View source for Sea lion

{{short description|Subfamily of aquatic mammals}}
{{about|the aquatic mammal}}
{{pp-move-indef}}
{{Use dmy dates|date=May 2016}}
{{Automatic taxobox
| fossil_range = {{Fossil range|Late Oligocene | Present}}
| image = California sea lion in La Jolla (70568).jpg
| image_caption = [[California sea lion]] (''Zalophus californianus'')
| taxon = Otariinae
| authority = Gray 1825
| subdivision_ranks = Genera
| subdivision =
''[[Eumetopias]]''<br />
''[[Neophoca]]''<br />
''[[Otaria]]''<br />
''[[Phocarctos]]''<br />
''[[Zalophus]]''
}}

'''Sea lions''' are [[pinniped]]s characterized by external [[pinna (anatomy)|ear flaps]], long foreflippers, the ability to walk on all fours, short and thick hair, and a big chest and belly. Together with the [[fur seal]]s, they make up the family [[Otariidae]], [[eared seal]]s.  The sea lions have six [[extant taxa|extant]] and one extinct species (the [[Japanese sea lion]]) in five [[genera]]. Their range extends from the [[subarctic]] to [[tropical]] waters of the [[Ocean|global ocean]] in both the [[Northern Hemisphere|Northern]] and [[Southern Hemisphere|Southern]] hemispheres, with the notable exception of the northern [[Atlantic Ocean]].<ref name=seaworld>{{cite web |url=http://seaworld.org/en/Animal-Info/Animal-Bytes/Mammals/California-Sea-Lion |title=California Sea Lion – SeaWorld Info Book |access-date=26 December 2013 |publisher=SeaWorld |archive-url=https://web.archive.org/web/20150414073258/http://seaworld.org/en/animal-info/animal-bytes/mammals/california-sea-lion/ |archive-date=14 April 2015 |url-status=dead |df=dmy-all }}</ref> 

Sea lions have an [[Life expectancy|average lifespan]] of 20–30 years.<ref>{{Cite web |date=2016-04-25 |title=California sea lion |url=https://nationalzoo.si.edu/animals/california-sea-lion |access-date=2023-09-24 |website=Smithsonian's National Zoo |language=en |archive-date=27 September 2023 |archive-url=https://web.archive.org/web/20230927160443/https://nationalzoo.si.edu/animals/california-sea-lion |url-status=live }}</ref> A male California sea lion weighs on average about {{convert|300|kg|lb|abbr=on}} and is about {{convert|8|ft|m|abbr=on|order=flip}} long, while the female sea lion weighs {{convert|100|kg|lb|abbr=on}} and is {{convert|6|ft|m|abbr=on|order=flip}} long. The largest sea lions are [[Steller's sea lion]]s, which can weigh {{convert|1000|kg|lb|abbr=on}} and grow to a length of {{convert|10|ft|m|abbr=on|order=flip}}. Sea lions consume large quantities of food at a time and are known to eat about 5–8% of their body weight (about {{convert|15|-|35|lb|kg|abbr=on|order=flip}}) at a single feeding. Sea lions can move around {{convert|16|knots|km/h mph}} in water and at their fastest they can reach a speed of about {{convert|30|knots|km/h mph}}.<ref>{{cite book|last1=Riedman|first1=Marianne|title=The Pinnipeds: Seals, Sea lions, and Walruses|url=https://archive.org/details/pinnipedssealsse0000ried|url-access=registration|date=13 December 1989|publisher=University of California Press|isbn=9780520064973|page=[https://archive.org/details/pinnipedssealsse0000ried/page/7 7]}}</ref> Three species, the [[Australian sea lion]], the [[Galápagos sea lion]] and the [[New Zealand sea lion]], are listed as [[IUCN Red List endangered species (Animalia)|endangered]].<ref>{{Cite journal|last=Chilvers|first=B. L.|author-link=Louise Chilvers|date=2015|title=Phocarctos hookeri. The IUCN Red List of Threatened Species|url=|journal=International Union for Conservation of Nature and Natural Resources|volume=|pages=|doi=10.2305/IUCN.UK.2015-2.RLTS.T17026A1306343.en|doi-access=free}}</ref><ref>{{Cite journal|last=Trillmich|first=F.|date=2015|title=Arctocephalus galapagoensis. The IUCN Red List of Threatened Species|journal=International Union for Conservation of Nature and Natural Resources|doi=10.2305/IUCN.UK.2015-2.RLTS.T2057A45223722.en|doi-access=free}}</ref><ref>{{Cite journal|last=Goldsworthy|first=S. D.|date=2015|title=Neophoca cinerea. The IUCN Red List of Threatened Species|journal=International Union for Conservation of Nature and Natural Resources|doi=10.2305/IUCN.UK.2015-2.RLTS.T14549A45228341.en|doi-access=free}}</ref>

