail stock forward, dipping down to the flipper insertion and sweeping back up, below the eyes, to cross the melon between the blowhole and snout crease. Younger individuals can be grey/brownish dorsally but develop adult coloration within the first year. The flippers of the southern right whale dolphins are small, recurved, predominantly white and located about one-quarter of the way back from the snout tip. Their flukes are small, have a white underside and dark grey upper side, with a notch in the middle and concave trailing edges.
Variability in the size of these black and white areas exists. More extensive anomalous pigmentation has been observed, with records of pure all-white individuals, as well as melanistic (all-black) individuals. In 1998, a potential hybrid of a southern right whale dolphin and a dusky dolphin (Lagenorhynchus obscurus) was observed and subsequently described in 2002. This animal showed intermediate morphological features between the two species.
Newborn calves measure around in length and weigh around , while adults range between and weight between on average. The maximum weight for southern right whale dolphins is 116 kg, with maximum lengths reaching in males and in females but few specimens have been examined and it is expected they grow larger. On average, males tend to grow slightly larger than females. Little is known of this species' reproductive biology. Research suggests that males reach sexual maturity at lengths between and females between .
Population status There are no current global abundance and mortality estimates of the species although it is considered a fairly common and abundant species along its range, particularly in Chile. The very low sighting rate is most likely caused by a lack of sampling effort and due to the difficulties of sighting the animals in their offshore habitat.
Distribution Southern right whale dolphins have a circumpolar distribution across the Southern Hemisphere, generally occurring in cool temperate to Sub-Antarctic waters between 30°S and 65°S. The precise boundary of their range has not been estimated or closely studied but the southern limit of the species appears to be bounded by the Antarctic Convergence while the northern limit seems bounded by the Tropical Convergence although rare sightings beyond these limits have been recorded. Most sightings of the southern right whale dolphins occur in offshore and deep waters, with temperatures ranging between 1 and 20 °C. In regions where deep waters approach the coast and in upwelling areas, they have occasionally been observed near shore.
South America The species is known to be abundant along the western coasts of South America, ranging from Cape Horn (55°58'S) to Arica (18°28'S), with the northernmost record at 12°30'S near Pucusana (Peru). Although the southern right whale dolphin is considered abundant, only few confirmed records of the species in the Eastern South Pacific exist.
Preliminary boat surveys and stranding and fishery records suggest that southern right whale dolphins may be one of the most common species of cetacean in northern Chile. The range extends until offshore north of 40°S and off the southern coast of Chile and it has been suggested that at least a part of this Chilean population migrates northbound in the austral winter and spring, when the coastal component of the cold Humboldt Current and cool coastal upwelling are strongest. An extension of the range to the North, associated to cold-water currents and food availability, has also been observed in Brazil, where a stranded individual was found in 1995 in an area where the warm Brazil Current meets the cold Malvinas Current.
In 2018, two groups were sighted in the western area of the Strait of Magellan in Chile. It was unclear through which route and why they entered the Magellan Strait but these were the first sightings of live southern right whales dolphins in this shallow area. A few reports of solitary stranded specimens in exterior channels south of 40°S and the Beagle Channel have also shown their occurrence inside shallow channel systems. It has been hypothesized they may enter these channels accidentally or because of poor health. In the past, a high number of stranded southern right whale dolphins were reported on beaches of north-central chile, most of which were discarded animals by-caught In fishing nets. An increase in strandings is possibly due to the developing swordfish gillnet fishery off northern Chile.
The waters of the Patagonian continental shelf of Argentina harbor a high diversity of cetaceans, including southern right whale dolphins. They are known to occur in cold waters off Santa Cruz Province, the Falkland Islands, as well as off Tierra del Fuego. Sightings in coastal areas are rare but exist in Mar del Plata and in Golfo Nuevo, where three southern right whale dolphins were observed once during the summer of 1992.
Africa In Southern Africa, the range is associated with cold currents up the western and southern coasts, ranging northwards as far as about 23°S due to the cold counter clockwise Benguela Current. The species has been found to occur year-round in a localized area on the southwestern coast of Namibia, in Lüderitz, linked to the strong Lüderitz upwelling cell area and high productivity waters. These animals may occasionally extend their range into South African waters although more sampling effort is needed to support this. Just one confirmed sighting of the species exists from the South African coast, just south of the Orange River. Southern right whale dolphins have also been observed in waters around Marion Island.
Australia The species has been observed in Australian waters since 1802, although only few actual records exist since then. They are found off southern continental Australia including sightings south and southwestward of Tasmania, in the Great Australian Bight and off south-western Australia. One pair was sighted on the 20th of October 1910 at 42°51S, 153°56E, approximately 460 km to the east of Australia, in the Tasman Sea. No localised areas where the species occurs year-round are known from the coast of Australia, although more survey effort could result in the identification of these areas, similar to the one off the west coast of Namibia.
Few stranded individuals have been documented in Australian waters. In December 2019, a dolphin washed up on a beach at Port Fairy, Victoria, with the deceased animal being assessed by state authorities, researchers and local Australian aboriginal elders. Another dolphin washed up in January 2020 and was photographed, but the dead animal washed back off the beach. The dual strandings were described as 'very unusual' by authorities.
New Zealand One of the earliest records of this species in New Zealand waters was during the Terra Nova Expedition, when a pair was sighted approximately 145 km west-south-west of Nugget Point Lighthouse, South Island at 47°04'S, 171°33'E. Southern right whale dolphins have been observed at sea to the southeast of New Zealand and are largely found between the Subtropical Convergence and the subantarctic waters to the south of it, between surface temperatures of 9°-17 °C.
The first recorded photographs of the species globally, were from a stranding of three individuals in New Zealand in 1952, which were apparently rescued. Since then there have been a number of strandings around the country, including seven events between 1970 and 1981 and a mass stranding of 75 individuals occurred at the Chatham In 1988. More recently a stranding of a single animal occurred at Mahia Beach, North Island in April 2020 which was euthanised by the Department of Conservation. The northernmost record of a stranding in New Zealand was of a ~200 cm long male at Whananaki (35° 31'S, 174° 28'), Northland, in November 1979.
Southern right whale dolphins are occasionally observed off the coast of Kaikōura, on the eastern coast of South Island, typically in groups of 50–200, although larger groups of >500 are also encountered. In 1967, research showed that the species could also be found off-shore from the Chatham, Bounty and Antipodes Islands (approximately 43-57°S, 168-158°E) between January and March.
Behavior Social
Southern right whale dolphins are generally gregarious and have been documented in aggregations of more than 1000 individuals although small groups of one to 10 have also been reported. Mean group size estimates differ and range between 52 and 368 off northern Chile, however, they typically live in groups of 100-200 individuals. Pods of just a few animals have also been observed, often associated with other cetacean species. Mixed groups with Dusky dolphins (Lagenorhynchus obscurus) appear common in the southern Atlantic and have occasionally been reported in New-Zealand, off Southwest Africa and along the coast of southern Chile. They have been observed to intermix freely with pilot whales (Globicephala spp.) and in Chile, associations with common dolphins (Delphinus delphis) have been reported. Along their range they have also occasionally been sighted with hourglass dolphins (Lagenorhynchus cruciger), common bottlenose dolphins (Tursiops truncatus) and fin whales (Balaenoptera physalus).