Editing Cetacea (section)

== Behaviour ==

=== Sleep ===
Conscious breathing cetaceans [[sleep]] but cannot afford to be [[unconsciousness|unconscious]] for long, because they may [[drowning|drown]]. While knowledge of sleep in wild cetaceans is limited, toothed cetaceans in captivity have been recorded to exhibit [[unihemispheric slow-wave sleep]] (USWS), which means they sleep with one [[brain hemisphere|side of their brain]] at a time, so that they may swim, breathe consciously and avoid both predators and social contact during their period of rest.<ref>{{cite journal | vauthors = Sekiguchi Y, Arai K, Kohshima S | title = Sleep behaviour: sleep in continuously active dolphins | journal = Nature | volume = 441 | issue = 7096 | pages = E9-10; discussion E11 | date = June 2006 | pmid = 16791150 | doi = 10.1038/nature04898 | s2cid = 4406032 | bibcode = 2006Natur.441E...9S }}</ref>

A 2008 study found that sperm whales sleep in vertical postures just under the surface in passive shallow 'drift-dives', generally during the day, during which whales do not respond to passing vessels unless they are in contact, leading to the suggestion that whales possibly sleep during such dives.<ref>{{cite journal | vauthors = Miller PJ, Aoki K, Rendell LE, Amano M | title = Stereotypical resting behavior of the sperm whale | journal = Current Biology | volume = 18 | issue = 1 | pages = R21-3 | date = January 2008 | pmid = 18177706 | doi = 10.1016/j.cub.2007.11.003 | s2cid = 10587736 | doi-access = free | bibcode = 2008CBio...18..R21M }}</ref>

=== Diving ===
{{see also|Physiology of underwater diving#Mammals}}
While diving, the animals reduce their oxygen consumption by lowering the heart activity and blood circulation; individual organs receive no oxygen during this time. Some [[rorqual]]s can dive for up to 40 minutes, [[sperm whales]] between 60 and 90 minutes and [[bottlenose whale]]s for two hours. Diving depths average about {{convert|100|m|ft|abbr=on}}. Species such as sperm whales can dive to {{convert|3,000|m|ft|abbr=on}}, although more commonly {{convert|1,200|m|ft}}.<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><ref>{{cite journal|author1=Bruno Cozzi|author2=Paola Bagnoli|author3=Fabio Acocella|author4=Maria Laura Costantino|title=Structure and biomechanical properties of the trachea of the striped dolphin Stenella coeruleoalba: Evidence for evolutionary adaptations to diving|journal=The Anatomical Record|volume=284|issue=1|pages=500–510|year=2005|doi=10.1002/ar.a.20182|pmid=15791584}}</ref>

=== Social relations ===
Most cetaceans are social animals, although a few species live in pairs or are solitary. A group, known as a pod, usually consists of ten to fifty animals, but on occasion, such as mass availability of food or during mating season, groups may encompass more than one thousand individuals. Inter-species socialization can occur.<ref name=mann>{{cite book|editor1=Janet Mann|editor2=Richard C. Connor|editor3=Peter L. Tyack|editor4=Hal Whitehead| display-editors = 3|title=Cetacean Societies: Field Study of Dolphins and Whales|publisher=University of Chicago}}</ref>

Pods have a fixed hierarchy, with the priority positions determined by biting, pushing or ramming. The behavior in the group is aggressive only in situations of stress such as lack of food, but usually it is peaceful. Contact swimming, mutual fondling and nudging are common. The playful behavior of the animals, which is manifested in air jumps, somersaults, surfing, or fin hitting, occurs more often than not in smaller cetaceans, such as dolphins and porpoises.<ref name=mann />

=== Whale song ===
Males in some baleen species communicate via [[Whale vocalization|whale song]], sequences of high pitched sounds. These "songs" can be heard for hundreds of kilometers. Each population generally shares a distinct song, which evolves over time. Sometimes, an individual can be identified by its distinctive vocals, such as the [[52-hertz whale]] that sings at a higher frequency than other whales. Some individuals are capable of generating over 600 distinct sounds.<ref name="mann" /> In baleen species such as humpbacks, blues and fins, male-specific song is believed to be used to attract and display fitness to females.<ref>{{cite journal |last1=Janik |first1=Vincent |title=Cetacean vocal learning and communication |journal=Current Opinion in Neurobiology |date=2014 |volume=28 |pages=60–65 |doi= 10.1016/j.conb.2014.06.010|pmid=25057816 |s2cid=40334723 }}</ref>

=== Hunting ===
Pod groups also hunt, often with other species. Many species of dolphins accompany large tunas on hunting expeditions, following large schools of fish. The orca hunts in pods and targets belugas and even larger whales. Humpback whales, among others, form in collaboration [[bubble net|bubble carpets]] to herd krill or plankton into bait balls before lunging at them.<ref name=mann />

=== Intelligence ===
{{Main|Cetacean intelligence}}[[File:Whales Bubble Net Feeding-edit1.jpg|thumb|Bubble net feeding]]

