Eared seal: Difference between revisions

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| type_genus_authority = [[François Péron|Péron]], 1816
| type_genus_authority = [[François Péron|Péron]], 1816
| subdivision_ranks = Genera
| subdivision_ranks = Genera
| subdivision = ''[[Arctocephalus]]''<br/>
| subdivision = {{collapsible list|''[[Arctocephalus]]''<br/>
''[[Callorhinus]]''<br/>
''[[Callorhinus]]''<br/>
{{extinct}}''[[Eotaria]]''<br/>
{{extinct}}''[[Eotaria]]''<br/>
Line 21: Line 21:
{{extinct}}''[[Thalassoleon]]''<br/>
{{extinct}}''[[Thalassoleon]]''<br/>
''[[Zalophus]]''
''[[Zalophus]]''
}}
}} }}


An '''eared seal''', '''otariid''', or '''otary''' is any member of the [[marine mammal]] family '''Otariidae''', one of three groupings of [[pinnipeds]]. They comprise 15 [[extant taxon|extant]] [[species]] in seven [[genus|genera]] (another species became extinct in the 1950s) and are commonly known either as [[sea lion]]s or [[fur seal]]s, distinct from [[true seals]] (phocids) and the [[walrus]] ([[Odobenidae|odobenids]]). Otariids are adapted to a semiaquatic lifestyle, feeding and migrating in the water, but breeding and resting on land or ice. They reside in subpolar, temperate, and equatorial waters throughout the [[Pacific]] and [[Southern Oceans]], the southern [[Indian Ocean|Indian]], and [[Atlantic]] Oceans. They are conspicuously absent in the north Atlantic.
An '''eared seal''', '''otariid''', or '''otary''', is any member of the [[marine mammal]] family '''Otariidae''', one of three groupings of [[pinnipeds]]. They comprise 15 [[extant taxon|extant]] [[species]] in seven [[genus|genera]] (another species became extinct in the 1950s) and are commonly known either as [[sea lion]]s or [[fur seal]]s, distinct from [[true seals]] (phocids) and the [[walrus]] ([[Odobenidae|odobenids]]). Otariids are adapted to a semiaquatic lifestyle, feeding and migrating in the water, but breeding and resting on land or ice. They reside in subpolar, temperate, and equatorial waters throughout the [[Pacific]] and [[Southern Oceans]], the southern [[Indian Ocean|Indian]], and [[Atlantic]] Oceans. They are conspicuously absent in the north Atlantic.


The words "otariid" and "otary" come from the [[Greek language|Greek]] ''{{Transliteration|grc|otarion}}'' meaning "little ear",<ref>"Otary, n., etymology of" The Oxford English Dictionary. 2nd ed. 1989. OED Online. Oxford University Press. http://dictionary.oed.com/ {{Webarchive|url=https://web.archive.org/web/20060625103623/http://dictionary.oed.com/ |date=2006-06-25 }} Accessed November 2007</ref> referring to the small but visible external ear flaps ([[Pinna (anatomy)|pinnae]]), which distinguishes them from the [[Phocidae|phocids]].
The words "otariid" and "otary" come from the [[Ancient Greek]] ὠτάριον (''ōtárion''), meaning "little ear",<ref>"Otary, n., etymology of" The Oxford English Dictionary. 2nd ed. 1989. OED Online. Oxford University Press. http://dictionary.oed.com/ {{Webarchive|url=https://web.archive.org/web/20060625103623/http://dictionary.oed.com/ |date=2006-06-25 }} Accessed November 2007</ref> referring to the small but visible external ear flaps ([[Pinna (anatomy)|pinnae]]), which distinguishes them from the [[Phocidae|phocids]].
[[File:Otaria fg02.jpg|thumb|right|Ear flaps of a [[South American sea lion]] (''Otaria flavescens'')]]


