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{{Short description|Informal classification of marine mammals, closely related to whales and porpoises}}
{{otheruses}}
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{{Use mdy dates|date=December 2018}}
{{Paraphyletic group
|name = Dolphins
|image = Tursiops truncatus 01.jpg
|image_caption = A [[common bottlenose dolphin]] (''Tursiops truncatus'')
|auto = yes
|parent = Odontoceti
|includes = * [[Delphinidae]]
* [[Iniidae]]
* {{extinct}}[[Lipotidae]]
* [[Platanistidae]]
* [[Pontoporiidae]]
|excludes = * [[Monodontidae]]
* [[Phocoenidae]]
* [[Physeteroidea]]
* [[Ziphiidae]]
}}
A '''dolphin''' is a [[common name]] used for some of the [[aquatic mammal]]s in the [[cetacean]] [[clade]] '''Odontoceti''', the [[toothed whale]]s. Dolphins belong to the families [[Delphinidae]] (the oceanic dolphins), along with the [[river dolphin]] families [[Platanistidae]] (the Indian river dolphins), [[Iniidae]] (the New World river dolphins), [[Pontoporiidae]] (the [[brackish]] dolphins), and probably extinct [[Lipotidae]] (baiji or Chinese river dolphin). There are 40 [[extant species]] named as dolphins.
Dolphins range in size from the {{convert|1.7|m|ftin|adj=mid|-long}} and {{convert|50|kg|lb|abbr=off|adj=on}} [[Maui's dolphin]] to the {{convert|9.5|m|ft|abbr=on}} and {{convert|10|tonne|ST|adj=on}} [[orca]]. Various species of dolphins exhibit [[sexual dimorphism]] where the males are larger than females. They have streamlined bodies and two limbs that are modified into flippers. Though not quite as flexible as [[Pinniped|seal]]s, they are faster; some dolphins can briefly travel at speeds of {{Convert|29|kph|mph}} or leap about {{Convert|9|m|ft}}.<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|pages=eaat4220|doi=10.1126/science.aat4220|pmid=30679341|s2cid=59248474|issn=0036-8075|doi-access=free}}</ref> Dolphins use their conical teeth to capture fast-moving [[Predation|prey]]. They have well-developed hearing which is adapted for both air and water; it is so well developed that some can survive even if they are blind.{{Citation needed|date=August 2025}} 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.
Dolphins are widespread. Most species prefer the warm waters of the tropic zones, but some, such as the [[right whale dolphin]], prefer colder climates. Dolphins feed largely [[Piscivore|on fish]] and [[squid]], but a few large-bodied dolphins, such as the [[orca]], feed on large prey such as seals, sharks, and other dolphins. 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 months and females bear all the responsibility for raising them. Mothers of some species fast and nurse their young for a relatively long period of time.
Dolphins produce a [[Whale vocalization|variety of vocalizations]], usually in the form of clicks and whistles.
Dolphins are sometimes [[Whaling|hunted]] in places such as [[Whaling in Japan|Japan]], in an activity known as [[dolphin drive hunting]]. Besides drive hunting, they also face threats from [[bycatch]], [[habitat loss]], and [[marine pollution]]. Dolphins feature in various cultures worldwide, such as in art or folklore. Dolphins are sometimes kept in captivity within [[dolphinarium]]s and trained to perform tricks; the most common dolphin species in captivity is the [[bottlenose dolphin]], while there are around 60 [[captive orca|orcas in captivity]].
==Etymology==
The name is originally from [[Ancient Greek|Greek]] {{lang|grc|δελφίς}} (''delphís''), "dolphin",<ref name=Liddel>{{cite web|url=https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0057%3Aentry%3Ddelfi%2Fs|title=δελφίς |first1=Henry George|last1=Liddell|first2=Robert|last2=Scott|work=A Greek-English Lexicon|publisher=Perseus Digital Library}}</ref> which was related to the Greek {{lang|grc|δελφύς}} (''delphus''), "womb".<ref name=Liddel/> The animal's name can therefore be interpreted as meaning "a 'fish' with a womb".<ref>{{cite book
|title=Dolphin
|series=The American Heritage Dictionary of the English Language
|edition=Fourth
|publisher=[[Reference.com|Dictionary.com]]
|url=http://dictionary.reference.com/browse/Dolphin
|access-date= December 17, 2006}}</ref> The name was transmitted via the [[Latin]] ''delphinus''<ref>{{cite web| url = https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0059%3Aentry%3Ddelphinus| title = delphinus, Charlton T. Lewis, Charles Short, ''A Latin Dictionary'', on Perseus Digital Library}}</ref> (the [[romanization]] of the later Greek δελφῖνος – ''delphinos''<ref name=Liddel/>), which in [[Medieval Latin]] became {{Lang|la-x-medieval|dolfinus}} and in [[Old French]] ''daulphin'', which reintroduced the spelling ''ph'' into the word ''dolphin''. The term ''mereswine'' ("sea pig") is also used.<ref name="c959">{{cite news| title=Killer Zionist dolphins? Hamas claims they exist | website= The Jerusalem Post | date=January 11, 2022 | url=https://www.jpost.com/omg/article-692167 | access-date=May 9, 2024}}</ref><ref name="l962">{{cite web | last=Caracciolo | first=Frankie | title=Biology Says It Sucks to Be This Rare Albino Dolphin | website=Inverse | date=June 19, 2017 | url=https://www.inverse.com/science/33125-rare-albino-dolphin-kate-risso-moby-dick | access-date=May 9, 2024}}</ref>
{{anchor|Definition}}
The term ''dolphin'' can be used to refer to most species in the family [[Delphinidae]] (oceanic dolphins) and the river dolphin families of [[Iniidae]] (South American river dolphins), Pontoporiidae ([[La Plata dolphin]]), [[Lipotidae]] (Yangtze river dolphin) and [[Platanistidae]] (Ganges river dolphin and Indus river dolphin).<ref>{{cite book|title=Aquatic Life of the World|url={{google books|plainurl=y|id=p5IiaOb5XxgC|page=652}}|access-date=July 23, 2013|date=November 1, 2000|publisher=Marshall Cavendish|isbn=978-0-7614-7170-7|page=652}}</ref><ref name="Walker2007"/> Meanwhile, the [[mahi-mahi]] fish is called the dolphinfish.<ref>{{cite web|title=Coryphaena hippurus|url=http://www.fishbase.org/Summary/SpeciesSummary.php?id=6|work=FishBase|access-date=January 15, 2016}}</ref> In common usage, the term ''whale'' is used only for the larger cetacean species,<ref name="Leatherwood1988">{{cite book|author=Stephen Leatherwood|title=Whales, Dolphins, and Porpoises of the Eastern North Pacific and Adjacent Arctic Waters: A Guide to Their Identification|url={{google books|plainurl=y|id=LpMxr35NBCcC|page=6}}|access-date=July 23, 2013|year=1988|publisher=Courier Dover Publications|isbn=978-0-486-25651-1|page=6}}</ref> while the smaller ones with a beaked or longer nose are considered dolphins.<ref name="Hirschi2002">{{cite book|author=Ron Hirschi|title=Dolphins|url={{google books|plainurl=y|id=GnBz5ygfUKwC|page=7}}|access-date=July 23, 2013|date=April 2002|publisher=Marshall Cavendish|isbn=978-0-7614-1443-8|page=7}}</ref> The name ''dolphin'' is used casually as a synonym for [[bottlenose dolphin]], the most common and familiar species of dolphin.<ref name="NowacekNowacek2006">{{cite book|author1=Stephanie Nowacek|author2=Douglas Nowacek|title=Discovering Dolphins|url={{google books|plainurl=y|id=PF8LlgiRUMIC|page=5}}|access-date=July 23, 2013|year=2006|publisher=Voyageur Press|isbn=978-0-7603-2561-2|pages=5, 9}}</ref> There are six species of dolphins commonly thought of as whales, collectively known as [[blackfish]]: the [[orca]], the [[melon-headed whale]], the [[pygmy killer whale]], the [[false killer whale]], and the two species of [[pilot whale]]s, all of which are classified under the family Delphinidae and qualify as dolphins.<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> Although the terms ''dolphin'' and ''porpoise'' are sometimes used interchangeably, ''porpoise'' usually refers to the Phocoenidae family, which have a shorter beak and spade-shaped teeth and differ in their behavior.<ref name="NowacekNowacek2006"/>
A group of dolphins is called a ''school'' or a ''pod''. Male dolphins are called ''bulls'', females are called ''cows'' and young dolphins are called ''calves''.<ref>{{cite web |title=Style guide, animal names |url=http://dictionary.reference.com/writing/styleguide/animal.html |publisher=[[Reference.com|Dictionary.com]] |access-date=November 4, 2007 |url-status=dead |archive-url=https://web.archive.org/web/20071114065446/http://dictionary.reference.com/writing/styleguide/animal.html |archive-date=November 14, 2007 }}</ref>
==Evolution{{anchor|Evolution and anatomy}}==
{{Main|Evolution of cetaceans}}
[[File:Ichthyosaur vs dolphin.svg|thumb|Dolphins display [[convergent evolution]] with fish and [[Ichthyosauria|aquatic reptiles]].]]
Dolphins are descendants of land-dwelling mammals of the [[artiodactyl]] [[order (biology)|order]] (even-toed ungulates). They are related to the ''[[Indohyus]]'', an extinct [[chevrotain]]-like ungulate, from which they split approximately 48 million years ago.<ref name=science_news>{{cite web |url=https://www.sciencedaily.com/releases/2007/12/071220220241.htm |title=Whales Descended From Tiny Deer-like Ancestors |access-date=December 21, 2007 |author=Northeastern Ohio Universities Colleges of Medicine and Pharmacy |website=ScienceDaily}}</ref><ref name="Ancestors_Tale">{{cite book|last=Dawkins|first=Richard|title=The Ancestor's Tale: A Pilgrimage to the Dawn of Evolution|url={{google books |plainurl=y |id=wojUDAAAQBAJ}}|date=September 6, 2016|publisher=Houghton Mifflin Harcourt|isbn=978-0-547-52512-9}}</ref>
The primitive cetaceans, or [[archaeocetes]], first took to the sea approximately 49 million years ago and became fully aquatic by 5–10 million years later.<ref name=radiations>{{cite journal |last=[[Hans Thewissen|Thewissen]]|first=J. G. M. |author2=Williams, E. M. |title=THE EARLY RADIATIONS OF CETACEA (MAMMALIA): Evolutionary Pattern and Developmental Correlations |journal=Annual Review of Ecology and Systematics |date=November 1, 2002 |volume=33 |issue=1 |pages=73–90 |doi=10.1146/annurev.ecolsys.33.020602.095426|bibcode=2002AnRES..33...73T }}</ref>
[[Archaeoceti]] is a parvorder comprising ancient whales. These ancient whales are the predecessors of modern whales, stretching back to their first ancestor that spent their lives near (rarely in) the water. Likewise, the archaeocetes can be anywhere from near fully terrestrial, to semi-aquatic to fully aquatic, but what defines an archaeocete is the presence of visible legs or asymmetrical teeth.<ref>{{cite web |url=http://www.ucmp.berkeley.edu/mammal/cetacea/cetacean.html |title=Introduction to Cetacea: Archaeocetes: The Oldest Whales |publisher=University of Berkeley |access-date=July 25, 2015}}</ref><ref>{{cite journal |last1=Thewissen|first1=J. G. M. |last2=Cooper |first2=L. N. |last3=Clementz |first3=M. T. |last4=Bajpai |first4=S. |last5=Tiwari |first5=B. N. |title=Whales originated from aquatic artiodactyls in the Eocene epoch of India |year=2007 |journal=Nature |volume=450 |issue=7173 |pages=1190–1194 |url=http://repository.ias.ac.in/4642/1/316.pdf |doi=10.1038/nature06343 |pmid=18097400 |bibcode=2007Natur.450.1190T|s2cid=4416444 |author1-link=Hans Thewissen }}</ref><ref>{{cite journal |last1=Fahlke |first1=Julia M. |last2=Gingerich |first2=Philip D. |last3=Welsh |first3=Robert C. |last4=Wood |first4=Aaron R. |title=Cranial asymmetry in Eocene archaeocete whales and the evolution of directional hearing in water |year=2011 |journal=PNAS |volume=108 |issue=35 |pages=14545–14548 |doi=10.1073/pnas.1108927108 |pmid=21873217 |bibcode=2011PNAS..10814545F |pmc=3167538|doi-access=free }}</ref><ref>{{cite news |url=http://news.bbc.co.uk/1/hi/sci/tech/1974869.stm |title=More DNA Support for a Cetacea/Hippopotamidae Clade: The Blood-Clotting Protein Gene y-Fibrinogen |work=BBC News|date=May 8, 2002 |access-date=August 20, 2006}}</ref> Their features became adapted for living in the [[Sea|marine environment]]. Major anatomical changes include the hearing set-up that channeled vibrations from the jaw to the earbone which occurred with ''[[Ambulocetus]]'' 49 million years ago, a [[streamline (fluid dynamics)|streamlining]] of the body and the growth of flukes on the tail which occurred around 43 million years ago with ''[[Protocetus]]'', the migration of the nasal openings toward the top of the [[cranium]] and the modification of the forelimbs into flippers which occurred with ''[[Basilosaurus]]'' 35 million years ago, and the shrinking and eventual disappearance of the hind limbs which took place with the first odontocetes and mysticetes 34 million years ago.<ref>{{cite episode |series=[[Walking with Prehistoric Beasts]] |title=New Dawn |network=Discovery Channel |airdate=2002 }}</ref><ref>{{cite web |url=http://courses.washington.edu/biol354/Rose_Science_WHIPPO.pdf |title=The Ancestry of Whales |author=Rose, Kenneth D. |publisher=University of Washington |volume=239 |year=2001 |pages=2216–2217}}</ref><ref>{{cite journal |last1=Bebej |first1=R. M. |last2=ul-Haq |first2=M. |last3=Zalmout |first3=I. S. |last4=Gingerich |first4=P. D. |title=Morphology and Function of the Vertebral Column in ''Remingtonocetus domandaensis'' (Mammalia, cetacea) from the Middle Eocene Domanda Formation of Pakistan |journal=Journal of Mammalian Evolution |date=June 2012 |volume=19 |issue=2 |doi=10.1007/S10914-011-9184-8 |pages=77–104|s2cid=17810850 }}</ref> The modern dolphin [[skeleton]] has two small, rod-shaped pelvic bones thought to be [[vestigial]] hind limbs. In October 2006, an unusual bottlenose dolphin was captured in Japan; it had small [[fin]]s on each side of its genital slit, which scientists believe to be an unusually pronounced development of these vestigial hind limbs.<ref>{{cite news
|url=http://news.nationalgeographic.com/news/2006/11/061106-dolphin-legs.html |archive-url=https://web.archive.org/web/20061113052710/http://news.nationalgeographic.com/news/2006/11/061106-dolphin-legs.html |url-status=dead |archive-date=November 13, 2006 |title=Dolphin With Four Fins May Prove Terrestrial Origins |work=National Geographic |last=Lovett |first=Richard A. |date=November 8, 2006 |access-date=July 27, 2012}}</ref>
Today, the closest living relatives of cetaceans are the [[hippopotamus]]es; these share a semi-aquatic ancestor that branched off from other artiodactyls some 60 million years ago.<ref>{{cite web |url=http://mbe.oxfordjournals.org/content/14/5/537.full.pdf |archive-url=https://web.archive.org/web/20151015214719/http://mbe.oxfordjournals.org/content/14/5/537.full.pdf |url-status=dead |archive-date=October 15, 2015 |title=whales' closest relative |author=Gatesy, John |publisher=University of Arizona |date=February 3, 1997 |access-date=August 29, 2015}}</ref> Around 40 million years ago, a common ancestor between the two branched off into cetacea and [[anthracotheres]]; anthracotheres became extinct at the end of the Pleistocene two-and-a-half million years ago, eventually leaving only one surviving lineage: the two species of hippo.<ref>{{cite web |url=http://evolution.berkeley.edu/evolibrary/article/evograms_03 |title=The evolution of whales |publisher=University of Berkeley |access-date=August 29, 2015}}</ref><ref>{{cite journal |author1=Boisserie, Jean-Renaud |author2=Lihoreau, Fabrice |author3=Brunet, Michel |year=2005 |title=The position of Hippopotamidae within Cetartiodactyla |journal=Proceedings of the National Academy of Sciences |volume=102 |issue=5 |pages=1537–1541 |doi=10.1073/pnas.0409518102 |pmid=15677331 |bibcode=2005PNAS..102.1537B |pmc=547867|doi-access=free }}</ref>
==Anatomy==
[[File:Dolphin Anatomy.svg|thumb|upright=1.35|The anatomy of a dolphin showing its skeleton, major organs, tail and body shape.]]
