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. Although some doubts remain on the validity of these two species, most authors currently retain them as separate species.
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. 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. 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. 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. Under the New Zealand Threat Classification System this species is listed locally as Data Deficient.
Southern right whale dolphins are listed in Appendix II of the Convention on International Trade in Endangered Species (CITES) and the species is subject to International Whaling Commission (IWC) regulations. In South-Africa, the species is protected by the Marine Living Resources Act (No. 18 of 1998). 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.