==Evolution and taxonomy==
==Evolution and taxonomy==
Morphological and molecular evidence supports a [[Monophyly|monophyletic]] origin of pinnipeds, sharing a common ancestor with [[Musteloidea]],<ref>{{Cite journal |last1=Hassanin |first1=Alexandre |last2=Veron |first2=Géraldine |last3=Ropiquet |first3=Anne |last4=Vuuren |first4=Bettine Jansen van |last5=Lécu |first5=Alexis |last6=Goodman |first6=Steven M. |last7=Haider |first7=Jibran |last8=Nguyen |first8=Trung Thanh |date=2021-02-16 |title=Evolutionary history of Carnivora (Mammalia, Laurasiatheria) inferred from mitochondrial genomes |journal=PLOS ONE |language=en |volume=16 |issue=2 |article-number=e0240770 |doi=10.1371/journal.pone.0240770 |issn=1932-6203 |pmc=7886153 |pmid=33591975|doi-access=free |bibcode=2021PLoSO..1640770H }}</ref><ref>{{cite encyclopedia |last=Berta |first=Annalisa |title=Pinniped Evolution |date=2009 |encyclopedia=Encyclopedia of Marine Mammals |pages=861–868 |publisher=Elsevier |doi=10.1016/b978-0-12-373553-9.00199-1 |isbn=978-0-12-373553-9 }}</ref> though an earlier hypothesis suggested that Otаriidae are descended from a [[Enaliarctos|common ancestor]] most closely related to modern [[bear]]s.<ref>{{cite journal |author1=Lento, G.M. |author2=Hickson, R.E. |author3=Chambers, G.K. |author4=Penny, D. | date=1 January 1995| title = Use of spectral analysis to test hypotheses on the origin of pinnipeds | journal = Molecular Biology and Evolution | volume = 12 | issue = 1 | pages = 28–52 | pmid = 7877495 | doi=10.1093/oxfordjournals.molbev.a040189| doi-access =  }}</ref> Debate remains as to whether the phocids diverged from the otariids before or after the walrus.
Otariids arose in the [[Miocene]] (15–17 million years ago) in the North Pacific, diversifying rapidly into the Southern Hemisphere, where most species now live. The earliest known fossil otariid is ''[[Eotaria crypta]]'' from southern California,<ref name=eotaria>{{Cite journal | doi = 10.1098/rsbl.2014.0835| pmid = 25672999| title = The oldest known fur seal| journal = Biology Letters| volume = 11| issue = 2| article-number = 20140835| year = 2015| last1 = Boessenecker | first1 = R. W.| last2 = Churchill | first2 = M.| pmc = 4360102}}</ref> while the genus ''Callorhinus'' ([[northern fur seal]]) has the oldest fossil record of any living otariid, extending to the middle Pliocene. It probably arose from the extinct fur seal genus ''[[Thalassoleon]]''.
Traditionally, otariids had been subdivided into the fur seal (Arctocephalinae) and sea lion (Otariinae) subfamilies, with the major distinction between them being the presence of a thick underfur layer in the former. Under this categorization, the fur seals comprised two genera: ''Callorhinus'' in the North Pacific with a single representative, the northern fur seal (''C. ursinus''), and eight species in the Southern Hemisphere under the genus ''Arctocephalus''; while the sea lions comprise five species under five genera.<ref>{{cite book | author = J.E. King | year = 1983 | title = Seals of the World
| url = https://archive.org/details/sealsofworld0000king_b3o0 | url-access = registration | edition = 2nd | publisher = Cornell University Press | location = New York | isbn = 978-0-7022-1694-7}}</ref> Recent analyses of the [[molecular phylogeny|genetic evidence]] suggests that ''Callorhinus ursinus'' is in fact more closely related to several sea lion species.<ref>{{cite journal | year = 2001 | doi = 10.1006/mpev.2001.1012 | title = Phylogenetic relationships within the eared seals (Otariidae: Carnivora): implications for the historical biogeography of the family | journal = Mol. Phylogenet. Evol. | volume = 21 | pages = 270–284 | author = Wynen, L | pmid = 11697921 | last2 = Goldsworthy | first2 = SD | last3 = Insley | first3 = SJ | last4 = Adams | first4 = M | last5 = Bickham | first5 = JW | last6 = Francis | first6 = J | last7 = Gallo | first7 = JP | last8 = Hoelzel | first8 = AR | last9 = Majluf | first9 = P | last10 = White | first10 = Robert W.G. | last11 = Slade | first11 = Rob | issue = 2 | bibcode = 2001MolPE..21..270W | display-authors = 8 }}</ref> Furthermore, many of the Otariinae appear to be more [[phylogeny|phylogenetically]] distinct than previously assumed; for example, the [[Japanese sea lion]] (''Zalophus japonicus'') is now considered a separate species, rather than a subspecies of the [[California sea lion]] (''Zalophus californius'').
In light of this evidence, the subfamily separation has been removed entirely and the family Otariidae has been organized into seven genera with 16 species and two subspecies.<ref>{{cite journal | author = Brunner, S. | year = 2003 | url = http://journals.cambridge.org/action/displayAbstract?aid=198243 | title = Fur seals and sea lions (Otariidae): identification of species and taxonomic review | journal = Systematics and Biodiversity | volume = 1 | issue = 3 | pages = 339–439 | doi = 10.1017/S147720000300121X| s2cid = 86375627 | url-access = subscription }}</ref><ref>{{ITIS |id=180615 |taxon=Otariidae |access-date= }}</ref>
Nonetheless, because of morphological and behavioral similarities among the "fur seals" and "sea lions", these remain useful categories when discussing differences between groups of species. Compared to sea lions, fur seals are generally smaller, exhibit greater [[sexual dimorphism]], eat smaller prey and go on longer foraging trips; and, of course, there is the contrast between the coarse short sea lion hair and the fur seal's fur.
[[Cladogram]] showing relationships among the otarids, combining several phylogenetic analyses. The fur seal branch has not been resolved.<ref name="Berta Churchill Boessenecker 2018">{{cite journal | last1=Berta | first1=Annalisa | last2=Churchill | first2=Morgan | last3=Boessenecker | first3=Robert W. | title=The Origin and Evolutionary Biology of Pinnipeds: Seals, Sea Lions, and Walruses | journal=Annual Review of Earth and Planetary Sciences | publisher=Annual Reviews | volume=46 | issue=1 | date=2018-05-30 | issn=0084-6597 | doi=10.1146/annurev-earth-082517-010009 | pages=203–228| bibcode=2018AREPS..46..203B | s2cid=135439365 | doi-access=free }}</ref>{{Clarify|reason=Why does Otariinae not contain ''Otaria''?|date=July 2025 }}