Dolphins have torpedo-shaped bodies with generally non-flexible necks, limbs modified into flippers, a tail fin, and bulbous heads. Dolphin skulls have small eye orbits, long snouts, and eyes placed on the sides of its head; they lack external ear flaps. Dolphins range in size from the {{cvt|1.7|m|ftin}} long and {{convert|50|kg|lb|abbr=on}} [[Maui's dolphin]] to the {{convert|9.5|m|ftin|abbr=on}} and {{convert|10|MT|ST|abbr=on}} [[orca]]. Overall, they tend to be dwarfed by other [[Cetartiodactyl]]s. Several species have female-biased sexual dimorphism, with the females being larger than the males.<ref>{{cite book |url=http://www.cetus.ucsd.edu/SIO133/PDF/Sexual%20Dimorphism.pdf |title=Sexual Dimorphism |author1=Katherine Ralls |author2=Sarah Mesnick |pages=1005–1011 |access-date=August 29, 2015 |archive-url=https://web.archive.org/web/20190725004132/http://www.cetus.ucsd.edu/SIO133/PDF/Sexual%20Dimorphism.pdf |archive-date=July 25, 2019 |url-status=dead }}</ref><ref name="Cetacean anatomy">{{cite web |url=http://acsonline.org/wp-content/uploads/2011/03/ACS-Cetacean-Curriculum.pdf |title=Cetacean Curriculum – A teacher's guide to introducing and using whales, dolphins, & porpoises in the classroom |date=November 28, 2004 |publisher=American Cetacean Society |access-date=December 20, 2013 |quote=Sound production in cetaceans is a complex phenomenon not fully understood by scientists. |archive-url=https://web.archive.org/web/20120807092419/http://acsonline.org/wp-content/uploads/2011/03/ACS-Cetacean-Curriculum.pdf |archive-date=August 7, 2012 |url-status=dead |df=mdy-all }}</ref>
Dolphins have conical teeth, as opposed to [[porpoise]]s' spade-shaped teeth. These conical teeth are used to catch swift prey such as fish, squid or large mammals, such as seals.<ref name="Cetacean anatomy"/>
Breathing involves expelling stale air from their [[blowhole (anatomy)|blowhole]], in an upward blast, which may be visible in cold air, followed by inhaling fresh air into the lungs. Dolphins have rather small, unidentifiable spouts.<ref name="Cetacean anatomy"/><ref>{{cite journal |last=Scholander |first=Per Fredrik |title=Experimental investigations on the respiratory function in diving mammals and birds |year=1940 | journal=Hvalraadets Skrifter | volume=22 }}</ref>
All dolphins have a thick layer of [[blubber]], thickness varying on climate. This blubber can help with buoyancy, protection to some extent as predators would have a hard time getting through a thick layer of fat, and energy for leaner times; the primary usage for blubber is insulation from the harsh climate. Calves, generally, are born with a thin layer of blubber, which develops at different paces depending on the habitat.<ref name="Cetacean anatomy"/><ref name="Dolphins"/>
Dolphins have a two-chambered<ref name=Stevens1995>{{cite book |author1=Stevens, C. Edward |author2=Hume, Ian D. |title=Comparative Physiology of the Vertebrate Digestive System |publisher=Cambridge University Press |page=317 |year=1995}}</ref> or three-chambered<ref name=Biancani2022>{{cite journal |last1= Biancani |first1= B. |last2= Galosi |first2= L. |display-authors=etal |date= October 2022 |title= Comparative study of the gastric mucosa of Risso's dolphin (''Grampus griseus'') and bottlenose dolphin (''Tursiops truncatus'') |journal= Veterinary Sciences |volume= 9 |issue= 10 |pages= 571 |doi= 10.3390/vetsci9100571|doi-access= free |pmid= 36288184 |pmc= 9609225 |hdl= 11581/485468 |hdl-access= free }}</ref> stomach that is similar in cellular structure to that of terrestrial carnivores. They have [[Fundic stomach|fundic]] and [[Pyloric stomach|pyloric]] chambers.<ref name=Stevens1995/>
Dolphins' reproductive organs are located inside the body, with genital slits on the ventral (belly) side. Males have two slits, one concealing the [[penis]] and one further behind for the [[anus]].<ref name="PerrinWursig2009">{{cite book|author1=William F. Perrin|author2=Bernd Wursig|author3=J. G.M. [[Hans Thewissen|Thewissen]]|title=Encyclopedia of Marine Mammals|url={{google books|plainurl=y|id=2rkHQpToi9sC}}|access-date=June 28, 2013|date=February 26, 2009|publisher=Academic Press|isbn=978-0-08-091993-5}}</ref> Females have one genital slit, housing the [[vagina]] and the anus, with a [[Mammary gland|mammary slit]] on either side.<ref>{{cite book|author=Carol J. Howard |title=Dolphin Chronicles |url={{google books|plainurl=y|id=pewZhNQ7jggC|page=129}} |access-date=November 26, 2012 |date=December 1, 1995 |publisher=Random House Digital, Inc. |isbn=978-0-553-37778-1 |pages=129–}}</ref><ref>{{cite book|author1=Bernd G. Würsig |author2=Bernd Wursig, Melany Wursig |title=The Dusky Dolphin: Master Acrobat Off Different Shores |url={{google books|plainurl=y|id=KudBOfRXjWAC|page=156}} |access-date=November 26, 2012 |year=2010 |publisher=Academic Press |isbn=978-0-12-373723-6 |pages=156–}}</ref><ref>{{cite book|author1=Edward F. Gibbons Jr. |author2=Barbara Susan Durrant |author3=Jack Demarest |title=Conservation Endangered Spe: An Interdisciplinary Approach |url={{google books|plainurl=y|id=OuYcepU_YjMC|page=435}} |access-date=November 26, 2012 |year=1995 |publisher=SUNY Press |isbn=978-0-7914-1911-3 |pages=435–}}</ref>
=== Integumentary system ===
The integumentary system is an organ system mostly consisting of skin, hair, nails and endocrine glands. The skin of dolphins is specialized to satisfy specific requirements, including protection, fat storage, heat regulation, and sensory perception. The skin of a dolphin is made up of two parts: the epidermis and the blubber, which consists of two layers including the dermis and subcutis.<ref name="Cozzi-2017">{{Cite book|last1=Cozzi|first1=Bruno|title=Anatomy of Dolphins: Insights into Body Structure and Function|last2=Huggenberger|first2=Stefan|last3=Oelschläger|first3=Helmut|publisher=Elsevier Inc.|year=2017|isbn=978-0124072299|pages=23}}</ref>
The dolphin's skin is known to have a smooth rubber texture and is without hair and glands, except mammary glands. At birth, a newborn dolphin has hairs lined up in a single band on both sides of the rostrum, which is their jaw, and usually has a total length of 16–17 cm .<ref name="Cozzi-2017" /> The epidermis is characterized by the lack of keratin and by a prominent intertwine of epidermal [[rete pegs]] and long dermal papillae.<ref name="Cozzi-2017" /> The epidermal rete pegs are the epithelial extensions that project into the underlying connective tissue in both skin and mucous membranes. The dermal papillae are finger-like projections that help adhesion between the epidermal and dermal layers, as well as providing a larger surface area to nourish the epidermal layer.<ref>{{Cite web|last1=Paxton|first1=Steve|last2=Peckham|first2=Michelle|last3=Knibbs|first3=Adele|date=2003|title=The Leeds Histology Guide|url=https://www.histology.leeds.ac.uk/skin/skin_layers.php|language=en}}</ref> The thickness of a dolphin's epidermis varies, depending on species and age.
==
Blubber is found within the dermis and subcutis layer. The dermis blends gradually with the adipose layer, which is known as fat, because the fat may extend up to the epidermis border and collagen fiber bundles extend throughout the whole subcutaneous blubber which is fat found under the skin.<ref name="Cozzi-2017" /> The thickness of the subcutaneous blubber or fat depends on the dolphin's health, development, ___location, reproductive state, and how well it feeds. This fat is thickest on the dolphin's back and belly. Most of the dolphin's body fat is accumulated in a thick layer of blubber. Blubber differs from fat in that, in addition to fat cells, it contains a fibrous network of connective tissue.<ref>{{Cite web|title=All About Bottlenose Dolphins – Adaptations|url=https://seaworld.org/animals/all-about/bottlenose-dolphin/adaptations/|access-date=2020-12-06|website=seaworld.org}}</ref>
The blubber functions to streamline the body and to form specialized locomotor structures such as the dorsal fin, propulsive fluke blades and caudal keels.<ref name="Cozzi-2017" /> There are many nerve endings that resemble small, onion-like configurations that are present in the superficial portion of the dermis. Mechanoreceptors are found within the interlocks of the epidermis with dermal ridges. There are nerve fibers in the dermis that extend to the epidermis. These nerve endings are known to be highly [[proprioception|proprioceptive]], which explains sensory perception.<ref name="Cozzi-2017" /> Proprioception, which is also known as kinesthesia, is the body's ability to sense its ___location, movements and actions. Dolphins are sensitive to vibrations and small pressure changes.<ref name="Kremers">{{cite journal|display-authors=3 | last1=Kremers | first1=Dorothee | last2=Célérier | first2=Aurélie | last3=Schaal | first3=Benoist | last4=Campagna | first4=Sylvie | last5=Trabalon | first5=Marie | last6=Böye | first6=Martin | last7=Hausberger | first7=Martine | last8=Lemasson | first8=Alban | title=Sensory Perception in Cetaceans: Part I—Current Knowledge about Dolphin Senses As a Representative Species | journal=Frontiers in Ecology and Evolution | volume=4 | date=2016-05-11 | issn=2296-701X | doi=10.3389/fevo.2016.00049 | page= 49| doi-access=free | bibcode=2016FrEEv...4...49K }}</ref> Blood vessels and nerve endings can be found within the dermis. There is a plexus of parallel running arteries and veins in the dorsal fin, fluke, and flippers.<ref name="Cozzi-2017" /> The blubber manipulates the blood vessels to help the dolphin stay warm. When the temperature drops, the blubber constricts the blood vessels to reduce blood flow in the dolphin.<ref>{{Cite web|title=How Does Blubber Keep Animals Warm?|url=https://animals.mom.com/blubber-keep-animals-warm-2735.html|access-date=2020-12-06|website=animals.mom.com|language=en|archive-date=January 25, 2021|archive-url=https://web.archive.org/web/20210125141647/https://animals.mom.com/blubber-keep-animals-warm-2735.html|url-status=dead}}</ref> This allows the dolphin to spend less energy heating its own body, ultimately keeping the animal warmer without burning energy as quick. In order to release heat, the heat must pass the blubber layer. There are thermal windows that lack blubber, are not fully insulated and are somewhat thin and highly vascularized, including the dorsal fin, flukes, and flippers.<ref name="WDC-2012">{{Cite web|date=2012-10-27|title=How does blubber keep whales warm?|url=https://us.whales.org/2012/10/27/how-does-blubber-keep-whales-warm/|access-date=2020-12-06|website=Whale & Dolphin Conservation USA|language=en-US}}</ref> These thermal windows are a good way for dolphins to get rid of excess heat if overheating. Additionally in order to conserve heat, dolphins use countercurrent heat exchange. Blood flows in different directions in order for heat to transfer across membranes. Heat from warm blood leaving the heart will heat up the cold blood that is headed back to the heart from the extremities, meaning that the heart always has warm blood and it decreases the heat lost to the water in those thermal windows.<ref name="WDC-2012" />
[[File:Bottlenose dolphin - kanagawa - 2025 March 21.webm|thumb|[[Bottlenose dolphin]]s swimming and jumping in captivity, 2025]]
===Locomotion===
Dolphins have two pectoral flippers, each containing four digits, a boneless [[dorsal fin]] for stability, and a fluke for propulsion. Although dolphins do not possess external hind limbs, some possess discrete rudimentary appendages, which may contain feet and digits. Orcas are fast swimmers in comparison to seals which typically cruise at {{convert|9|–|28|km/h|mph|abbr=on}}; the orca, in comparison, can travel at speeds up to {{convert|55.5|km/h|mph|abbr=on}}.{{Citation needed|date=February 2024}} A study of a Pacific white-sided dolphin in an aquarium found fast burst acceleration, with the individual being able with 5 strokes (2.5 fluke beats) to go from 5.0 m s-1 to 8.7 m s-1 in 0.7 seconds.<ref name="Tanaka Li Uchida Nakamura 2019 p. e0210860">{{cite journal |last1=Tanaka |first1=Hiroto |last2=Li |first2=Gen |last3=Uchida |first3=Yusuke |last4=Nakamura |first4=Masashi |last5=Ikeda |first5=Teruaki |last6=Liu |first6=Hao |date=2019 |title=Measurement of time-varying kinematics of a dolphin in burst accelerating swimming |journal=PLOS ONE |volume=14 |issue=1 |page=e0210860 |doi=10.1371/journal.pone.0210860 |issn=1932-6203 |pmc=6353170 |pmid=30699184 |doi-access=free|bibcode=2019PLoSO..1410860T }}</ref>
The fusing of the neck vertebrae, while increasing stability when swimming at high speeds, decreases flexibility, which means most dolphins are unable to turn their heads.<ref>{{cite web|url=http://yellowmagpie.com/beluga-whale/ |title=Beluga Whale: The White Melon-headed Creature Of The Cold |publisher=Yellowmagpie.com |date=June 27, 2012 |access-date=August 12, 2013}}</ref><ref>{{cite web |url=http://www.whalesalive.org.au/aboutwhales.html |title=About Whales |publisher=Whalesalive.org.au |date=June 26, 2009 |access-date=August 12, 2013 |archive-url=https://web.archive.org/web/20130812000655/http://whalesalive.org.au/aboutwhales.html |archive-date=August 12, 2013 |url-status=dead }}</ref> [[River dolphin]]s have non-fused neck vertebrae and can turn their heads up to 90°.<ref>{{cite journal|url=http://acsonline.org/fact-sheets/boto-amazon-river-dolphin/|title=Boto (Amazon river dolphin) ''Inia geoffrensis''|journal=American Cetacean Society|year=2002|access-date=September 12, 2015}}</ref> Dolphins swim by moving their fluke and rear body vertically, while their flippers are mainly used for steering. Some species [[Cetacean surfacing behaviour#Porpoising|porpoise]] out of the water, which allows 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=August 29, 2015}}</ref>
