View source for Oceanic dolphin

{{Short description|Family of marine mammals}}
{{Automatic taxobox
| name = Oceanic dolphin
| fossil_range = {{Fossil range|Late Oligocene | Recent}}
| image = Eilat Dolphin Reef (3).jpg
| image_caption = [[Indo-Pacific bottlenose dolphin]]
| taxon = Delphinidae
| authority = [[John Edward Gray|Gray]], 1821
| type_genus = ''[[Common dolphin|Delphinus]]''
| type_genus_authority = [[Carl Linnaeus|Linnaeus]], [[10th edition of Systema Naturae|1758]]
| subdivision_ranks = Genera
| subdivision = See [[#Taxonomy|text]].
}}

'''Oceanic dolphins''' or '''Delphinidae''' are a widely distributed family of [[dolphin]]s that live in the [[sea]]. Close to forty extant species are recognised. They include several big species whose common names contain "whale" rather than "dolphin", such as the [[Globicephalinae]] (round-headed whales, which include the [[false killer whale]] and [[pilot whale]]). Delphinidae is a family within the superfamily [[Delphinoidea]], which also includes the [[porpoise]]s (Phocoenidae) and the [[Monodontidae]] ([[beluga whale]] and [[narwhal]]). [[River dolphin]]s are relatives of the Delphinoidea.

Oceanic dolphins range in size from the {{convert|1.7|m|ftin|adj=mid|-long}} and {{convert|110|lb|kg|adj=on|order=flip|abbr=off}} [[Maui's dolphin]] to the {{convert|31|ft|m|adj=on|order=flip}} and {{convert|11|ST|MT|adj=on|order=flip|0}} [[orca]], the largest known dolphin. Several species exhibit [[sexual dimorphism]]; the males are larger than females. They have streamlined muscular bodies  and two limbs that are modified into flippers. Though not quite as flexible as [[Pinniped|seal]]s, some dolphins can travel at speeds 29&nbsp;km/h (18&nbsp;mph) for short distances.<ref>{{Cite journal|last1=Grady|first1=John M.|last2=Maitner|first2=Brian S.|last3=Winter|first3=Ara S.|last4=Kaschner|first4=Kristin|last5=Tittensor|first5=Derek P.|last6=Record|first6=Sydne|last7=Smith|first7=Felisa A.|last8=Wilson|first8=Adam M.|last9=Dell|first9=Anthony I.|last10=Zarnetske|first10=Phoebe L.|last11=Wearing|first11=Helen J.|date=2019-01-24|title=Metabolic asymmetry and the global diversity of marine predators|journal=Science|volume=363|issue=6425|article-number=eaat4220|doi=10.1126/science.aat4220|pmid=30679341|s2cid=59248474|issn=0036-8075|doi-access=free}}</ref> Most delphinids primarily eat fish, along with a smaller number of squid and small crustaceans, but some species specialise in eating squid, or, in the case of the orca, also eat marine mammals and birds. All, however, are purely [[carnivore|carnivorous]]. They typically have between 100 and 200 teeth, although a few species have considerably fewer. Delphinids travel in large pods, which may number a thousand individuals in some species. Each pod forages over a range of tens to hundreds of square kilometres. Some pods have a loose social structure, with individuals frequently joining or leaving, but others seem to be more permanent, perhaps dominated by a male and a [[Harem (zoology)|harem]] of females.<ref name=EoM/> Individuals communicate by sound, producing low-frequency whistles, and also produce high-frequency broadband clicks of 80–220&nbsp;kHz, which are primarily used for [[Animal echolocation|echolocation]]. [[Gestation]] lasts from 10 to 18 months, and results in the birth of a single calf. Some species are well adapted for diving to great depths. They have a layer of fat, or [[blubber]], under the skin to keep warm in the cold water.

Although oceanic dolphins are widespread, most species prefer the warmer waters of the tropic zones, but some, like the [[right whale dolphin]], prefer colder climates. Some have a global distribution, like the orca. Oceanic dolphins feed largely on fish and squid, but a few, like the orca, feed on large mammals, like seals. Male dolphins typically mate with multiple females every year, but females only mate every two to three years. Calves are typically born in the spring and summer, and females bear all the responsibility for raising them. Mothers of some species fast and nurse their young for relatively long times. Dolphins produce a variety of vocalizations, usually in the form of clicks and whistles.

Oceanic dolphins are sometimes hunted in places such as Japan, in an activity known as [[dolphin drive hunting]]. Besides drive hunting, they also face threats from [[bycatch]], habitat loss, and [[marine pollution]]. Dolphins have been depicted in various cultures worldwide. They occasionally feature in literature and film, as in the Warner Bros film ''[[Free Willy (film series)|Free Willy]]''. Dolphins are sometimes kept in captivity and trained to perform in shows. The most common species of dolphin in captivity is the [[bottlenose dolphin]], and less than 50 orca were found in [[oceanarium]]s in 2012.

== Taxonomy ==
{{See also|Dolphin}}
[[File:Etruridelphis-giuliiBologna.JPG|thumb|''Etruridelphis giulii'' skull in Bologna]]

Delphinids, especially bottlenose dolphins, are able to [[Hybrid (biology)|hybridize]] with a wide variety of other delphinid species; [[wholphin]]s are just one of many possible hybrids.<ref>{{cite news|url=https://www.nytimes.com/2010/09/14/science/14creatures.html?src=me&ref=general&_r=0|title=Hybrids May Thrive Where Parents Fear to Tread |last=Carroll|first=Sean| journal=Science: Remarkable Creatures| year=2010|access-date=31 October 2015}}</ref>

Six species, sometimes referred to as "blackfish", are dolphins commonly called whales: the [[orca]], the [[melon-headed whale]], the [[pygmy killer whale]], the [[false killer whale]], and the two species of [[pilot whale]]s, but they are classified under the family [[Delphinidae]].<ref>{{cite book|last1=Leatherwood|first1=S.|last2=Prematunga|first2=W.P.|last3=Girton|first3=P.|last4=McBrearty|first4=D.|last5=Ilangakoon|first5=A.|last6=McDonald| first6=D|title=''Records of 'blackfish' (killer, false killer, pilot, pygmy killer, and melon-headed whales) in the Indian Ocean Sanctuary, 1772–1986 in'' Cetaceans and cetacean research in the Indian Ocean Sanctuary |pages=33–65|year=1991|publisher=UNEP Marine Mammal Technical Report|asin=B00KX9I8Y8}}</ref>