{{Cladogram|align=left|title=
|clade=
{{clade
{{clade
|style=font-size:75%;line-height:75%;width:500px;
|style=font-size:100%;line-height:100%;
|label1=[[Pinnipedia]]
|label1=[[Pinnipedia]]
|1={{clade
|1={{clade
   |1=[[Phocidae]]|sublabel1=(earless seals)
   |label1=[[Phocidae]]
  |1="Earless" seals
  |label2=[[Otarioidea]]
   |2={{clade
   |2={{clade
       |label1='''Otariidae'''|sublabel1=(eared seals)
       |label1=[[Odobenidae]]
       |1={{clade
      |1=[[Walrus]]
      |label2='''Otariidae'''|sublabel2=(eared seals)
       |2={{clade
         |1=[[Northern fur seal]]<!-- Callorhinus ursinus -->
         |1=[[Northern fur seal]]<!-- Callorhinus ursinus -->
         |2={{clade
         |2={{clade
            |label1=Otariinae
          |1={{clade
            |1={{clade
            |1=[[South American sea lion]]<!-- Otaria flavescens (= O. byronia) -->
              |1=[[Steller sea lion]]<!-- Eumetopias jubatus -->
            |2={{clade
              |label2=''[[Zalophus]]''
              |1=[[Australian sea lion]]<!-- Neophoca cinerea -->
              |2={{clade
              |2=[[New Zealand sea lion]]<!-- Phocarctos hookeri -->
                  |1=[[California sea lion]]<!-- Zalophus californianus -->
                  |2=[[Galápagos sea lion]]<!-- Zalophus wollebaeki -->
                  }}
              }}
            |2={{clade
              |1=[[South American sea lion]]<!-- Otaria flavescens (= O. byronia) -->
              |2={{clade
                  |1=[[Australian sea lion]]<!-- Neophoca cinerea -->
                  |2=[[New Zealand sea lion]]<!-- Phocarctos hookeri -->
                   }}
                   }}
              |label3=''[[Arctocephalus]]''|sublabel3=(fur seals)
            |label3=''[[Arctocephalus]]''|sublabel3=(fur seals)
              |3={{clade<!--yes, tree in Fig. 5 is not fully resolved-->
            |3={{clade hidden<!--yes, tree in Fig. 5 is not fully resolved-->
                  |1={{clade
              |expanded=true|mode=left|expand-text=8 species
                    |1=[[Brown fur seal]]<!-- Arctocephalus pusillus -->
                |1={{clade
                    |2=[[Subantarctic fur seal]]<!-- Arctocephalus tropicalis -->
                |1=[[Cape fur seal]]<!-- Arctocephalus pusillus -->
                |2=[[Subantarctic fur seal]]<!-- Arctocephalus tropicalis -->
                     }}
                     }}
                   |2={{clade
                   |2={{clade
                    |1=[[Antarctic fur seal]]<!-- Arctocephalus gazella -->
                  |1=[[Antarctic fur seal]]<!-- Arctocephalus gazella -->
                  |2={{clade
                    |1=[[Guadalupe fur seal]]<!-- Arctocephalus townsendi -->
                    |2=[[Juan Fernández fur seal]]<!-- Arctocephalus philippii -->
                        }}
                    |3={{clade<!--yes, tree in Fig. 5 is not fully resolved here either-->
                    |1=[[Arctophoca forsteri|Antipodean fur seal]]<!--Arctocephalus forsteri-->
                     |2={{clade
                     |2={{clade
                        |1=[[Guadalupe fur seal]]<!-- Arctocephalus townsendi -->
                      |1=[[Galápagos fur seal]]<!-- Arctocephalus galapagoensis -->
                        |2=[[Juan Fernández fur seal]]<!-- Arctocephalus philippii -->
                      |2=[[South American fur seal]]<!--Arctocephalus australis--> }} }} }} }} }}
                        }}
          |label2=Otariinae
                    |3={{clade<!--yes, tree in Fig. 5 is not fully resolved here either-->
          |2={{clade
                        |1=[[Arctophoca forsteri|Antipodean fur seal]]<!--Arctocephalus forsteri-->
            |1=[[Steller sea lion]]<!-- Eumetopias jubatus -->
                        |2={{clade
            |label2=''[[Zalophus]]''
                          |1=[[Galápagos fur seal]]<!-- Arctocephalus galapagoensis -->
            |2={{clade
                          |2=[[South American fur seal]]<!--Arctocephalus australis-->
              |1=[[California sea lion]]<!-- Zalophus californianus -->
                          }}
              |2=[[Galápagos sea lion]]<!-- Zalophus wollebaeki --> }} }} }}
                        }}
}} }} }} }}
                    }}
                  }}
              }}
            }}
        }}
      |label2=[[Odobenidae]]
      |2=&nbsp;[[Walrus]]
      }}
  }}
}}
|caption=[[Cladogram]] showing relationships among the otarids, combining several phylogenetic analyses. The fur seal tree is not fully resolved.<ref name="Berta Churchill Boessenecker 2018">{{cite journal | last1=Berta | first1=Annalisa | last2=Churchill | first2=Morgan | last3=Boessenecker | first3=Robert W. | title=The Origin and Evolutionary Biology of Pinnipeds: Seals, Sea Lions, and Walruses | journal=Annual Review of Earth and Planetary Sciences | publisher=Annual Reviews | volume=46 | issue=1 | date=2018-05-30 | issn=0084-6597 | doi=10.1146/annurev-earth-082517-010009 | pages=203–228| bibcode=2018AREPS..46..203B | s2cid=135439365 | doi-access=free }}</ref>
}}


Morphological and molecular evidence supports a [[Monophyly|monophyletic]] origin of pinnipeds, sharing a common ancestor with [[Musteloidea]],<ref>{{Cite journal |last1=Hassanin |first1=Alexandre |last2=Veron |first2=Géraldine |last3=Ropiquet |first3=Anne |last4=Vuuren |first4=Bettine Jansen van |last5=Lécu |first5=Alexis |last6=Goodman |first6=Steven M. |last7=Haider |first7=Jibran |last8=Nguyen |first8=Trung Thanh |date=2021-02-16 |title=Evolutionary history of Carnivora (Mammalia, Laurasiatheria) inferred from mitochondrial genomes |journal=PLOS ONE |language=en |volume=16 |issue=2 |pages=e0240770 |doi=10.1371/journal.pone.0240770 |issn=1932-6203 |pmc=7886153 |pmid=33591975|doi-access=free |bibcode=2021PLoSO..1640770H }}</ref><ref>{{Citation |last=Berta |first=Annalisa |title=Pinniped Evolution |date=2009 |url=http://dx.doi.org/10.1016/b978-0-12-373553-9.00199-1 |encyclopedia=Encyclopedia of Marine Mammals |pages=861–868 |publisher=Elsevier |doi=10.1016/b978-0-12-373553-9.00199-1 |isbn=9780123735539 |access-date=2022-07-04|url-access=subscription }}</ref> though an earlier hypothesis suggested that Otаriidae are descended from a [[Enaliarctos|common ancestor]] most closely related to modern [[bear]]s.<ref>{{cite journal |author1=Lento, G.M. |author2=Hickson, R.E. |author3=Chambers, G.K. |author4=Penny, D. | date=1 January 1995| title = Use of spectral analysis to test hypotheses on the origin of pinnipeds | journal = Molecular Biology and Evolution | volume = 12 | issue = 1 | pages = 28–52 | pmid = 7877495 | doi=10.1093/oxfordjournals.molbev.a040189| doi-access =  }}</ref> Debate remains as to whether the phocids diverged from the otariids before or after the walrus.
==Anatomy==