Some dolphins are adapted for diving to great depths. In addition to their streamlined bodies, some can selectively slow their [[heart rate]] to conserve oxygen.<ref name="phys-dolphins">{{cite news |title=Dolphins conserve oxygen and prevent dive-related problems by consciously decreasing their heart rates before diving |url=https://phys.org/news/2020-11-dolphins-oxygen-dive-related-problems-consciously.html |access-date=8 December 2020 |work=phys.org |language=en}}</ref><ref>{{cite journal |last1=Fahlman |first1=Andreas |last2=Cozzi |first2=Bruno |last3=Manley |first3=Mercy |last4=Jabas |first4=Sandra |last5=Malik |first5=Marek |last6=Blawas |first6=Ashley |last7=Janik |first7=Vincent M. |title=Conditioned Variation in Heart Rate During Static Breath-Holds in the Bottlenose Dolphin (Tursiops truncatus) |journal=[[Frontiers in Physiology]] |date=2020 |volume=11 |page=604018 |doi=10.3389/fphys.2020.604018 |pmid=33329056 |pmc=7732665 |s2cid=227128277 |language=en |issn=1664-042X|doi-access=free }} [[File:CC-BY icon.svg|50px]] Available under [https://creativecommons.org/licenses/by/4.0/ CC BY 4.0].</ref> Some can also re-route blood from tissue tolerant of water pressure to the heart, brain and other organs. Their [[hemoglobin]] and [[myoglobin]] store oxygen in body tissues, and they have twice as much myoglobin as hemoglobin.<ref>{{cite journal |author1=Norena, S. R. |author2=Williams, T. M. |title=Body size and skeletal muscle myoglobin of cetaceans: adaptations for maximizing dive duration |journal= Comparative Biochemistry and Physiology. Part A, Molecular & Integrative Physiology|volume=126 |issue=2 |year=2000 |pages=181–191|doi=10.1016/s1095-6433(00)00182-3 |pmid=10936758}}</ref>
===Senses===
[[File:Delfinekko.gif|thumb|[[Biosonar]] by cetaceans]]
[[File:Toothed whale sound production.svg|upright=1.35|Diagram illustrating sound generation, propagation, and reception in a toothed whale. Outgoing sounds are in cyan and incoming ones are in green]]
A dolphin ear has specific adaptations 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 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 |url=http://repository.ias.ac.in/4651/1/321.pdf |author2-link=Hans Thewissen |doi-access=free }}<!--|access-date=August 29, 2015 --></ref>
Dolphins generate sounds independently of respiration using recycled air that passes through air sacs and phonic (alternatively monkey) lips. Integral to the lips are oil-filled organs called dorsal bursae that have been suggested to be homologous to the sperm whale's spermaceti organ.<ref name="n010">{{cite journal |last1=Cranford |first1=Ted W. |last2=Amundin |first2=Mats |last3=Norris |first3=Kenneth S. |date=1996 |title=Functional morphology and homology in the odontocete nasal complex: Implications for sound generation |journal=Journal of Morphology |volume=228 |issue=3 |pages=223–285 |doi=10.1002/(SICI)1097-4687(199606)228:3<223::AID-JMOR1>3.0.CO;2-3 |pmid=8622183 |issn=0362-2525}}</ref> High-frequency clicks pass through the sound-modifying organs of the extramandibular fat body, intramandibular fat body and the [[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 use [[Animal echolocation|echolocation]] 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=10.1007/978-4899-0858-2 |year=2002 |url={{google books |plainurl=y |id=VWz1BwAAQBAJ}}|doi-broken-date=July 1, 2025 }}</ref><ref name="Thewissen-Hearing">{{cite book|editor-first1=William F. |editor-last1=Perrin|editor-first2=Bernd |editor-last2= Wursig|editor-first3=J.G.M. 'Hans' |editor-last3=[[Hans Thewissen|Thewissen]]|title=Encyclopedia of Marine Mammals|url={{google books |plainurl=y |id=2rkHQpToi9sC}}|date=February 26, 2009|publisher=Academic Press|isbn=978-0-08-091993-5}}</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 |chapter-url=https://www.researchgate.net/publication/230691464 |access-date=March 1, 2013 |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 |author2=Ulf Eysel |author3=Guide Dehnhardt |journal=Journal of Experimental Biology |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, [[Animal echolocation|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 small hairs on the rostrum of the [[boto]] (river dolphins of South America) are believed to function as a [[somatosensory system|tactile sense]], possibly to compensate for the boto's poor eyesight.<ref>{{cite web|title= Amazon River Dolphin (''Inia geoffrensis'')|first=Laurie|last=Stepanek|date=May 19, 1998|publisher=Texas Marine Mammal Stranding Network|url=http://www.tmmsn.org/mmgulf/inia_geoffrensis.html|access-date= November 20, 2013 |archive-url = https://web.archive.org/web/20070206051622/http://www.tmmsn.org/mmgulf/inia_geoffrensis.html |archive-date = February 6, 2007}}</ref>
A dolphin eye 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 water's refraction of light. Their eyes contain both [[rod cell|rod]] and [[cone cell|cone]] cells, meaning they can see in both dim and bright light, but they have far more rod cells than they do cone cells. They lack short wavelength sensitive visual pigments in their cone cells, indicating a more limited capacity for color vision than most mammals.<ref>{{cite journal |author1=Mass, Alla M. |author2=Supin, Alexander Y. A. |title=Adaptive features of aquatic mammals' eyes |journal=Anatomical Record |volume=290 |issue=6 |pages=701–715 |date=May 21, 2007 |doi=10.1002/ar.20529 |pmid=17516421|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]]'' (eye tissue behind the retina); 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]] and [[olfactory nerve|nerve]] are absent in dolphins, suggesting that they have no sense of smell.<ref name="Dolphin senses"/>
Dolphins are not thought to have a good sense of taste, as their taste buds are atrophied or missing altogether. Some have preferences for different kinds of fish, indicating some ability to taste.<ref name="Dolphin senses"/>
==Intelligence==
{{further|Cetacean intelligence|Cetacean surfacing behaviour}}
[[File:Dolphin Encounter-9563.jpg|thumb|The face of a [[common bottlenose dolphin]]]]
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=July 8, 2009|access-date=August 29, 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 }}<!--|access-date=August 29, 2015--></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 analogous 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 |s2cid=15460266 |pmid=17441195|doi-access=free }}<!--|access-date=August 29, 2015--></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 two-thirds or three-fourths exponent of the body mass. {{Clarify|date=June 2022}}<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=August 9, 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]]s 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://archive.today/20120703134702/http://articles.orlandosentinel.com/2010-03-06/news/os-seaworld-killer-whale-brains-20100302_1_killer-whales-orcas-dolphin-or-porpoise|url-status=dead|archive-date=July 3, 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? | work=Scientific American |access-date=August 9, 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=October 30, 2006 |access-date=August 29, 2015}}</ref>
The most widely used test for self-awareness in animals is the [[mirror test]] in which a mirror is introduced to an animal, and the animal is then marked with a temporary dye. If the animal then goes to the mirror in order to view the mark, it has exhibited strong evidence of self-awareness.<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=August 3, 2015}}</ref>
Some disagree with these findings, arguing that the results of these tests are open to human interpretation and susceptible to the [[Clever Hans]] effect. This test is much less definitive than when used for primates, because primates can touch the mark or the mirror, while cetaceans cannot, making their alleged self-recognition behavior less certain. Skeptics argue that behaviors that are said to identify self-awareness resemble existing social behaviors, and so researchers could be misinterpreting self-awareness for social responses to another individual. The researchers counter-argue that the behaviors shown are evidence of self-awareness, as they are very different from normal responses to another individual. Whereas apes can merely touch the mark on themselves with their fingers, cetaceans show less definitive behavior of self-awareness; they can only twist and turn themselves to observe the mark.<ref name="Mirror test"/>
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 video of themselves, video of another dolphin and recorded footage. 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"/> Some researchers have argued that evidence for self-awareness has not been convincingly demonstrated.<ref>Gallup Jr, Gordon G., and James R. Anderson. "Self-recognition in animals: Where do we stand 50 years later? Lessons from cleaner wrasse and other species." Psychology of Consciousness: Theory, Research, and Practice (2019).</ref>
==Behavior==
[[File:Dolphins gesture language.jpg|thumb|A pod of [[Indo-Pacific bottlenose dolphin]]s in the [[Red Sea]]]]
===Socialization===
[[File:Dolphinsurfresize.jpg|thumb|Dolphins surfing at [[Snapper Rocks]], [[Queensland]], Australia]]
Dolphins are highly social animals, often living in pods of up to a dozen individuals, though pod sizes and structures vary greatly between species and locations. In places with a high abundance of food, pods can merge temporarily, forming a ''superpod''; such groupings may exceed 1,000 dolphins. Membership in pods is not rigid; interchange is common. They establish strong social bonds, and will stay with injured or ill members, helping them to breathe by bringing them to the surface if needed.<ref>{{cite web
|title= Bottlenose Dolphins – Altruism
|author=Davidson College, biology department
|year=2001
|url=http://www.bio.davidson.edu/people/vecase/behavior/Spring2001/Ewart/Altruism.html
|access-date= March 12, 2008
|archive-url = https://web.archive.org/web/20100106122007/http://www.bio.davidson.edu/people/vecase/behavior/Spring2001/Ewart/Altruism.html
|archive-date = January 6, 2010
|url-status = dead
}}</ref> This [[altruism]] does not appear to be limited to their own species. The dolphin ''[[Moko (dolphin)|Moko]]'' in [[New Zealand]] has been observed guiding a female [[pygmy sperm whale]] together with her calf out of shallow water where they had stranded several times.<ref>{{cite news
|title= Dolphin Saves Stuck Whales, Guides Them Back to Sea
|first=Ray | last = Lilley | agency = Associated Press | work = National Geographic | date = March 12, 2008|url=http://news.nationalgeographic.com/news/2008/03/080312-AP-dolph-whal.html
|archive-url=https://web.archive.org/web/20080313141839/http://news.nationalgeographic.com/news/2008/03/080312-AP-dolph-whal.html
|url-status=dead
|archive-date=March 13, 2008
|access-date= July 8, 2012 }}</ref> They have also been seen protecting swimmers from sharks by swimming circles around the swimmers<ref>{{cite news
|title= Dolphins save swimmers from shark
|publisher=CBC News
|url=https://www.cbc.ca/news/world/dolphins-save-swimmers-from-shark-1.513716
|access-date= March 11, 2007
| date=November 24, 2004}}</ref><ref>{{cite web
| last =Celizic
| first =Mike
| title =Dolphins save surfer from becoming shark's bait
| publisher =Today
| date =November 8, 2007
| url = https://www.today.com/news/dolphins-save-surfer-becoming-sharks-bait-2d80555123
| archive-url =https://web.archive.org/web/20071110040906/http://today.msnbc.msn.com/id/21689083/?GT1=10547
| archive-date =November 10, 2007
| access-date = March 2, 2022 }}</ref> or charging the sharks to make them go away.
Dolphins communicate using a variety of clicks, whistle-like sounds and other vocalizations. Dolphins also use [[nonverbal communication]] by means of touch and [[Posture (psychology)|posturing]].<ref>{{cite book|title=Dolphin Mysteries: Unlocking the Secrets of Communication|url={{google books |plainurl=y |id=3gXV0lUeOV4C|page=83}}|access-date=March 16, 2014|date=2008|publisher=Yale University Press|isbn=978-0-300-12112-4|page=83}}</ref>
Dolphins also display culture, something long believed to be unique to humans (and possibly other [[primate]] species). In May 2005, a discovery in Australia found [[Indo-Pacific bottlenose dolphin]]s (''Tursiops aduncus'') teaching their young to use tools. They cover their [[snout]]s with [[sea sponge|sponges]] to protect them while foraging. This knowledge is mostly transferred by mothers to daughters, unlike [[simian]] primates, where knowledge is generally passed on to both sexes. Using sponges as mouth protection is a learned behavior.<ref>{{cite web
|title= Dolphins teach their children to use sponges
|author=Rowan Hooper
|year=2005
|url=https://www.newscientist.com/article/dn7475-dolphins-teach-their-children-to-use-sponges/
|access-date= June 28, 2021}}</ref> Another learned behavior was discovered among river dolphins in Brazil, where some male dolphins use weeds and sticks as part of a sexual display.<ref>{{Cite news
|title= Dolphins woo females with bunches of weeds
|author=Nic Fleming
|url= https://www.telegraph.co.uk/news/earth/earthnews/3317206/Dolphins-woo-females-with-bunches-of-weeds.html
|archive-url=https://web.archive.org/web/20071208002950/http://www.telegraph.co.uk/earth/main.jhtml?xml=/earth/2007/12/05/eadolphin105.xml
|archive-date=December 8, 2007
|access-date= March 2, 2022
| work=The Daily Telegraph
| ___location=London| date=December 5, 2007}}</ref>
Forms of care-giving between fellows and even for members of different species<ref>{{cite web |last1=Bathgate |first1=Adrian |title=Dolphin saves 2 whales stuck on New Zealand beach |url=https://www.reuters.com/article/us-newzealand-dolphin-idUSWEL1524120080313 |website=Reuters |access-date=March 2, 2022 |date=March 13, 2008}}</ref> (see [[Moko (dolphin)]]) are recorded in various species – such as trying to save weakened fellows<ref>{{cite web|url=https://www.bbc.co.uk/nature/21146455|title=Dolphins try to save dying companion|date=January 28, 2013|access-date=December 30, 2016|publisher=BBC}}</ref> or female [[pilot whale]]s holding up dead calves for long periods.
