Editing Walrus (section)

==Anatomy==
[[File:Walrus2.jpg|thumb|right|Young male Pacific walruses on Cape Pierce, [[Alaska]], showing variation in the curvature and orientation of the tusks and the bumpy skin (bosses) typical of males.|alt=Photo of several walruses, with prominently displayed white pairs of tusks]]
[[File:Morse IRSNB.JPG|thumb|right|Skeleton]]
While some outsized Pacific males can weigh as much as {{convert|2000|kg|lb|abbr=on}}, most weigh between {{convert|800|and|1700|kg|lb|abbr=on}}. An occasional male of the Pacific subspecies far exceeds normal dimensions. In 1909, a walrus hide weighing {{convert|500|kg|lb|abbr=on}} was collected from an enormous bull in [[Franz Josef Land]], while in August 1910, Jack Woodson shot a {{convert|4.9|m|ft|frac=2|adj=mid|-long}} walrus, harvesting its {{convert|450|kg|lb|-2|abbr=on}} hide. Since a walrus's hide usually accounts for about 20% of its body weight, the total body mass of these two giants is estimated to have been at least {{convert|2300|kg|lb|-3|abbr=on}}.<ref name = "Wood">{{cite book | last = Wood | first = Gerald | name-list-style = vanc | title =The Guinness Book of Animal Facts and Feats| year = 1983 | publisher = Guinness Superlatives | isbn = 978-0-85112-235-9|url={{google books |plainurl=y |id=AWhFAQAAIAAJ}}}}</ref> The Atlantic subspecies weighs about 10–20% less than the Pacific subspecies.<ref name="Fay85"/> Male Atlantic walrus weigh an average of {{convert|900|kg|lb|abbr=on}}.<ref name="Walrus: Physical Characteristics" /> The Atlantic walrus also tends to have relatively shorter tusks and somewhat more of a flattened [[snout]]. Females weigh about two-thirds as much as males, with the Atlantic females averaging {{convert|560|kg|lb|abbr=on}}, sometimes weighing as little as {{convert|400|kg|lb|abbr=on}}, and the Pacific female averaging {{convert|800|kg|lb|abbr=on}}.<ref>{{cite web | vauthors = Carling M | date = 1999 | url = http://141.213.176.11/site/accounts/information/Odobenus_rosmarus.html | title = Odobenus rosmarus walrus | archive-url = https://archive.today/20160320011518/http://141.213.176.11/site/accounts/information/Odobenus_rosmarus.html | archive-date=20 March 2016 | work = Animal Diversity Web }}</ref> Length typically ranges from {{convert|2.2|to|3.6|m|ftin|abbr=on}}.<ref>{{cite web | first = Tobi | last = McIntyre | name-list-style = vanc | url = http://animals.nationalgeographic.com/animals/mammals/walrus/ | archive-url = https://web.archive.org/web/20100114005532/http://animals.nationalgeographic.com/animals/mammals/walrus/ | url-status = dead | archive-date = 14 January 2010 | title = Walrus. Odobenus rosmarus | work = National Geographic | date = 11 November 2010 }}</ref><ref>{{cite web |url=http://www.hww.ca/en/species/mammals/atlantic-walrus.html |title=Hinterland Who's Who – Atlantic walrus |publisher=Hww.ca |access-date=23 June 2012 |url-status=dead |archive-url=https://web.archive.org/web/20120626230539/http://www.hww.ca/en/species/mammals/atlantic-walrus.html |archive-date=26 June 2012  }}</ref> Newborn walruses are already quite large, averaging {{convert|33|to|85|kg|lb|abbr=on}} in weight and {{convert|1|to|1.4|m|ftin|abbr=on}} in length across both sexes and subspecies.<ref name="iucn status 19 November 2021" /> All told, the walrus is the third largest pinniped species, after the two [[elephant seals]]. Walruses maintain such a high body weight because of the blubber stored underneath their skin. This blubber keeps them warm and the fat provides energy to the walrus.

The walrus's body shape shares features with both sea lions ([[eared seal]]s: Otariidae) and seals ([[earless seal|true seals]]: Phocidae). As with otariids, it can turn its rear flippers forward and move on all fours; however, its swimming technique is more like that of true seals, relying less on flippers and more on sinuous whole body movements.<ref name="Fay85"/> Also like phocids, it lacks external ears.

The [[extraocular muscles]] of the walrus are well-developed. This and its lack of [[Orbit (anatomy)|orbital roof]] allow it to protrude its eyes and see in both a frontal and dorsal direction. However, vision in this species appears to be more suited for short-range.<ref name="PerrinWursig2009">{{cite encyclopedia | veditors = Perrin WF, Wursig B, Thewissen JG |encyclopedia=Encyclopedia of Marine Mammals |url={{google books |plainurl=y |id=2rkHQpToi9sC}} |date=26 February 2009 |publisher=Academic Press |isbn=978-0-08-091993-5| vauthors = Kastelein RA |contribution=Walrus ''Odobenus rosmarus'' |page=1214 }}</ref>