Recent [[molecular phylogeny|molecular]] analyses indicate that several delphinid [[genus|genera]] (especially ''[[Stenella]]'') are not [[monophyly|monophyletic]] as currently recognized.<ref name=LeDuc1999>{{Cite journal | last1 = LeDuc | first1 = R.G. | last2 = Perrin | first2 = W.F. | last3 = Dizon | first3 = A.E. | title = Phylogenetic relationships among the delphinid cetaceans based on full cytochrome ''b'' sequences |date=July 1999 | journal = Marine Mammal Science | volume = 15  | issue = 3 | pages = 619–648 | doi = 10.1111/j.1748-7692.1999.tb00833.x | bibcode = 1999MMamS..15..619L | issn = 0824-0469}}</ref> Thus, significant taxonomic revisions within the family are likely.<ref name=Hassanin2012>{{cite journal | author = Hassanin, A.| year = 2012 | title = Pattern and timing of diversification of Cetartiodactyla (Mammalia, Laurasiatheria), as revealed by a comprehensive analysis of mitochondrial genomes | journal = Comptes Rendus Biologies | volume = 335 | issue = 1 | pages = 32–50 | doi = 10.1016/j.crvi.2011.11.002|display-authors=etal | pmid=22226162| doi-access = free }}</ref>  In 2025 there was significant revision of the genus ''[[Lagenorhynchus]]''.<ref name=marine2025/> 
<!-- A similar but broader list exits in the article dolphin and should be kept in sync with this one. -->
{| class="wikitable"
|- style="vertical-align: top;"
! A classification of the family Delphinidae from Perrin (1989) reflecting a traditional view of species interrelationships.
! Revised classification of the family Delphinidae based on molecular systematic analysis; adapted from LeDuc et al. (1999) and McGowen et al. (2019).<ref>{{Cite book| last = LeDuc| first = Rick| chapter = Delphinids, Overview| pages = [https://archive.org/details/encyclopediaofma2002unse/page/310 310–4]| title = Encyclopedia of Marine Mammals| editor1-last = Perrin| editor1-first = William R| editor2-last = Wiirsig| editor2-first = Bernd| editor3-last = [[Hans Thewissen|Thewissen]]| editor3-first = J G M| year = 2002| publisher = Academic Press| isbn = 978-0-12-551340-1| chapter-url = https://archive.org/details/encyclopediaofma2002unse/page/310}}</ref><ref>{{Cite journal| last1 = Harlin-Cognato | first1 = April D| last2 = Honeycutt | first2 = Rodney L| title = Multi-locus phylogeny of dolphins in the subfamily Lissodelphininae: character synergy improves phylogenetic resolution| year = 2006 | journal = BMC Evol Biol | volume = 6 | issue = 87| page = 87| doi = 10.1186/1471-2148-6-87 | pmc = 1635737 | pmid=17078887| doi-access = free}}</ref><ref>{{Cite journal| last1 = Cunha | first1 = Haydée A| last2 = Moraes | first2 = Lucas C| last3 = Medeiros | first3 = Bruna V.| last4 = Lailson-Brito Jr | first4 = José |author5=da Silva, Vera M. F. |author6=Solé-Cava, Antonio M. |author7=Schrago, Carlos G. | title = Phylogenetic Status and Timescale for the Diversification of ''Steno'' and ''Sotalia'' Dolphins| year = 2011 | journal = PLOS ONE | volume = 6 | issue = 12 | article-number = e28297| doi = 10.1371/journal.pone.0028297 | pmid=22163290 | pmc=3233566| bibcode = 2011PLoSO...628297C| doi-access = free}}</ref><ref>{{Cite journal|last1=McGowen|first1=Michael R|last2=Tsagkogeorga|first2=Georgia|last3=Álvarez-Carretero|first3=Sandra|last4=dos Reis|first4=Mario|last5=Struebig|first5=Monika|last6=Deaville|first6=Robert|last7=Jepson|first7=Paul D|last8=Jarman|first8=Simon|last9=Polanowski|first9=Andrea|last10=Morin|first10=Phillip A|last11=Rossiter|first11=Stephen J|date=2019-10-21|title=Phylogenomic Resolution of the Cetacean Tree of Life Using Target Sequence Capture|journal=Systematic Biology|volume=69|issue=3|pages=479–501|doi=10.1093/sysbio/syz068|issn=1063-5157|pmc=7164366|pmid=31633766}}</ref>
!Species recognized by Society for Marine Mammalogy's taxonomic Committee (2025)<ref>{{Cite web|title=Society for Marine Mammalogy|url=http://marinemammalscience.org/|access-date=2022-02-07|website=Society for Marine Mammalogy|language=en}}</ref><ref name=marine2025>{{cite web|title=List of Marine Mammal Species and Subspecies|date=13 November 2016 |access-date=2025-07-17|publisher=Marine Mammal Science Taxonomy Committee|url=https://marinemammalscience.org/science-and-publications/list-marine-mammal-species-subspecies/}}</ref>
|- style="vertical-align: top;"
|
* Family [[Delphinidae]]
** Subfamily [[Stenoninae]]
*** ''[[Steno bredanensis]]''
*** ''[[Sousa chinensis]]''
*** ''[[Sousa teuszii]]''
*** ''[[Sotalia fluviatilis]]''
** Subfamily Delphininae
*** ''[[Lagenorhynchus albirostris]]''
*** ''[[Lagenorhynchus acutus]]''
*** ''[[Lagenorhynchus obscurus]]''
*** ''[[Lagenorhynchus obliquidens]]''
*** ''[[Lagenorhynchus cruciger]]''
*** ''[[Lagenorhynchus australis]]''
*** ''[[Grampus griseus]]''
*** ''[[Tursiops truncatus]]''
*** ''[[Stenella frontalis]]''
*** ''[[Stenella attenuata]]''
*** ''[[Stenella longirostris]]''
*** ''[[Stenella clymene]]''
*** ''[[Stenella coeruleoalba]]''
*** ''[[Delphinus delphis]]''
*** ''[[Lagenodelphis hosei]]''
** Subfamily Lissodelphininae
*** ''[[Lissodelphis borealis]]''
*** ''[[Lissodelphis peronii]]''
** Subfamily [[Cephalorhynchinae]]
*** ''[[Cephalorhynchus commersonii]]''
*** ''[[Cephalorhynchus eutropia]]''
*** ''[[Cephalorhynchus heavisidii]]''
*** ''[[Cephalorhynchus hectori]]''
** Subfamily [[Globicephalinae]]
*** ''[[Peponocephala electra]]''
*** ''[[Feresa attenuata]]''
*** ''[[Pseudorca crassidens]]''
*** ''[[Orcinus orca]]''
*** ''[[Globicephala melas]]''
*** ''[[Globicephala macrorhynchus]]''
** Subfamily [[Orcaellinae]]
*** ''[[Orcaella brevirostris]]''
|
* Family [[Delphinidae]]
** Subfamily Delphininae
*** ''[[Sotalia fluviatilis]]''
*** ''[[Sotalia guianensis]]''
***''[[Sousa chinensis]]''
***''[[Australian humpback dolphin|Sousa sahulensis]]''
***''[[Indian Ocean humpback dolphin|Sousa plumbea]]''
*** ''[[Sousa teuszii]]''
***''[[Tursiops truncatus]]''
*** ''[[Tursiops aduncus]]''
***''[[Stenella frontalis]]''
*** ''[[Stenella attenuata]]''
***''[[Stenella coeruleoalba]]''
***''[[Delphinus delphis]]''
*** ''[[Lagenodelphis hosei]]''
*** ''[[Stenella clymene]]''
*** ''[[Stenella longirostris]]''
** Subfamily Lissodelphininae
*** ''[[Lissodelphis borealis]]''
*** ''[[Lissodelphis peronii]]''
***''[[Dusky dolphin|Sagmatias obscurus]]''
*** ''[[Pacific white-sided dolphin|Sagmatias obliquidens]]''
*** ''[[Hourglass dolphin|Sagmatias cruciger]]''
*** ''[[Cephalorhynchus heavisidii]]''
*** ''[[Cephalorhynchus hectori]]''
*** ''[[Cephalorhynchus eutropia]]''
*** ''[[Cephalorhynchus commersonii]]''
*** ''[[Peale's dolphin|Sagmatias australis]]''
** Subfamily [[Globicephalinae]]
*** ''[[Orcaella brevirostris]]''
*** ''[[Orcaella heinsohni]]''
***''[[Steno bredanensis]]''
***''[[Grampus griseus]]''
***''[[Pseudorca crassidens]]''
*** ''[[Globicephala melas]]''
*** ''[[Globicephala macrorhynchus]]''
*** ''[[Peponocephala electra]]''
***''[[Feresa attenuata]]''
** Subfamily [[Orcininae]]
*** ''[[Orcinus orca]]''
**Subfamily ''[[incertae sedis]]''
*** ''[[Lagenorhynchus albirostris]]''
*** [[Atlantic white-sided dolphin|''Leucopleurus acutus'']]
|
* Family [[Delphinidae]]
** Subfamily Delphininae
*** ''[[Common dolphin|Delphinus delphis]]''
*** ''[[Fraser's dolphin|Lagenodelphis hosei]]''
*** ''[[Atlantic humpback dolphin|Sousa teuszii]]''
*** ''[[Indo-Pacific humpback dolphin|Sousa chinensis]]''
*** ''[[Indian Ocean humpback dolphin|Sousa plumbea]]''
*** ''[[Australian humpback dolphin|Sousa sahulensis]]''
*** ''[[Tucuxi|Sotalia fluviatilis]]''
*** ''[[Guiana dolphin|Sotalia guianensis]]''
*** ''[[Pantropical spotted dolphin|Stenella attenuata]]''
*** ''[[Clymene dolphin|Stenella clymene]]''
*** ''[[Striped dolphin|Stenella coeruleoalba]]''
*** ''[[Atlantic spotted dolphin|Stenella frontalis]]''
*** ''[[Spinner dolphin|Stenella longirostris]]''
*** ''[[Indo-Pacific bottlenose dolphin|Tursiops aduncus]]''
*** ''[[Tamanend's bottlenose dolphin|Tursiops erebennus]]''
*** ''[[Common bottlenose dolphin|Tursiops truncatus]]''
** Subfamily Lissodelphininae
*** ''[[Pacific white-sided dolphin|Aethalodelphis obliquidens]]''
*** ''[[Dusky dolphin|Aethalodelphis obscurus]]''
*** ''[[Peale's dolphin|Cephalorhynchus australis]]''
*** ''[[Commerson's dolphin|Cephalorhynchus commersonii]]''
*** ''[[Hourglass dolphin|Cephalorhynchus cruciger]]''
*** ''[[Chilean dolphin|Cephalorhynchus eutropia]]''
*** ''[[Heaviside's dolphin|Cephalorhynchus heavisidii]]''
*** ''[[Hector's dolphin|Cephalorhynchus hectori]]''
*** ''[[Northern right whale dolphin|Lissodelphis borealis]]''
*** ''[[Southern right whale dolphin|Lissodelphis peronii]]''
** Subfamily [[Globicephalinae]]
*** ''[[Pygmy killer whale|Feresa attenuata]]''
*** ''[[Short-finned pilot whale|Globicephala macrorhynchus]]''
*** ''[[Long-finned pilot whale|Globicephala melas]]''
*** ''[[Risso's dolphin|Grampus griseus]]''
*** ''[[Irrawaddy dolphin|Orcaella brevirostris]]''
*** ''[[Australian snubfin dolphin|Orcaella heinsohni]]''
*** ''[[Melon-headed whale|Peponocephala electra]]''
*** ''[[False killer whale|Pseudorca crassidens]]''
*** ''[[Rough-toothed dolphin|Steno bredanensis]]''
** Subfamily [[Orcininae]]
*** ''[[Orca|Orcinus orca]]''
** Subfamily [[Incertae sedis|incerta sedis]]
*** ''[[White-beaked dolphin|Lagenorhynchus albirostris]]''
*** ''[[Atlantic white-sided dolphin|Leucopleurus acutus]]''
|-
|
|
|
|}
Extinct taxa:<ref>{{Cite web |title=Paleobiology Database - Delphinidae (Dolphin) |url=https://paleobiodb.org/classic/checkTaxonInfo?taxon_no=42953 |website=Paleobiology Database}}</ref>

