Peale's dolphin

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Peale's dolphin
Lagenorhynchus australis.jpg
CITES Appendix II (CITES) [2]
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Artiodactyla
Infraorder: Cetacea
Family: Delphinidae
Genus: Lagenorhynchus
Species:
L. australis
Binomial name
Lagenorhynchus australis
(Peale, 1848)
Cetacea range map Black-chinned Dolphin.PNG
  Peale's dolphin range

Peale's dolphin (Lagenorhynchus australis) is a small dolphin found in the waters around Tierra del Fuego at the foot of South America. It is also commonly known as the black-chinned dolphin or even Peale's black-chinned dolphin. However, since Rice's work [3] Peale's dolphin has been adopted as the standard common name.

Contents

Taxonomy

Though it is traditionally placed in the genus Lagenorhynchus, recent molecular 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, hourglass dolphin and dusky dolphin is the resurrected genus Sagmatias . [4] Some behavioral and morphological data support moving Peale's dolphin to Cephalorhynchus. According to Schevill & Watkins 1971, 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 Peale's Dolphin Ventisquero Pio XI, Chilean Patagonia.jpg
Peale's dolphin

Peale's dolphin is of typical size in its family — about 1 m in length at birth and 2.1 m (6.9 ft) when fully mature. Its adult weight is about 115 kg. 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 is large for this size cetacean 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 leaping off Falkland Islands Dolphin leaping out of the ocean (5656231914).jpg
Peale's dolphin leaping off Falkland Islands

Peale's dolphin is endemic to the coastal waters around southern South America. On the Pacific side, they have been seen as far north as Valdivia, Chile at 38°S. On the Atlantic side, sightings typically diminish at about 44°S  — near Golfo San Jorge, Argentina. In the south, they have been seen at almost 60°S  — well into the Drake Passage.

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. [5]

Behaviour

Peale's dolphins congregate in small groups — usually about five in number, and sometimes up to 20. [6] 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. [5]

Peale's dolphins are often found swimming slowly near kelp beds. [6] [7] They have been found to associate with other cetaceans such as Commerson's dolphins. [7]

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. [7]

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. [5] [7] This practice has decreased, but not been made illegal. [5] [7]

In Argentina, Peale's dolphins have been reported becoming trapped in gill nets, but the extent of this is not known. [5] Conservation groups such as the Whale and Dolphin Conservation demand further research be made into this species.

The Peale's dolphin or black-chinned dolphin is listed on Appendix II [8] of the Convention on the Conservation of Migratory Species of Wild Animals (CMS). It is listed on Appendix II [8] as it has an unfavourable conservation status or would benefit significantly from international co-operation organised by tailored agreements. [9]

See also

Related Research Articles

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<span class="mw-page-title-main">Commerson's dolphin</span> Species of mammal

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<i>Lagenorhynchus</i> Genus of mammals

Lagenorhynchus is a genus of oceanic dolphins in the infraorder Cetacea, presently containing six extant species. However, there is consistent molecular evidence that the genus is polyphyletic and several of the species are likely to be moved to other genera. In addition, the extinct species Lagenorhynchus harmatuki is also classified in this genus.

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<span class="mw-page-title-main">Hourglass dolphin</span> Species of mammal

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<span class="mw-page-title-main">Pacific white-sided dolphin</span> Species of mammal

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Sagmatias was a genus of dolphins, defined in 1866 by Edward Drinker Cope with Peale's dolphin as type species, described as Sagmatias amblodon. It has been proposed to resurrect the genus to include four species of oceanic dolphins currently classified in the genus Lagenorhynchus. Mitochondrial DNA studies have indicated that Pacific white-sided dolphin, Peale's dolphin, dusky dolphin and hourglass dolphin are more closely related to dolphins in the Lissodelphininae subfamily, than to the two other members of the genus: Atlantic white-sided dolphin and white-beaked dolphin. This phylogenetic relationship is further supported by cladistic analysis of morphological characters. However, resurrection of the genus Sagmatias has not been accepted by the Society for Marine Mammalogy's taxonomic Committee, because the finer details of the phylogenetic relationships between the four species in the proposed Sagmatias genus and the four species of dolphins in the genus Cephalorhynchus remains to be resolved. Genetic and bioacoustical evidence suggest that Peale's dolphin and hourglass dolphin are closer related to the Cephalorhynchus species than to the Pacific white-sided dolphin and dusky dolphin, which, if true, would make the genus Sagmatias paraphyletic.

References

  1. Heinrich, S.; Dellabianca, N. (2019). "Lagenorhynchus australis". IUCN Red List of Threatened Species . 2019: e.T11143A50361589. doi: 10.2305/IUCN.UK.2019-1.RLTS.T11143A50361589.en .
  2. "Appendices | CITES". cites.org. Retrieved 14 January 2022.
  3. "Marine Mammals of the World. Systematics and Distribution", by Dale W. Rice (1998). Published by the Society of Marine Mammalogy as Special Publication No. 4
  4. Vollmer, Nicole L.; Ashe, Erin; Brownell, Robert L.; Cipriano, Frank; Mead, James G.; Reeves, Randall R.; Soldevilla, Melissa S.; Williams, Rob (2019). "Taxonomic revision of the dolphin genus Lagenorhynchus". Marine Mammal Science. 35 (3): 957–1057. doi:10.1111/mms.12573. ISSN   1748-7692. S2CID   92421374.
  5. 1 2 3 4 5 IUCN (30 July 2018). "Lagenorhynchus australis: Heinrich, S. & Dellabianca, N.: The IUCN Red List of Threatened Species 2019: e.T11143A50361589". IUCN Red List of Threatened Species . 2018-07-30. doi: 10.2305/iucn.uk.2019-1.rlts.t11143a50361589.en .
  6. 1 2 Ridgway, Sam H., Harrison, Richard J. (1999). Handbook of Marine Mammals: The Second Book of Dolphins and the Porpoises. Academic Press. pp. 105–120. ISBN   978-0125885065.{{cite book}}: CS1 maint: multiple names: authors list (link)
  7. 1 2 3 4 5 Berta, Annalisa, editor. Whales, Dolphins & Porpoises: A Natural History and Species Guide. University of Chicago Press, 2015.
  8. 1 2 "Appendix II Archived 11 June 2011 at the Wayback Machine " 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.
  9. Convention on Migratory Species page on the Peale's dolphin / Black-chinned dolphin