===Tusks and dentition===
[[File:WalrusBreathing.jpg|thumb|right|Walrus using its tusks to hang on a breathing hole in the ice near [[St. Lawrence Island]], Bering Sea|alt=Photo of walrus in ice-covered sea.]]
[[File:BLW Teeth in the skull of a large Walrus.jpg|thumb|right|Tooth]]
While this was not true of all extinct walruses,<ref name="US National Library of Medicine">{{cite journal | vauthors = Magallanes I, Parham JF, Santos GP, Velez-Juarbe J | title = A new tuskless walrus from the Miocene of Orange County, California, with comments on the diversity and taxonomy of odobenids | journal = PeerJ | volume = 6 | pages = e5708 | date = 2018 | pmid = 30345169 | pmc = 6188011 | doi = 10.7717/peerj.5708 | doi-access = free }}</ref> the most prominent feature of the living species is its long tusks. These are elongated [[canine teeth|canines]], which are present in both male and female walruses and can reach a length of 1 m (3&nbsp;ft 3 in) and weigh up to 5.4&nbsp;kg (12&nbsp;lb).<ref>{{cite book| vauthors = Berta A, Sumich JL |year = 1999|title = Marine mammals: evolutionary biology|publisher = Academic Press|location = San Diego, CA|url={{google books |plainurl=y |id=zcycBAAAQBAJ}}}}</ref> Tusks are slightly longer and thicker among males, which use them for fighting, dominance and display; the strongest males with the largest tusks typically dominate social groups. Tusks are also used to form and maintain holes in the ice and aid the walrus in climbing out of water onto ice.<ref name="Fay82">{{cite journal| vauthors = Fay FH |year = 1982|title = Ecology and Biology of the Pacific Walrus, ''Odobenus rosmarus divergens'' Illiger|journal= North American Fauna |volume=74 |pages=1–279 |doi=10.3996/nafa.74.0001|doi-access= free}}</ref> Tusks were once thought to be used to dig out prey from the seabed, but analyses of abrasion patterns on the tusks indicate they are dragged through the sediment while the upper edge of the snout is used for digging.<ref name="Ray06">{{cite journal| vauthors = Ray C, McCormick-Ray J, Berg P, Epstein HE |year = 2006|title = Pacific Walrus: Benthic bioturbator of Beringia|journal = Journal of Experimental Marine Biology and Ecology|pages = 403–419|doi = 10.1016/j.jembe.2005.12.043|volume = 330| issue=1 | bibcode=2006JEMBE.330..403R }}</ref> While the [[dentition]] of walruses is highly variable, they generally have relatively few teeth other than the tusks. The maximal number of teeth is 38 with dentition formula: {{DentalFormula|upper=3.1.4.2|lower=3.1.3.2}}, but over half of the teeth are rudimentary and occur with less than 50% frequency, such that a typical dentition includes only 18 teeth {{DentalFormula|upper=1.1.3.0|lower=0.1.3.0}}<ref name="Fay85"/>

===Vibrissae (whiskers)===
Surrounding the tusks is a broad mat of stiff bristles ("mystacial [[vibrissae]]"), giving the walrus a characteristic whiskered appearance. There can be 400 to 700 vibrissae in 13 to 15 rows reaching 30&nbsp;cm (12&nbsp;in) in length, though in the wild they are often worn to much shorter lengths due to constant use in foraging.<ref name=Kastelein1990>{{cite journal |vauthors = Kastelein RA, Stevens S, Mosterd P |year = 1990 |title = The sensitivity of the vibrissae of a Pacific Walrus (''Odobenus rosmarus divergens''). Part 2: Masking |url = http://www.aquaticmammalsjournal.org/share/AquaticMammalsIssueArchives/1988/Aquatic_Mammals_14_3/Kastelein.pdf |journal = Aquatic Mammals |volume = 16 |issue = 2 |pages = 78–87 |access-date = 6 September 2017 |archive-date = 27 February 2020 |archive-url = https://web.archive.org/web/20200227015748/https://www.aquaticmammalsjournal.org/share/AquaticMammalsIssueArchives/1988/Aquatic_Mammals_14_3/Kastelein.pdf |url-status = dead }}</ref> The vibrissae are attached to muscles and are supplied with blood and nerves, making them highly sensitive organs capable of differentiating shapes {{convert|3|mm|in|frac=32|abbr=on}} thick and {{convert|2|mm|in|frac=32|abbr=on}} wide.<ref name="Kastelein1990"/>

===Skin===
Aside from the vibrissae, the walrus is sparsely covered with fur and appears bald. Its skin is highly wrinkled and thick, up to {{convert|10|cm|in|0|abbr=on}} around the neck and shoulders of males. The [[blubber|blubber layer]] beneath is up to {{convert|15|cm|in|0|abbr=on}} thick. Young walruses are deep brown and grow paler and more cinnamon-colored as they age. Old males, in particular, become nearly pink. Because skin blood vessels constrict in cold water, the walrus can appear almost white when swimming. As a [[secondary sexual characteristic]], males also acquire significant nodules, called "bosses", particularly around the neck and shoulders.<ref name="Fay82"/>

The walrus has an [[throat sac|air sac under its throat]] which acts like a flotation bubble and allows it to bob vertically in the water and sleep. The males possess a large [[baculum]] (penis bone), up to {{convert|63|cm|in|abbr=on}} in length, the largest of any land mammal, both in absolute size and relative to body size.<ref name="Fay85"/>