Otariids arose in the [[Miocene]] (15–17 million years ago) in the North Pacific, diversifying rapidly into the Southern Hemisphere, where most species now live. The earliest known fossil otariid is ''[[Eotaria crypta]]'' from southern California,<ref name=eotaria>{{Cite journal | doi = 10.1098/rsbl.2014.0835| pmid = 25672999| title = The oldest known fur seal| journal = Biology Letters| volume = 11| issue = 2| pages = 20140835| year = 2015| last1 = Boessenecker | first1 = R. W.| last2 = Churchill | first2 = M.| pmc = 4360102}}</ref> while the genus ''Callorhinus'' ([[northern fur seal]]) has the oldest fossil record of any living otariid, extending to the middle Pliocene. It probably arose from the extinct fur seal genus ''[[Thalassoleon]]''.
{{Multiple image
 
| image1            = Otaria fg02.jpg
Traditionally, otariids had been subdivided into the fur seal (Arctocephalinae) and sea lion (Otariinae) subfamilies, with the major distinction between them being the presence of a thick underfur layer in the former. Under this categorization, the fur seals comprised two genera: ''Callorhinus'' in the North Pacific with a single representative, the northern fur seal (''C. ursinus''), and eight species in the Southern Hemisphere under the genus ''Arctocephalus''; while the sea lions comprise five species under five genera.<ref>{{cite book | author = J.E. King | year = 1983 | title = Seals of the World
| image2            = Ohrenrobbe vor der Küste Namibias.jpg
| url = https://archive.org/details/sealsofworld0000king_b3o0 | url-access = registration | edition = 2nd | publisher = Cornell University Press | location = New York | isbn = 978-0-7022-1694-7}}</ref> Recent analyses of the [[molecular phylogeny|genetic evidence]] suggests that ''Callorhinus ursinus'' is in fact more closely related to several sea lion species.<ref>{{cite journal | year = 2001 | doi = 10.1006/mpev.2001.1012 | title = Phylogenetic relationships within the eared seals (Otariidae: Carnivora): implications for the historical biogeography of the family | journal = Mol. Phylogenet. Evol. | volume = 21 | pages = 270–284 | author = Wynen, L | pmid = 11697921 | last2 = Goldsworthy | first2 = SD | last3 = Insley | first3 = SJ | last4 = Adams | first4 = M | last5 = Bickham | first5 = JW | last6 = Francis | first6 = J | last7 = Gallo | first7 = JP | last8 = Hoelzel | first8 = AR | last9 = Majluf | first9 = P | last10 = White | first10 = Robert W.G. | last11 = Slade | first11 = Rob | issue = 2 | bibcode = 2001MolPE..21..270W | display-authors = 8 }}</ref> Furthermore, many of the Otariinae appear to be more [[phylogeny|phylogenetically]] distinct than previously assumed; for example, the [[Japanese sea lion]] (''Zalophus japonicus'') is now considered a separate species, rather than a subspecies of the [[California sea lion]] (''Zalophus californius'').
| footer        = The ear flaps ([[Pinna (anatomy)|pinnae]]) of Otariids are small yet evident
 
| total_width    = 500
In light of this evidence, the subfamily separation has been removed entirely and the family Otariidae has been organized into seven genera with 16 species and two subspecies.<ref>{{cite journal | author = Brunner, S. | year = 2003 | url = http://journals.cambridge.org/action/displayAbstract?aid=198243 | title = Fur seals and sea lions (Otariidae): identification of species and taxonomic review | journal = Systematics and Biodiversity | volume = 1 | issue = 3 | pages = 339–439 | doi = 10.1017/S147720000300121X| s2cid = 86375627 | url-access = subscription }}</ref><ref>{{ITIS |id=180615 |taxon=Otariidae |access-date= }}</ref>
}}
Nonetheless, because of morphological and behavioral similarities among the "fur seals" and "sea lions", these remain useful categories when discussing differences between groups of species. Compared to sea lions, fur seals are generally smaller, exhibit greater [[sexual dimorphism]], eat smaller prey and go on longer foraging trips; and, of course, there is the contrast between the coarse short sea lion hair and the fur seal's fur.


==Anatomy and appearance==
Otariids have proportionately much larger fore-[[Flipper (anatomy)|flippers]] and pectoral muscles than phocids, and have the ability to turn their hind limbs forward and walk on all fours, making them far more maneuverable on land.{{Citation needed|date=July 2025}} They are generally considered to be less adapted to an aquatic lifestyle, since they breed primarily on land and haul out more frequently than true seals. However, they can attain higher bursts of speed and have greater maneuverability in the water. Their swimming power derives from the use of flippers more so than the sinuous whole-body movements typical of phocids and walruses.{{Citation needed|date=July 2025}}
[[File:Sea lion family.JPG|right|thumb|[[California sea lion]]s]]<!-- I think that this picture is of a family, but I'm not sure, so I didn't want to be too bold! -->
[[File:Ohrenrobbe vor der Küste Namibias.jpg|thumb|Eared seal off the Namibian coast]]
Otariids have proportionately much larger foreflippers and pectoral muscles than phocids, and have the ability to turn their hind limbs forward and walk on all fours, making them far more maneuverable on land. They are generally considered to be less adapted to an aquatic lifestyle, since they breed primarily on land and haul out more frequently than true seals. However, they can attain higher bursts of speed and have greater maneuverability in the water. Their swimming power derives from the use of flippers more so than the sinuous whole-body movements typical of phocids and walruses.