Dolphins engage in acts of aggression towards each other. The older a male dolphin is, the more likely his body is to be covered with bite scars. Male dolphins can get into disputes over companions and females. Acts of aggression can become so intense that targeted dolphins sometimes go into exile after losing a fight.
Male bottlenose dolphins have been known to engage in [[infanticide (zoology)|infanticide]]. Dolphins have also been known to kill [[porpoises]] (porpicide) for reasons which are not fully understood, as porpoises generally do not share the same diet as dolphins and are therefore not competitors for food supplies.<ref>{{Cite news |date=2023-08-24 |title=Dolphin spotters shaken by Ceredigion porpoise killing |language=en-GB |work=BBC News |url=https://www.bbc.com/news/uk-wales-66589355 |access-date=2023-08-24}}</ref><ref>{{cite web
|title= Is Flipper A Senseless Killer?
|author= George Johnson
|url= http://www.txtwriter.com/Onscience/Articles/Flipper.html
|access-date= December 17, 2006
|url-status= dead
|archive-url= https://web.archive.org/web/20061111055736/http://www.txtwriter.com/Onscience/Articles/Flipper.html
|archive-date= November 11, 2006
}}</ref> The [[Cornwall Wildlife Trust]] records about one such death a year. Possible explanations include misdirected infanticide, misdirected sexual aggression or [[play behaviour]].<ref>[https://www.bbc.com/news/uk-england-devon-37616961 Dolphin pictured killing porpoise by flipping it into air], BBC</ref>
===Reproduction and sexuality{{anchor|Reproductive_system}}===
{{See also|Bottlenose dolphin#Reproduction|Dusky dolphin#Social behavior and reproduction|Short-beaked common dolphin#Reproduction}}
[[File:cmglee Horniman dolphin skin skeleton.jpg|thumb|A skin-skeletal preparation<!-- of what?! -->.]]
Dolphin [[copulation (zoology)|copulation]] happens belly to belly; though many species engage in lengthy [[foreplay]], the actual act is usually brief, but may be repeated several times within a short timespan.<ref name=Silva>{{cite web|first1=J. Jr. |last1=Silva |first2=F. |last2=Silva |first3=I. |last3=Sazima |year=2005 |url=http://mardecetaceos.net/media_files/download/04spinner-dolphin.pdf |title=Rest, nurture, sex, release, and play: diurnal underwater behaviour of the spinner dolphin at Fernando de Noronha Archipelago, SW Atlantic – Mating behaviour |access-date=March 16, 2014 |url-status=dead |archive-url=https://web.archive.org/web/20140316211613/http://mardecetaceos.net/media_files/download/04spinner-dolphin.pdf |archive-date=March 16, 2014 }}</ref> The [[gestation period]] varies with species; for the small [[tucuxi dolphin]], this period is around 11 to 12 months,<ref>CMS [http://www.cms.int/reports/small_cetaceans/data/S_fluviatilis/s_fluviatilis.htm Sotalia fluviatilis – Reproduction] {{Webarchive|url=https://web.archive.org/web/20130520100257/http://www.cms.int/reports/small_cetaceans/data/S_fluviatilis/s_fluviatilis.htm |date=May 20, 2013 }}, article. Retrieved March 16, 2013.</ref> while for the orca, the gestation period is around 17 months.<ref>[http://marinebio.org/species.asp?id=84 Orcas (Killer Whales), Orcinus orca – Life History], Marinebio.org. Retrieved March 16, 2014.</ref> Typically dolphins give birth to a single calf, which is, unlike most other mammals, born tail first in most cases.<ref name="Simmonds2007">{{cite book|last=Simmonds|first=Mark|title=Whales and Dolphins of the World|url={{google books |plainurl=y |id=TQxyo8O5KD8C|page=32}}|year=2007|publisher=New Holland Publishers|isbn=978-1-84537-820-2|page=32}}{{Dead link|date=March 2024 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> They usually become sexually active at a young age, even before reaching [[sexual maturity]].<ref name=Silva/> The age of sexual maturity varies by species and sex.<ref>{{Cite book
|title=Reproductive Parameters of Dolphins
|author1=W. Perrin |author2=S. Reilly |year=1984|url=http://swfsc.noaa.gov/publications/CR/1984/8470.PDF}}</ref>
Dolphins are known to display [[Animal co-opted sexual behavior|non-reproductive sexual behavior]], engaging in [[Animal sexual behavior#Autoeroticism or masturbation|masturbation]],<ref>{{Cite book |last1=Würsig |first1=Bernd |url=https://books.google.com/books?id=mfjYEAAAQBAJ&pg=PA164 |title=Sex in Cetaceans: Morphology, Behavior, and the Evolution of Sexual Strategies |last2=Orbach |first2=Dara N. |date=2023-09-25 |publisher=Springer Nature |isbn=978-3-031-35651-3 |language=en}}</ref> stimulation of the genital area of other individuals using the [[rostrum (anatomy)|rostrum]] or flippers, and [[Homosexual behavior in animals|homosexual contact]].<ref name=Silva/><ref>{{Cite book
|title=Homosexual Behaviour in Animals – an Evolutionary perspective.
|author1=Volker Sommer |author2=Paul L. Vasey |year=2006
|chapter=Chapter 4
|chapter-url={{google books |plainurl=y |id=KXM3F59y1jkC}}}}</ref><ref>{{Cite book
|title=Biological Exuberance – Animal Homosexuality and Natural Diversity
|author=Bruce Bagemihl
|url={{google books |plainurl=y |id=0xpi2NI-Dz4C}}
|year=1999}}</ref>
Various species of dolphin have been known to engage in sexual behavior including copulation with dolphins of other species, and occasionally exhibit [[Cross-species sex|sexual behavior towards other animals]], including humans.<ref>{{Cite news|url=http://www.huffingtonpost.com/2012/09/06/frisky-dolphin-tries-to-get-busy-divers_n_1862148.html|title=SCARY VIDEO: Dolphin Gets Too Frisky With Scuba Divers|first1=David|last1=Moye|date=September 7, 2012|newspaper=HuffPost|access-date=December 30, 2016}}</ref><ref>{{Cite book |author1=Amy Samuels |title=Cetaceans that are typically lonely and seek human company |author2=Lars Bejder |author3=Rochelle Constantine |author4=Sonja Heinrich |year=2003 |pages=266–268 |chapter=chapter 15 Marine Mammals: Fisheries, Tourism and Management Issues |author-link3=Rochelle Constantine |access-date=December 17, 2006 |chapter-url=http://whitelab.biology.dal.ca/lb/Samuels%20Bejder%20et%20al%202003.pdf}}</ref> Sexual encounters may be violent, with male bottlenose dolphins sometimes showing aggressive behavior towards both females and other males.<ref>{{cite journal|last=Scott|first=Erin|author2=Mann, Janet |author3=Watson-Capps, Jana |author4=Sargeant, Brooke |author5= Connor, Richard |s2cid=4502911|title=Aggression in bottlenose dolphins: Evidence for sexual coercion, male-male competition, and female tolerance through analysis of tooth-rake marks and behaviour|journal=Behaviour|year=2005|volume=142|issue=1|pages=21–44|doi=10.1163/1568539053627712}}</ref> Male dolphins may also work together and attempt to herd females in [[Estrus#Estrus|estrus]], keeping the females by their side by means of both physical aggression and intimidation, to increase their chances of reproductive success.<ref>{{Cite book
|title=Two levels of alliance formation among male bottlenose dolphins
|author1=R. Connor |author2=R. Smolker |author3=A. Richards |year=1992|url=http://www.pnas.org/content/89/3/987.full.pdf}}</ref>
====Hybridization====
In 1933, three hybrid dolphins beached off the Irish coast; they were [[hybrid (biology)|hybrids]] between [[Risso's dolphin|Risso's]] and bottlenose dolphins.<ref>{{cite web
|title=Dolphin Safari sightings log
|year=2006
|url=http://www.dolphinsafari.com/sightingslog.html
|access-date=December 17, 2006
|archive-url=https://web.archive.org/web/20061110045750/http://dolphinsafari.com/sightingslog.html
|archive-date=November 10, 2006
|url-status=dead
}}</ref> This mating was later repeated in captivity, producing a hybrid calf. In captivity, a bottlenose and a [[rough-toothed dolphin]] produced hybrid offspring.<ref>{{cite web
|title=Mammals of Texas – Rough-toothed Dolphin
|publisher=Texas Tech University
|year=1997
|url=http://www.nsrl.ttu.edu/tmot1/stenbred.htm
|access-date=December 8, 2006
|archive-url=https://web.archive.org/web/20080915025738/http://www.nsrl.ttu.edu/tmot1/stenbred.htm
|archive-date=September 15, 2008
|url-status=dead
}}</ref> A common-bottlenose hybrid lives at [[SeaWorld]] California.<ref>{{cite web
|url=http://www.robins-island.org/dolphins_database.php?filter=Sea_World_California
|archive-url=https://web.archive.org/web/20110723112550/http://www.robins-island.org/dolphins_database.php?filter=Sea_World_California
|archive-date=July 23, 2011
|title=Dolphins at SeaWorld California
|author= Robin's Island
|access-date= December 17, 2006}}</ref> Other dolphin hybrids live in captivity around the world or have been reported in the wild, such as a bottlenose-[[Atlantic spotted dolphin|Atlantic spotted]] hybrid.<ref>{{cite web
|title=Interspecies interactions between Atlantic spotted dolphins, Stenella frontalis and bottlenose dolphins, Tursiops truncatus, on Great Bahama Bank, Bahamas
|author1=Denise L. Herzing
|author2=Kelly Moewe
|author3=Barbara J. Brunnick
|year=2003
|url=http://www.trustedpartner.com/docs/library/000059/Herzing%20Moewe%20Brunnick%20final.pdf
|access-date=December 17, 2006
|url-status=dead
|archive-url=https://web.archive.org/web/20070614013211/http://www.trustedpartner.com/docs/library/000059/Herzing%20Moewe%20Brunnick%20final.pdf
|archive-date=June 14, 2007
}}</ref> The best known hybrid is the [[wholphin]], a false killer whale-bottlenose dolphin hybrid. The wholphin is a fertile hybrid. Two wholphins currently live at the [[Sea Life Park]] in Hawaii; the first was born in 1985 from a male false killer whale and a female bottlenose. Wholphins have also been observed in the wild.<ref>{{cite news
|title=Whale-Dolphin Hybrid Has Baby 'Wholphin'
|last=Lee |first= Jeanette J.
|date=April 15, 2005
|archive-url=https://web.archive.org/web/20050417001241/http://www.livescience.com/animalworld/ap_050415_wolphin.html
|publisher=Livescience.com
|agency=Associated Press
|archive-date=April 17, 2005
|access-date= March 2, 2013|url=http://www.livescience.com/animalworld/ap_050415_wolphin.html
}}</ref>
===Sleeping===
[[File:דולפין ישן.svg|thumb|Sleeping dolphin in captivity: a tail kick reflex keeps the dolphin's blowhole above the water.]]
{{further|Sleep in animals}}
Generally, dolphins sleep with only one brain [[Cerebral hemisphere|hemisphere]] in [[slow-wave sleep]] at a time, thus maintaining enough consciousness to breathe and to watch for possible predators and other threats. Sleep stages earlier in sleep can occur simultaneously in both hemispheres.<ref>
{{cite conference
| last = Mukhametov | first = L. M.
|author2=Supin, A. Ya.
| title = Sleep and vigil in dolphins
| book-title = Marine mammals
| ___location= Moscow
| publisher=[[Nauka (publisher)|Nauka]]
|year=1978}}</ref><ref name="Mukhametov, 1984">{{Cite book
| last=Mukhametov| first=Lev
| chapter=Sleep in Marine Mammals
| title=Sleep Mechanisms
| year=1984
| volume=8
| pages=227–238
| doi=10.1007/978-3-642-69554-4_17
| series=Experimental Brain Research Supplementum
| doi-broken-date=July 1, 2025
| isbn=978-3-642-69556-8}}</ref><ref>{{Cite journal
|title= Excerpts from 'Sleep in marine mammals', L.M. Mukhametov
|author=Dallas Grasby
|year=1994
|url=http://www.bio.net/bionet/mm/neur-sci/1994-August/003910.html
|journal=Experimental Brain Research
|volume= 8 (suppl.)
|access-date= February 11, 2008}}</ref>
In captivity, dolphins seemingly enter a fully asleep state where both eyes are closed and there is no response to mild external stimuli. In this case, respiration is automatic; a tail kick [[reflex]] keeps the blowhole above the water if necessary. [[anesthesia|Anesthetized]] dolphins initially show a tail kick reflex.<ref>{{cite journal|last=McCormick|first=James G.|title=Behavioral Observations of Sleep and Anesthesia in the Dolphin: Implications for Bispectral Index Monitoring of Unihemispheric Effects in Dolphins|journal=Anesthesia & Analgesia|year=2007|volume=104|issue=1|pages=239–241|doi=10.1213/01.ane.0000250369.33700.eb|pmid=17179314|s2cid=40939919 |doi-access=free}}</ref> Though a similar state has been observed with wild [[sperm whale]]s, it is not known if dolphins in the wild reach this state.<ref>{{cite news
|title= Sperm whales caught 'cat napping'
|work=BBC News|url=http://news.bbc.co.uk/1/hi/scotland/edinburgh_and_east/7254522.stm
|access-date= April 9, 2008 | date=February 20, 2008
}}</ref> The [[Indus river dolphin]] has a sleep method that is different from that of other dolphin species. Living in water with strong currents and potentially dangerous floating debris, it must swim continuously to avoid injury. As a result, this species sleeps in very short bursts which last between 4 and 60 seconds.<ref>{{cite book |first1=G. Neil |last1=Martin |first2= Neil R. |last2=Carlson |first3=William |last3=Buskist |year=1997|url={{google books|plainurl=y|id=j4XE89_3vj8C}} |title=Psychology, third edition |publisher=Pearson Allyn & Bacon |page=383 |isbn=978-0-273-71086-8}}</ref>
===Feeding===
There are various feeding methods among and within 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. Orcas on occasion also hunt whale species larger than themselves.<ref name="FactsDiet">{{Cite web|url=http://www.whalefacts.org/dolphins-diet/|archive-url=https://web.archive.org/web/20130927175656/http://www.whalefacts.org/dolphins-diet/|url-status= dead|title=Dolphin's diet|archive-date=September 27, 2013}}</ref> Different breeds of dolphins vary widely in the number of teeth they possess. The orca usually carries 40–56 teeth while the popular bottlenose dolphin has anywhere from 72 to 116 conical teeth and its smaller cousin the common dolphin has 188–268 teeth: the number of teeth that an individual carries varies widely between within a single species. Hybrids between common and bottlenose bred in captivity had a number of teeth intermediate between that of their parents.
