Editing Steller sea lion

{{Short description|Species of carnivore}}
{{Distinguish|Steller's sea cow}}
{{Use dmy dates|date=December 2020}}
{{speciesbox
| name = Steller sea lion
| fossil_range = {{longitem|style=line-height:1.25em|{{nowrap|[[Calabrian (stage)|Early Pleistocene]] – [[Holocene|present]]}} {{nowrap|(~800,000–0 [[Before Present|YBP]])<ref name="Tsuzuku2020">{{Cite journal|last1=Tsuzuku|first1=Nahoko|last2=Kohno|first2=Naoki|date=27 August 2020|title=The oldest record of the Steller sea lion Eumetopias jubatus (Schreber, 1776) from the early Pleistocene of the North Pacific|journal=PeerJ|language=en|volume=8|pages=e9709|doi=10.7717/peerj.9709|issn=2167-8359|pmc=7456534|pmid=32913674 |doi-access=free|quote=The mandibular fossil (GKZ-N 00001) from the lower Pleistocene Omma Formation (0.8 Ma) is specifically identified as ''E. jubatus'' based on the morphometric analyses.}}</ref>}}}}
| image = Sivuchi.jpg
| image_caption = Adult male, female and pup on [[Yamsky Islands]] in the northeast [[Sea of Okhotsk]]
| image2            = Steller Sea Lion comparison png.png
| image2_caption    = {{longitem|Size of male (left) and female (middle) compared to a {{convert|1.75|m|adj=on|}} human}}
| status = NT
| status_system = IUCN3.1
| status_ref =<ref name="iucn status 19 November 2021">{{cite iucn |author=Gelatt, T. |author2=Sweeney, K. |date=2016 |title=''Eumetopias jubatus'' |volume=2016 |page=e.T8239A45225749 |doi=10.2305/IUCN.UK.2016-1.RLTS.T8239A45225749.en |access-date=19 November 2021}}</ref>
| status2 = G3
| status2_system = TNC
| status2_ref =<ref>{{cite web |title=NatureServe Explorer 2.0 |url=https://explorer.natureserve.org/Taxon/ELEMENT_GLOBAL.2.104433/Eumetopias_jubatus |website=explorer.natureserve.org |access-date=11 October 2022}}</ref>
| genus = Eumetopias
| parent_authority = [[Theodore Nicholas Gill|Gill]], 1866
| species = jubatus
| authority = ([[Johann Christian Daniel von Schreber|Schreber]], 1776)
| range_map = Eumetopias jubatus distribution continent labels.jpg
| range_map_caption = Range of Steller sea lions (purple = overall range, red = breeding rookeries)
}}

The '''Steller sea lion''' ('''''Eumetopias jubatus'''''), also known as '''Steller's sea lion''' or the '''northern sea lion''', is a large, [[near-threatened]] species of sea lion, predominantly found in the coastal marine habitats of the [[northeast Pacific Ocean]] and the [[Pacific Northwest]] regions of [[North America]], from north-central [[California]] to [[Oregon]], [[Washington (state)|Washington]] and [[British Columbia]] to [[Alaska]]. Its range continues across the [[Pacific Ocean|Northern Pacific]] and the [[Aleutian Islands]], all the way to [[Kamchatka]], [[Magadan Oblast]], and the [[Sea of Okhotsk]], south to [[Honshu]]'s northern coastline. It is the [[Monotypic taxon|sole member]] of the genus '''''Eumetopias''''', and the largest of the so-called [[eared seal]]s (Otariidae). Among [[pinnipeds]], only the [[walrus]] and the two species of [[elephant seal]] are bigger. The [[species]] is named for the naturalist and explorer [[Georg Wilhelm Steller]], who first described them in 1741. Steller sea lions have attracted considerable attention in recent decades, both from scientists and the general public, due to significant (and largely unexplained) declines in their numbers over an extensive portion of their northern range, notably in Alaska.