Otariids are further distinguished by a more dog-like head, sharp, well-developed canines, and the aforementioned visible external pinnae. Their postcanine teeth are generally simple and conical in shape. The [[dentition|dental formula]] for eared seals is: {{DentalFormula|upper=3.1.4.1-3|lower=2.1.4.1}}. Sea lions are covered with coarse guard hairs, while fur seals have a thick underfur, which has historically made them the objects of commercial [[seal hunting|exploitation]].
Otariids are further distinguished by a more dog-like head, sharp, well-developed canines, and the aforementioned visible external pinnae. Their postcanine teeth are generally simple and conical in shape. The [[dentition|dental formula]] for eared seals is: {{DentalFormula|upper=3.1.4.1-3|lower=2.1.4.1}}. Sea lions are covered with coarse guard hairs, while fur seals have a thick underfur, which has historically made them the objects of commercial [[seal hunting|exploitation]].{{Citation needed|date=July 2025}}


Male otariids range in size from the {{convert|70|kg|lb|abbr=on}} [[Galápagos fur seal]], smallest of all otariids, to the over 1,000-kg (2,200-lb) [[Steller sea lion]]. Mature male otariids weigh two to six times as much as females, with proportionately larger heads, necks, and chests, making them the most [[sexually dimorphic]] of all mammals.<ref>{{cite journal |last= Weckerly |first= FW |year= 1998 |title=Sexual-size dimorphism: influence of mass and mating systems in the most dimorphic mammals. |journal= Journal of Mammalogy|volume=79 |issue= 1|pages=33–42|doi=10.2307/1382840 |jstor= 1382840|doi-access= free }}</ref>
Male otariids range in size from the {{convert|70|kg|lb|abbr=on}} [[Galápagos fur seal]], smallest of all otariids, to the over 1,000-kg (2,200-lb) [[Steller sea lion]]. Mature male otariids weigh two to six times as much as females, with proportionately larger heads, necks, and chests, making them the most [[sexually dimorphic]] of all mammals.<ref>{{cite journal |last= Weckerly |first= FW |year= 1998 |title=Sexual-size dimorphism: influence of mass and mating systems in the most dimorphic mammals. |journal= Journal of Mammalogy|volume=79 |issue= 1|pages=33–42|doi=10.2307/1382840 |jstor= 1382840|doi-access= free }}</ref>


