Editing Cetacean intelligence (section)

==Communication==
{{Further|Whale vocalization|Human–animal communication}}
[[File:Humpbackwhale singing.webm|thumb|left|300px|thumbtime=0:19|Audiovisual material of a [[humpback whale]] singing while diving]]Whales use a variety of sounds for [[animal communication|their communication]] and sensation.<ref>Communication and behavior of whales, R Payne. 1983. Westview Press.</ref> [[Odontocete]] (toothed whale) vocal production is classified in three categories: clicks, whistles, and pulsed calls:
*Clicks are very brief vocal sounds produced in rapid series for [[Animal echolocation|echolocation]].<ref name=Souhaut>{{cite journal |author1=Souhaut M |author2=Shields MW |title=Stereotyped whistles in southern resident killer whales |journal=Aquatic Biology |date=2021 |volume=9 |pages=e12085 |publisher=[[PeerJ]]|doi=10.7717/peerj.12085 |pmid=34532160 |pmc=8404572 |doi-access=free }}</ref> Echoes of the clicks contain sound data about the surroundings transmitted through the ears to the brain, which is able to resolve echoes into information.<ref name="Nummela et al., 2007">{{cite journal |last1=Nummela |first1=Sirpa |last2=Thewissen |first2=J.G.M. |last3=Bajpai |first3=Sunil |last4=Hussain |first4=Taseer |last5=Kumar |first5=Kishor |title=Sound transmission in archaic and modern whales: Anatomical adaptations for underwater hearing |journal=[[The Anatomical Record]] |date=2007 |volume=290 |issue=6 |pages=716–733 |doi=10.1002/ar.20528|pmid=17516434 |s2cid=12140889 }}</ref>
* Whistles{{spaced ndash}}narrow-band [[frequency modulation|frequency modulated (FM)]] signals{{spaced ndash}}are used for communicative purposes, such as contact calls, or the signature whistle of [[bottlenose dolphin]]s. Whistles are the primary social vocalization among the majority of [[Delphinidae]] species.<ref name=Souhaut/><ref name="Janik & Slater, 1998">{{cite journal |author1=Vincent M Janik |author2=Peter J.B Slater |title=Context-specific use suggests that bottlenose dolphin signature whistles are cohesion calls |journal=Animal Behaviour |publisher=[[Elsevier]] Ltd. |date=1998 |volume=56 |issue=4 |pages=829–838 |doi=10.1006/anbe.1998.0881 |pmid=9790693 |s2cid=32367435 |url=https://www.sciencedirect.com/science/article/pii/S0003347298908818 |issn=0003-3472|url-access=subscription }}</ref>
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*Pulsed calls are significant for a few cetacean species, such as the [[narwhal]],<ref name="Marcoux 2011">{{cite thesis |last= Marcoux|first= M.|date= 2011|title= Narwhal communication and grouping behaviour: a case study in social cetacean research and monitoring |type= PhD|chapter= 1|publisher= McGill University | place= Montreal}}</ref> and the orca. These calls have distinct tonal qualities and a complex harmonic structure. Typically 0.5–1.5 s in duration, they are the primary social vocalization of orcas.<ref name="Souhaut"/> Researchers John Ford, Graeme Ellis, and Ken Balcomb wrote, "By varying the timbre and frequency structure of the calls, the whales can generate a variety of signals…Most calls contain sudden shifts or rapid sweeps in pitch, which give them distinctive qualities recognizable over distance and background noise."<ref name="Ford, Ellis & Balcomb, 2000">{{cite book |last1=Ford |first1=John K.B. |last2=Ellis |first2=Graeme M. |last3=Balcomb |first3=Kenneth C. |title=Killer Whales: the natural history and genealogy of ''Orcinus orca'' in British Columbia and Washington |date=2000 |publisher=[[UBC]] Press |location=Vancouver, BC |isbn=9780774808002 |edition=2nd |page=96}}</ref>