One common feeding method is herding, where a pod squeezes a school of fish into a small volume, known as a [[bait ball]]. Individual members then take turns plowing through the ball, feeding on the stunned fish.<ref name=FactsDiet /> Corralling is a method where dolphins chase fish into shallow water to catch them more easily.<ref name=FactsDiet /> Orcas and bottlenose dolphins have also been known to drive their prey onto a beach to feed on it, a behaviour known as beach or strand feeding.<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 – 14 September 1993
|url=http://www.nmfs.noaa.gov/pr/pdfs/species/coastalbottlenosestock.pdf
|author=U.S. Department of Commerce National Oceanic and Atmospheric Administration National Marine Fisheries Service
|pages=56–57}}</ref><ref>Gregory K. Silber, Dagmar Fertl (1995) – ''Intentional beaching by bottlenose dolphins (Tursiops truncatus) in the Colorado River Delta, Mexico.''</ref> Some species also whack fish with their flukes, stunning them and sometimes knocking them out of the water.<ref name=FactsDiet />
Reports of cooperative human-dolphin fishing date back to the [[ancient Rome|ancient Roman]] author and [[natural philosophy|natural philosopher]] [[Pliny the Elder]].<ref>{{cite journal
|title= Variability in the diet of bottlenose dolphin, ''Tursiops truncatus'', in Galician waters, north-western Spain, 1990–2005
|author1=M.B. Santos |author2=R. Fernández |author3=A. López |author4=J.A. Martínez |author5=G.J. Pierce |s2cid=85767272 |year=2007
|doi=10.1017/S0025315407055233
|journal= Journal of the Marine Biological Association of the UK
|volume= 87
|issue=1 |page= 231|bibcode=2007JMBUK..87..231S }}</ref> A modern human-dolphin partnership currently operates in [[Laguna, Santa Catarina|Laguna]], Santa Catarina, Brazil. Here, dolphins drive fish towards fishermen waiting along the shore and signal the men to cast their nets. The dolphins' reward is the fish that escape the nets.<ref>{{Cite news
|title= Brazil's sexiest secret
|url=https://www.telegraph.co.uk/travel/southamerica/brazil/734722/Brazil%27s-sexiest-secret.html
|archive-url=https://web.archive.org/web/20080313043242/http://www.telegraph.co.uk/travel/southamerica/brazil/734722/Brazil%27s-sexiest-secret.html
|archive-date=March 13, 2008
|access-date= March 11, 2007
| work=The Daily Telegraph
| ___location=London
|url-status= dead
| date=March 8, 2006}}</ref><ref>{{cite web
|title= Bottlenose Dolphins in Laguna Requesting a Throw Net Supporting material for Dr. Nissani's presentation at the 2007 International Ethological Conference
|author= Moti Nissani
|website= [[YouTube]]
|year=2007
|url=https://www.youtube.com/watch?v=ECk0yMifmzw
| archive-url=https://ghostarchive.org/varchive/youtube/20211211/ECk0yMifmzw| archive-date=2021-12-11 | url-status=live|access-date=February 13, 2008}}{{cbignore}}</ref>
In [[Shark Bay]], Australia, dolphins catch fish by trapping them in huge [[conch|conch shell]]s.<ref>{{cite web|last=Hunt|first=Katie|title=Dolphins are learning smart fish-catching trick from peers, not mothers|url=https://www.cnn.com/2020/06/25/world/dolphins-tools-shell-learning-scn/index.html|date=June 25, 2020|access-date=June 25, 2020|work=CNN}}</ref> In "shelling", a dolphin brings the shell to the surface and shakes it, so that fish sheltering within fall into the dolphin's mouth. From 2007 to 2018, in 5,278 encounters with dolphins, researchers observed 19 dolphins shelling 42 times. The behavior spreads mainly within generations, rather than being passed from mother to offspring.
===Vocalization===
[[File:Dolphin1.jpg|thumb|upright=1.35|[[Spectrogram]] of dolphin vocalizations. Whistles, whines, and clicks are visible as upside down V's, horizontal striations, and vertical lines, respectively.]]
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 |url-status = dead }}</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 name="Au2012">{{cite book|last=Au|first=Whitlow W.L.|title=The Sonar of Dolphins|url={{google books |plainurl=y |id=NEXTBwAAQBAJ}}|date=December 6, 2012|publisher=Springer Science & Business Media|isbn=978-1-4612-4356-4}}</ref>
Bottlenose dolphins have been found to have signature whistles, a whistle that is unique to a specific individual. 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' |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=May 7, 2013|volume=199|issue=6|pages=479–489|doi=10.1007/s00359-013-0817-7|pmid=23649908|s2cid=15378374}}<!--|access-date=January 30, 2014--></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 distinguishing.<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 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>
Because dolphins generally associate in groups, communication is necessary. Signal masking is when other similar sounds (conspecific sounds) interfere with the original acoustic sound.<ref>{{cite journal|last=Quick|first=Nicola|author2=Vincent Janik|title=Whistle Rates of Wild Bottlenose Dolphins (''Tursiops truncatus''): Influences of Group Size and Behavior|journal=Journal of Comparative Psychology|year=2008|volume=122|issue=3|pages=305–311|doi=10.1037/0735-7036.122.3.305|pmid=18729659}}<!--|access-date=January 27, 2014--></ref> In larger groups, individual whistle sounds are less prominent. Dolphins tend to travel in pods, upon which there are groups of dolphins that range from a few to many. Although they are traveling in these pods, the dolphins do not necessarily swim right next to each other. Rather, they swim within the same general vicinity. In order to prevent losing one of their pod members, there are higher whistle rates. Because their group members were spread out, this was done in order to continue traveling together.
===Jumping and playing===
[[File:PacificWhiteSidedDolphine.jpg|thumb|Pacific white-sided dolphins porpoising.]]
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>David Lusseau (2006), ''Why do dolphins jump? Interpreting the behavioural repertoire of bottlenose dolphins (Tursiops sp.) in Doubtful Sound, New Zealand''</ref><ref>Corey Binns – LiveScience (2006), [http://www.livescience.com/678-dolphins-spin.html How Dolphins Spin, and Why], article. Retrieved September 8, 2013.</ref>
Dolphins show various types of 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 name=dolphinplay>Robin D. Paulos (2010), ''Play in Wild and Captive Cetaceans''</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=August 2, 2010 |archive-url=https://web.archive.org/web/20100610140808/http://faculty.vetmed.ucdavis.edu/faculty/bjmccowan/Pubs/McCowanetal.JCP.2000.pdf |archive-date=June 10, 2010 |url-status=dead |df=mdy-all }}</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=dolphinplay /> 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=dolphinplay /> Playful behaviour that involves another animal species with active participation of the other animal has also been observed. Playful dolphin interactions with humans are the most obvious examples, followed by those with [[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>Cathy Hayes for Irish Central (2011), [http://www.irishcentral.com/news/Amazing-footage-of-a-dog-playing-with-a-dolphin-off-the-coast-of-Ireland--VIDEO-127888298.html Amazing footage of a dog playing with a dolphin off the coast of Ireland], article. Retrieved September 8, 2013.</ref>
Juvenile dolphins off the coast of Western Australia have been observed chasing, capturing, and chewing on [[blowfish]].<ref>{{cite news|last1=Staff writers|title='Puff, puff, pass': How WA's dolphins are using blowfish to get high|url=http://www.watoday.com.au/wa-news/puff-puff-pass-how-was-dolphins-using-blowfish-to-get-high-20170208-gu86nv.html|access-date=June 9, 2017|work=WAToday|issue=February 8, 2017|date=February 8, 2017}}</ref> While some reports state that the dolphins are becoming intoxicated on the [[tetrodotoxin]] in the fishes' skin,<ref>{{cite magazine|url=https://www.vice.com/en/article/apparently-dolphins-in-australia-like-to-get-stoned-by-chewing-on-toxic-blowfish-vgtrn/|title=Apparently Dolphins in Australia Like to Get Stoned by Chewing on Toxic Blowfish|magazine=Vice|first=Brian|last=Moylan|date=February 10, 2017|access-date=April 6, 2017}}</ref> other reports have characterized this behavior as the normal curiosity and exploration of their environment in which dolphins engage.<ref>{{cite web|last1=Wilcox|first1=Christie|title=Do Stoned Dolphins Give 'Puff Puff Pass' A Whole New Meaning?|url=http://blogs.discovermagazine.com/science-sushi/2013/12/30/stoned-dolphins-give-puff-puff-pass-whole-new-meaning/|website=Science Sushi|publisher=Discover|access-date=June 9, 2017|date=December 30, 2013|archive-date=November 14, 2019|archive-url=https://web.archive.org/web/20191114073142/http://blogs.discovermagazine.com/science-sushi/2013/12/30/stoned-dolphins-give-puff-puff-pass-whole-new-meaning/|url-status=dead}}</ref>
===Tail-walking===
Although this behaviour is highly unusual in wild dolphins, several [[Indo-Pacific bottlenose dolphin]]s (''Tursiops aduncus'') of the [[Port River]], north of [[Adelaide]], [[South Australia]], have been seen to have exhibit "tail-walking".<ref name=dd2018/><ref name=study2018>{{cite journal|vauthors=Bossley M, Steiner A, Brakes P, Shrimpton J, Foster C, Rendell L |title=Tail walking in a bottlenose dolphin community: the rise and fall of an arbitrary cultural 'fad'. |journal= [[Biol. Lett.]] |date= September 2018 |volume= 14| issue=9| doi= 10.1098/rsbl.2018.0314| pmid= 30185606| pmc= 6170752}}</ref> This activity mimicks a standing posture, using the tail to run backwards along the water.<ref name=mess2018>{{cite web| url=https://www.adelaidenow.com.au/messenger/west-beaches/the-incredible-tale-of-billie-the-port-river-dolphin-the-worlds-first-wild-tailwalker/news-story/8cae9ccf3771a93e149cbd2e62fb1b27| website= [[Adelaide Now]]| title=The incredible tale of Billie the Port River dolphin — the world's first wild tailwalker| series= Portside Messenger | date=9 May 2018| first=Ashleigh |last=Pisani}}</ref> To perform this movement, the dolphin "forces the majority of its body vertically out of the water and maintains the position by vigorously pumping its tail".<ref name=study2018/>
This started in 1988 when a female named Billie was rescued after becoming trapped in a polluted [[marina]],<ref name="Sutton 2022">{{cite web | last=Sutton | first=Malcolm | title=Why are the dolphins dying? | website=ABC News| publisher= Australian Broadcasting Corporation | date=4 April 2022 | url=https://www.abc.net.au/news/2022-04-04/dolphin-deaths-mystery-adelaide-dolphin-sanctuary/100795994 | access-date=4 April 2022}}</ref> and spent two weeks recuperating with captive dolphins. Billie had previously been observed swimming and frolicking with [[racehorse]]s exercising in the Port River in the 1980s. After becoming trapped in a reedy estuary further down the coast, she was rescued and placed with several captive dolphins at a marine park to recuperate. There she observed the captive dolphins performing tail-walking.<ref name=mess2018/> After being returned to the Port River, she continued to perform this trick, and another dolphin, Wave, copied her. Wave, a very active tail-walker, passed on the skill to her daughters, Ripple and Tallula.<ref name=dd2018>{{cite web | title=Billie | website=Dolphin Dock | date=15 February 2018 | url=https://www.dolphindock.com.au/meet-the-dolphins/billie/ | access-date=4 April 2022}}</ref>
After Billie's premature death, Wave started tail-walking much more frequently, and other dolphins in the group were observed also performing the behaviour.<ref name=study2018/> In 2011, up to 12 dolphins were observed tail-walking, but only females appeared to learn the skill.<ref name=gentside>{{cite web | title=The amazing story of Billie, the dolphin who taught her peers how to moonwalk | website=Gentside UK | date=15 October 2018 | url=https://www.gentside.co.uk/animal/the-amazing-story-of-billie-the-dolphin-who-taught-her-peers-how-to-moonwalk_art1800.html | access-date=4 April 2022}}</ref> In October 2021, a dolphin was observed tail-walking over a number of hours.<ref name="Sutton 2022"/>
Scientists have found the spread of this behaviour, through up to two generations, surprising, as it brings no apparent advantage, and is very energy-consuming.<ref name=gentside/> A 2018 study by Mike Rossley et al. suggested:<ref name=dd2018/>{{blockquote|Social learning is the most likely mechanism for the introduction and spread of this unusual behaviour, which has no known adaptive function. These observations demonstrate the potential strength of the capacity for spontaneous imitation in bottlenose dolphins, and help explain the origin and spread of foraging specializations observed in multiple populations of this genus.}}
==Threats==
[[File:Bottle-nosed-dolphin-Lobomycosis-disease.jpg|thumb|Lesions in the [[dorsum (anatomy)|dorsal]] fin of a bottlenose dolphin caused by [[lobomycosis]], a [[mycosis|fungal infection]] of the skin.]]