==Behavior==
==Behavior==
[[File:Sea lion family.JPG|left|thumb|[[California sea lion]]s]]<!-- I think that this picture is of a family, but I'm not sure, so I didn't want to be too bold! -->
All otariids breed on land during well-defined breeding seasons. Except for the [[Australian sea lion]], which has an atypical 17.5 month breeding cycle, they form strictly annual aggregations on beaches or rocky substrates, often on islands. All species are [[Polygyny in animals|polygynous]]; i.e. successful males breed with several females. In most species, males arrive at breeding sites first and establish and maintain territories through vocal and visual displays and occasional fighting. Females typically arrive on shore a day or so before giving birth. While considered social animals, no permanent hierarchies or statuses are established on the colonies. The extent to which males control females or territories varies between species. Thus, the northern fur seal and the [[South American sea lion]] tend to herd specific [[Harem (zoology)|harem]]-associated females, occasionally injuring them, while the Steller sea lion and the [[New Zealand sea lion]] control spatial territories, but do not generally interfere with the movement of the females. Female New Zealand sea lions are the only otariids that move up to {{Convert|2|km|mi|abbr=on}} into forests to protect their pups during the breeding season.<ref>{{Cite journal|last1=Augé|first1=Amélie|last2=Chilvers|last3=Moore|last4=Mathieu|last5=Robertson|date=2009-01-01|title=Aggregation and dispersion of female New Zealand sea lions at the Sandy Bay breeding colony, Auckland Islands: How unusual is their spatial behaviour?|url=https://brill.com/view/journals/beh/146/9/article-p1287_7.xml|journal=Behaviour|language=en|volume=146|issue=9|pages=1287–1311|doi=10.1163/15683909X427687|issn=0005-7959|url-access=subscription}}</ref><ref>{{Cite journal|last1=Augé|first1=Amélie A.|last2=Chilvers|first2=B. Louise|last3=Mathieu|first3=Renaud|last4=Moore|first4=Antoni B.|date=2012|title=On-land habitat preferences of female New Zealand sea lions at Sandy Bay, Auckland Islands|url=https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1748-7692.2011.00515.x|journal=Marine Mammal Science|language=en|volume=28|issue=3|pages=620–637|doi=10.1111/j.1748-7692.2011.00515.x|bibcode=2012MMamS..28..620A |issn=1748-7692|url-access=subscription}}</ref><ref>{{Cite journal|last1=Frans|first1=Veronica F.|last2=Augé|first2=Amélie A.|last3=Edelhoff|first3=Hendrik|last4=Erasmi|first4=Stefan|last5=Balkenhol|first5=Niko|last6=Engler|first6=Jan O.|date=2018|title=Quantifying apart what belongs together: A multi-state species distribution modelling framework for species using distinct habitats|journal=Methods in Ecology and Evolution|language=en|volume=9|issue=1|pages=98–108|doi=10.1111/2041-210X.12847|s2cid=91050320|issn=2041-210X|doi-access=free|bibcode=2018MEcEv...9...98F }}</ref><ref>{{Cite journal|last1=Frans|first1=Veronica F.|last2=Augé|first2=Amélie A.|last3=Fyfe|first3=Jim|last4=Zhang|first4=Yuqian|last5=McNally|first5=Nathan|last6=Edelhoff|first6=Hendrik|last7=Balkenhol|first7=Niko|last8=Engler|first8=Jan O.|title=Integrated SDM database: Enhancing the relevance and utility of species distribution models in conservation management|url=https://onlinelibrary.wiley.com/doi/abs/10.1111/2041-210X.13736|journal=Methods in Ecology and Evolution|year=2022|volume=13|issue=1 |pages=243–261|language=en|doi=10.1111/2041-210X.13736|bibcode=2022MEcEv..13..243F |s2cid=243893898|issn=2041-210X}}</ref>
All otariids breed on land during well-defined breeding seasons. Except for the [[Australian sea lion]], which has an atypical 17.5 month breeding cycle, they form strictly annual aggregations on beaches or rocky substrates, often on islands. All species are [[Polygyny in animals|polygynous]]; i.e. successful males breed with several females. In most species, males arrive at breeding sites first and establish and maintain territories through vocal and visual displays and occasional fighting. Females typically arrive on shore a day or so before giving birth. While considered social animals, no permanent hierarchies or statuses are established on the colonies. The extent to which males control females or territories varies between species. Thus, the northern fur seal and the [[South American sea lion]] tend to herd specific [[Harem (zoology)|harem]]-associated females, occasionally injuring them, while the Steller sea lion and the [[New Zealand sea lion]] control spatial territories, but do not generally interfere with the movement of the females. Female New Zealand sea lions are the only otariids that move up to {{Convert|2|km|mi|abbr=on}} into forests to protect their pups during the breeding season.<ref>{{Cite journal|last1=Augé|first1=Amélie|last2=Chilvers|last3=Moore|last4=Mathieu|last5=Robertson|date=2009-01-01|title=Aggregation and dispersion of female New Zealand sea lions at the Sandy Bay breeding colony, Auckland Islands: How unusual is their spatial behaviour?|url=https://brill.com/view/journals/beh/146/9/article-p1287_7.xml|journal=Behaviour|language=en|volume=146|issue=9|pages=1287–1311|doi=10.1163/15683909X427687|issn=0005-7959|url-access=subscription}}</ref><ref>{{Cite journal|last1=Augé|first1=Amélie A.|last2=Chilvers|first2=B. Louise|last3=Mathieu|first3=Renaud|last4=Moore|first4=Antoni B.|date=2012|title=On-land habitat preferences of female New Zealand sea lions at Sandy Bay, Auckland Islands|url=https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1748-7692.2011.00515.x|journal=Marine Mammal Science|language=en|volume=28|issue=3|pages=620–637|doi=10.1111/j.1748-7692.2011.00515.x|bibcode=2012MMamS..28..620A |issn=1748-7692|url-access=subscription}}</ref><ref>{{Cite journal|last1=Frans|first1=Veronica F.|last2=Augé|first2=Amélie A.|last3=Edelhoff|first3=Hendrik|last4=Erasmi|first4=Stefan|last5=Balkenhol|first5=Niko|last6=Engler|first6=Jan O.|date=2018|title=Quantifying apart what belongs together: A multi-state species distribution modelling framework for species using distinct habitats|journal=Methods in Ecology and Evolution|language=en|volume=9|issue=1|pages=98–108|doi=10.1111/2041-210X.12847|s2cid=91050320|issn=2041-210X|doi-access=free|bibcode=2018MEcEv...9...98F }}</ref><ref>{{Cite journal|last1=Frans|first1=Veronica F.|last2=Augé|first2=Amélie A.|last3=Fyfe|first3=Jim|last4=Zhang|first4=Yuqian|last5=McNally|first5=Nathan|last6=Edelhoff|first6=Hendrik|last7=Balkenhol|first7=Niko|last8=Engler|first8=Jan O.|title=Integrated SDM database: Enhancing the relevance and utility of species distribution models in conservation management|url=https://onlinelibrary.wiley.com/doi/abs/10.1111/2041-210X.13736|journal=Methods in Ecology and Evolution|year=2022|volume=13|issue=1 |pages=243–261|language=en|doi=10.1111/2041-210X.13736|bibcode=2022MEcEv..13..243F |s2cid=243893898|issn=2041-210X}}</ref>


Line 115: Line 110:
==Species==
==Species==
'''Family Otariidae'''
'''Family Otariidae'''
{{Columns-list|
* '''Subfamily [[Arctocephalinae]]''' (fur seals)
* '''Subfamily [[Arctocephalinae]]''' (fur seals)
** Genus ''[[Arctocephalus]]''
** Genus ''[[Arctocephalus]]''
Line 140: Line 136:
** Genus ''[[Zalophus]]''
** Genus ''[[Zalophus]]''
*** [[California sea lion]], ''Z. californianus''
*** [[California sea lion]], ''Z. californianus''
*** †[[Japanese sea lion]], ''Z. japonicus'' – [[extinct]] (1970s)<ref name=IUCN>{{cite iucn |author=Lowry, L. |date=2017 |title=''Zalophus japonicus'' |volume=2017 |page=e.T41667A113089431 |doi=10.2305/IUCN.UK.2017-1.RLTS.T41667A113089431.en |access-date=13 November 2021}}</ref><ref name=JIBIS>{{in lang|ja}} [https://www.biodic.go.jp/cgi-db/gen/RDB_G2000_DO.RDB_DETAIL?wamei=%a5%cb%a5%db%a5%f3%a5%a2%a5%b7%a5%ab ''Zalophus californianus japonicus'' (CR)], Red Data Book, Japan Integrated Biodiversity Information System, [[Ministry of the Environment (Japan)]]. "The Japanese sea lion (''Zalophus californianus japonicus'') was common in the past around the coast of the Japanese Archipelago, but declined rapidly after the 1930s from overhunting and increased competition with commercial fisheries. The last record in Japan was a juvenile, captured in 1974 off the coast of [[Rebun Island]], northern Hokkaido."</ref>
*** †[[Japanese sea lion]], ''Z. japonicus'' – [[extinct]] (1970s)<ref name=IUCN>{{cite iucn |author=Lowry, L. |date=2017 |title=''Zalophus japonicus'' |volume=2017 |article-number=e.T41667A113089431 |doi=10.2305/IUCN.UK.2017-1.RLTS.T41667A113089431.en |access-date=13 November 2021}}</ref><ref name=JIBIS>{{in lang|ja}} [https://www.biodic.go.jp/cgi-db/gen/RDB_G2000_DO.RDB_DETAIL?wamei=%a5%cb%a5%db%a5%f3%a5%a2%a5%b7%a5%ab ''Zalophus californianus japonicus'' (CR)], Red Data Book, Japan Integrated Biodiversity Information System, [[Ministry of the Environment (Japan)]]. "The Japanese sea lion (''Zalophus californianus japonicus'') was common in the past around the coast of the Japanese Archipelago, but declined rapidly after the 1930s from overhunting and increased competition with commercial fisheries. The last record in Japan was a juvenile, captured in 1974 off the coast of [[Rebun Island]], northern Hokkaido."</ref>
*** [[Galápagos sea lion]], ''Z. wollebaeki''
*** [[Galápagos sea lion]], ''Z. wollebaeki''
 