== Description ==
{{multiple image
| align             = right
| direction         = vertical
| image1            = Description iconographique comparée du squelette et du système dentaire des mammifères récents et fossiles (Eumetopias jubatus skull).jpg
| caption1          = Skull
| image2            = Description iconographique comparée du squelette et du système dentaire des mammifères récents et fossiles (Eumetopias jubatus).jpg
| caption2          = Skeleton
| image3            = Steller sea lion (Eumetopias jubatus) forelimb at the Field Museum, Chicago, IL (15130145368).jpg
| caption3          = Forelimb
}}
Adult animals are lighter in color than most sea lions, ranging from pale yellow to tawny and occasionally reddish. Steller sea lion pups are born almost black, weighing around {{convert|23|kg|lb|abbr=on}}, and remain dark in coloration for several months. Females reach sexual maturity between four and six years of age, while males have a wider window, reaching maturity between three and eight years of age.<ref name=":3" /> Females and males both grow rapidly until the fifth year, after which female growth slows considerably. Adult females measure {{convert|2.3|-|2.9|m|ft|abbr=on}} in length, on average being {{convert|2.5|m|ft|abbr=on}}, and weigh {{convert|240|-|350|kg|lb|abbr=on}}, with an average of {{convert|263|kg|lb|abbr=on}}.<ref>[https://marinebio.org/species.asp?id=314 Steller Sea Lions, Eumetopias jubatus]. marinebio.org</ref><ref>[http://www.nwr.noaa.gov/Marine-Mammals/Seals-and-Sea-Lions/Stellers.cfm Steller Sea Lions] {{Webarchive|url=https://web.archive.org/web/20120319035134/http://www.nwr.noaa.gov/Marine-Mammals/Seals-and-Sea-Lions/Stellers.cfm |date=19 March 2012 }}. Northwest Regional Office. noaa.gov</ref> Males continue to grow until their [[Secondary sex characteristic|secondary sexual traits]] appear in their fifth to eighth year. Males are slightly longer than the females, growing to about {{convert|2.82|–|3.25|m|ft|abbr=on}} long and averaging {{convert|3|m|ft|abbr=on}} in length.<ref>{{cite journal |author1=Loughlin, Thomas R |author2=Perez, Michael A |author3=Merrick, Richard L |title=Eumetopias jubatus |journal=Mammalian Species |issue=283 |pages=1–7 |url=http://www.science.smith.edu/msi/pdf/i0076-3519-283-01-0001.pdf |doi=10.2307/3503908 |jstor=3503908 |year=1987 |access-date=27 October 2012 |archive-date=3 March 2016 |archive-url=https://web.archive.org/web/20160303221734/http://www.science.smith.edu/msi/pdf/i0076-3519-283-01-0001.pdf |url-status=dead }}</ref> Males have much wider chests, necks, and general forebody structure. Males can weigh between {{convert|450|–|1120|kg|lb|abbr=on}}, weighing on average {{convert|544|kg|lb|abbr=on}}.<ref name="Animal">{{cite book |last=Kindersley |first= Dorling |year=2001 |title=Animal |location=New York City |publisher=DK Publishing |isbn=978-0-7894-7764-4}}</ref><ref>Keranen, Danielle. [http://animaldiversity.ummz.umich.edu/site/accounts/information/Eumetopias_jubatus.html ''Eumetopias jubatus''. Steller sea lion]. [[Animal Diversity Web]]</ref><ref>Olesiuk, Peter F, and Bigg, Michael A. (~1984) [http://www.racerocks.com/racerock/rreo/rreoref/mmammals/sealsandsealions.htm Marine mammals in British Columbia].</ref> Males are further distinguished from females by broader and higher foreheads, flatter snouts, and a thick mane of coarse hair<ref>{{cite web|title=Steller Sea Lion (Eumetopias jubatus)|url=https://www.fisheries.noaa.gov/pr/species/mammals/sealions/steller-sea-lion.html|website=NOAA Fisheries|access-date=21 May 2017}}</ref> around their large necks. Their Latin name translates roughly as "maned one with the broad forehead".

== Range ==
[[Image:Steller sealions bc 1.jpg|thumb|Steller sea lions congregate on rocks in the [[Gulf Islands]] of [[British Columbia]], Canada.]]

The [[Range (biology)|range]] of the Steller sea lion extends from the north shore of [[Honshu]] in Japan to the [[Gulf of Alaska]] in the north, down to [[Año Nuevo Island]] off the coast of central California to the south. They formerly bred as far south as the [[Channel Islands of California|Channel Islands]], but have not been observed there since the 1980s. Based on genetic anаlyses and local migration patterns, the global Steller sea lion population has traditionally been divided into an eastern and western stock at 144°W longitude, roughly through the middle of the Gulf of Alaska.<ref>[http://www.nmfs.noaa.gov/pr/pdfs/sars/ak2009slst-w.pdf Alaska Marine Mammal Stock Assessments, 2009]. (PDF) . Retrieved on 16 September 2011.</ref><ref>Allen, B. M., and R. P. Angliss (revised 25 November 2008) [http://www.nmfs.noaa.gov/pr/pdfs/sars/ak2009slst-e.pdf NOAA-TM-AFSC-206. STELLER SEA LION (''Eumetopias jubatus''): Eastern U. S. Stock]. (PDF).</ref> Recent evidence suggests the sea lions in Russia in the [[Sea of Okhotsk]] and the [[Kuril Islands]] comprise a third Asian stock, while the sea lions on the eastern seaboard of [[Kamchatka]] and the [[Commander Islands]] belong to the western stock.

In the summer, Steller sea lions tend to shift their range somewhat southward. Therefore, though there are no reproductive rookeries in Japan, several consistent [[hauling-out|haul-out]] sites are found around [[Hokkaidō]] in the winter and spring. Vagrants have been spotted in the [[Yellow Sea]] and [[Bohai Gulf]] and along the coast of the [[Korean Peninsula]] and China.<ref name="iucn status 19 November 2021" /><ref>[https://www.pinnipeds.org/seal-information/species-information-pages/sea-lions-and-fur-seals/steller-sea-lion "Steller Sea Lion (''Eumetopias jubatus'')" Seal Conservation Society] Accessed 25 April 2013</ref> The oldest fossil known of the species was found near [[Kanazawa]], Japan and dates to the late [[Early Pleistocene]], approximately 800,000 years ago.<ref name="Tsuzuku2020"/>

