Editing Dolphin (section)

===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=November 1, 2024
| 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&nbsp;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>