Southern right whale dolphin

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. 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. 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, 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. 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. 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. as well as off Tierra del Fuego. and in Golfo Nuevo, where three southern right whale dolphins were observed once during the summer of 1992. 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. Few stranded individuals have been documented in Australian waters. 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 Since then there have been a number of strandings around the country, including seven events between 1970 and 1981 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. 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, They have been observed to intermix freely with pilot whales (Globicephala spp.) and in Chile, associations with common dolphins (Delphinus delphis) have been reported. Their movement is very graceful and they often move by leaping out of the water continuously. When they swim slowly, they expose only a small area of the head and back while surfacing to breathe. When travelling at higher speeds they have been observed to either (1) swim just below the surface, surfacing briefly to breathe and then submerge or (2) swim rapidly at the surface, performing low-angle leaps covering much surface distance. Breaching, belly-flopping, side-slapping, and lob-tailing (slapping the flukes on the water surface) have been witnessed. Geographical variability in prey species has been observed by comparing stomach contents of animals from central Chile and New Zealand. The species itself is presumably occasionally predated upon by larger sharks and killer whales (Orcinus orca) however, other predators might exist. In 1983, an intact dolphin measuring was found in the stomach of a Patagonian toothfish (Dissostichus eleginoides) taken off central Chile, and in 1990, a foetus was discovered inside a sleeper shark (Somniosus cf. pacificus). ==Threats==

Overall, clear evidence of the impact of potential threats on the species are sparse. Southern right whale dolphins were taken by whaling operations of the 19th century, primarily for their meat. and to a lesser extent, the species has also been incidentally caught in driftnets along the coast of Peru. Large numbers of southern right whale dolphins are sometimes taken by gillnetting and longline fishing in oceans off the southern coast of Australia. No reported attempts to capture live southern right whale dolphins exist. ==Conservation status==

As of 2018, the Global IUCN Red List classifies the southern right whale dolphin as Least Concern (LC), due to their apparent wide distribution in pelagic waters of the sub-Antarctic and the lack of evidence of severe threats to the populations. However, the species remains extremely data-poor throughout its range so the assessment should be considered provisional until more knowledge is obtained. Under the New Zealand Threat Classification System this species is listed locally as Data Deficient. and the Memorandum of Understanding for the Conservation of Cetaceans and Their Habitats in the Pacific Islands Region (Pacific Cetaceans MoU). Within the Australian Whale Sanctuary, all cetaceans, including the southern right whale dolphins are protected under the Environment Protection and Biodiversity Conservation Act (EPBC Act). The Sanctuary includes all Commonwealth waters from the three nautical mile state waters limit out to the boundary of the Australian Exclusive Economic Zone (out to 200 nautical miles and further in some places). The species is also protected within the Indian Ocean Sanctuary and Southern Ocean Sanctuary. Although the species is included in legislation, no specific conservation measures have been identified for this species as throughout its range, there is still a clear deficiency of data to build these measures upon. ==See also==