There is strong evidence that some specific whistles, called ''signature whistles'', are used by dolphins to identify and/or call each other; dolphins have been observed emitting both other specimens' signature whistles, and their own. A unique signature whistle develops quite early in a dolphin's life, and it appears to be created in imitation of the signature whistle of the dolphin's mother.<ref>{{Cite news |date=8 May 2006 |title=Dolphins 'have their own names' |work=BBC News |url=http://news.bbc.co.uk/1/hi/scotland/edinburgh_and_east/4750471.stm |access-date=2006-10-24}}</ref> Imitation of the signature whistle seems to occur only among the mother and its young, and among befriended adult males.<ref>{{Cite journal |last1=King |first1=S. L. |last2=Sayigh |first2=L. S. |last3=Wells |first3=R. S. |last4=Fellner |first4=W. |last5=Janik |first5=V. M. |year=2013 |title=Vocal copying of individually distinctive signature whistles in bottlenose dolphins |journal=Proceedings of the Royal Society B: Biological Sciences |volume=280 |issue=1757 |page=20130053 |doi=10.1098/rspb.2013.0053 |pmc=3619487 |pmid=23427174}}</ref>

Xitco reported the ability of dolphins to eavesdrop passively on the active echolocative inspection of an object by another dolphin. [[Louis Herman|Herman]] calls this effect the "acoustic flashlight" hypothesis, and may be related to findings by both Herman and Xitco on the comprehension of variations on the pointing gesture, including human pointing, dolphin postural pointing, and human gaze, in the sense of a redirection of another individual's attention, an ability which may require [[theory of mind]].{{Citation needed|date=February 2016}}

The environment where dolphins live makes experiments much more expensive and complicated than for many other species; additionally, the fact that cetaceans can emit and hear sounds (which are believed to be their main means of communication) in a range of frequencies much wider than humans can means that sophisticated equipment, which was scarcely available in the past, is needed to record and analyse them. For example, clicks can contain significant energy in frequencies greater than 110 [[kHz]] (for comparison, it is unusual for a human to be able to hear sounds above 20 kHz), requiring that equipment have a [[sampling frequency|sampling rates]] of at least 220&nbsp;kHz; [[MHz]]-capable hardware is often used.

In addition to the acoustic communication channel, the [[visual perception|visual modality]] is also significant. The contrasting [[pigmentation]] of the body may be used, for example with "flashes" of the hypopigmented ventral area of some species, as can the production of bubble streams during signature whistling. Also, much of the synchronous and cooperative behaviors, as described in the [[Cetacean intelligence#Pack characteristics|Behavior]] section of this entry, as well as cooperative foraging methods, likely are managed at least partly by visual means.

Experiments have shown that they can learn human sign language and can use whistles for 2-way [[Human–animal communication#Herman|human–animal communication]]. Phoenix and [[Akeakamai]], bottlenose dolphins, understood individual words and basic sentences like "touch the frisbee with your tail and then jump over it".<ref>{{cite journal |last1=Herman |first1=Louis M. |last2=Richards |first2=Douglas G. |last3=Wolz |first3=James P. |title=Comprehension of sentences by bottlenosed dolphins |journal=Cognition |date=1 March 1984 |volume=16 |issue=2 |pages=129–219 |doi=10.1016/0010-0277(84)90003-9|pmid=6540652 |s2cid=43237011 }}</ref> Phoenix learned whistles, and Akeakamai learned sign language. Both dolphins understood the significance of the ordering of tasks in a sentence.

A study conducted by Jason Bruck of the [[University of Chicago]] showed that bottlenose dolphins can remember [[Animal echolocation|whistles]] of other dolphins they had lived with after 20 years of separation. Each dolphin has a unique whistle that functions like a name, allowing the marine mammals to keep close social bonds.
The new research shows that dolphins have the longest memory yet known in any species other than [[humans]].<ref>Bruck, Jason N. (2013), "Decades-long social memory in bottlenose dolphins", ''Proceedings of the Royal Society B: Biological Sciences''. Vol. 280, article 20131726.</ref><ref name="news.nationalgeographic.com">{{Cite web |date=2013-08-06 |title=Dolphins Have Longest Memories in Animal Kingdom |url=http://news.nationalgeographic.com/news/2013/08/130806-dolphins-memories-animals-science-longest/ |archive-url=https://web.archive.org/web/20130810181705/http://news.nationalgeographic.com/news/2013/08/130806-dolphins-memories-animals-science-longest |url-status=dead |archive-date=August 10, 2013 |access-date=2018-08-14 |publisher=News.nationalgeographic.com}}</ref>