|colwidth=30}}
Although the two subfamilies of otariids, the Otariinae (sea lions) and Arctocephalinae (fur seals), are still widely used, recent molecular studies have demonstrated that they may be invalid.<ref name=Yonezawa2009>{{cite journal | author = Yonezawa, T. | year = 2009 | title = The monophyletic origin of sea lions and fur seals (Carnivora; Otariidae) in the Southern Hemisphere | journal = Gene | volume = 441 | issue = 1–2 | pages = 89–99 | doi = 10.1016/j.gene.2009.01.022 | pmid=19254754|display-authors=etal}}</ref><ref name=Arnason2006>{{cite journal | author = Arnason, U. | year = 2006 | title = Pinniped phylogeny and a new hypothesis for their origin and dispersal | journal = Molecular Phylogenetics and Evolution | volume = 41 | issue = 2 | pages = 345–354 | doi = 10.1016/j.ympev.2006.05.022 | pmid=16815048| bibcode = 2006MolPE..41..345A |display-authors=etal}}</ref> Instead, they suggest three [[clade]]s within the family; one consisting of the northern sea lions (''Eumetopias'' and ''Zalophus''), one of the northern fur seal (''Callorhinus'') and its extinct relatives, and the third of all the remaining Southern Hemisphere species.<ref name=Berta2012>{{cite journal |author1=Berta, A.  |author2=Churchill, M. | year = 2012 | title = Pinniped Taxonomy: evidence for species and subspecies | journal = Mammal Review | volume = 42 | issue = 3 | pages = 207–234 | doi = 10.1111/j.1365-2907.2011.00193.x}}</ref>
Although the two subfamilies of otariids, the Otariinae (sea lions) and Arctocephalinae (fur seals), are still widely used, recent molecular studies have demonstrated that they may be invalid as traditionally defined.<ref name=Yonezawa2009>{{cite journal | author = Yonezawa, T. | year = 2009 | title = The monophyletic origin of sea lions and fur seals (Carnivora; Otariidae) in the Southern Hemisphere | journal = Gene | volume = 441 | issue = 1–2 | pages = 89–99 | doi = 10.1016/j.gene.2009.01.022 | pmid=19254754|display-authors=etal}}</ref><ref name=Arnason2006>{{cite journal | author = Arnason, U. | year = 2006 | title = Pinniped phylogeny and a new hypothesis for their origin and dispersal | journal = Molecular Phylogenetics and Evolution | volume = 41 | issue = 2 | pages = 345–354 | doi = 10.1016/j.ympev.2006.05.022 | pmid=16815048| bibcode = 2006MolPE..41..345A |display-authors=etal}}</ref> Instead, they suggest three [[clade]]s within the family; one consisting of the northern sea lions (''Eumetopias'' and ''Zalophus''), one of the northern fur seal (''Callorhinus'') and its extinct relatives, and the third of all the remaining Southern Hemisphere species.<ref name=Berta2012>{{cite journal |author1=Berta, A.  |author2=Churchill, M. | year = 2012 | title = Pinniped Taxonomy: evidence for species and subspecies | journal = Mammal Review | volume = 42 | issue = 3 | pages = 207–234 | doi = 10.1111/j.1365-2907.2011.00193.x}}</ref>
<!-- Syst.Biodivers.1:339 -->
<!-- Syst.Biodivers.1:339 -->


Latest revision as of 14:32, 3 November 2025

Template:Short description Template:Automatic taxobox

An eared seal, otariid, or otary, is any member of the marine mammal family Otariidae, one of three groupings of pinnipeds. They comprise 15 extant species in seven genera (another species became extinct in the 1950s) and are commonly known either as sea lions or fur seals, distinct from true seals (phocids) and the walrus (odobenids). Otariids are adapted to a semiaquatic lifestyle, feeding and migrating in the water, but breeding and resting on land or ice. They reside in subpolar, temperate, and equatorial waters throughout the Pacific and Southern Oceans, the southern Indian, and Atlantic Oceans. They are conspicuously absent in the north Atlantic.

The words "otariid" and "otary" come from the Ancient Greek ὠτάριον (ōtárion), meaning "little ear",[1] referring to the small but visible external ear flaps (pinnae), which distinguishes them from the phocids.

Evolution and taxonomy

Morphological and molecular evidence supports a monophyletic origin of pinnipeds, sharing a common ancestor with Musteloidea,[2][3] though an earlier hypothesis suggested that Otаriidae are descended from a common ancestor most closely related to modern bears.[4] Debate remains as to whether the phocids diverged from the otariids before or after the walrus.

Otariids arose in the Miocene (15–17 million years ago) in the North Pacific, diversifying rapidly into the Southern Hemisphere, where most species now live. The earliest known fossil otariid is Eotaria crypta from southern California,[5] while the genus Callorhinus (northern fur seal) has the oldest fossil record of any living otariid, extending to the middle Pliocene. It probably arose from the extinct fur seal genus Thalassoleon.