* Subfamily Delphininae
** †''[[Astadelphis]]''
** †''[[Etruridelphis]]''
** †''[[Septidelphis]]''
* Subfamily Globicephalinae
** †''[[Platalearostrum]]''
** †''[[Protoglobicephala]]''
** †''[[Rododelphis]]''
* †''[[Arimidelphis]]''
* †''[[Australodelphis]]''
* †''[[Eodelphinus]]''
* †''[[Hemisyntrachelus]]''
* †''[[Norisdelphis]]''
* †''[[Pliodelphis]]''
<gallery style="text-align:center;" mode="packed">
File:Delphinidae Delphinoidae.jpg|''Dolphins and dolphinlike toothed whales''
File:Commdolph01.jpg|''[[Cephalorhynchus commersonii]]''
File:DELFIN DEL ORINOCO2.JPG|''[[Sotalia fluviatilis]]''
File:Dolphin-Musandam 2.jpg|''[[Sousa plumbea]]''
File:Delphinus capensis.JPG|''[[Delphinus capensis]]''
File:Frazer´s dolphin group.jpg|''[[Lagenodelphis hosei]]''
File:DuskyDolphin (cropped).jpg|''[[Lagenorhynchus obscurus]]''
File:Northern right whale dolphin.jpg|''[[Lissodelphis borealis]]''
File:Anim1018 - Flickr - NOAA Photo Library.jpg|''[[Stenella attenuata]]''
File:Steno bredanensis 2.jpg|''[[Steno bredanensis]]''
File:Tursiops truncatus 01.jpg|''[[Tursiops truncatus]]''
File:Feresa attenuata-2.jpg|''[[Feresa attenuata]]''
File:LF Pilot Whale Goban Spur.jpg|''[[Globicephala melas]]''
File:Risso's dolphin.jpg|''[[Grampus griseus]]''
File:Peponocephala electra Mayotte.jpg|''[[Peponocephala electra]]''
File:Irrawaddy dolphin-Orcaella brevirostris by 2eight.jpg|''[[Orcaella brevirostris]]''
File:Killerwhales jumping.jpg|''[[Orcinus orca]]''
File:Pseudorca crassidens at Okichan Theater 20070201.jpg|''[[Pseudorca crassidens]]''  
</gallery>

==Biology==

===Anatomy===
[[File:Dolphind.jpg|thumb|left|[[Atlantic spotted dolphin]]]]
The Delphinidae are the most diverse of the cetacean families, with numerous variations between species. They range in size from {{convert|1.2|m|ftin|abbr=on}} and {{convert|40|kg|lb|abbr=on}} ([[Haviside's dolphin]]), to {{convert|9|m|ft|abbr=on}} and 10 tonnes (orca). Most species weigh between {{convert|50|and|200|kg|lb|abbr=on}}. They typically have curved dorsal fins, clear 'beaks' at the front of their heads, and forehead [[melon (whale)|melon]]s, although exceptions to all of these rules are found. They have a wide range of colors and patterns.<ref name=EoM>{{cite book|editor= Macdonald, D.|author= Evans, Peter G.H.|year= 1984|title= The Encyclopedia of Mammals|publisher= Facts on File|location= New York|pages= [https://archive.org/details/encyclopediaofma00mals_0/page/180 180–185]|isbn= 978-0-87196-871-5|url-access= registration|url= https://archive.org/details/encyclopediaofma00mals_0/page/180}}</ref>

Oceanic dolphins have a torpedo-shaped, muscular body with an inflexible neck, limbs modified into flippers, nonexistent external ear flaps, a large tail fin, and a bulbous head. A dolphin skull has small eye orbits, a long snout, but not as long as its [[river dolphin]] counterpart, and eyes placed on the sides of its head. Several species exhibit sexual dimorphism, with the males being larger than the females.<ref name="Cetacean anatomy">{{cite journal|last1=Reidenberg |first1=Joy S. |title=Anatomical adaptations of aquatic mammals |journal=The Anatomical Record |date=2007 |volume= 290 |issue=6 |pages=507–513 |doi=10.1002/ar.20541 |pmid=17516440|s2cid=42133705 |doi-access=free }}</ref><ref>{{cite book |chapter-url=http://www.cetus.ucsd.edu/SIO133/PDF/Sexual%20Dimorphism.pdf |title=Encyclopedia of Marine Mammals |chapter=Sexual Dimorphism |last1=Ralls |first1=Katherine |last2=Mesnick |first2=Sarah |pages=1005–1011 |edition=2nd |publisher=Academic Press |location=San Diego |isbn=978-0-08-091993-5 |date=2009-02-26 |access-date=2015-10-31 |archive-date=2019-07-25 |archive-url=https://web.archive.org/web/20190725004132/http://www.cetus.ucsd.edu/SIO133/PDF/Sexual%20Dimorphism.pdf }}</ref>

Breathing involves expelling stale air from the [[blowhole (anatomy)|blowhole]], forming an upward, steamy spout, followed by inhaling fresh air into the lungs; a spout only occurs when the warm air from the lungs meets the cold external air, so it may only form in colder climates.<ref name="Cetacean anatomy"/><ref>{{cite web |url=http://www.afsc.noaa.gov/nmml/education/cetaceans/baleen1.php |title=Baleen |work=NOAA Fisheries |publisher= United States Department of Commerce |access-date=29 August 2015}}</ref><ref>{{cite journal |last1=Scholander |first1=Per Fredrik |title=Experimental investigations on the respiratory function in diving mammals and birds |year=1940 |journal=Hvalraadets Skrifter |volume=22 |pages=1–131}}</ref>

