Editing Elephant seal (section)

==Physiology==
[[File:Miroungaskull.jpg|thumb|left|Skull of a northern elephant seal]]
Elephant seals spend up to 80% of their lives in the ocean. They can hold their breath for more than 100 minutes<ref name=divebbc>{{cite news|last=Amos|first=Jonathan|title=Elephant seals dive for science|url=http://news.bbc.co.uk/1/hi/sci/tech/4736196.stm|work=2006|publisher=BBC News|access-date=23 April 2013|date=2006-02-21}}</ref><ref>{{cite web |url= http://www.eleseal.org/pdf_lay/book_2004.pdf |title= Southern Elephant Seals of Sea Lion Island – A Long-term Research Project |website=Eleseal.org |access-date=2010-05-21}}</ref> – longer than any other [[cetacea|noncetacean]] mammal. Elephant seals dive to {{convert|1550|m|ft|abbr=on}} beneath the ocean's surface<ref name=divebbc/> (the deepest recorded dive of an elephant seal is {{convert|2388|m|ft|abbr=on}} by a southern elephant seal, while the record for the northern elephant seal is {{convert|1735|m|ft|abbr=on}}).<ref name=plosone-2014>{{cite journal |author1=Gregory S. Schorr |author2=Erin A. Falcone |author3=David J. Moretti |author4=Russel D. Andrews |year=2014 |title=First long-term behavioral records from Cuvier's beaked whales (''Ziphius cavirostris'') reveal record-breaking dives |journal=[[PLOS ONE]] |volume=9 |issue=3 |page=e92633 |doi=10.1371/journal.pone.0092633 |pmid=24670984 |ref=Schorr |pmc=3966784|bibcode=2014PLoSO...992633S |doi-access=free }}</ref><ref>{{cite web |url= http://www.coml.org/comlfiles/press/CoML_Beyond_Sunlight_11.17.2009_Public.pdf |title= Census of Marine Life – From the Edge of Darkness to the Black Abyss |publisher=Coml.org |access-date=2009-12-15}}</ref><ref>{{cite journal | vauthors = Robinson PW, Costa DP, Crocker DE, Gallo-Reynoso JP, Champagne CD, Fowler MA, Goetsch C, Goetz KT, Hassrick JL, Hückstädt LA, Kuhn CE, Maresh JL, Maxwell SM, McDonald BI, Peterson SH, Simmons SE, Teutschel NM, Villegas-Amtmann S, Yoda K | title = Foraging behavior and success of a mesopelagic predator in the northeast Pacific Ocean: insights from a data-rich species, the northern elephant seal | journal = PLOS ONE | volume = 7 | issue = 5 | pages = e36728 | date = 2012-05-15 | pmid = 22615801 | pmc = 3352920 | doi = 10.1371/journal.pone.0036728 | bibcode = 2012PLoSO...736728R | doi-access = free }}</ref> The average depth of their dives is about {{convert|300|to|600|m|ft|sigfig=1|abbr=on}}, typically for around 20&nbsp;minutes for females and 60&nbsp;minutes for males, as they search for their favorite foods, which are [[Skate (fish)|skate]]s, [[Batoidea|rays]], [[squid]], [[octopuses]], [[eel]]s, small [[shark]]s and large fish. Their stomachs also often contain [[gastrolith]]s. They spend only brief amounts of time at the surface to rest between dives (2–3 minutes).<ref name=":2" /> Females tend to dive a bit deeper due to their prey source.<ref name=":2" />
[[File:Northern elephant seals fighting.webm|thumb|Male elephant seals fighting for mates]]

Elephant seals are shielded from extreme cold more by their [[blubber]] than by fur. Their hair and outer layers of skin [[molting|molt]] in large patches. The skin has to be regrown by blood vessels reaching through the blubber. When molting occurs, the seal is susceptible to the cold, and must rest on land, in a safe place called a "[[Hauling-out|haul out]]". Northern males and young adults haul out during June to July to molt; northern females and immature seals during April to May.

Elephant seals have a very large volume of blood, allowing them to hold a large amount of oxygen for use when diving. They have large sinuses in their [[abdomens]] to hold blood and can also store oxygen in their muscles with increased [[myoglobin]] concentrations in muscle. In addition, they have a larger proportion of oxygen-carrying [[red blood cell]]s. These adaptations allow elephant seals to dive to such depths and remain underwater for up to two hours.<ref>{{Cite web | title = 5.4 Seals | publisher = Classroom Antarctica | url = http://www.classroom.antarctica.gov.au/5-southern-life/5-4-seals | url-status = dead | archive-url = https://web.archive.org/web/20110601184942/http://www.classroom.antarctica.gov.au/5-southern-life/5-4-seals/ | archive-date = 2011-06-01 }}</ref>

Unlike some other marine mammals, such as dolphins, elephant seals do not have [[unihemispheric slow-wave sleep]]. Instead they sleep deeply for a little less than 20 minutes at the time while sinking through the water to depths that has been measured to 377 meters. When being near the continental shelf, where the ocean is less deep, they will often reach bottom, which sometimes wakes them up. But more often they continue to sleep on the seabed. On average, they get about two hours of sleep a day over a period of seven months, which is among the lowest amount of sleep of any mammal.<ref>[https://www.abc.net.au/news/science/2023-04-21/sleeping-elephant-seals-plummet-hundreds-of-metres-in-ocean/102232320 Sleeping elephant seals fall through ocean's depths, and some even nap on the sea floor]</ref>

They are able to slow down their heartbeat ([[bradycardia]]) and divert blood flow from the external areas of the body to important core organs.<ref name=":2" /> They can also slow down their metabolism while performing deep dives.<ref name=":2" />

Elephant seals have a helpful feature in their bodies known as the [[Rete mirabile|countercurrent heat exchanger]] to help conserve energy and prevent heat loss.<ref name=":2" /> In this system, [[Artery|arteries]] and [[vein]]s are organized in a way to maintain a constant body temperature by having the cool blood flowing to the heart warmed by blood going to external areas of the animal.<ref name=":2" />

Milk produced by elephant seals is remarkably high in [[milkfat]] compared to other mammals.  After an initially lower state, it rises to over 50% milkfat (human breast milk is about 4% milkfat, and cow milk is about 3.5% milkfat).<ref>{{cite web|url=http://www.coastsidestateparks.org/pdfs/Elephant%20Seal%20Fact%20Sheet.pdf |title=Northern Elephant Seal Fact Sheet |publisher=Coastside State Parks Association |access-date=26 March 2013 |url-status=dead |archive-url=https://web.archive.org/web/20130513045204/http://www.coastsidestateparks.org/pdfs/Elephant%20Seal%20Fact%20Sheet.pdf |archive-date=13 May 2013 }}</ref>