==Taxonomy==
[[Image:Alaska 2007 056.jpg|thumb|[[Steller sea lion]]s [[hauling-out|haul out]] on a rock off the coast of [[Raspberry Island (Alaska)]].]]
Sea lions are related to walruses and seals. Together with the [[fur seal]]s, they constitute the family [[Otariidae]], collectively known as eared seals. Until recently, sea lions were grouped under a single subfamily called Otariinae, whereas fur seals were grouped in the subfamily Arcocephalinae. This division was based on the most prominent common feature shared by the fur seals and absent in the sea lions, namely the dense underfur characteristic of the former. Recent genetic evidence, suggests ''Callorhinus'', the genus of the [[northern fur seal]], is more closely related to some sea lion species than to the other fur seal genus, ''Arctocephalus''.<ref>{{cite journal | last1 = Wynen | first1 = L.P. | year = 2001 | title = Phylogenetic relationships within the eared seals (Otariidae: Carnivora): implications for the historical biogeography of the family | doi = 10.1006/mpev.2001.1012 | journal = Mol. Phylogenet. Evol. | volume = 21 | issue = 2| pages = 270–284 | 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 | bibcode = 2001MolPE..21..270W | display-authors = 8 }}</ref> Therefore, the fur seal/sea lion subfamily distinction has been eliminated from many taxonomies.

Nonetheless, all fur seals have certain features in common: the fur, generally smaller sizes, farther and longer foraging trips, smaller and more abundant prey items, and greater [[sexual dimorphism]]. All sea lions have certain features in common, in particular their coarse, short fur, greater bulk, and larger prey than fur seals. For these reasons, the distinction remains useful. The family Otariidae (Order Carnivora) contains the 15 extant species of fur seals and sea lions. Traditional classification of the family into the subfamilies Arctocephalinae (fur seals) and Otariinae (sea lions) is not supported, with the fur seal ''Callorhinus ursinus'' having a basal relationship relative to the rest of the family.<ref name=":0">{{Cite journal|title = Phylogenetic Relationships within the Eared Seals (Otariidae: Carnivora): Implications for the Historical Biogeography of the Family|journal = Molecular Phylogenetics and Evolution|date = 1 November 2001|pages = 270–284|volume = 21|issue = 2|doi = 10.1006/mpev.2001.1012|first1 = Louise P.|last1 = Wynen|first2 = Simon D.|last2 = Goldsworthy|first3 = Stephen J.|last3 = Insley|first4 = Mark|last4 = Adams|first5 = John W.|last5 = Bickham|first6 = John|last6 = Francis|first7 = Juan Pablo|last7 = Gallo|first8 = A. Rus|last8 = Hoelzel|first9 = Patricia|last9 = Majluf|pmid=11697921| bibcode=2001MolPE..21..270W }}</ref> This is consistent with the fossil record which suggests that this genus diverged from the line leading to the remaining fur seals and sea lions about 6 million years ago (mya). Similar genetic divergences between the sea lion clades as well as between the major Arctocephalus fur seal clades, suggest that these groups underwent periods of rapid radiation at about the time they diverged from each other. The phylogenetic relationships within the family and the genetic distances among some taxa highlight inconsistencies in the current taxonomic classification of the family.<ref name=":0" />

''Arctocephalus'' is characterized by ancestral character states such as dense underfur and the presence of double rooted cheek teeth and is thus thought to represent the most "primitive" line. It was from this basal line that both the sea lions and the remaining fur seal genus, ''Callorhinus'', are thought to have diverged. The fossil record from the western coast of North America presents evidence for the divergence of ''Callorhinus'' about 6 mya, whereas fossils in both California and Japan suggest that sea lions did not diverge until years later.<ref name=":0" />

