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Peale's dolphin (''Lagenorhynchus australis'') is a small
dolphin A dolphin is an aquatic mammal in the cetacean clade Odontoceti (toothed whale). Dolphins belong to the families Delphinidae (the oceanic dolphins), Platanistidae (the Indian river dolphins), Iniidae (the New World river dolphins), Pontopori ...
found in the waters around
Tierra del Fuego Tierra del Fuego (, ; Spanish for "Land of Fire", rarely also Fireland in English) is an archipelago off the southernmost tip of the South America, South American mainland, across the Strait of Magellan. The archipelago consists of the main is ...
at the foot of
South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...
. It is also commonly known as the black-chinned dolphin or even Peale's black-chinned dolphin. However, since Rice's work Peale's dolphin has been adopted as the standard common name.


Taxonomy

Though it is traditionally placed in the genus ''Lagenorhynchus'', recent
molecular A molecule is a group of two or more atoms that are held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions that satisfy this criterion. In quantum physics, organic chemistry, ...
analyses indicate Peale's dolphin is actually more closely related to the dolphins of the genus '' Cephalorhynchus''. If true, this would mean this species must either be transferred to ''Cephalorhynchus'' or be given a new genus of its own. An alternate genus proposed for this species (as well as the
Pacific white-sided dolphin The Pacific white-sided dolphin (''Lagenorhynchus obliquidens''), also known as the hookfin porpoise, is an active dolphin found in the cool or temperate waters of the North Pacific Ocean. Taxonomy The Pacific white-sided dolphin was named by Sm ...
, hourglass dolphin and dusky dolphin is the resurrected genus '' Sagmatias''. Some behavioral and morphological data support moving Peale's dolphin to ''Cephalorhynchus''. According to , Peale's dolphin and the ''Cephalorhynchus'' species are the only dolphins that do not whistle. Peale's dolphin also shares with several ''Cephalorhynchus'' species the possession of a distinct white "armpit" marking behind the pectoral fin.


Physical description

Peale's dolphin is of typical size in its family — about in length at birth and when fully mature. Its adult weight is about . It has a dark-grey face and chin. The back is largely black with a single off-white stripe running curving and thickened as it runs down the back on each side. The belly is white. Conspicuously, also a white patch occurs under just behind each flippers. These are known as the "armpits". The flanks also have a large white-grey patch above the flipper. The
dorsal fin A dorsal fin is a fin on the back of most marine and freshwater vertebrates. Dorsal fins have evolved independently several times through convergent evolution adapting to marine environments, so the fins are not all homologous. They are found ...
is large for this size
cetacean Cetacea (; , ) is an infraorder of aquatic mammals belonging to the order Artiodactyla that includes whales, dolphins and porpoises. Key characteristics are their fully aquatic lifestyle, streamlined body shape, often large size and exclusively c ...
and distinctively falcated. The flippers themselves are small and pointed. The tail fin, too, has pointed tips, as well as a notch at its middle. The species looks similar to the dusky dolphin when viewed at a distance, and may be confused with it.


Population and distribution

Peale's dolphin is endemic to the coastal waters around southern
South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...
. On the Pacific side, they have been seen as far north as
Valdivia Valdivia (; Mapuche: Ainil) is a city and commune in southern Chile, administered by the Municipality of Valdivia. The city is named after its founder, Pedro de Valdivia, and is located at the confluence of the Calle-Calle, Valdivia, and ...
,
Chile Chile, officially the Republic of Chile, is a country in western South America. It is the southernmost country in the world and the closest to Antarctica, stretching along a narrow strip of land between the Andes, Andes Mountains and the Paci ...
at 38°S. On the Atlantic side, sightings typically diminish at about 44°S — near Golfo San Jorge,
Argentina Argentina, officially the Argentine Republic, is a country in the southern half of South America. It covers an area of , making it the List of South American countries by area, second-largest country in South America after Brazil, the fourt ...
. In the south, they have been seen at almost 60°S — well into the
Drake Passage The Drake Passage is the body of water between South America's Cape Horn, Chile, Argentina, and the South Shetland Islands of Antarctica. It connects the southwestern part of the Atlantic Ocean (Scotia Sea) with the southeastern part of the Pa ...
. They are often found in areas of fast-moving waters, such as entrances to channels and narrows, as well as close to shore in safe areas such as bays. The total population is unknown, but recent research estimates there to be ~21,800 individuals in the South Atlantic part of its range.


Behaviour

Peale's dolphins congregate in small groups — usually about five in number, and sometimes up to 20. On rare occasions in summer and autumn, much larger groups have been recorded (100 individuals). A typical pattern is for the group to move in a line parallel to the shore. They usually swim slowly, but are prone to bursts of activity. Peale's dolphins are often found swimming slowly near kelp beds. They have been found to associate with other cetaceans such as Commerson's dolphins.


Food and foraging

In the southwestern South Atlantic, Peale's dolphin forages in the coastal ecosystem, feeding mainly on the demersal and bottom fish such as southern cod and Patagonian grenadier; also octopus, squid, and shrimps have also been found in stomachs examined. They feed in or near kelp beds and in open waters, with cooperative feeding, such as straight-line and large circle formations or star-burst feeding in which large groups encircle prey.Berta, Annalisa, editor. ''Whales, Dolphins & Porpoises: A Natural History and Species Guide''. University of Chicago Press, 2015.


Conservation

Peale's dolphins' propensity for moving over only small areas, and staying close to shore, has rendered them vulnerable to interference by man. During the 1970s and '80s, Chilean fisherman killed and used thousands of Peale's dolphins for crab bait each year. This practice has decreased, but not been made illegal. In Argentina, Peale's dolphins have been reported becoming trapped in gill nets, but the extent of this is not known. Conservation groups such as the
Whale and Dolphin Conservation Whale and Dolphin Conservation (WDC), formerly Whale and Dolphin Conservation Society in the UK, is a wildlife charity that is dedicated solely to the worldwide conservation and welfare of all whales, dolphins and porpoises (cetaceans). It ha ...
demand further research be made into this species. The Peale's dolphin or black-chinned dolphin is listed on Appendix IIAppendix II
" of the Convention on the Conservation of Migratory Species of Wild Animals (CMS). As amended by the Conference of the Parties in 1985, 1988, 1991, 1994, 1997, 1999, 2002, 2005 and 2008. Effective: 5 March 2009.
of the Convention on the Conservation of Migratory Species of Wild Animals ( CMS). It is listed on Appendix II as it has an unfavourable conservation status or would benefit significantly from international co-operation organised by tailored agreements.Convention on Migratory Species page on the Peale's dolphin / Black-chinned dolphin
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See also

* List of cetaceans *
Marine biology Marine biology is the scientific study of the biology of marine life, organisms that inhabit the sea. Given that in biology many scientific classification, phyla, family (biology), families and genera have some species that live in the sea and ...


References

*''National Audubon Society: Guide to Marine Mammals of the World'' *''Encyclopedia of Marine Mammals'' * * * {{Taxonbar, from=Q300991 Mammals of Argentina Mammals of Chile Mammals of Patagonia Marine fauna of South America Fauna of Tierra del Fuego Peale's dolphin Taxa named by Titian Peale Taxobox binomials not recognized by IUCN Lagenorhynchus