All oceanic dolphins have a thick layer of [[blubber]], the thickness of which depends on how far the species lives from the equator. This blubber also helps keep the animal warm providing insulation from the harsh climate or cold depths. It can also aid in protection to some extent as predators would have a hard time getting through a thick layer of fat. Calves are born with only a thin layer of blubber, but some species compensate for this with [[lanugo]]s.<ref name="Cetacean anatomy"/><ref name="Dolphins"/>

===Locomotion===
Oceanic dolphins have two flippers on the underside toward the head, a [[dorsal fin]], and a tail fin. These flippers contain four digits. Although oceanic dolphins do not possess fully developed hind limbs, some possess discrete rudimentary appendages, which may contain feet and digits. Oceanic dolphins are fast swimmers in comparison to seals who typically cruise at {{convert|7|–|17|mph|km/h|order=flip|abbr=on}}; the orca, in comparison, can travel at speeds of up to {{convert|34.5|mph|km/h|order=flip|abbr=on}}. The fusing of the neck vertebrae, while increasing stability when swimming at high speeds, decreases flexibility, which means they are unable to turn their heads. Oceanic dolphins swim by moving their tail fin and rear body vertically, while their flippers are mainly used for steering. Some species [[Cetacean surfacing behaviour|log]] out of the water, which may allow them to travel faster. Their skeletal anatomy allows them to be fast swimmers. All species have a [[dorsal fin]] to prevent themselves from involuntarily spinning in the water.<ref name="Cetacean anatomy"/><ref name="Dolphins">{{cite book |author1=Klinowska, Margaret |author2=Cooke, Justin |year=1991 |title=Dolphins, Porpoises, and Whales of the World: the IUCN Red Data Book |url=https://portals.iucn.org/library/sites/library/files/documents/RD-1991-001.pdf |access-date=29 August 2015}}</ref>

===Senses===
[[File:Delfinekko.gif|thumb|right|[[Biosonar]] by cetaceans]]

The oceanic dolphin ear is specifically adapted to the [[Marine (ocean)|marine]] environment. In humans, the [[middle ear]] works as an impedance equalizer between the outside air's low [[Acoustic impedance|impedance]] and the [[cochlea]]r fluid's high impedance. In dolphins, and other marine mammals, there is no great difference between the outer and inner environments. Instead of sound passing through the outer ear to the middle ear, dolphins receive sound through the throat, from which it passes through a low-impedance fat-filled cavity to the inner ear. The dolphin ear is acoustically isolated from the skull by air-filled sinus pockets, which allow for greater directional hearing underwater.<ref>{{cite journal |author=Nummela, Sirpa |title=Sound transmission in archaic and modern whales: Anatomical adaptations for underwater hearing |journal=The Anatomical Record |volume=290 |issue=6 |pages=716–733 |year=2007 |doi=10.1002/ar.20528 |last2=Thewissen|first2=J.G.M |last3=Bajpai |first3=Sunil |last4=Hussain |first4=Taseer |last5=Kumar |first5=Kishor |pmid=17516434|s2cid=12140889 |author2-link=Hans Thewissen |doi-access=free }}</ref> Dolphins send out high frequency clicks from an organ known as a [[melon (cetacean)|melon]]. This melon consists of fat, and the skull of any such creature containing a melon will have a large depression. This allows dolphins to produce [[biosonar]] for orientation.<ref name="Cetacean anatomy"/><ref name="Dolphin senses">{{cite book |editor1=Thomas, Jeanette A. |editor2=Kastelein, Ronald A. |title=Sensory Abilities of Cetaceans: Laboratory and Field Evidence |volume=196 |isbn=978-1-4899-0860-5 |doi=10.1007/978-1-4899-0858-2 |year=2002 |s2cid=32801659 |url=https://books.google.com/books?id=VWz1BwAAQBAJ }}</ref><ref name="Thewissen-Hearing">{{cite book| last=[[Hans Thewissen|Thewissen]]| first=J. G. M.| chapter=Hearing| pages=[https://archive.org/details/encyclopediaofma2002unse/page/570 570–2]| title=Encyclopedia of Marine Mammals| editor1-last=Perrin| editor1-first=William R.| editor2-last=Wirsig| editor2-first=Bernd| editor3-last=[[Hans Thewissen|Thewissen]]| editor3-first=J.G.M.| year=2002| publisher=Academic Press| isbn=978-0-12-551340-1| chapter-url=https://archive.org/details/encyclopediaofma2002unse/page/570}}</ref><ref>{{cite book |last=Ketten |first=Darlene R.|chapter=The Marine Mammal Ear: Specializations for Aquatic Audition and Echolocation |title=The Evolutionary Biology of Hearing |editor1-last=Webster |editor1-first=Douglas B. |editor2-last=Fay |editor2-first=Richard R. |editor3-last=Popper |editor3-first=Arthur N. |year=1992 |publisher=Springer |doi= 10.1007/978-1-4612-2784-7_44 |isbn=978-1-4612-2784-7 |pages=725–727}}</ref><ref>{{Cite book|title=A Proposed Echolocation Receptor for the Bottlenose Dolphin (''Tursiops truncatus''): Modelling the Receive Directivity from Tooth and Lower Jaw Geometry ''NATO ASI Series A: Sensory Abilities of Cetaceans'' |volume=196|pages=255–267|location=NY|publisher=Plenum|year=1990|isbn=978-0-306-43695-6|editor1=Jeanette A. Thomas |editor2=Ronald A. Kastelein. }}</ref> Though most dolphins do not have hair, they do have [[hair follicle]]s that may perform some sensory function.<ref>{{cite journal|title= Selective heating of vibrissal follicles in seals (''Phoca vitulina'') and dolphins (''Sotalia fluviatilis guianensis'')|author1=Bjorn Mauck, Ulf Eysel  |author2=Guide Dehnhardt |journal=Journal of Experimental Biology |name-list-style=amp |year=2000|volume=203 |issue=14 |pages=2125–2131 |doi=10.1242/jeb.203.14.2125 |pmid=10862725 |bibcode=2000JExpB.203.2125M |url=http://jeb.biologists.org/cgi/reprint/203/14/2125.pdf|access-date= March 11, 2007}}</ref> Beyond locating an object, echolocation also provides the animal with an idea on an object's shape and size, though how exactly this works is not yet understood.<ref>{{cite journal|last=Harley|first=Heidi E.|author2=DeLong, Caroline M.|title=Echoic Object Recognition by the Bottlenose Dolphin|journal=Comparative Cognition & Behavior Reviews|year=2008|volume=3|pages=45–65|doi=10.3819/ccbr.2008.30003|doi-access=free}}</ref>

The eye of oceanic dolphins is relatively small for its size, yet they do retain a good degree of eyesight. As well as this, the eyes of a dolphin are placed on the sides of its head, so their vision consists of two fields, rather than a binocular view like humans have. When dolphins surface, their lens and cornea correct the nearsightedness that results from the refraction of light; they contain both [[rod cell|rod]] and [[cone cell|cone]] cells, meaning they can see in both dim and bright light. Dolphins do, however, lack short wavelength sensitive visual pigments in their cone cells indicating a more limited capacity for color vision than most mammals.<ref>{{Cite journal|last1=Mass|first1=Alla M.|last2=Supin|first2=Alexander Ya|title=Adaptive features of aquatic mammals' eye|journal=The Anatomical Record |volume=290|issue=6|pages=701–715|doi=10.1002/ar.20529|issn=1932-8486|pmid=17516421|year=2007|s2cid=39925190|doi-access=free}}</ref> Most dolphins have slightly flattened eyeballs, enlarged pupils (which shrink as they surface to prevent damage), slightly flattened corneas and a [[tapetum lucidum]]; these adaptations allow for large amounts of light to pass through the eye and, therefore, a very clear image of the surrounding area. They also have glands on the eyelids and [[corneal epithelium|outer corneal layer]] that act as protection for the cornea.<ref name="Dolphin senses"/>

The [[olfactory lobes]] are absent in oceanic dolphins, suggesting that they have no sense of smell.<ref name="Dolphin senses"/>

Oceanic dolphins are not thought to have a good sense of taste, as their taste buds are atrophied or missing altogether.  However, some have preferences between different kinds of fish, indicating some sort of attachment to taste.<ref name="Dolphin senses"/>