== Ecology ==

=== Habitat ===
Steller sea lions tend to live in the coastal waters of the [[Subarctic climate|subarctic]] because of the cooler temperate climate of the area.<ref name=":3">{{Cite web|url=https://www.fisheries.noaa.gov/species/steller-sea-lion|title=Steller Sea Lion {{!}} NOAA Fisheries|last=Fisheries|first=NOAA|date=29 May 2018|website=www.fisheries.noaa.gov|access-date=7 June 2018}}</ref> Like all [[Eared seal|otariids]], Steller sea lions are amphibious and spend some time in water and some on land.<ref name=":1">{{Citation|last=Gentry|first=Roger L.|date=2009|pages=339–342|publisher=Elsevier|doi=10.1016/b978-0-12-373553-9.00083-3|isbn=9780123735539|title=Encyclopedia of Marine Mammals|chapter=Eared Seals}}</ref> Typically, Steller sea lions spend their time in the water feeding but [[Hauling-out|haul-out]] onto land to reproduce, raise their pups, [[Moulting|molt]], and rest.<ref>{{Cite journal|last1=Sepúlveda|first1=Maritza|last2=Santos|first2=Macarena|last3=Veas|first3=Rodrigo|last4=Muñoz|first4=Lily|last5=Olea|first5=Danai|last6=Moraga|first6=Rodrigo|last7=Sielfeld|first7=Walter|date=August 2015|title=Annual, seasonal and daily variation in the abundance of the South American sea lion Otaria flavescens in two breeding colonies in northern Chile|journal=Revista de Biología Marina y Oceanografía|volume=50|issue=2|pages=205–220|doi=10.4067/S0718-19572015000300001|issn=0718-1957|doi-access=free}}</ref> Steller sea lions usually congregate on isolated islands because they are the ideal terrestrial habitat. These isolated islands are preferred by Steller sea lions because they can avoid predation from terrestrial predators, easily [[Thermoregulation|thermoregulate]] (by means of cooling winds), and access offshore prey more easily.<ref name=":1" /> Some haul-out sites, known as [[Rookery|rookeries]], are commonly used for reproduction while other haul-out sites are used for other purposes like molting.<ref name=":2">{{Cite journal|last1=Loughlin|first1=Thomas R.|last2=Rugh|first2=David J.|last3=Fiscus|first3=Clifford H.|date=1984|title=Northern Sea Lion Distribution and Abundance: 1956–80|jstor=3801420|journal=The Journal of Wildlife Management|volume=48|issue=3|pages=729–740|doi=10.2307/3801420}}</ref> However, both [[Biotic factor|biotic]] and [[Abiotic component|abiotic]] factors can influence the amount of time that Steller sea lions spend on land. Haul-out sites and haul-out abundance of the Steller sea lion can be determined by prey availability, predator abundance, tide levels, weather, etc.<ref name=":2" />

=== Foraging ===
[[File:Sea lion and Sturgeon.jpg|thumb|upright=1.25|Sea lion with [[white sturgeon]]]]

Steller sea lions are skilled and [[opportunism|opportunistic]] marine predators, feeding on a wide range of fish and [[cephalopod]] species. Important diet components include [[Alaska pollock|walleye pollock]],<ref name="Sinclair 2002" /><ref name="Keyes 1968">Keyes, M. C. (1968). "The nutrition of pinnipeds", pp. 359–395 in R. J. Harrison, R. C. Hubbard, R. S. Peterson, C. E. Rice, and R. J. Schusterman (eds.) ''The behavior and physiology of pinnipeds''. Appleton, Century-Crofts, New York.</ref> [[Atka mackerel]],<ref name="Sinclair 2002" /> [[halibut]],<ref name="Keyes 1968" /> [[herring]], [[capelin]],<ref name="Mathisen 1962" /> [[flatfish]]<ref name="Mathisen 1962" /><ref name="Fiscus">{{cite journal|title=Food and Feeding Behavior of Steller and California Sea Lions|journal=Journal of Mammalogy|volume=47|issue=2 |year=1966|pages=195–200|jstor=1378115|doi=10.2307/1378115|last1=Fiscus|first1=C. H.|last2=Baines|first2=G. A.}}</ref> [[Pacific cod]],<ref name="Sinclair 2002">{{cite journal|jstor=1383503|journal=Journal of Mammalogy|volume=83|issue=4 |year=2002|pages=973–990|title=Seasonal and Spatial Differences in Diet in the Western Stock of Steller Sea Lions (''Eumetopias jubatus'')|doi=10.1644/1545-1542(2002)083<0973:SASDID>2.0.CO;2|last1=Sinclair|first1=E. H.|last2=Zeppelin|first2=T. K.|doi-access=free}}</ref><ref name="Keyes 1968" /> [[Sebastes|rockfish]],<ref name="Mathisen 1962">{{cite journal|title=Breeding Habits, Growth and Stomach Contents of the Steller Sea Lion in Alaska|journal=Journal of Mammalogy|volume=43|issue=4|year=1962|pages=469–477|jstor=1376909|doi=10.2307/1376909|last1=Mathisen|first1=O. A.|last2=Baade|first2=R. T.|last3=Lopp|first3=R. J.}}</ref><ref name="Fiscus" /> [[sculpins]],<ref name="Mathisen 1962" /> salmon, sand lance, and [[cephalopod]]s such as various squid and octopus.<ref name="Sinclair 2002" /> They seem to prefer schooling fish and forage primarily between [[Tidal zone|intertidal zones]] and [[Continental shelf|continental shelves]]. They usually aggregate in groups of up to twelve in areas of prey abundance. They are known to aggregate near fishing vessels, preying on [[bycatch]] discards. Most of the data on their foraging comes from data collected off the coast of Alaska; little is known of their foraging behavior elsewhere.