Dolphins have few marine enemies. Some species or specific populations have none, making them [[apex predator]]s. For most of the smaller species of dolphins, only a few of the larger sharks, such as the [[bull shark]], [[dusky shark]], [[tiger shark]] and [[great white shark]], are a potential risk, especially for calves.<ref>Michael R. Heithaus (1999), ''Predator-prey and competitive interactions between sharks (order Selachii) and dolphins (parvorder Odontoceti): a review''</ref> Some of the larger dolphin species, especially [[orcas]], may also prey on smaller dolphins, but this seems rare.<ref>[[Nadia Drake]] for WIRED (2013), [https://www.wired.com/2013/05/killer-whale-flips-dolphin/ Photographer Captures Stunning Killer Whale Attack on Dolphin], article. Retrieved March 14, 2022.</ref> Dolphins also suffer from a wide variety of diseases and parasites.<ref>{{cite journal | last1 = Bossart | first1 = G. D. | year = 2007 | title = Emerging diseases in marine mammals: from dolphins to manatees | url = http://www.marineland.net/images/pdfs/Bossart%20Emerging%20Dis.pdf | journal = Microbe | volume = 2 | issue = 11 | pages = 544–549 | url-status = dead | archive-url = https://web.archive.org/web/20140114091150/http://www.marineland.net/images/pdfs/Bossart%20Emerging%20Dis.pdf | archive-date = January 14, 2014 }}</ref><ref>{{cite journal|last=Woodard|first=J. C.|author2=Zam, S. G. |author3=Caldwell, D. K. |author4= Caldwell, M. C. |title=Some Parasitic Diseases of Dolphins|journal=Veterinary Pathology|year=1969|volume=6|issue=3|pages=257–272|doi=10.1177/030098586900600307|pmid=5817449|s2cid=26842976|doi-access=free}}</ref> The [[Cetacean morbillivirus]] in particular has been known to cause regional [[epizootics]] often leaving hundreds of animals of various species dead.<ref>{{Cite journal | last1 = Bellière | first1 = E. N. | last2 = Esperón | first2 = F. | last3 = Sánchez-Vizcaíno | first3 = J. M. | doi = 10.1016/j.meegid.2011.08.018 | title = Genetic comparison among dolphin morbillivirus in the 1990–1992 and 2006–2008 Mediterranean outbreaks | journal = Infection, Genetics and Evolution | volume = 11 | issue = 8 | pages = 1913–1920 | year = 2011 | pmid = 21888991 | bibcode = 2011InfGE..11.1913B }}</ref><ref>Jane J. Lee for [[National Geographic Society|National Geographic]] (2013), [https://www.nationalgeographic.com/?rptregcta=reg_free_np&rptregcampaign=20131016_rw_membership_r1p_us_se_w What's Killing Bottlenose Dolphins? Experts Discover Cause.], article. Retrieved December 4, 2013.</ref> Symptoms of infection are often a severe combination of [[pneumonia]], [[encephalitis]] and damage to the immune system, which greatly impair the cetacean's ability to swim and stay afloat unassisted.<ref name=mass >{{Cite journal | last1 = Guardo | first1 = G. D. | last2 = Marruchella | first2 = G. | last3 = Agrimi | first3 = U. | last4 = Kennedy | first4 = S. | title = Morbillivirus Infections in Aquatic Mammals: A Brief Overview | doi = 10.1111/j.1439-0442.2005.00693.x | journal = Journal of Veterinary Medicine, Series A | volume = 52 | issue = 2 | pages = 88–93 | year = 2005 | pmid = 15737178 | hdl = 11575/80640 | hdl-access = free }}</ref><ref name=austurs>{{Cite journal | last1 = Stone | first1 = B. M. | last2 = Blyde | first2 = D. J. | last3 = Saliki | first3 = J. T. | last4 = Blas-Machado | first4 = U. | last5 = Bingham | first5 = J. | last6 = Hyatt | first6 = A. | last7 = Wang | first7 = J. | last8 = Payne | first8 = J. | last9 = Crameri | first9 = S. | doi = 10.1111/j.1751-0813.2011.00849.x | title = Fatal cetacean morbillivirus infection in an Australian offshore bottlenose dolphin (Tursiops truncatus) | journal = Australian Veterinary Journal | volume = 89 | issue = 11 | pages = 452–457 | year = 2011 | pmid = 22008125 | doi-access = free }}</ref> A study at the U.S. National Marine Mammal Foundation revealed that dolphins, like humans, develop a natural form of [[Diabetes mellitus|type 2 diabetes]] which may lead to a better understanding of the disease and new treatments for both humans and dolphins.<ref>{{cite web|url=http://nmmpfoundation.org/pressrelease.htm|archive-url=https://web.archive.org/web/20100411081512/http://nmmpfoundation.org/pressrelease.htm|archive-date=April 11, 2010|date=February 18, 2010 |title=Scientists Find Clues in Dolphins to Treat Diabetes in Humans |author=US National Marine Mammal Foundation |access-date=February 20, 2010}}</ref>
Dolphins can tolerate and recover from extreme injuries such as [[shark]] bites although the exact methods used to achieve this are not known. The [[healing]] process is rapid and even very deep wounds do not cause dolphins to [[hemorrhage]] to death. Furthermore, even gaping wounds restore in such a way that the animal's body shape is restored, and infection of such large wounds seems rare.<ref>{{cite web |url=http://explore.georgetown.edu/news/?ID=57991&PageTemplateID=295 |title=Dolphins' "Remarkable" Recovery from Injury Offers Important Insights for Human Healing |author=Georgetown University Medical Center |access-date=July 26, 2011 |url-status=dead |archive-url=https://web.archive.org/web/20111205105601/http://explore.georgetown.edu/news/?ID=57991&PageTemplateID=295 |archive-date=December 5, 2011 |author-link=Georgetown University Medical Center }}</ref>
A study published in the journal ''Marine Mammal Science'' suggests that at least some dolphins survive shark attacks using everything from sophisticated combat moves to teaming up against the shark.<ref>{{Cite news|url=http://www.seeker.com/shark-vs-dolphin-battles-can-have-surprising-outcomes-1768940807.html|title=Shark vs. Dolphin Battles Can Have Surprising Outcomes|last=Viegas|first=Jen|date=August 14, 2014|newspaper=Seeker – Science. World. Exploration. Seek for yourself.|access-date=November 27, 2016}}</ref><ref>{{cite web|url=http://animalquestions.org/mammals/dolphins/can-dolphins-kill-sharks/|title=Can Dolphins Kill Sharks?|date=December 2, 2011|website=animalquestions.org}}</ref><ref>{{cite web|url=http://www.elasmo-research.org/education/topics/b_corner.htm|title=Do dolphins really beat up sharks?|publisher=ReefQuest Centre for Shark Research}}</ref>
===Humans===
{{See also|Dolphin drive hunting|Cetacean bycatch}}
[[File:Whaling in the Faroe Islands.jpg|thumb|Dead Atlantic white-sided dolphins in [[Hvalba]] on the [[Faroe Islands]], killed in a [[dolphin drive hunting|drive hunt]].|alt=Rows of dead dolphin lying on concrete]]
Some dolphin species are at risk of extinction, especially some river dolphin species such as the Amazon river dolphin, and the [[Ganges river dolphin|Ganges]] and [[Baiji|Yangtze river dolphin]], which are critically or seriously endangered. A 2006 survey found no individuals of the Yangtze river dolphin. The species now appears to be [[functionally extinct]].<ref>{{cite web |title= Yangtze dolphin may be extinct |author=Douglas Williams for Shanghai Daily |date=December 4, 2006 |url=http://english.cri.cn/3100/2006/12/04/63@170330.htm |archive-url=https://web.archive.org/web/20180114073844/http://english.cri.cn/3100/2006/12/04/63@170330.htm |url-status=dead |archive-date=January 14, 2018 |access-date=January 13, 2018}}</ref>
[[Pesticides]], heavy metals, plastics, and other industrial and agricultural pollutants that do not disintegrate rapidly in the environment concentrate in predators such as dolphins.<ref>{{cite web|first=Stephen R. |last=Palumbi |author-link=Stephen Palumbi |url=https://www.youtube.com/watch?v=ooAIIeo4AJQ&feature=youtube_gdata | archive-url=https://ghostarchive.org/varchive/youtube/20211211/ooAIIeo4AJQ| archive-date=2021-12-11 | url-status=live|title=TED: Stephen Palumbi: Following the mercury trail |via=YouTube |date=June 30, 2010 |access-date=July 25, 2011}}{{cbignore}}</ref> Injuries or deaths due to collisions with boats, especially their [[propeller]]s, are also common.
Various fishing methods, most notably purse [[seine fishing]] for [[tuna]] and the use of [[drift net|drift]] and [[gill net]]s, unintentionally kill many dolphins.<ref name="Clover2008">{{cite book|last=Clover|first=Charles|title=The End of the Line: How Overfishing is Changing the World and what We Eat|url={{google books |plainurl=y |id=OMY-gEKMod8C}}|year=2008|publisher=University of California Press|isbn=978-0-520-25505-0}}</ref> Accidental [[by-catch]] in gill nets and incidental captures in antipredator nets that protect marine fish farms are common and pose 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| bibcode=2006ICJMS..63..946D
| doi-access=free
}}</ref> In some parts of the world, such as [[Taiji, Wakayama|Taiji]] in Japan and the [[Faroe Islands]], dolphins are traditionally considered food and are killed in [[harpoon]] or [[dolphin drive hunting|drive hunts]].<ref name="auto">
{{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
|work = [[Japan Times]]
|date = September 23, 2009
|page = 3
|url-status = dead
|archive-url = https://web.archive.org/web/20090927022232/http://search.japantimes.co.jp/cgi-bin/nn20090923f1.html
|archive-date = September 27, 2009
}}</ref> Dolphin meat is high in mercury and may thus pose a health danger to humans 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
|work=[[Japan Times]]
|date=September 23, 2009
|page=3
}}</ref>
[[Queensland|Queensland's]] [[shark culling]] program, which has killed roughly 50,000 sharks since 1962, has also killed thousands of dolphins as bycatch.<ref>{{cite web| url = https://www.news.com.au/technology/science/animals/aussie-shark-population-is-staggering-decline/news-story/49e910c828b6e2b735d1c68e6b2c956e| title = Aussie shark population in staggering decline. Rhian Deutrom. December 14, 2018. Retrieved December 26, 2018.}}</ref><ref name="afd_cull"/> "Shark control" programs in both Queensland and [[New South Wales]] use [[shark nets]] and [[drum line (shark control)|drum lines]], which entangle and kill dolphins.<ref>{{cite web |url = https://www.marineconservation.org.au/pages/shark-culling.html |title = "Shark Culling". marineconservation.org.au. Archived from the original on 2018-10-02. Retrieved December 26, 2018. |archive-url=https://web.archive.org/web/20181002102324/https://www.marineconservation.org.au/pages/shark-culling.html |archive-date=2 October 2018 |url-status=dead}}</ref> Queensland's "shark control" program has killed more than 1,000 dolphins in recent years,<ref name="afd_cull">{{cite web| url = http://www.afd.org.au/news-articles/queenslands-shark-control-program-has-snagged-84000-animals| title = Action for Dolphins. Queensland's Shark Control Program Has Snagged 84,000 Animals. Thom Mitchell. November 20, 2015. Retrieved December 26, 2018.| date = May 12, 2023}}</ref> and at least 32 dolphins have been killed in Queensland since 2014.<ref>{{cite web| url = https://hsi.org.au/blog/separating-fact-from-fiction-in-qlds-shark-culling-program| title = ''Separating fact from fiction in QLD's shark culling program.'' Nicola Beynon. October 19, 2018. Retrieved December 26, 2018| date = October 19, 2018}}</ref> A [[shark culling]] program in [[KwaZulu-Natal]] has killed at least 2,310 dolphins.<ref>{{cite web| url = http://www.sharkangels.org/index.php/media/news/157-shark-nets| title = "Shark Nets". sharkangels.org. Retrieved December 26, 2018.}}</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=August 29, 2015 |url-status=dead |archive-url=https://web.archive.org/web/20151015221118/http://www.atuna.com/NewsArchive/ViewArticle.asp?ID=12719 |archive-date=October 15, 2015}}</ref>
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
|publisher=CBC News
|date=October 9, 2003}}</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=July 22, 2007
|access-date= October 27, 2008}}</ref>
Dolphins and other smaller cetaceans are also hunted in an activity known as dolphin drive hunting. This is accomplished by driving a pod together with boats and usually into a bay or onto a beach. Their escape is prevented by closing off the route to the ocean with other boats or nets. Dolphins are hunted this way in several places around the world, including the [[Solomon Islands]], the [[Faroe Islands]], [[Peru]], and Japan, the most well-known practitioner of this method. By numbers, dolphins are mostly hunted for their [[whale meat|meat]], though some end up in [[dolphinarium]]s. Despite the controversial nature of the hunt resulting in international criticism, and the possible health risk that the often polluted meat causes, thousands of dolphins are caught in drive hunts each year.