* '''''Suborder [[Caniformia]]'''''
** '''Family Otariidae'''
***'''Subfamily''' [[Arctocephalinae]]
**** Genus ''[[Arctocephalus]]'' (southern fur seal; eight species)
**** Genus ''[[Callorhinus]]'' (northern fur seal; one species)
*** '''Subfamily''' [[Otariinae]]
**** Genus ''Eumetopias''
***** [[Steller's sea lion]], ''E. jubatus''
**** Genus ''Neophoca''
***** [[Australian sea lion]], ''N. cinerea''
**** Genus ''Otaria''
***** [[South American sea lion]], ''O. flavescens''
**** Genus ''Phocarctos''
***** [[New Zealand sea lion]] or Hooker's sea lion, ''P. hookeri''
**** Genus ''Zalophus''
***** [[California sea lion]], ''Z. californianus''
***** [[Japanese sea lion]], ''Z. japonicus'' – [[extinct]] (1950s)
***** [[Galapagos sea lion]], ''Z. wollebaeki''
** Family [[Phocidae]]: true seals
** Family [[Odobenidae]]: walrus

== Physiology ==

===Diving adaptations===
[[File:Sea lion heart.jpg|thumb|Sea lion heart]]
There are many components that make up sea lion physiology and these processes control aspects of their behavior. Physiology dictates thermoregulation, osmoregulation, reproduction, metabolic rate, and many other aspects of sea lion ecology including but not limited to their ability to dive to great depths. The sea lions' bodies control heart rate, gas exchange, digestion rate, and blood flow to allow individuals to dive for a long period of time and prevent side effects of high pressure at depth.

The high pressures associated with deep dives cause gases such as nitrogen to build up in tissues which are then released upon surfacing, possibly causing death. One of the ways sea lions deal with the extreme pressures is by limiting the amount of gas exchange that occurs when diving. The sea lion allows the alveoli to be compressed by the increasing water pressure thus forcing the surface air into cartilage lined airway just before the gas exchange surface.<ref name=":7" /> This process prevents any further oxygen exchange to the blood for muscles, requiring all muscles to be loaded with enough oxygen to last the duration of the dive. However, this shunt reduces the amount of compressed gases from entering tissues therefore reducing the risk of decompression sickness.<ref name=":7">{{Cite journal|last1=Kooyman|first1=G. L.|last2=Sinnett|first2=E. E.|date=1 January 1982|title=Pulmonary Shunts in Harbor Seals and Sea Lions during Simulated Dives to Depth|jstor=30158447|journal=Physiological Zoology|volume=55|issue=1|pages=105–111|doi=10.1086/physzool.55.1.30158447|s2cid=87390381}}</ref> 

The collapse of alveoli does not allow for any oxygen storage in the lungs, however. This means that sea lions must mitigate oxygen use in order to extend their dives. Oxygen availability is prolonged by the physiological control of heart rate in sea lions. By reducing heart rate to well below surface rates, oxygen is saved by reducing gas exchange as well as reducing the energy required for a high heart rate.<ref name=":8">{{Cite journal|last1=McDonald|first1=Birgitte I.|last2=Ponganis|first2=Paul J.|date=2014|title=Deep-diving sea lions exhibit extreme bradycardia in long-duration dives|journal=Journal of Experimental Biology|language=en|volume=217|issue=9|pages=1525–1534|doi=10.1242/jeb.098558|issn=0022-0949|pmid=24790100|doi-access=free|bibcode=2014JExpB.217.1525M |url=http://journals.biologists.com/jeb/article-pdf/217/9/1525/1883736/1525.pdf}}</ref> [[Bradycardia]] is a control mechanism to allow a switch from pulmonary oxygen to oxygen stored in the muscles which is needed when the sea lions are diving to depth.<ref name=":8" /> Another way sea lions mitigate the oxygen obtained at the surface in dives is to reduce digestion rate. Digestion requires metabolic activity and therefore energy and oxygen are consumed during this process; however, sea lions can limit digestion rate and decrease it by at least 54%.<ref name=":9">{{Cite journal|last1=Rosen|first1=David A. S.|last2=Gerlinsky|first2=Carling D.|last3=Trites|first3=Andrew W.|date=1 August 2015|title=Evidence of partial deferment of digestion during diving in Steller sea lions (''Eumetopias jubatus'')|journal=Journal of Experimental Marine Biology and Ecology|volume=469|pages=93–97|doi=10.1016/j.jembe.2015.04.017|bibcode=2015JEMBE.469...93R }}</ref> This reduction in digestion results in a proportional reduction in oxygen use in the stomach and therefore a correlated oxygen supply for diving. Digestion rate in these sea lions increases back to normal rates immediately upon resurfacing.<ref name=":9" /> 