The composition of the diet of Steller sea lions varies seasonally and geographically; as opportunistic predators, they concentrate on the locally most abundant prey species.<ref>{{Cite web|url=https://www.afsc.noaa.gov/Education/factsheets/10_SSL_FS.pdf|title=Alaska &#124; NOAA Fisheries|date=7 September 2021}}</ref> In addition to their primary marine environment, they sometimes enter [[estuarine|estuaries]] and feed on brackish-water fish such as [[sturgeon]]. Very occasionally, they have been known to prey on [[northern fur seal]]s, [[harbor seal]]s, and [[sea otter]] pups. Records suggest that the range of their prey species has broadened over time.<ref name="iucn status 19 November 2021" />

=== Predation ===
Steller sea lions are top-tier carnivores, but are susceptible to predation, primarily by [[killer whale]]s. Shark species are also possible predators: [[sleeper shark|sleeper]]s and [[great white shark|great white]]s may prey on juvenile sea lions.<ref name="iucn status 19 November 2021" />

== Behavior and life history ==

=== Reproduction ===
[[File:2008 Juneau Steller Sea Lion Haram (8101629225).jpg|thumb|Adult bull, females, and pups near [[Juneau, Alaska]], US]]

Reproductively mature male sea lions gather together mid-spring on traditional, well-defined reproductive [[rookery|rookeries]], usually on beaches on isolated islands. The larger, older males establish and defend distinct territories on the rookery. A week or so later, adult females arrive, accompanied occasionally by sexually immature offspring, and form fluid aggregations throughout the rookery. Like all other [[Otariidae|otariids]], Steller sea lions are [[Polygyny in animals|polygynous]]. However, unlike some other species, they do not coerce individual females into harems, but control spatial territories among which females freely move. Steller sea lions have used aquatic, semiaquatic, and terrestrial territories. Males with semiaquatic territories have the most success in defending them. The boundaries are defined by natural features, such as rocks, faults, or ridges in rocks, and territories can remain stable for&nbsp;60 days.<ref name="Gentry 1970">Gentry, R. L. (1970). "Social Behavior of the Steller’s Sea Lion". PhD Thesis, University of California, Santa Cruz, CA.</ref><ref name= 'Sandergen 1970'>Sandergen, F. E. (1970). 'Breeding and Maternal Behavior of the Steller's Sea Lion (''Eumetopias jubatus'') in Alaska', M. S. Thesis, University of Alaska, College.</ref> Though Steller sea lion males are generally tolerant of pups, one male filmed on [[Medny Island]] in Russia was documented killing and eating several pups in a first-ever recorded incident of [[cannibalism]]. Though researchers are uncertain as to the motives or reasons behind said attacks, it is suggested that the bull involved may have an abnormal personality akin to being psychotic.<ref>{{cite web|url=http://news.nationalgeographic.com/2017/08/sea-lions-cannibalism-russia-killing/|archive-url=https://web.archive.org/web/20170816075755/http://news.nationalgeographic.com/2017/08/sea-lions-cannibalism-russia-killing/|url-status=dead|archive-date=16 August 2017|title=Cannibal Sea Lion Kills and Eats Pup—Never Before Seen|date=16 August 2017|website=nationalgeographic.com}}</ref>

Pregnant females give birth soon after arriving on a rookery, and copulation generally occurs one to two weeks after giving birth,<ref name="Gentry 1970"/><ref name="Sandergen 1970"/> but the fertilized egg does not become implanted in the uterus until the fall. A fertilized egg may remain in [[embryonic diapause]] for up to three months before implanting and beginning to divide.<ref name=":0">{{Cite journal|last=Pitcher|first=Kenneth W.|date=1998|title=Reproductive Performance of female Steller sea lions: an energetics-based reproductive strategy?|journal=Canadian Journal of Zoology|volume=76|issue=11|pages=2075–2083|doi=10.1139/z98-149|bibcode=1998CaJZ...76.2075P }}</ref> Twins are rare.<ref>[https://www.adfg.alaska.gov/index.cfm?adfg=stellersealion.main Alaska Department of Fish and Game, "Life History"]. Adfg.alaska.gov. Retrieved on 17 December 2011.</ref> After a week or so of nursing without leaving the rookery, females begin to take progressively longer and more frequent foraging trips leaving their pups behind until at some point in late summer, when both the mother and pup leave the rookery together. This maternal attendance pattern is common in otariids. As pups get older the amount of time spent by females foraging out at sea increases. This continues until pups obtain the ideal body weight and energy reserves to eat on their own. A study conducted by the University of California, Santa Cruz found that on average male pups consume more milk than females. This may be due to the sexual dimorphism common to otariids.<ref>{{Cite journal|last=Higgins|first=Lesley V.|date=January 1988|title=Behavioral and Physiological Measurements of Maternal Investment in the Steller Sea Lion, Eumetopias jubatus|journal=Marine Mammal Science|volume=4|issue=1 |pages=44–58|doi=10.1111/j.1748-7692.1988.tb00181.x|bibcode=1988MMamS...4...44H }}</ref> Reproductive males fast throughout the reproductive season,<ref>Riedman, M. (1990). [https://archive.org/details/pinnipedssealsse0000ried/page/200 ''The Pinnipeds: Seals, Sea lions, and Walruses.''] Los Angeles, University of California Press. p. 200 {{ISBN|0-520-06497-6}}.</ref> often without entering the water once from mid-May until August, when the structure of the reproductive rookeries begins to fall apart and most animals leave for the open seas and disperse throughout their range.
[[Image:wikipup.jpg|thumb|Steller sea lion pup on Antsiferov Island in the Kuril Islands, Russia]]
The age at weaning is highly variable; pups may remain with their mothers for as long as four years. Incidents of mothers feeding daughters that are simultaneously feeding their own newborn pups have been documented, which is an extremely rare occurrence among mammals. A study done at Año Nuevo in 1983 found that female attendance and time spent with their pup was shaped by increasing nutritional demands of the pup and the pups suckling efficiency. Females averaged 21 hours ashore and 36 hours at sea. As the pups aged, females began to spend more time at sea again. As the pups matured, specifically at the sixth week past birth, the mother's sea time declined by 30 percent. There was no relationship between the pups' activity or physical excursion and their suckling time, age, or sex. Their suckling time, and age, and sex are unrelated to their use of energy. Labeled water studies showed that the pups' milk intake had a direct relationship to their size. Pups that consumed more milk were heavier than those that did not. These findings show that the amount of time females spend onshore with their pups is based on their pup's suckling efficiency and nutritional demands.<ref>{{Cite journal|last1=Higgins|first1=Lesley V.|last2=Costa|first2=Daniel P.|last3=Huntley|first3=Anthony C.|last4=Boeuf|first4=Burney J.|date=January 1988|journal=Marine Mammal Science|volume=4|issue=1|pages=44–58|doi=10.1111/j.1748-7692.1988.tb00181.x|issn=0824-0469|title=Behavioral and Physiological Measurements of Maternal Investment in the Steller Sea Lion, Eumetopias Jubatus|bibcode=1988MMamS...4...44H }}</ref>