==Behavior==

===Feeding===
Most delphinids primarily eat fish, along with a smaller number of squid and small crustaceans, but some species specialize in eating squid, or, in the case of the orca, also eat marine mammals and birds. All, however, are purely [[carnivore|carnivorous]]. They typically have between 100 and 200 teeth, although a few species have considerably fewer. Various methods of feeding exist among and within oceanic species, some apparently exclusive to a single population. Fish and squid are the main food, but the [[false killer whale]] and the orca also feed on other marine mammals. Orca on occasion also hunt [[whale]]s larger than themselves.<ref>{{cite journal |url=https://www.science.org/content/article/killer-whale-menu-finally-revealed |title=Killer Whale Menu Finally Revealed |author=Morrel, Virginia |journal=Science |date=30 January 2012 |access-date=29 August 2015}}</ref>

One common feeding method is herding, where a pod squeezes a school of fish into a [[bait ball]]. Individual members then take turns plowing through the ball, feeding on the stunned fish. Corralling is a method where dolphins chase fish into shallow water to catch them more easily. Orca and bottlenose dolphins have also been known to drive their prey onto a beach to feed on it, a behavior known as beach or strand feeding. Some species also whack fish with their flukes, stunning them and sometimes knocking them out of the water.<ref>{{cite web|title=Coastal Stock(s) of Atlantic Bottlenose Dolphin: Status Review and Management Proceedings and Recommendations from a Workshop held in Beaufort, North Carolina, 13 September 1993&nbsp;– 14 September 1993 |url=http://www.nmfs.noaa.gov/pr/pdfs/species/coastalbottlenosestock.pdf|work=U.S. Department of Commerce, National Oceanic and Atmospheric Administration, National Marine Fisheries Service|pages=56–57}}</ref>

===Vocalizations===
{{Main|Whale vocalisation}}
Oceanic dolphins are capable of making a broad range of sounds using nasal airsacs located just below the blowhole. Roughly three categories of sounds can be identified: [[frequency modulated]] whistles, burst-pulsed sounds, and clicks. Dolphins communicate with whistle-like sounds produced by vibrating connective tissue, similar to the way human vocal cords function,<ref>{{cite web |last = Viegas |first = Jennifer |title = Dolphins Talk Like Humans |work = Discovery News |year = 2011 |url = http://news.discovery.com/animals/dolphin-talk-communication-humans-110906.html |access-date = September 19, 2011 |archive-date = September 24, 2011 |archive-url = https://web.archive.org/web/20110924060555/http://news.discovery.com/animals/dolphin-talk-communication-humans-110906.html }}</ref> and through burst-pulsed sounds, though the nature and extent of that ability is not known. The clicks are directional and are for echolocation, often occurring in a short series called a click train. The click rate increases when approaching an object of interest. Dolphin echolocation clicks are amongst the [[Whale sound|loudest sounds made by marine animals]].<ref>{{Cite book|title= The Sonar of Dolphins|last1= Au |first1=W. W. L.|publisher=Springer|location=New York|year=1993|isbn= 978-3-540-97835-0}}</ref>

Bottlenose dolphins have been found to have signature whistles. These whistles are used in order for dolphins to communicate with one another by identifying an individual. It can be seen as the dolphin equivalent of a [[name]] for humans.<ref>{{cite news |url=https://www.bbc.co.uk/news/science-environment-23410137 |title=Dolphins 'call each other by name' |author=Rebecca Morelle |author-link=Rebecca Morelle |date=July 22, 2013 | work=BBC News}}</ref> These signature whistles are developed during a dolphin's first year; it continues to maintain the same sound throughout its lifetime.<ref>{{cite journal|last=Janik|first=Vincent|author2=Laela Sayigh|title=Communication in bottlenose dolphins: 50 years of signature whistle research|journal=Journal of Comparative Physiology|date=7 May 2013|volume=199|issue=6|pages=479–489|doi=10.1007/s00359-013-0817-7|pmid=23649908|s2cid=15378374}}</ref> In order to obtain each individual whistle sound, dolphins undergo vocal production learning. This consists of an experience with other dolphins that modifies the signal structure of an existing whistle sound. An auditory experience influences the whistle development of each dolphin. Dolphins are able to communicate to one another by addressing another dolphin through mimicking their whistle. The signature whistle of a male bottlenose dolphin tends to be similar to that of his mother, while the signature whistle of a female bottlenose dolphin tends to be more distinguishable.<ref>{{cite web |url=http://www.whoi.edu/science/B/people/kamaral/marinemammalacoustics.html |title=Marine Mammal vocalizations: language or behavior? |date=August 24, 2013}}</ref> Bottlenose dolphins have a strong memory when it comes to these signature whistles, as they are able to relate to a signature whistle of an individual they have not encountered for over twenty years.<ref>{{cite web |url=http://news.uchicago.edu/article/2013/08/06/dolphins-keep-lifelong-social-memories-longest-non-human-species |title=Dolphins keep lifelong social memories, longest in a non-human species |date=August 24, 2013}}</ref> Research done on signature whistle usage by other dolphin species is relatively limited. The research on other species done so far has yielded varied outcomes and inconclusive results.<ref>Emily T. Griffiths (2009). "[http://www.seawatchfoundation.org.uk/wp-content/uploads/2012/08/Griffiths2009_SBCDwhistle-repertoire.pdf Whistle repertoire analysis of the short beaked Common Dolphin, ''Delphinus delphis'', from the Celtic Deep and the Eastern and the Eastern Tropical Pacific Ocean]", Master's Thesis, School of Ocean Sciences, Bangor University</ref><ref>Melba C. Caldwell Et Al. – ''Statistical Evidence for Signature Whistles in the Spotted Dolphin, ''Stenella plagiodon''.''</ref><ref>Melba C. Caldwell Et Al. – ''Statistical Evidence for Signature Whistles in the Pacific Whitesided Dolphin, ''Lagenorhynchus obliquidens''.''</ref><ref>Rüdiger Riesch Et Al. – ''Stability and group specificity of stereotyped whistles in resident killer whales, Orcinus orca, off British Columbia.''</ref>

===Surfacing behavior and play===
{{Main|Cetacean surfacing behaviour}}
[[File:PacificWhiteSidedDolphine.jpg|thumb|left|Pacific white-sided dolphins porpoising]]
Oceanic dolphins frequently leap above the water surface, this being done for various reasons. When travelling, jumping can save the dolphin energy as there is less friction while in the air.<ref name=Weihs>{{cite journal|last=Weihs|first=D.|title=Dynamics of Dolphin Porpoising Revisited|journal=Integrative and Comparative Biology|year=2002|volume=42|issue=5|pages=1071–1078|doi=10.1093/icb/42.5.1071|pmid=21680390|doi-access=free}}</ref> This type of travel is known as porpoising.<ref name=Weihs /> Other reasons include orientation, social displays, fighting, [[non-verbal communication]], entertainment and attempting to dislodge [[parasite]]s.<ref>{{cite journal|first=David|last=Lusseau|year=2006|title=Why do dolphins jump? Interpreting the behavioural repertoire of bottlenose dolphins (''Tursiops'' sp.) in Doubtful Sound, New Zealand|journal=Behavioural Processes|volume=73|issue=3|pages=257–65|doi=10.1016/j.beproc.2006.06.006|pmid=16884864|s2cid=14920587}}</ref><ref>{{cite web|first=Corey|last=Binns|work=LiveScience|year=2006|url=http://www.livescience.com/678-dolphins-spin.html|title=How Dolphins Spin, and Why}}</ref>