=== Impacts of climate change ===
{{See also|Effects of climate change on oceans}}
Dolphins are marine mammals with broad geographic extent, making them susceptible to climate change in various ways. The most common effect of climate change on dolphins is the increasing water temperatures across the globe.<ref name="Evans-2013-2">{{Cite journal |last1=Evans |first1=Peter G.H. |last2=Bjørge |first2=Arne |date=November 28, 2013 |title=Impacts of climate change on marine mammals |url=https://www.seawatchfoundation.org.uk/wp-content/uploads/2015/05/Evans-Bj%C3%B8rge_2013.pdf |journal=MCCIP Science Review 2013}}</ref> This has caused a large variety of dolphin species to experience range shifts, in which the species move from their typical geographic region to cooler waters.<ref name="Würsig-2001"/><ref name="auto1">{{Cite journal |last1=Salvadeo |first1=CJ |last2=Lluch-Belda |first2=D |last3=Gómez-Gallardo |first3=A |last4=Urbán-Ramírez |first4=J |last5=MacLeod |first5=CD |date=2010-03-10 |title=Climate change and a poleward shift in the distribution of the Pacific white-sided dolphin in the northeastern Pacific |url=https://www.int-res.com/abstracts/esr/v11/n1/p13-19/ |journal=Endangered Species Research |language=en |volume=11 |issue=1 |pages=13–19 |doi=10.3354/esr00252 |issn=1863-5407 |doi-access=free}}</ref> Another side effect of increasing water temperatures is the increase in [[Harmful algal bloom|harmful algae blooms]], which has caused a mass die-off of bottlenose dolphins.<ref name="Evans-2013-2" />
In [[California]], the 1982–83 [[El Niño]] warming event caused the near-bottom spawning [[market squid]] to leave southern California, which caused their predator, the [[pilot whale]], to also leave. As the market squid returned six years later, [[Risso's dolphin|Risso's dolphins]] came to feed on the squid. [[Bottlenose dolphin|Bottlenose dolphins]] expanded their range from southern to central California, and stayed even after the warming event subsided.<ref name="Würsig-2001">{{Citation |last1=Würsig |first1=Bernd |title=Global Climate Change and Marine Mammals |date=2001 |url=https://doi.org/10.1007/978-1-4615-0529-7_17 |work=Marine Mammals: Biology and Conservation |pages=589–608 |editor-last=Evans |editor-first=Peter G. H. |place=Boston, MA |publisher=Springer US |language=en |doi=10.1007/978-1-4615-0529-7_17 |isbn=978-1-4615-0529-7 |access-date=2021-05-01 |last2=Reeves |first2=Randall R. |last3=Ortega-Ortiz |first3=J. G. |editor2-last=Raga |editor2-first=Juan Antonio|url-access=subscription }}</ref> The [[Pacific white-sided dolphin]] has had a decline in population in the southwest [[Gulf of California]], the southern boundary of their distribution. In the 1980s they were abundant with group sizes up to 200 across the entire cool season. Then, in the 2000s, only two groups were recorded with sizes of 20 and 30, and only across the central cool season. This decline was not related to a decline of other marine mammals or prey, so it was concluded to have been caused by climate change as it occurred during a period of warming. Additionally, the Pacific white-sided dolphin had an increase in occurrence on the west coast of [[Canada]] from 1984 to 1998.<ref name="auto1"/>
In the [[Mediterranean]], [[Sea surface temperature|sea surface temperatures]] have increased, as well as [[salinity]], [[upwelling]] intensity, and sea levels. Because of this, prey resources have been reduced causing a steep decline in the [[short-beaked common dolphin]] Mediterranean subpopulation, which was deemed endangered in 2003. This species now only exists in the [[Alboran Sea]], due to its high productivity, distinct ecosystem, and differing conditions from the rest of the Mediterranean.<ref>{{Cite journal |last1=Cañadas |first1=A. |last2=Vázquez |first2=J.A. |date=2017-07-01 |title=Common dolphins in the Alboran Sea: Facing a reduction in their suitable habitat due to an increase in Sea surface temperature |journal=Deep Sea Research Part II: Topical Studies in Oceanography |language=en |volume=141 |pages=306–318 |bibcode=2017DSRII.141..306C |doi=10.1016/j.dsr2.2017.03.006 |issn=0967-0645 |doi-access=free}}</ref>
In northwest Europe, many dolphin species have experienced range shifts from the region's typically colder waters. Warm water dolphins, like the short-beaked common dolphin and [[striped dolphin]], have expanded north of western Britain and into the northern [[North Sea]], even in the winter, which may displace the [[White-beaked dolphin|white-beaked]] and [[Atlantic white-sided dolphin]] that are in that region. The white-beaked dolphin has shown an increase in the southern North Sea since the 1960s because of this. The [[rough-toothed dolphin]] and [[Atlantic spotted dolphin]] may move to northwest Europe.<ref name="Evans-2013-2"/> In northwest [[Scotland]], white-beaked dolphins (local to the colder waters of the North Atlantic) have decreased while common dolphins (local to warmer waters) have increased from 1992 to 2003.<ref>{{Cite journal |last1=MacLeod |first1=Colin D. |last2=Bannon |first2=Sarah M. |last3=Pierce |first3=Graham J. |last4=Schweder |first4=Caroline |last5=Learmonth |first5=Jennifer A. |last6=Herman |first6=Jerry S. |last7=Reid |first7=Robert J. |date=2005-08-01 |title=Climate change and the cetacean community of north-west Scotland |url=https://www.sciencedirect.com/science/article/abs/pii/S0006320705000789 |journal=Biological Conservation |language=en |volume=124 |issue=4 |pages=477–483 |doi=10.1016/j.biocon.2005.02.004 |bibcode=2005BCons.124..477M |issn=0006-3207|url-access=subscription }}</ref> Additionally, [[Fraser's dolphin]], found in tropical waters, was recorded in the UK for the first time in 1996.<ref name="Evans-2013-2"/>
[[River dolphin|River dolphins]] are highly affected by climate change as high evaporation rates, increased water temperatures, decreased precipitation, and increased [[Ocean acidification|acidification]] occur.<ref name="Würsig-2001" /><ref name="Gomez-Salazar-2012">{{Cite journal |last1=Gomez-Salazar |first1=Catalina |last2=Coll |first2=Marta |last3=Whitehead |first3=Hal |date=2012-12-01 |title=River dolphins as indicators of ecosystem degradation in large tropical rivers |url=https://www.sciencedirect.com/science/article/abs/pii/S1470160X12000805 |journal=Ecological Indicators |language=en |volume=23 |pages=19–26 |doi=10.1016/j.ecolind.2012.02.034 |bibcode=2012EcInd..23...19G |issn=1470-160X|url-access=subscription }}</ref> River dolphins typically have a higher densities when rivers have a lox index of freshwater degradation and better water quality. {{Explain|date=April 2025}}<ref name="Gomez-Salazar-2012" /> Specifically looking at the [[Ganges river dolphin]], the high evaporation rates and increased flooding on the plains may lead to more human river regulation, decreasing the dolphin population.<ref name="Würsig-2001" />
As warmer waters lead to a decrease in dolphin prey, this led to other causes of dolphin population decrease. In the case of bottlenose dolphins, [[Mullet (fish)|mullet]] populations decrease due to increasing water temperatures, which leads to a decrease in the dolphins' health and thus their population.<ref name="Würsig-2001" /> At the Shark Bay World Heritage Area in Western Australia, the local [[Indo-Pacific bottlenose dolphin]] population had a significant decline after a marine heatwave in 2011. This heatwave caused a decrease in prey, which led to a decline in dolphin reproductive rates as female dolphins could not get enough nutrients to sustain a calf.<ref>{{Cite journal |last1=Wild |first1=Sonja |last2=Krützen |first2=Michael |last3=Rankin |first3=Robert W. |last4=Hoppitt |first4=William J.E. |last5=Gerber |first5=Livia |last6=Allen |first6=Simon J. |date=2019-04-01 |title=Long-term decline in survival and reproduction of dolphins following a marine heatwave |journal=Current Biology |language=en |volume=29 |issue=7 |pages=R239–R240 |doi=10.1016/j.cub.2019.02.047 |issn=0960-9822 |pmid=30939303 |doi-access=free|bibcode=2019CBio...29.R239W |hdl=1983/1a397eb9-1713-49b5-a2fb-f0d7c747e724 |hdl-access=free }}</ref> The resultant decrease in fish population due to warming waters has also influenced humans to see dolphins as fishing competitors or even bait. Humans use [[Dusky dolphin|dusky dolphins]] as bait or are killed off because they consume the same fish humans eat and sell for profit.<ref name="Würsig-2001" /> In the central Brazilian Amazon alone, approximately 600 [[Pink River Dolphin|pink river dolphins]] are killed each year to be used as bait.<ref name="Gomez-Salazar-2012" />
==Relationships with humans==
===In history and religion===
[[File:Akrotiri dolphins.jpg|thumb|Fresco of dolphins, c. 1600 BC, from [[Knossos]], [[Crete]]]]
[[File:Silver stater from Tarentum from 290-280 BC.jpg|thumb|Silver stater from [[Taranto|Tarentum]] c. 290 BC showing Phalanthos riding a dolphin on one side and a rider with a shield decorated with a dolphin on the other side]]
[[File:Vessel in form of killer whale - Nazca pottery in the American Museum of Natural History - DSC06105.JPG|thumb|Vessel in form of [[orca]], [[Nazca culture]], circa 200 AD. [[American Museum of Natural History]] collections.]]
Dolphins have long played a role in human culture.
In [[Greek mythology|Greek myths]], dolphins 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]]. During the 2009 excavations of a major [[Mycenaean Greece|Mycenaean]] city at [[Iklaina]], a striking fragment of a wall painting came to light, depicting a ship with three human figures and dolphins. 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 |archive-url=https://web.archive.org/web/20070208015112/http://dougsmith.ancients.info/feac50tar.html |archive-date=February 8, 2007 |title=Taras |access-date=October 3, 2010}}</ref> The [[Ancient Greece|Ancient Greeks]] welcomed dolphins; spotting dolphins riding in a ship's wake was considered a good omen.<ref name="Eyers2012">{{cite book|last=Eyers|first=Jonathan|title=Don't Shoot the Albatross!: Nautical Myths and Superstitions|url={{google books |plainurl=y |id=b0fM9aimdooC}}|date=December 3, 2012|publisher=Bloomsbury Publishing|isbn=978-1-4081-3213-5}}</ref> In both ancient and later art, [[Cupid]] is often shown [[Cupid#Cupid and dolphins|riding a dolphin]]. [[Delphinus|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>
The Greeks reimagined the [[Phoenicia]]n god [[Melqart]] as Melikertês ([[Melicertes]]) and made him the son of [[Athamas]] and [[Ino (Greek mythology)|Ino]]. He drowned but was transfigured as the marine deity Palaemon, while his mother became [[Leucothea]]. (''cf'' [[Ino (Greek mythology)|Ino]].) At Corinth, he was so closely connected with the cult of Poseidon that the [[Isthmian Games]], originally instituted in Poseidon's honor, came to be looked upon as the funeral games of [[Melicertes]]. [[Phalanthus of Tarentum|Phalanthus]] was another legendary character brought safely to shore (in Italy) on the back of a dolphin, according to [[Pausanias (geographer)|Pausanias]].
[[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]].
"Dolfin" was the name of an aristocratic family in the maritime [[Republic of Venice]], whose most prominent member was the 13th-century [[Doge of Venice|Doge]] [[Giovanni Dolfin]].
In [[Hindu mythology]] the [[Ganges river dolphin]] is associated with [[Ganga in Hinduism|Ganga]], the deity of the [[Ganges]] river. The dolphin is said to be among the creatures which heralded the goddess' descent from the heavens and her mount, the [[Makara (Hindu mythology)|Makara]], is sometimes depicted as a dolphin.<ref name="Singh1997">{{cite book|last=Singh|first=Vijay |title=The River Goddess|url={{google books |plainurl=y |id=VKEKAAAACAAJ}}|year=1997|publisher=Creative Education|isbn=978-0-88682-825-7}}</ref>
The [[Boto]], a species of [[river dolphin]] that resides in the [[Amazon River]], are believed to be shapeshifters, or ''[[Encantado (mythology)|encantado]]s'', who are capable of having children with human women.
There are comparatively few surviving myths of dolphins in [[Polynesia]]n cultures, in spite of their maritime traditions and reverence of other marine animals such as [[sharks]] and [[seabirds]]; unlike these, they are more often perceived as food than as totemic symbols. Dolphins are most clearly represented in [[Rapa Nui]] [[Rongorongo]], and in the traditions of the [[Caroline Islands]] they are depicted similarly to the Boto, being sexually active shapeshifters.<ref>{{cite web |last1=Cressey |first1=Jason |title=Making a Splash in the Pacific: Dolphin and Whale Myths and Legends of Oceania |url=http://islandheritage.org/wordpress/wp-content/uploads/2010/06/RNJ_12_3_Cressey.pdf |website=islandheritage.org |publisher=The POD-People, Oceans, Dolphins (Vancouver, Canada) |access-date=October 19, 2018 |date=September 1998 |archive-date=November 20, 2018 |archive-url=https://web.archive.org/web/20181120050556/http://islandheritage.org/wordpress/wp-content/uploads/2010/06/RNJ_12_3_Cressey.pdf |url-status=dead }}</ref>
====Heraldry====
{{main|Dolphin (heraldry)}}
[[File:Dauphin of Viennois Arms.svg|thumb|upright|Coat of arms of the [[Dauphiné]], France, featuring a stylised heraldic dolphin]]
Dolphins are also used as symbols, for instance in heraldry. When heraldry developed in the [[Middle Ages]], little was known about the biology of the dolphin and it was often depicted as a sort of fish. The [[Dolphin (heraldry)|stylised heraldic dolphin]] still conventionally follows this tradition, sometimes showing the dolphin skin covered with [[fish scale]]s.
A well-known historical example was the coat of arms of the former province of the [[Dauphiné]] in southern France, from which were derived the arms and the title of the [[Dauphin of France]], the heir to the former throne of France (the title literally meaning "The Dolphin of France").
Dolphins are present in the [[coat of arms of Anguilla]] and the [[coat of arms of Romania]],<ref name="Hentea2007">{{cite book|last=Hentea|first=Călin|title=Brief Romanian Military History|url={{google books |plainurl=y |id=lwcWDFZWuJgC}}|year=2007|publisher=Scarecrow Press|isbn=978-0-8108-5820-6}}</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|year=1996|page=16|isbn=978-1-870518-54-3|publisher=Hansib Publications|___location=Hertford, UK}}</ref><ref name="Ali1996">{{cite book|last=Ali|first=Arif|title=Barbados: Just Beyond Your Imagination|url={{google books |plainurl=y |id=0k8sAQAAMAAJ|page=16}}|year=1996|page=16|publisher=Hansib|isbn=978-1-870518-54-3}}</ref>
The [[Coat of arms of Poole|coat of arms of the town of Poole]], Dorset, England, first recorded in 1563, includes a dolphin, which was historically depicted in stylised heraldic form, but which since 1976 has been depicted naturalistically.<ref>''Description of the coat of arms'', Borough of Poole information sheet, undated</ref>
===In captivity===
[[File:Sea World1.jpg|thumb|[[SeaWorld]] show featuring bottlenose dolphins and pilot whales.]]
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]]<ref>{{cite web|url=https://www.atlantisthepalm.com/marine-water-park/dolphin-bay|author=Atlantis: The Palm, Dubai|title=Swim With the Dolphins in Dubai|work=atlantisthepalm.com|access-date=March 11, 2016|archive-date=March 12, 2016|archive-url=https://web.archive.org/web/20160312075249/https://www.atlantisthepalm.com/marine-water-park/dolphin-bay|url-status=dead}}</ref> and the [[Dubai Dolphinarium]].<ref>{{cite web|url=http://www.dubaidolphinarium.ae/|author=Dubai Dolphinarium|title=The Dubai Dolphinarium|work= dubaidolphinarium.ae|access-date=March 11, 2016}}</ref>
[[File:Short-finned Pilot Whale (8793172995).jpg|thumb|[[SeaWorld San Diego]] pilot whale with trainers.]]