In the past, the low pup production has been tied to an increase in nutritional stress found in females. This was believed to have contributed to the decline in Steller sea lions common to Alaska.<ref name=":0" />

=== Locomotion ===
The largest of the eared seals, Steller sea lions are quick swimmers, about as fast as the smaller [[California sea lion]]s. Glide velocity of individual Steller sea lions has been measured as 2.9–3.4 meters or 1.2–1.5 body lengths per second, which is close to the optimal swim velocity of 1.4 body lengths per second based on the minimum [[cost of transport]] for California sea lions.<ref>{{Cite journal|last1=Stelle|first1=Liu|last2=Blake|first2=R|last3=Trites|first3=Andrew|date=1 July 2000|title=Hydrodynamic drag in Steller sea lions (|url=https://www.researchgate.net/publication/12495826|journal=The Journal of Experimental Biology|volume=203|issue=Pt 12|pages=1915–23|doi=10.1242/jeb.203.12.1915|pmid=10821748}}</ref>

A 2007 study of Steller sea lions found that a majority of thrust was produced during the [[Anatomy of a rowing stroke|drive phase]] of the fore flipper stroke cycle. Although previous findings on eared seals suggested that thrust was generated by the initial outward movement of the [[Flipper (anatomy)|foreflippers]] or the terminal drag-based paddling phase, the 2007 study found that little or no thrust was generated during those phases. Swimming performance in sea lions is modulated by changes in the duration and intensity of movements without changing their sequence. Using criteria based on velocity and the minimum radius of turns, Steller sea lions' maneuverability is similar to that of other eared seals, superior to that of cetaceans, and inferior to that of many fish.<ref>{{Cite journal|last1=Cheneval|first1=O.|last2=Blake|first2=R.|last3=Trites|first3=Andrew|last4=Chan|first4=K.|date=1 January 2007|title=Turning maneuvers in Steller sea lions (Eumatopias jubatus)|url=https://www.researchgate.net/publication/227643867|journal=Marine Mammal Science|volume=23|issue=1 |pages=94–109|doi=10.1111/j.1748-7692.2006.00094.x|bibcode=2007MMamS..23...94C }}</ref>

=== Diving ===
[[Image:Ejbubbles1.jpg|thumb|right|Sea lion releasing air underwater]]

To be able to dive for a long period of time, Steller sea lions exhibit [[apnea]], [[bradycardia]], and [[Vasoconstriction|peripheral vasoconstriction]]. This allows them to maximize their oxygen stores and efficiently forage during their dives. In addition to those adaptations, their thick [[blubber]] layer and outer fur layer keep their body insulated during dives.<ref>{{Cite report|last1=Maser|first1=Chris|last2=Mate|first2=Bruce R.|last3=Franklin|first3=Jerry F.|last4=Dyrness|first4=C.T.|date=1981|title=Natural History of Oregon Coast Mammals|series=General technical report PNW; 133|publisher=Pacific Northwest Forest and Range Experiment Station, U.S. Dept. of Agriculture, Forest Service|location=Portland, OR|doi=10.2737/pnw-gtr-133|hdl=2027/uc1.31822028174480|s2cid=128550106|hdl-access=free}}</ref>

Trained Steller sea lions from [[Vancouver Aquarium]] were placed in the open ocean at the University of British Columbia's Open Water Research Station to study their diving [[metabolism]] and behavior.<ref>{{Cite journal|last1=Rosen|first1=David A. S.|last2=Hindle|first2=Allyson G.|last3=Gerlinsky|first3=Carling D.|last4=Goundie|first4=Elizabeth|last5=Hastie|first5=Gordon D.|last6=Volpov|first6=Beth L.|last7=Trites|first7=Andrew W.|date=29 September 2016|title=Physiological constraints and energetic costs of diving behaviour in marine mammals: a review of studies using trained Steller sea lions diving in the open ocean|journal=Journal of Comparative Physiology B|volume=187|issue=1|pages=29–50|doi=10.1007/s00360-016-1035-8|pmid=27686668|issn=0174-1578|hdl=10023/11765|s2cid=7209195|hdl-access=free}}</ref> Steller sea lions' dives are more energetically costly if they perform dive bouts. The aerobic diving limit of Steller sea lions was observed to be affected by their nutritional state and feeding.<ref>{{Cite journal|last1=Svärd|first1=C|last2=Fahlman|first2=A|last3=Rosen|first3=DAS|last4=Joy|first4=R|last5=Trites|first5=A|date=28 December 2009|title=Fasting affects the surface and diving metabolic rates of Steller sea lions Eumetopias jubatus|journal=Aquatic Biology|volume=8|pages=71–82|doi=10.3354/ab00211|issn=1864-7782|doi-access=free|bibcode=2009AquaB...8...71S}}</ref>

=== Communication ===
[[File:Steller sea lions in the Bukhta Russkaya, Kamchatka.webm|thumb|150px|upright=1.25|Steller sea lions congregate on Cape of Kekurny rocks in the Bukhta Russkaya of [[Kamchatka Krai|Kamchatka]].]]