Traditionally, otariids had been subdivided into the fur seal (Arctocephalinae) and sea lion (Otariinae) subfamilies, with the major distinction between them being the presence of a thick underfur layer in the former. Under this categorization, the fur seals comprised two genera: Callorhinus in the North Pacific with a single representative, the northern fur seal (C. ursinus), and eight species in the Southern Hemisphere under the genus Arctocephalus; while the sea lions comprise five species under five genera.[6] Recent analyses of the genetic evidence suggests that Callorhinus ursinus is in fact more closely related to several sea lion species.[7] Furthermore, many of the Otariinae appear to be more phylogenetically distinct than previously assumed; for example, the Japanese sea lion (Zalophus japonicus) is now considered a separate species, rather than a subspecies of the California sea lion (Zalophus californius).

In light of this evidence, the subfamily separation has been removed entirely and the family Otariidae has been organized into seven genera with 16 species and two subspecies.[8][9] Nonetheless, because of morphological and behavioral similarities among the "fur seals" and "sea lions", these remain useful categories when discussing differences between groups of species. Compared to sea lions, fur seals are generally smaller, exhibit greater sexual dimorphism, eat smaller prey and go on longer foraging trips; and, of course, there is the contrast between the coarse short sea lion hair and the fur seal's fur.

Cladogram showing relationships among the otarids, combining several phylogenetic analyses. The fur seal branch has not been resolved.[10]Template:Clarify

Template:Clade

Anatomy

Template:Multiple image

Otariids have proportionately much larger fore-flippers and pectoral muscles than phocids, and have the ability to turn their hind limbs forward and walk on all fours, making them far more maneuverable on land.Script error: No such module "Unsubst". They are generally considered to be less adapted to an aquatic lifestyle, since they breed primarily on land and haul out more frequently than true seals. However, they can attain higher bursts of speed and have greater maneuverability in the water. Their swimming power derives from the use of flippers more so than the sinuous whole-body movements typical of phocids and walruses.Script error: No such module "Unsubst".

Otariids are further distinguished by a more dog-like head, sharp, well-developed canines, and the aforementioned visible external pinnae. Their postcanine teeth are generally simple and conical in shape. The dental formula for eared seals is: Template:DentalFormula. Sea lions are covered with coarse guard hairs, while fur seals have a thick underfur, which has historically made them the objects of commercial exploitation.Script error: No such module "Unsubst".

Male otariids range in size from the Template:Convert Galápagos fur seal, smallest of all otariids, to the over 1,000-kg (2,200-lb) Steller sea lion. Mature male otariids weigh two to six times as much as females, with proportionately larger heads, necks, and chests, making them the most sexually dimorphic of all mammals.[11]

Behavior

File:Sea lion family.JPG
California sea lions

All otariids breed on land during well-defined breeding seasons. Except for the Australian sea lion, which has an atypical 17.5 month breeding cycle, they form strictly annual aggregations on beaches or rocky substrates, often on islands. All species are polygynous; i.e. successful males breed with several females. In most species, males arrive at breeding sites first and establish and maintain territories through vocal and visual displays and occasional fighting. Females typically arrive on shore a day or so before giving birth. While considered social animals, no permanent hierarchies or statuses are established on the colonies. The extent to which males control females or territories varies between species. Thus, the northern fur seal and the South American sea lion tend to herd specific harem-associated females, occasionally injuring them, while the Steller sea lion and the New Zealand sea lion control spatial territories, but do not generally interfere with the movement of the females. Female New Zealand sea lions are the only otariids that move up to Template:Convert into forests to protect their pups during the breeding season.[12][13][14][15]

Otariids are carnivorous, feeding on fish, squid and krill. Sea lions tend to feed closer to shore in upwelling zones, feeding on larger fish, while the smaller fur seals tend to take longer, offshore foraging trips and can subsist on large numbers of smaller prey items. They are visual feeders. Some females are capable of dives of up to Template:Convert.

Species

Family Otariidae Template:Columns-list Although the two subfamilies of otariids, the Otariinae (sea lions) and Arctocephalinae (fur seals), are still widely used, recent molecular studies have demonstrated that they may be invalid as traditionally defined.[16][17] Instead, they suggest three clades within the family; one consisting of the northern sea lions (Eumetopias and Zalophus), one of the northern fur seal (Callorhinus) and its extinct relatives, and the third of all the remaining Southern Hemisphere species.[18]

References

Template:Reflist

Further reading

  • Berta, A., and L. Sumich (1999) Marine Mammals: Evolutionary Biology. San Diego: Academic Press.
  • Gentry, R. L (1998) Behavior and Ecology of the Northern Fur Seal. Princeton: Princeton University Press.
  • Perrin, W. F., B. Würsig, and J. G. M. Thewissen (2002) Encyclopedia of Marine Mammals. San Diego: Academic Press.
  • Riedman, M. (1990) The Pinnipeds: Seals, Sea Lions and Walruses. Berkeley: University of California Press.

External links

Template:Carnivora Template:Pan-Pinnipedia Template:Taxonbar Template:Authority control

  1. ↑ "Otary, n., etymology of" The Oxford English Dictionary. 2nd ed. 1989. OED Online. Oxford University Press. http://dictionary.oed.com/ Template:Webarchive Accessed November 2007
  2. ↑ Script error: No such module "Citation/CS1".
  3. ↑ Script error: No such module "citation/CS1".
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  8. ↑ Script error: No such module "Citation/CS1".
  9. ↑ Script error: No such module "template wrapper".
  10. ↑ Script error: No such module "Citation/CS1".
  11. ↑ Script error: No such module "Citation/CS1".
  12. ↑ Script error: No such module "Citation/CS1".
  13. ↑ Script error: No such module "Citation/CS1".
  14. ↑ Script error: No such module "Citation/CS1".
  15. ↑ Script error: No such module "Citation/CS1".
  16. ↑ Script error: No such module "Citation/CS1".
  17. ↑ Script error: No such module "Citation/CS1".
  18. ↑ Script error: No such module "Citation/CS1".
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