Dolphins show various types of [[Play (activity)|playful behavior]], often including objects, self-made [[bubble ring]]s, other dolphins, or other animals.<ref name="Walker2007">{{Cite book|last=Walker|first=Sally M. |title=Dolphins|url={{google books|plainurl=y|id=5Buh9FtAG8AC|page=6}}|date=November 2007|publisher=Lerner Publications|isbn=978-0-8225-6767-7|pages=6, 30}}</ref><ref>{{cite journal |journal=Journal of Comparative Psychology |year=2000 |pages=98–106 |volume=114 |issue=1 |doi=10.1037/0735-7036.114.1.98 |pmid=10739315 |title=Bubble Ring Play of Bottlenose Dolphins (''Tursiops truncatus''): Implications for Cognition |author1=Brenda McCowan |author2=Lori Marino |author3=Erik Vance |author4=Leah Walke |author5=Diana Reiss |url=http://faculty.vetmed.ucdavis.edu/faculty/bjmccowan/Pubs/McCowanetal.JCP.2000.pdf |access-date=2015-10-31 |archive-url=https://web.archive.org/web/20100610140808/http://faculty.vetmed.ucdavis.edu/faculty/bjmccowan/Pubs/McCowanetal.JCP.2000.pdf |archive-date=2010-06-10 }}</ref> When playing with objects or small animals, common behavior includes carrying the object or animal along using various parts of the body, passing it along to other members of the group or taking it from another member, or throwing it out of the water.<ref name="Walker2007"/> Dolphins have also been observed harassing animals in other ways, for example by dragging birds underwater without showing any intent to eat them.<ref name="Walker2007"/> Playful behaviour that involves another animal species with active participation of the other animal can also be observed, however.  Playful human interaction with dolphins is one example, but playful interactions have been observed in the wild with a number of other species as well, including [[humpback whale]]s and [[dog]]s.<ref>Mark H. Deakos et al. (2010), ''Two Unusual Interactions Between a Bottlenose Dolphin (''Tursiops truncatus'') and a Humpback Whale (''Megaptera novaeangliae'') in Hawaiian Waters''.</ref><ref>{{cite web|first=Cathy|last=Hayes|year=2011|url=http://www.irishcentral.com/news/Amazing-footage-of-a-dog-playing-with-a-dolphin-off-the-coast-of-Ireland--VIDEO-127888298.html|title=Amazing footage of a dog playing with a dolphin off the coast of Ireland|access-date=31 October 2015}}</ref>

===Intelligence===
{{Main|Cetacean intelligence}}
{{See also|Cetacean surfacing behaviour}}

Oceanic dolphins are known to teach, learn, cooperate, scheme, and grieve.<ref name=wwwu>{{cite news |last=Siebert |first=Charles |title=Watching Whales Watching Us |work=[[The New York Times]] Magazine |date=8 July 2009|access-date=29 August 2015 |url=https://www.nytimes.com/2009/07/12/magazine/12whales-t.html?pagewanted=all}}</ref> The neocortex of many species is home to elongated [[spindle neurons]] that, prior to 2007, were known only in hominids.<ref>{{cite journal |author=Watson, K.K. |title=Dendritic architecture of the Von Economo neurons |journal=Neuroscience |volume=141 |issue=3 |pages=1107–1112 |year=2006 |doi=10.1016/j.neuroscience.2006.04.084 |last2=Jones |first2=T. K. |last3=Allman |first3=J. M. |pmid=16797136|s2cid=7745280 }}</ref> In humans, these cells are involved in social conduct, emotions, judgment, and theory of mind.<ref>{{cite journal |author=Allman, John M. |title=Intuition and autism: a possible role for Von Economo neurons |journal=Trends Cogn Sci |volume=9 |issue=8 |pages=367–373 |year=2005 |doi=10.1016/j.tics.2005.06.008 |last2=Watson |first2=Karli K. |last3=Tetreault |first3=Nicole A. |last4=Hakeem |first4=Atiya Y. |pmid=16002323|s2cid=14850316 }}</ref> Cetacean spindle neurons are found in areas of the brain that are homologous to where they are found in humans, suggesting that they perform a similar function.<ref>{{cite journal |author=Hof, Patrick R. |title=Structure of the cerebral cortex of the humpback whale, ''Megaptera novaeangliae'' (Cetacea, Mysticeti, Balaenopteridae) |journal=The Anatomical Record |volume=290 |issue=1 |pages=1–31 |year=2007 |doi=10.1002/ar.20407 |last2=Van Der Gucht |first2=Estel |pmid=17441195|s2cid=15460266 |doi-access=free }}</ref>

[[Brain size]] was previously considered a major indicator of the intelligence of an animal. Since most of the brain is used for maintaining bodily functions, greater ratios of brain to body mass may increase the amount of brain mass available for more complex cognitive tasks. [[Allometric]] analysis indicates that mammalian brain size scales at approximately the {{sfrac|2|3}} or {{sfrac|3|4}} exponent of the body mass.<ref>{{cite web |url=http://pages.ucsd.edu/~jmoore/courses/allometry/allometry.html |title=Allometry |first=Jim |last=Moore| publisher=University of California San Diego |access-date=9 August 2015}}</ref> Comparison of a particular animal's brain size with the expected brain size based on such allometric analysis provides an [[encephalization quotient]] that can be used as another indication of animal intelligence. [[Orca]] have the second largest brain mass of any animal on earth, next to the [[sperm whale]].<ref>{{cite journal|url=http://articles.orlandosentinel.com/2010-03-06/news/os-seaworld-killer-whale-brains-20100302_1_killer-whales-orcas-dolphin-or-porpoise|archive-url=https://web.archive.org/web/20120607033009/http://articles.orlandosentinel.com/2010-03-06/news/os-seaworld-killer-whale-brains-20100302_1_killer-whales-orcas-dolphin-or-porpoise|archive-date=June 7, 2012|title=How smart are they?|journal=Orlando Sentinel|date=March 7, 2010}}</ref> The [[brain to body mass ratio]] in some is second only to humans.<ref>{{cite web |url=http://blogs.scientificamerican.com/news-blog/are-whales-smarter-than-we-are/ |author=Fields, R. Douglas |title=Are whales smarter than we are? | publisher=Scientific American |access-date=9 August 2015}}</ref>

[[Self-awareness]] is seen, by some, to be a sign of highly developed, abstract thinking. Self-awareness, though not well-defined scientifically, is believed to be the precursor to more advanced processes like [[metacognition|meta-cognitive reasoning]] (thinking about thinking) that are typical of humans. Research in this field has suggested that cetaceans, among others, possess self-awareness.<ref>{{cite web | url=http://www.livescience.com/4272-elephant-awareness-mirrors-humans.html | title=Elephant Self-Awareness Mirrors Humans |publisher=Live Science |date=30 October 2006 |access-date=29 August 2015}}</ref>
The most widely used test for self-awareness in animals is the [[mirror test]] in which a temporary dye is placed on an animal's body, and the animal is then presented with a mirror; they then see if the animal shows signs of self-recognition.<ref name="Mirror test">{{cite news |url=https://www.nytimes.com/2001/05/01/science/brainy-dolphins-pass-the-human-mirror-test.html |title=Mirror test |author=Derr, Mark |work=[[The New York Times]] |date=May 2001 |access-date=3 August 2015}}</ref>

In 1995, Marten and Psarakos used television to test dolphin self-awareness.<ref>{{cite journal|last1=Marten|first1=Ken|last2=Psarakos|first2=Suchi|title=Using Self-View Television to Distinguish between Self-Examination and Social Behavior in the Bottlenose Dolphin (''Tursiops truncatus'')|journal=Consciousness and Cognition|volume=4|number=2|date=June 1995|doi=10.1006/ccog.1995.1026|pages=205–224|pmid=8521259|s2cid=44372881}}</ref> They showed dolphins real-time footage of themselves, recorded footage, and another dolphin. They concluded that their evidence suggested self-awareness rather than social behavior. While this particular study has not been repeated since then, dolphins have since passed the mirror test.<ref name="Mirror test"/>