Like most otariids, Steller sea lions are vocal in air. Mature male sea lions have a range of vocalizations as part of their territorial behaviors, including belches, growls, snorts, and hisses that serve as warnings to others. Both males and females also produce underwater noises similar to their above water sounds, described as clicks, barks, and belches.<ref>{{cite journal | last1 = Schusterman | first1 = R. J. | last2 = Balliet | first2 = R. F. | last3 = John | first3 = S. S. | year = 1970 | title = Vocal displays under water by the gray seal, the harbor seal,. and the stellar sea lion | journal = Psychonomic Science | volume = 18 | issue = 5| pages = 303–305 | doi = 10.3758/bf03331839 | doi-access = free }}</ref> The primary function of their vocalizations is for social behavior. Sonogram readings reported that Steller Sea Lions make discrete, low frequency pulses underwater that resemble the male "belching" territorial noise made in air. These underwater vocalizations have an average of 20–30 pulses per second.<ref>{{Cite journal|url=https://link.springer.com/content/pdf/10.3758/BF03331839.pdf|doi=10.3758/bf03331839|title=Vocal displays under water by the gray seal, the harbor seal,. And the stellar sea lion|journal=Psychonomic Science|volume=18|issue=5|pages=303–305|year=1970|last1=Schusterman|first1=Ronald J.|last2=Balliet|first2=Richard F.|last3=St. John|first3=Stanley|s2cid=130930524|doi-access=free}}</ref>

Vocalizations are critical to mother-pup pairs, as the mothers must find their pups in a crowded breeding area when they return from foraging. The mother and pup both use distinctive calls, like names, to help differentiate themselves among the crowd of other sea lions.<ref>{{cite journal | last1 = Campbell | first1 = G. S. | last2 = Gisiner | first2 = R. C. | last3 = Helweg | first3 = D. A. | last4 = Milette | first4 = L. L. | year = 2002 | title = Acoustic identification of female Steller sea lions (Eumetopias jubatus) | journal = The Journal of the Acoustical Society of America | volume = 111 | issue = 6| pages = 2920–2928 | doi = 10.1121/1.1474443 | pmid = 12083225 | bibcode = 2002ASAJ..111.2920C }}</ref> Their aerial vocalizations have been described as similar to the bleats of sheep, and bellows.

Because Steller sea lions are sexually dimorphic in size, their hearing differs in sensitivity, possibly due to differences in size of the hearing structures. Females have a higher sensitivity than males, perhaps to hear the higher frequency calls of their pups. The Steller sea lion's hearing range also suggests that they are capable of hearing the underwater calls of one of their main predators, the killer whale.<ref>{{cite journal | last1 = Kastelein | first1 = R. A. | last2 = van Schie | first2 = R. | last3 = Verboom | first3 = W. C. | last4 = de Haan | first4 = D. | year = 2005 | title = Underwater hearing sensitivity of a male and a female Steller sea lion (Eumetopias jubatus) | journal = The Journal of the Acoustical Society of America | volume = 118 | issue = 3| pages = 1820–1829 | doi = 10.1121/1.1992650 | pmid = 16240840 | bibcode = 2005ASAJ..118.1820K }}</ref>

== Interactions with humans ==
[[File:Amak Island, Steller's Sea Lion haul out.jpg|thumb|Sea lions haul out on [[Amak Island]].]]

Steller sea lion were hunted for meat and other commodities by prehistoric communities everywhere their range intersected with human communities. Aside from food and clothing, their skin was used to cover [[baidarka]]s and [[kayak]]s. A subsistence harvest on the order of 300 animals or less continues to this day in some native communities in Alaska.<ref name="iucn status 19 November 2021" />

Historically, the sea lion has had only very slight commercial value. For example, in the 19th century their [[whisker]]s sold for a penny apiece for use as tobacco-[[pipe cleaner]]s.<ref>Haynes, Terry L. and Mishler, Craig (1991) [http://www.subsistence.adfg.state.ak.us/TechPap/tp198.pdf The subsistence harvest and use of Steller sea lions in Alaska]. Technical paper no. 198. Alaska Dept. of Fish and Game, Division of Subsistence. Juneau, Alaska</ref>

Steller sea lions are sometimes killed intentionally by fishermen, as they are seen as competitors and a threat to fish stocks.<ref name="iucn status 19 November 2021" /> Killing sea lions is strictly prohibited in the US and Russia; however, in Japan, a fixed number are still harvested annually, ostensibly to protect their fisheries. In Canada, commercial hunting is prohibited, but limited hunting permits are occasionally granted for [[First Nations in Canada|First Nations]] communities, or if local culling is deemed necessary, for example, nuisance animals destroying fish farms.<ref>{{Cite web |last=Canada |first=Environment and Climate Change |date=2009-11-27 |title=Steller sea lion (Eumetopias jubatus) COSEWIC assessment and status report: chapter 12 |url=https://www.canada.ca/en/environment-climate-change/services/species-risk-public-registry/cosewic-assessments-status-reports/steller-sea-lion/chapter-12.html |access-date=2025-02-10 |website=www.canada.ca}}</ref>