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.<ref>{{cite book|url=http://www.humanesociety.org/assets/pdfs/marine_mammals/case_against_marine_captivity.pdf|first1=Naoimi|last1=Rose|first2=E.C.M.|last2=Parsons|first3=Richard|last3=Farinato|title=The Case Against Marine Mammals in Captivity|edition=4|publisher=Humane Society of the United States|pages=13, 42, 43, 59|access-date=January 7, 2016|archive-date=September 30, 2018|archive-url=https://web.archive.org/web/20180930105929/http://www.humanesociety.org/assets/pdfs/marine_mammals/case_against_marine_captivity.pdf|url-status=dead}}</ref> An unusual and very rare [[Hybrid (biology)|hybrid]] dolphin, known as a [[wolphin]], is kept at the Sea Life Park in Hawaii, which is a cross between a bottlenose dolphin and a [[false killer whale]].<ref>{{cite newsgroup|author=[[Sean B. Carroll]] |title=Remarkable creatures |url=https://www.nytimes.com/2010/09/14/science/14creatures.html?src=me&ref=general |access-date=January 6, 2016}}</ref>
The number of [[orca]]s kept in captivity is very small, especially when compared to the number of bottlenose dolphins, with 60 [[List of captive orcas|captive orcas]] being held in aquaria {{As of|2017|lc=y}}.<ref>{{cite web|url=http://www.orcahome.de/orcastat.htm| title=Orcas in Captivity – A look at killer whales in aquariums and parks |date=November 23, 2009|access-date=September 6, 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 from Japan, and three from 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" />
Organizations such as the [[Mote Marine Laboratory]] rescue and [[Wildlife rehabilitation|rehabilitate]] sick, wounded, stranded or orphaned dolphins while others, such as the [[Whale and Dolphin Conservation]] and [[Hong Kong Dolphin Conservation Society]], work on dolphin conservation and welfare. [[India]] has declared the dolphin as its national aquatic animal in an attempt to protect the [[endangered species|endangered]] [[Ganges river dolphin]]. The [[Vikramshila Gangetic Dolphin Sanctuary]] has been created in the [[Ganges]] river for the protection of the animals.<ref>{{cite web|url=http://www.archive.india.gov.in/knowindia/national_symbols.php?id=8|title=National Aquatic Animal|author=india.gov|work=india.gov}}</ref>
====Military====
{{Main|Military dolphin}}
[[File:NMMP dolphin with locator.jpeg|thumb|upright|A military dolphin]]
A number of militaries have employed dolphins for various purposes from finding mines to rescuing lost or trapped humans. The [[military dolphins|military use of dolphins]] drew scrutiny during the Vietnam War, when rumors circulated that the [[United States Navy]] was training dolphins to kill Vietnamese divers.<ref>{{cite web
|title= The Story of Navy dolphins
|author=PBS – Frontline
|website=[[PBS]]
|url=https://www.pbs.org/wgbh/pages/frontline/shows/whales/etc/navycron.html
|access-date= June 8, 2008}}</ref> The United States Navy denies that at any point dolphins were trained for combat. Dolphins are still being trained by the United States Navy for other tasks as part of the [[U.S. Navy Marine Mammal Program]]. The Russian military is believed to have closed its marine mammal program in the early 1990s. In 2000 the press reported that dolphins trained to kill by the [[Soviet Navy]] had been sold to [[Iran]].<ref>{{cite news
|title= Iran buys kamikaze dolphins
|work=BBC News|url=http://news.bbc.co.uk/2/hi/world/middle_east/670551.stm
|access-date= June 7, 2008 | date=March 8, 2000}}</ref>
The military is also interested in disguising underwater communications as artificial dolphin clicks.<ref>{{cite news |last1=Hsu |first1=Jeremy |title=The Military Wants to Hide Covert Messages in Marine Mammal Sounds |url=https://www.hakaimagazine.com/news/the-military-wants-to-hide-covert-messages-in-marine-mammal-sounds/ |access-date=14 December 2020 |work=[[Hakai Magazine]] |date=10 December 2020}}</ref>
====Therapy====
Dolphins are an increasingly popular choice of [[animal-assisted therapy]] for psychological problems and developmental disabilities. For example, a 2005 study found dolphins an effective treatment for mild to moderate depression.<ref>{{cite journal
|title=Randomised controlled trial of animal facilitated therapy with dolphins in the treatment of depression
|year=2005
|jstor=25455488|pmc=1289317|pmid=16308382
|last1=Antonioli
|first1=C
|last2=Reveley
|first2=MA
|volume=331
|issue=7527
|pages=1231–1234
|doi=10.1136/bmj.331.7527.1231
|journal=BMJ (Clinical Research Ed.)}}</ref> This study was criticized on several grounds, including a lack of knowledge on whether dolphins are more effective than common pets.<ref>{{Cite journal
|journal= BMJ
|volume=331
|issue= 7529
|page=1407
|year=2005
|author1=Biju Basil |author2=Maju Mathews |title= Methodological concerns about animal-facilitated therapy with dolphins
|doi= 10.1136/bmj.331.7529.1407
|pmid= 16339258
|pmc= 1309662}}</ref> [[Review]]s of this and other published dolphin-assisted therapy (DAT) studies have found important methodological flaws and have concluded that there is no compelling scientific evidence that DAT is a legitimate therapy or that it affords more than fleeting mood improvement.<ref>{{Cite journal
|journal=Anthrozoös
|volume=20
|issue=3
|pages=239–49
|year=2007
|doi=10.2752/089279307X224782
|author1=Lori Marino
|author2=Scott O. Lilienfeld
|title=Dolphin-Assisted Therapy: more flawed data and more flawed conclusions
|url=http://www.marineconnection.org/docs/DAT%20Paper%202007.pdf
|access-date=February 20, 2008
|url-status=dead
|archive-url=https://web.archive.org/web/20080228025018/https://www.marineconnection.org/docs/DAT%20Paper%202007.pdf
|archive-date=February 28, 2008
|citeseerx=10.1.1.554.7777
|s2cid=6119940
}}</ref>
====Controversy====
{{See also|Captive orca}}
[[File:2009-Seaworld-Shamu.jpg|thumb|[[Shamu]] in 2009, with a collapsed dorsal fin.]]
There is debate over the welfare of cetaceans in captivity, and often welfare can vary greatly dependent on the levels of care being provided at a particular facility. In the United States, facilities are regularly inspected by federal agencies to ensure that a high standard of welfare is maintained.{{citation needed|date=March 2018}} Additionally, facilities can apply to become accredited by the Association of Zoos and Aquariums (AZA), which (for accreditation) requires "the highest standards of animal care and welfare in the world" to be achieved. Facilities such as SeaWorld and the Georgia Aquarium are accredited by the AZA. Organizations such as [[World Animal Protection]] and the [[Whale and Dolphin Conservation]] campaign against the practice of keeping them in captivity. In captivity, they often develop pathologies, such as the [[dorsal fin]] collapse seen in 60–90% of male orca. Captives have vastly reduced life expectancies, on average only living into their 20s, although there are examples of orcas living longer, including several over 30 years old, and two captive orcas, Corky II and Lolita, are in their mid-40s. In the wild, females who survive infancy live 46 years on average, and up to 70–80 years in rare cases. Wild males who survive infancy live 31 years on average, and up to 50–60 years.{{Unreliable sources|date=March 2024}}<ref>{{cite web|author=Rose, N. A.|year=2011|url=http://www.hsi.org/assets/pdfs/orca_white_paper.pdf|title=Killer Controversy: Why Orcas Should No Longer Be Kept in Captivity|publisher=Humane Society International and the Humane Society of the United States|access-date=December 21, 2014}}</ref> Captivity usually bears little resemblance to wild habitat, and captive whales' social groups are foreign to those found in the wild. Critics claim captive life is stressful due to these factors and the requirement to perform circus tricks that are not part of wild orca behavior. Wild orcas may travel up to {{convert|160|km|mi|-1}} in a day, and critics say the animals are too big and intelligent to be suitable for captivity.<ref name=cbs2010>{{cite news|url= https://www.cbsnews.com/news/whale-attack-renews-captive-animal-debate/|title=Whale Attack Renews Captive Animal Debate|work=CBS News|date=March 1, 2010|access-date=September 6, 2015}}</ref> Captives occasionally act aggressively towards themselves, their tankmates, or humans, which critics say is a result of [[stress (medicine)|stress]].<ref name=armstrong>{{cite book|last1=Armstrong|first1=Susan J.|last2=Botzler|first2=Richard G.|title=The Animal Ethics Reader|url={{google books |plainurl=y |id=tBuHDQAAQBAJ}}|date=November 18, 2016|publisher=Taylor & Francis|isbn=978-1-317-42196-2}}</ref>
Although dolphins generally interact well with humans, some attacks have occurred, most of them resulting in small injuries.<ref name="fishingnj.org">{{cite web|author=William Broad |url=http://www.fishingnj.org/artdolphagress.htm |title=An article on the aggressive nature of dolphins |publisher=Fishingnj.org |date=July 6, 1999 |access-date=July 25, 2011}}</ref> [[Orca]]s, the largest species of dolphin, have been involved in fatal [[Orca attacks on humans|attacks on humans]] in captivity. The record-holder of documented orca fatal attacks is a male named [[Tilikum (orca)|Tilikum]],<ref>{{cite book|chapter=The Killer in the Pool|first=Tim|last=Zimmerman|title=The Best American Sampler 2011|page=336|publisher=Houghton Mifflin Harcourt|year=2011}}</ref><ref>{{cite news
|url=https://www.nytimes.com/1999/07/07/us/corpse-is-found-on-whale.html|title=Corpse Is Found on Whale|newspaper=[[The New York Times]]|date=July 7, 1999|access-date=September 11, 2011}}</ref><ref>{{cite news
|url=http://www.cnn.com/2010/US/02/24/killer.whale.trainer.death/index.html|title=SeaWorld trainer killed by killer whale|publisher=CNN|date=February 25, 2010|access-date=March 11, 2010}}</ref> who lived at [[SeaWorld]] from 1992 until his death in 2017.<ref>{{cite web|url=https://www.nationalgeographic.com/news/2017/01/tilikum-seaworld-orca-killer-whale-dies/|archive-url=https://web.archive.org/web/20190802092644/https://www.nationalgeographic.com/news/2017/01/tilikum-seaworld-orca-killer-whale-dies/|url-status=dead|archive-date=August 2, 2019|first= Brian|last=Howard|date=January 6, 2017|title=Why Tilikum, SeaWorld's Killer Orca, Was Infamous|website=National Geographic|access-date=September 20, 2019}}</ref> Tilikum has played a role in the death of three people in three different incidents (1991, 1999 and 2010).<ref>{{cite news| url=https://www.theguardian.com/world/2010/feb/25/killer-whale-tilikum-drowned-trainer-hair | ___location=London | work=The Guardian | first=Ed | last=Pilkington | title=Killer whale Tilikum to be spared after drowning trainer by ponytail | date=February 25, 2010}}</ref> Tilikum's behaviour sparked the production of the documentary ''[[Blackfish (film)|Blackfish]]'', which focuses on the consequences of keeping orcas in captivity. There are documented incidents in the wild, too, but none of them fatal.<ref>{{cite web|url=http://www.juneauempire.com/stories/081905/sta_20050819039.shtml|archive-url=https://web.archive.org/web/20100411215249/http://www.juneauempire.com/stories/081905/sta_20050819039.shtml|archive-date=April 11, 2010|title=Killer whale bumps but doesn't bite boy |publisher=Juneau Empire – Alaska's Capital City Online Newspaper |date=August 19, 2005 |access-date=July 25, 2011}}</ref>
Fatal attacks from other species are less common, but there is a registered occurrence off the coast of [[Brazil]] in 1994, when a man died after being attacked by a [[bottlenose dolphin]] named [[Tião (dolphin)|Tião]].<ref>{{cite web|last=Wong |first=David |url=http://www.cracked.com/article_15853_the-6-cutest-animals-that-can-still-destroy-you.html |title=The 6 Cutest Animals That Can Still Destroy You |date=February 7, 2008 |publisher=Cracked.com |access-date=July 25, 2011}}</ref><ref>{{cite web|url=http://www.science-frontiers.com/sf101/sf101b07.htm |title=Male Dolphin Kills Man |publisher=Science-frontiers.com |date= Sep–Oct 1995|access-date=July 25, 2011}}</ref> [[Tião (dolphin)|Tião]] had suffered harassment by human visitors, including attempts to stick ice cream sticks down his [[blowhole (anatomy)|blowhole]].<ref>{{cite web|url=https://www.bbc.co.uk/insideout/south/series1/lone-dolphins.shtml |title=LONE DOLPHINS – FRIEND OR FOE? |publisher=BBC |date=September 9, 2002 |access-date=February 5, 2012}}</ref> Non-fatal incidents occur more frequently, both in the wild and in captivity.
While dolphin attacks occur far less frequently than attacks by other sea animals, such as [[shark attack|sharks]], some scientists are worried about the careless programs of human-dolphin interaction. Dr. Andrew J. Read, a biologist at the Duke University Marine Laboratory who studies dolphin attacks, points out that dolphins are large and wild predators, so people should be more careful when they interact with them.<ref name="fishingnj.org"/>
Several scientists who have researched dolphin behaviour have proposed that dolphins' unusually high intelligence in comparison to other animals means that dolphins should be seen as [[non-human person]]s who should have their own specific rights and that it is [[morality|morally]] unacceptable to keep them captive for entertainment purposes or to kill them either intentionally for consumption or unintentionally as by-catch.<ref name="White2009">{{cite book|last=White|first=Thomas I.|title=In Defense of Dolphins: The New Moral Frontier|url={{google books |plainurl=y |id=tGunrZU6AyEC}}|date=May 18, 2009|publisher=John Wiley & Sons|isbn=978-0-470-46969-9}}</ref><ref>{{cite web |url= http://www.dolphinmovie.com/background.pdf |title= Scientists say dolphins should be treated as 'non- human persons' |last1=Leake |first1= Jonathan |last2= Brooks |first2= Helen |date= January 3, 2010 |work=[[The Sunday Times]] |via= dolphinmovie.com |archive-url= https://web.archive.org/web/20160410080701/http://www.dolphinmovie.com/background.pdf | archive-date =April 10, 2016 | access-date =January 4, 2010 }}</ref> Four countries – [[Chile]], [[Costa Rica]], [[Hungary]], and [[India]] – have declared dolphins to be "non-human persons" and have banned the capture and import of live dolphins for entertainment.<ref>Land, Graham (July 29, 2013). ''[http://asiancorrespondent.com/111205/dolphin-rights-the-world-should-follow-indias-lead/ Dolphin rights: The world should follow India's lead]''. {{Webarchive|url=https://web.archive.org/web/20130829094716/http://asiancorrespondent.com/111205/dolphin-rights-the-world-should-follow-indias-lead/ |date=August 29, 2013 }}. [[Asian Correspondent|Asiancorrespondent.com]]. Hybrid News Ltd. Retrieved July 29, 2013.</ref><ref>{{Cite web |url=http://moef.nic.in/assets/ban%20on%20dolphanariums.pdf |title=Policy on establishment of dolphinarium |access-date=August 10, 2013 |archive-url=https://web.archive.org/web/20160322165915/http://www.moef.nic.in/assets/ban%20on%20dolphanariums.pdf |archive-date=March 22, 2016 |url-status=dead }}</ref><ref>{{Cite web|url=https://www.dw.com/en/dolphins-gain-unprecedented-protection-in-india/a-16834519|title=Dolphins gain unprecedented protection in India | DW | 24.05.2013|website=DW.COM}}</ref>
===Consumption===
====Cuisine====
[[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 name="auto"/>
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=September 14, 2009 | access-date=May 24, 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> While Japan may be the best-known and most controversial example, only a very small minority of the population has ever sampled it.<ref>{{Cite web |last=Kearney |first=Christine |date=2009-07-31 |title=Dolphin slaughter in Japan subject of new film |url=https://www.reuters.com/article/film-dolphins-japan/dolphin-slaughter-in-japan-subject-of-new-film-idUKN3030237020090731/ |access-date=2023-12-23 |website=[[Reuters]]}}</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= May 16, 2011}}</ref>
====Health concerns====
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|title=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|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= August 29, 2013}}</ref>
{{Quotes|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 numbers 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/>}}
== See also ==
* [[List of individual cetaceans]]
* {{Portal-inline|Cetaceans}}
==References==
<references />
==Further reading==
* Carwardine, M., ''Whales, Dolphins and Porpoises'', Dorling Kindersley, 2000. {{ISBN|978-0-7513-2781-6}}.
* [[Heathcote Williams|Williams, Heathcote]], ''Whale Nation'', New York, Harmony Books, 1988. {{ISBN|978-0-517-56932-0}}.
==External links==
{{Sister project links | wikt=dolphin | commons=Dolphin | b=no| n=no | q=no | s=no | v=no | voy= no| species=Delphinidae | d=Q7369| mw= no| display=Dolphins}}
'''Conservation, research and new:'''
* De Rohan, Anuschka. [https://www.theguardian.com/science/2003/jul/03/research.science "Why dolphins are deep thinkers"], ''[[The Guardian]]'', July 3, 2003.
* [https://web.archive.org/web/20051228135245/http://www.dolphin-institute.org/ The Dolphin Institute]
* [http://www.
* [https://web.archive.org/web/20090105203734/http://tursiops.org/ Tursiops.org: Current Cetacean-related news]
'''Photos:'''
* [https://www.pbs.org/wnet/nature/dolphins/index.html PBS NOVA: Dolphins: Close Encounters] {{Webarchive|url=https://web.archive.org/web/20081030055658/https://www.pbs.org/wnet/nature/dolphins/index.html |date=October 30, 2008 }}
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[[Category:Animals that use echolocation]]
[[Category:Extant Tortonian first appearances]]
[[Category:Paraphyletic groups]]
[[Category:Mammal common names]]
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