==Interactions with humans==

===Threats===

====Consumption====
[[File:Dolphin Sashimi.jpg|thumb|Plate of dolphin [[sashimi]]]]
In some parts of the world, such as [[Taiji, Wakayama|Taiji, Japan]] and the [[Faroe Islands]], dolphins are traditionally considered as food, and are killed in [[harpoon]] or [[dolphin drive hunting|drive hunts]].<ref>
{{cite web|last=Matsutani |first=Minoru|url=http://search.japantimes.co.jp/cgi-bin/nn20090923f1.html|title=Details on how Japan's dolphin catches work|publisher=[[Japan Times]]|date=September 23, 2009|page=3}}</ref>
Dolphin meat is consumed in a small number of countries worldwide, which include [[Japan]]<ref>{{cite news| last= McCurry | first= Justin | url=https://www.theguardian.com/world/2009/sep/14/dolphin-slaughter-hunting-japan-taiji | work=The Guardian | location=London | title=Dolphin slaughter turns sea red as Japan hunting season returns | date=2009-09-14 | access-date=24 May 2010}}</ref> and [[Peru]] (where it is referred to as ''chancho marino'', or "sea pork").<ref>{{Cite news  | last = Hall  | first = Kevin G.  | title = Dolphin meat widely available in Peruvian stores: Despite protected status, 'sea pork' is popular fare  | newspaper = The Seattle Times  | year = 2003  }}</ref>

Dolphin meat is dense and such a dark shade of red as to appear black. Fat is located in a layer of [[blubber]] between the meat and the skin. When dolphin meat is eaten in Japan, it is often cut into thin strips and eaten raw as ''[[sashimi]]'', garnished with onion and either [[horseradish]] or grated [[garlic]], much as with ''sashimi'' of [[whale meat|whale]] or [[horse meat]] (''basashi''). When cooked, dolphin meat is cut into bite-size cubes and then batter-fried or simmered in a ''[[miso]]'' sauce with vegetables. Cooked dolphin meat has a flavor very similar to [[beef liver]].<ref>{{cite web|script-title=ja:イルカの味噌根菜煮 |language=ja|trans-title= Dolphin in Miso Vegetable Stew |url= http://cookpad.com/recipe/1073593 |work= Cookpad |year=2010 |access-date= 16 May 2011}}</ref> Dolphin meat is high in mercury, and may pose danger to a humans health when consumed.<ref>
{{cite web|last=Johnston |first=Eric|url=http://search.japantimes.co.jp/cgi-bin/nn20090923f2.html|title=Mercury danger in dolphin meat|publisher=[[Japan Times]]|date=September 23, 2009|page=3}}</ref>

{{Quote box|width=30%|align=left|quote=The [[Faroe Islands]] population was exposed to [[methylmercury]] largely from contaminated pilot whale meat, which contained very high levels of about 2 mg methylmercury/kg. However, the Faroe Islands populations also eat significant amounts of fish. The study of about 900 Faroese children showed that prenatal exposure to methylmercury resulted in neuropsychological deficits at 7 years of age|source=–[[World Health Organization]]<ref name=WHO/>}}
There have been human health concerns associated with the consumption of dolphin meat in Japan after tests showed that dolphin meat contained high levels of [[mercury (element)|mercury]].<ref name=WHO/> There are no known cases of [[mercury poisoning]] as a result of consuming dolphin meat, though the government continues to monitor people in areas where dolphin meat consumption is high. The Japanese government recommends that children and pregnant women avoid eating dolphin meat on a regular basis.<ref>{{cite web|url=http://www.mhlw.go.jp/topics/2003/06/tp0605-1.html|script-title=ja:平成１５年６月３日に公表した「水銀を含有する魚介類等の 摂食に関する注意事項」について|author1=Ministry of Health |author2=Labour and Welfare |work=Ministry of Health, Labour and Welfare|language=ja}}</ref>

Similar concerns exist with the consumption of dolphin meat in the [[Faroe Islands]], where [[Prenatal development|prenatal]] exposure to [[methylmercury]] and [[Polychlorinated biphenyl|PCBs]] primarily from the consumption of pilot whale meat has resulted in [[Neuropsychology|neuropsychological]] deficits amongst children.<ref name=WHO>{{cite web|author= [[World Health Organization]] / [[United Nations Environment Programme]] DTIE Chemicals Branch |year= 2008 |title= Guidance for identifying populations at risk from mercury exposure|page= 36 |url=https://www.who.int/foodsafety/publications/chem/mercuryexposure.pdf |access-date= 29 August 2013}}</ref>

Legally [[Marine mammals as food|consuming dolphin meat]] in the United States would be near impossible for most due to the [[Marine Mammal Protection Act]], which forbids "...the act of hunting, killing, capture, and/or harassment of any marine mammal..."  (Exceptions are made for certain groups of people, such as [[Alaska Natives]].)  Theoretically, one could only eat the meat of a dolphin which died of natural causes, which would likely be highly undesirable (and potentially dangerous).{{citation needed|date=December 2024}}

====Fishing====
Various fishing methods, like [[seine fishing]] for [[tuna]] and the use of [[drift net|drift]] and [[gill net]]s, unintentionally kill many oceanic dolphins.<ref>{{Cite book|title=The End of the Line: How overfishing is changing the world and what we eat|author=Clover, Charles.|year=2004|publisher=Ebury Press, London.|isbn = 978-0-09-189780-2}}</ref> Accidental bycatch in gill nets is common and poses a risk for mainly local dolphin populations.<ref name="Díaz López, 2006">{{Cite journal|last1=Díaz López| first1=Bruno|last2=Bernal Shirai |first2=J.A.| year=2006| title=Bottlenose dolphin (''Tursiops truncatus'') presence and incidental capture in a marine fish farm on the north-eastern coast of Sardinia (Italy)| journal=Journal of the Marine Biological Association of the UK| volume=87| pages=113–117| doi=10.1017/S0025315407054215| s2cid=86115152}}</ref><ref name="Díaz López, 2006b">{{Cite journal| last=Díaz López| first=Bruno| year=2006| title= Interactions between Mediterranean bottlenose dolphins (''Tursiops truncatus'') and gillnets off Sardinia, Italy| journal= ICES Journal of Marine Science| volume=63| pages=946–951| doi=10.1016/j.icesjms.2005.06.012| issue=5| doi-access=free| bibcode=2006ICJMS..63..946D}}</ref>

[[Dolphin safe label]]s attempt to reassure consumers that fish and other marine products have been caught in a dolphin-friendly way. The earliest campaigns with "Dolphin safe" labels were initiated in the 1980s as a result of cooperation between marine activists and the major tuna companies, and involved decreasing incidental dolphin kills by up to 50% by changing the type of nets used to catch tuna. The dolphins are netted only while fishermen are in pursuit of smaller tuna. Albacore are not netted this way, making albacore the only truly dolphin-safe tuna.<ref>{{cite web|title=Time Of Truth For US Dolphin Safe Logos |url=http://www.atuna.com/NewsArchive/ViewArticle.asp?ID=12719 |website=atuna |access-date=29 August 2015 |archive-url=https://web.archive.org/web/20151015221118/http://www.atuna.com/NewsArchive/ViewArticle.asp?ID=12719 |archive-date=15 October 2015 }}</ref>

====Sonar====
Loud underwater noises, such as those resulting from [[navy|naval]] [[sonar]] use, live firing exercises, and certain [[offshore construction]] projects such as [[wind farm]]s, may be harmful to dolphins, increasing stress, damaging hearing, and causing [[decompression sickness]] by forcing them to surface too quickly to escape the noise.<ref>{{cite news|title= Navy sonar may be killing whales, dolphins|author=CBC news|url=https://www.cbc.ca/news/science/navy-sonar-may-be-killing-whales-dolphins-1.358039|access-date= October 27, 2008|work=CBC News|date=2003-10-09}}</ref><ref>{{cite web|title=Npower renewables Underwater noise & vibration, section 9.4 |url=http://www.natwindpower.co.uk/northhoyle/pdfs/fepa/chapter9.pdf|archive-url=https://web.archive.org/web/20070722160651/http://www.natwindpower.co.uk/northhoyle/pdfs/fepa/chapter9.pdf|archive-date=2007-07-22|access-date= October 27, 2008}}</ref>

===In captivity===
{{Main|Cetaceans in captivity}}
[[File:Sea World1.jpg|thumb|SeaWorld show featuring [[bottlenose dolphin]]s and [[false killer whale]]s]]
The renewed popularity of dolphins in the 1960s resulted in the appearance of many [[dolphinarium|dolphinaria]] around the world, making dolphins accessible to the public. Criticism and [[animal welfare]] laws forced many to close, although hundreds still exist around the world. In the [[United States]], the best known are the [[SeaWorld]] [[marine mammal park]]s.
In the Middle East the best known are Dolphin Bay at [[Atlantis, The Palm]] and the [[Dubai Dolphinarium]].{{citation needed|date=December 2024}}