In recent years, Steller sea lions have been known to enter the [[Columbia River]] estuary and feed on [[white sturgeon]], several [[Pacific salmon|salmon]] species, and [[rainbow trout]], some of which are also listed under the U.S. [[Endangered Species Act]]. They are found in the Columbia River nearly year round,<ref>{{Cite book|url=https://www.researchgate.net/publication/331354748|title=Evaluation of Pinniped Predation On Adult Salmonids and Other Fish In The Bonneville Dam Tailrace, 2018|last1=Tidwell|first1=Kyle|last2=Carrothers|first2=Brett|last3=Bayley|first3=Kristen|last4=Magill|first4=Lindsay|last5=van der Leeuw|first5=Bjorn|date=24 January 2019|doi=10.13140/rg.2.2.33686.60482}}</ref> with the exception of early summer, going as far upstream as [[Bonneville Dam]].<ref>{{citation |url=http://www.nwr.noaa.gov/marine-mammals/seals-and-sea-lions/upload/cr-pinniped-fs.pdf |date=March 2008 |title=Seal & Sea Lion Facts of the Columbia River & Adjacent Nearshore Marine Areas |publisher=[[NOAA]] |access-date=16 April 2012 |archive-url=https://web.archive.org/web/20120723020046/http://www.nwr.noaa.gov/Marine-Mammals/Seals-and-Sea-Lions/upload/CR-Pinniped-FS.pdf |archive-date=23 July 2012 |url-status=dead }}</ref> Though not as abundant as the [[California sea lion]], there is still concern amongst agencies tasked with managing and monitoring the fish populations; as the Steller sea lions are, themselves, protected under the [[Marine Mammal Protection Act of 1972|Marine Mammal Protection Act]],<ref name="iucn status 19 November 2021" /> managers are implored to use non-harmful, non-lethal deterrence methods (such as rubber bullets, bullhorns and other noisemakers). Interference or deterrence by the general public is unlawful, unregulated, and considered to be stressful (even disruptive) to the animals and their habits. Additionally, the massive size of the Steller sea lion—and potential for aggression—poses a real threat for humans; thus, the interfering with, molestation or frightening of marine mammals is strictly forbidden. Offenders are subject to varying fines, court appearances and even jail time.

=== Recent decline and subsequent recovery ===
[[File:Stellers Sea Lions BC.jpg|thumb|Near [[Vancouver Island]]]]
[[File:RBCM - Diorama Coastal Cliffs 2.jpg|right|thumb|Taxidermied specimens, [[Royal British Columbia Museum]]]]
While the populations of the eastern and Asian stocks appear stable, the population of the western stock, particularly along the [[Aleutian Islands]], was estimated to have fallen by 70–80% since the 1970s. As a consequence, in 1997 the western stock of Steller sea lions was listed as [[endangered]] and the eastern stock was listed as threatened under the United States [[Endangered Species Act]].<ref>[https://www.nmfs.noaa.gov/pr/species/mammals/pinnipeds/stellersealion.htm Steller Sea Lion]. US National Marine Fisheries Service .</ref><ref>[http://ecos.fws.gov/ecp0/profile/speciesProfile?spcode=A0FS Steller sea lion (''Eumetopias jubatus'')]. U.S. Fish & Wildlife Service.</ref> They have since been the object of intense study and the focus of much political and scientific debate in [[Alaska]].

One suspected cause of their precipitous decline was the overfishing of [[Alaska pollock]], [[herring]], and other fish stocks in the Gulf of Alaska. This stems largely from the "junk-food hypothesis" representing a shift in their diet from fatty herring and capelin to leaner fare such as pollock and flounder, thereby limiting their ability to consume and store fat.<ref>[https://www.economist.com/node/21556804 Biodiversity: Pity the copepod]. The Economist (16 June 2012). Retrieved on 27 October 2012.</ref> Other hypotheses include increased predation by [[orca]]s<ref>{{cite journal|title=Predation on an Upper Trophic Marine Predator, the Steller Sea Lion: Evaluating High Juvenile Mortality in a Density Dependent Conceptual Framework|doi=10.1371/journal.pone.0030173|year=2012|journal=PLOS ONE|volume=7|issue=1|pages=e30173 |pmid=22272296|pmc=3260237|last1=Horning|first1=M|last2=Mellish|first2=J. A.|bibcode=2012PLoSO...730173H|doi-access=free}}</ref> and sharks,<ref>{{cite journal|title=In cold blood: evidence of Pacific sleeper shark (''Somniosus pacificus'') predation on Steller sea lions (''Eumetopias jubatus'') in the Gulf of Alaska|doi=10.7755/FB.112.4.6|year=2014|journal=Fishery Bulletin|volume=112|issue=4|pages=297 |last1=Horning|first1=Markus|last2=Mellish|first2=Jo-Ann E.|url=https://ir.library.oregonstate.edu/xmlui/bitstream/1957/54605/1/HorningMarkusFisheriesWildlifeInColdBlood.pdf|doi-access=free}}</ref> indirect effects of prey [[species composition]] shifts due to changes in climate, effects of disease or contaminants, shooting by fishermen, and others. The decline is certainly due to a complex of interrelated factors which have yet to be defined by the research effort.<ref>Clover, Charles. 2004. ''The End of the Line: How overfishing is changing the world and what we eat''. Ebury Press, London. {{ISBN|0-09-189780-7}}</ref><ref>{{cite journal|author=Dalton, Rex|title=Is this any way to save a species?|doi=10.1038/436014a|year=2005|journal=Nature|volume=436|issue=7047|pages=14–6|pmid=16001032|s2cid=30885310|doi-access=free}}</ref>