Cetacea are known to teach, learn, cooperate, scheme and grieve.<ref name="wwwu">{{cite news |last=Siebert |first=Charles |title=Watching Whales Watching Us |work=[[The New York Times]] Magazine |date=8 July 2009 |access-date=29 August 2015 |url=https://www.nytimes.com/2009/07/12/magazine/12whales-t.html?pagewanted=all}}</ref>

Smaller cetaceans, such as dolphins and porpoises, engage in complex play behavior, including such things as producing stable underwater [[toroid]]al air-core [[vortex]] rings or "[[bubble ring]]s". The two main methods of bubble ring production are rapid puffing of air into the water and allowing it to rise to the surface, forming a ring, or swimming repeatedly in a circle and then stopping to inject air into the [[Helix|helical]] vortex currents thus formed. They also appear to enjoy biting the vortex rings, so that they burst into many separate bubbles and then rise quickly to the surface. Whales produce bubble nets to aid in herding prey.<ref>{{cite journal |author1=Wiley, David|s2cid=55168063 |title=Underwater components of humpback whale bubble-net feeding behaviour |journal=Behaviour |volume=148 |issue=5 |pages=575–602 |year=2011 |doi=10.1163/000579511X570893 |display-authors=etal}}</ref>

[[File:Orca porpoising.jpg|thumb|Killer whale [[Cetacean surfacing behaviour#Porpoising|porpoising]]]]

Larger whales are also thought to engage in play. The southern right whale elevates its tail fluke above the water, remaining in the same position for a considerable time. This is known as "sailing". It appears to be a form of play and is most commonly seen off the coast of Argentina and South Africa.<ref>{{cite book |last1=Carwardine |first1=M. H. |last2=Hoyt |first2=E. |year=1998 |title=Whales, Dolphins and Porpoises |journal=NSW: Reader's Digest |isbn=978-0-86449-096-4}}</ref> Humpback whales also display this behaviour.<ref>{{Cite web |author=A. O. L. Staff |date=2016-07-15 |title=Humpback whale 'tail-sails' as she watches her calf off the Maui coast |url=https://www.aol.com/article/2016/03/11/humpback-whale-tail-sails-as-she-watches-her-calf-off-maui-coast/21326396/?guccounter=1 |access-date=2025-02-08 |website=www.aol.com |language=en-US}}</ref>

[[Self-awareness]] appears to be a sign of abstract thinking. Self-awareness, although not well-defined, is believed to be a precursor to more advanced processes such as [[metacognition|metacognitive reasoning]] (thinking about thinking) that humans exploit. Dolphins appear to possess self-awareness.<ref>{{cite web | url=http://www.livescience.com/4272-elephant-awareness-mirrors-humans.html | title=Elephant Self-Awareness Mirrors Humans |publisher=Live Science |date=30 October 2006 |access-date=29 August 2015}}</ref> The most widely used test for self-awareness in animals is the [[mirror test]], in which a temporary dye is placed on an animal's body and the animal is then presented with a mirror. Researchers then explore whether the animal shows signs of self-recognition.<ref name="Mirror test">{{cite news |url=https://www.nytimes.com/2001/05/01/science/brainy-dolphins-pass-the-human-mirror-test.html |title=Mirror test |author=Derr, Mark |newspaper=New York Times |access-date=3 August 2015|date=May 2001 }}</ref>

Critics claim that the results of these tests are susceptible to the [[Clever Hans]] effect. This test is much less definitive than when used for [[primates]]. Primates can touch the mark or the mirror, while dolphins cannot, making their alleged self-recognition behavior less certain. Skeptics argue that behaviors said to identify self-awareness resemble existing social behaviors, so researchers could be misinterpreting self-awareness for social responses. Advocates counter that the behaviors are different from normal responses to another individual. Dolphins show less definitive behavior of self-awareness, because they have no pointing ability.<ref name="Mirror test" />

In 1995, Marten and Psarakos used video 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}}<!--|access-date=5 September 2015--></ref> They showed dolphins real-time footage of themselves, recorded footage and another dolphin. They concluded that their evidence suggested self-awareness rather than social behavior. While this particular study has not been replicated, dolphins later "passed" the mirror test.<ref name="Mirror test" />

=== Decision-making ===

Collective decisions are an important part of life as a cetacean for the many species that spend time in groups (whether these be temporary such as the fission-fusion dynamics of many smaller dolphin species or long-term stable associations as are seen in killer whale and sperm whale matrilines).<ref>{{cite journal | vauthors = Zwamborn E, Boon N, Whitehead H | title = Collective Decision-making in Aquatic Mammals | journal = Mammal Review| volume = 53 | issue = 4 | pages = 238–253| date = October 2023 | doi = 10.1111/mam.12321 | s2cid = 261141293 | doi-access = free | bibcode = 2023MamRv..53..238Z }}</ref> Little is known about how these decisions work, though studies have found evidence messy consensus decisions in groups of sperm whales and leadership in other species like bottlenose dolphins and killer whales.{{citation needed|date=October 2024}}