Various species of dolphins are kept in captivity. These small cetaceans are more often than not kept in theme parks, such as [[SeaWorld]], commonly known as a [[dolphinarium]]. [[Bottlenose dolphin]]s are the most common species of dolphin kept in dolphinariums as they are relatively easy to train, have a long lifespan in captivity and have a friendly appearance. Hundreds if not thousands of bottlenose dolphins live in captivity across the world, though exact numbers are hard to determine. Other species kept in captivity are [[Atlantic spotted dolphin|spotted dolphins]], [[false killer whale]]s, and [[common dolphin]]s, [[Commerson's dolphin]]s, as well as [[rough-toothed dolphin]]s, but all in much lower numbers than the bottlenose dolphin. There are also fewer than ten [[pilot whale]]s, [[Amazon river dolphin]]s, [[Risso's dolphin]]s, [[spinner dolphin]]s, or [[tucuxi]] in captivity. Two unusual and very rare [[Hybrid (biology)|hybrid]] dolphins, known as [[wholphin]]s, are kept at the Sea Life Park in [[Hawaii]], which is a cross between a bottlenose dolphin and a [[false killer whale]]. Also, two [[Common dolphin|common]]/bottlenose hybrids reside in captivity: one at [[Discovery Cove]] and the other at [[SeaWorld San Diego]].<ref name="Dolphins"/>

[[Orca]] are well known for their performances in shows, but the number of orcas kept in captivity is very small, especially when compared to the number of bottlenose dolphins, with only 44 [[List of captive orcas|captive orca]] being held in aquaria as of 2012.<ref>{{cite web|url=http://www.orcahome.de/orcastat.htm| title=Orcas in Captivity – A look at killer whales in aquariums and parks|date=23 November 2009|access-date=6 September 2015}}</ref> The orca's [[animal intelligence|intelligence]], trainability, striking appearance, playfulness in captivity and sheer size have made it a popular exhibit at aquaria and aquatic theme parks. From 1976 to 1997, 55 whales were taken from the wild in Iceland, 19 in Japan and three in Argentina. These figures exclude animals that died during capture. Live captures fell dramatically in the 1990s, and by 1999, about 40% of the 48 animals on display in the world were captive-born.<ref name="Dolphins"/>

===In history and mythology===
{{expand section|date=November 2015|Vikings and other coastal civilizations}}
[[File:Akrotiri dolphins.jpg|thumb|Fresco of dolphins, {{circa}} 1600 BC, from [[Knossos]], [[Crete]]]]

In [[Greek mythology|Greek myths]], they were seen invariably as helpers of humankind. Dolphins also seem to have been important to the [[Minoans]], judging by artistic evidence from the ruined palace at [[Knossos]]. Dolphins are common in [[Greek mythology]], and many coins from [[ancient Greece]] have been found which feature a man, a boy or a deity riding on the back of a dolphin.<ref>{{cite web|url=http://dougsmith.ancients.info/feac50tar.html|title=Taras|archive-url=https://web.archive.org/web/20070208015112/http://dougsmith.ancients.info/feac50tar.html|archive-date=2007-02-08|access-date=3 October 2010}}</ref> The [[Ancient Greece|Ancient Greeks]] welcomed dolphins; spotting dolphins riding in a ship's wake was considered a good omen.<ref>Eyers, Jonathan (2011). ''Don't Shoot the Albatross!: Nautical Myths and Superstitions''. A&C Black, London, UK. {{ISBN|978-1-4081-3131-2}}.</ref>  In both ancient and later art, [[Cupid]] is often shown [[Cupid#Cupid and dolphins|riding a dolphin]]. A dolphin rescued the poet [[Arion]] from drowning and carried him safe to land, at [[Cape Matapan]], a promontory forming the southernmost point of the [[Peloponnesus]]. There was a temple to [[Poseidon]] and a statue of Arion riding the dolphin.<ref>[[Herodotus]] I.23; [[Thucydides]] I.128, 133; [[Pausanias (geographer)|Pausanias]] iii.25, 4</ref>

[[Dionysus]] was once captured by [[Etruscan civilization|Etruscan]] [[pirate]]s who mistook him for a wealthy prince they could ransom. After the ship set sail Dionysus invoked his divine powers, causing vines to overgrow the ship where the mast and sails had been.  He turned the oars into serpents, so terrifying the sailors that they jumped overboard, but Dionysus took pity on them and [[shapeshifting|transformed]] them into dolphins so that they would spend their lives providing help for those in need. Dolphins were also the messengers of [[Poseidon]] and sometimes did errands for him as well. Dolphins were sacred to both [[Aphrodite]] and [[Apollo]].{{citation needed|date=December 2024}}

Dolphins are sometimes used as symbols, for instance in heraldry. When heraldry developed in the [[Middle Ages]], not much was known about the biology of the dolphin and it was often depicted as a sort of fish. Traditionally, the dolphins in heraldry still may take after this notion, sometimes showing the dolphin skin covered with [[fish scale]]s.{{citation needed|date=December 2024}}

In the [[Middle Ages]], the dolphin became an important [[Heraldry|heraldic element]] in the coats of arms of several European noble families, the most noticeable being those of the [[List of counts of Albon and dauphins of Viennois|Dauphin de Viennois]] (later [[Dauphin of France]]) through which it passed to the [[Forez|Counts of Forez]], [[List of counts of Albon and dauphins of Viennois|Albon]] and other French families, as well as several branches of the [[House of Bourbon|Bourbon family]] ([[Duchy of Montpensier|Count of Montpensier]], [[Louis Charles, Count of Beaujolais|Count of Beaujolais]], among others). The [[House of Pandolfini|Pandolfini]] of Florence, and the [[Delfini (family)|Delfini]] of Venice and Rome also used the dolphin as their "canting" armories. In the 19th century, [[Joseph Bonaparte]] adopted a dolphin in his coat of arms as King of Naples and Sicily.{{citation needed|date=December 2024}}

In contemporary days, a dolphin is still used in the coat of arms of many cities, as well as in the [[coat of arms of Anguilla]] and the [[coat of arms of Romania]],<ref>{{cite book|title=Brief Romanian Military History|url=https://archive.org/details/briefromanianmil00hent|url-access=limited|last=Hentea|first=Călin|publisher=Scarecrow Press|year=2007|isbn=978-0-8108-5820-6|location=Maryland, USA|page=[https://archive.org/details/briefromanianmil00hent/page/n105 91]}}</ref> and the [[coat of arms of Barbados]] has a dolphin [[supporter]].<ref>{{cite book|title=Barbados: Just Beyond Your Imagination|last=Ali|first=Arif|publisher=Hansib Publications|year=1996|isbn=978-1-870518-54-3|location=Hertford, UK|page=16}}</ref> [[Angelo Amato|Cardinal Angelo Amato]], prefect of the [[Congregation for the Causes of Saints|Congregation of the Causes of Saints]], has a dolphin in his coat of arms, as well as [[Godfried Danneels|Cardinal Godfried Danneels]], former [[Roman Catholic Archdiocese of Mechelen-Brussels|Metropolitan Archbishop of Mechelen-Brussels]].

==References==
{{Reflist|30em}}

* {{cite journal | last1 = May-Collado | first1 = L. | last2 = Agnarsson | first2 = I. | year = 2006 | title = Cytochrome ''b'' and Bayesian inference of whale phylogeny | journal = Molecular Phylogenetics and Evolution | volume = 38 | issue = 2| pages = 344–354 | doi=10.1016/j.ympev.2005.09.019 | pmid=16325433| bibcode = 2006MolPE..38..344M }}
* [https://web.archive.org/web/20091027174803/http://cf.geocities.com/orque_orca/  Site sur les differents orques et leur mode de reproduction évitant la consanguinité.] {{in lang|fr}}

{{Cetacea|O.}}
{{Odontoceti|D.}}
{{Taxonbar|from=Q215760}}
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[[Category:Oceanic dolphins| ]]
[[Category:Delphinoidea]]
[[Category:Extant Chattian first appearances]]
[[Category:Taxa named by John Edward Gray]]