Another possible reason for decline in this species has been tied to the nutritional stress hypothesis. The lack of prey corresponds to the decrease in population. In females specifically, obtaining an insufficient amount of nutrients has resulted in the failure to complete their pregnancies to full term.<ref>{{Cite journal|last=Trites|first=A. W.|date=2003|title=The decline of Steller sea lions Eumetopias jubatus in Alaska: a review of the nutritional stress hypothesis|journal=Mammal Review|volume=33| issue =  1|pages=3–28|doi=10.1046/j.1365-2907.2003.00009.x|bibcode=2003MamRv..33....3T |s2cid=52221241}}</ref>

In October 2013, the eastern Steller sea lion was taken off the [[United States Fish and Wildlife Service list of endangered mammals and birds|U.S. Endangered Species List]] after a major population comeback over the past several years.<ref>{{cite news|title=Sea Lion Species Removed from Endangered Species List|url=https://news.yahoo.com/sea-lion-species-removed-endangered-species-list-131925639.html|work=Yahoo News|access-date=27 October 2013}}</ref>

== See also ==
{{Portal|Marine life|Mammals}}
*[[Eared seal]]

== References ==
{{Reflist}}

== Further reading ==
{{Refbegin}}
*{{cite book |last1=Heptner |first1=V. G. |last2=Nasimovich |first2=A. A |last3=Bannikov |first3=Andrei Grigorevich |last4=Hoffmann |first4=Robert S |url=https://archive.org/details/mammalsofsov231996gept |title=Mammals of the Soviet Union |volume=II, part 3 |location=Washington, D.C. |publisher=[[Smithsonian Institution]] Libraries and [[National Science Foundation]]|year=1988 }}
{{refend}}

==External links==
{{Commons category|Eumetopias jubatus}}
* [https://www.marinemammalcenter.org/animal-care/learn-about-marine-mammals/pinnipeds/steller-sea-lion Marine Mammal Center – Steller Sea Lion]
* [https://www.fisheries.noaa.gov/species/steller-sea-lion US National Marine Fisheries Service Steller Sea Lion web page]
* [https://web.archive.org/web/20060509151120/http://www.arkive.org/species/GES/mammals/Eumetopias_jubatus/ ARKive – images and movies of the Steller sea lion ''(Eumetopias jubatus)'']
* [https://www.adfg.alaska.gov/index.cfm?adfg=specialstatus.fedsummary&species=stellersealion Alaska Department of Fish and Game page on Steller sea lions]
* [https://web.archive.org/web/20051113044716/http://stellersealions.noaa.gov/ Overview of Steller sea lion research at NOAA, National Marine Fisheries Service, National Marine Mammal Lab]
* [https://www.pbs.org/wnet/nature/alaska/index.html ''Nature'' documentary about the decline of Steller's sea lions] {{Webarchive|url=https://web.archive.org/web/20080617111654/http://www.pbs.org/wnet/nature/alaska/index.html |date=17 June 2008 }}
* [http://www.oregonlive.com/news/oregonian/index.ssf?/base/news/1172908545193250.xml&coll=7 News media report on Steller sea lions and sturgeon interactions] {{Webarchive|url=https://web.archive.org/web/20160303224407/http://www.oregonlive.com/news/oregonian/index.ssf?%2Fbase%2Fnews%2F1172908545193250.xml&coll=7 |date=3 March 2016 }}
* [https://web.archive.org/web/20071007193729/http://www.sealionpredation.com/ SeaLionPredation.com – news and information on seal and sea lion predation of salmon and steelhead in the Pacific Northwest]
* [https://web.archive.org/web/20120723020046/http://www.nwr.noaa.gov/Marine-Mammals/Seals-and-Sea-Lions/upload/CR-Pinniped-FS.pdf NOAA fact sheet on pinnipeds in the Columbia River]
* [https://digitalcommons.unl.edu/libraryscience/17/ Georg Steller's original description in ''De Bestiis Marinis, or, The Beasts of the Sea'' (1751)]
* [https://web.archive.org/web/20101027161731/http://www.bbc.co.uk/nature/species/Steller_Sea_Lion Steller sea lion (Eumetopias jubatus) video clips from the BBC archive on Wildlife Finder]
* [https://web.archive.org/web/20081201045544/http://www.alaskasealife.org/New/research/index.php?page=SSL.php Fifteen years of research into the Alaska populations of Steller Sea Lions at the Alaska SeaLife Center]
* Video: [https://www.youtube.com/watch?v=tMjok1ZNFgA&feature=emb_title Sea lions ward off attacking orcas]

{{Carnivora|C1.}}
{{Pan-Pinnipedia|O.|state=autocollapse}}
{{Taxonbar|from=Q431981}}
{{Authority control}}

[[Category:Mammals described in 1776]]
[[Category:Otariinae]]
[[Category:Extant Calabrian first appearances]]
[[Category:Fauna of the Pacific Ocean]]
[[Category:Fauna of the Western United States]]
[[Category:Mammals of Canada]]
[[Category:Mammals of Japan]]
[[Category:Mammals of Russia]]
[[Category:Mammals of the United States]]
[[Category:Pinnipeds of North America]]
[[Category:Pinnipeds of Asia]]
[[Category:Fauna of the Holarctic realm]]
[[Category:Fauna of the San Francisco Bay Area]]
[[Category:ESA endangered species]]
[[Category:Taxa named by Johann Christian Daniel von Schreber]]
[[Category:Biota of the Temperate Northern Pacific]]