Oxygen depletion limits dive duration, but carbon dioxide (CO<sub>2</sub>) build-up also plays a role in the dive capabilities of many [[marine mammal]]s. After a sea lion returns from a long dive, CO<sub>2</sub> is not expired as fast as oxygen is replenished in the blood, due to the unloading complications with CO<sub>2</sub>. However, having elevated levels of CO<sub>2</sub> in the blood does not seem to adversely affect dive behavior.<ref name=":10">{{Cite journal|last1=Gerlinsky|first1=Carling D.|last2=Rosen|first2=David A. S.|last3=Trites|first3=Andrew W.|date=7 March 2014|title=Sensitivity to hypercapnia and elimination of CO<sub>2</sub> following diving in Steller sea lions (''Eumetopias jubatus'')|journal=Journal of Comparative Physiology B|language=en|volume=184|issue=4|pages=535–544|doi=10.1007/s00360-014-0819-y|pmid=24604293|s2cid=4637738|issn=0174-1578}}</ref> Compared to terrestrial mammals, sea lions have a higher tolerance to storing CO<sub>2</sub> which is what normally tells mammals that they need to breathe.<ref name=":10" /> This ability to ignore a response to CO<sub>2</sub> is likely brought on by increased carotid bodies which are sensors for oxygen levels that let the animal know its available oxygen supply.<ref name=":10" /> Yet, the sea lions cannot avoid the effects of gradual CO<sub>2</sub> build-up which eventually causes the sea lions to spend more time at the surface after multiple repeated dives to allow for enough built up CO<sub>2</sub> to be expired.<ref name=":10" />

=== Parasites and diseases ===
Galapagos sea lions (''Zalophus wollebaeki'') can be infected with ''Philophthalmus zalophi'', an eye fluke. These infections have heavy impacts on the survival of juveniles.<ref name="Web of Science">{{cite journal |last1=Meise |first1=Kristine |last2=Garcia-Parra |first2=Carolina |title=Behavioural and environmental correlates of ''Philophthalmus zalophi'' infections and their impact on survival in juvenile Galapagos sea lions |journal=Marine Biology |date=October 2015 |volume=162 |issue=10 |pages=2107–2117 |doi=10.1007/s00227-015-2740-7|bibcode=2015MarBi.162.2107M |s2cid=83897007 }}</ref> The disease appears to be compounded by global warming, as the number of infectious stages of different parasites species has a strong correlation with temperature change. The Galapagos Islands go through seasonal changes in [[sea surface temperature]]s, which consist of high temperatures from the beginning of January through the month of May and lower temperatures throughout the rest of the year. Parasites surfaced in large numbers when the sea temperature was at its highest. Furthermore, data published in 2015 was collected by capturing sea lions in order to measure and determine their growth rates. Their growth rates were noted along with the sightings of parasites which were found under the eyelid. The results were that sea lions are affected by the parasites from the early ages of 3 weeks old up until the age of 4 to 8 months.<ref name="Web of Science" /> 

The parasites found in the eye fluke did serious damage to the eye. From the data collected, 21 of the 91 survived; with a total of 70 deaths in just a span of two years.<ref name="Web of Science" /> The parasites are attacking the pups at such young ages and causing the pups to not reach the age of reproduction. The death rates of the pups is surpassing the fertility rate by far. Since most pups are unable to reach the age of reproduction, the population is not growing fast enough to keep the species out of endangerment. Other parasites, like ''[[Anisakis]]'' and [[heartworm]], can also infect sea lions.

Australian sea lions (''Neophoca cinerea'') are also being affected by more frequent parasitic infections.<ref name="ScienceDirect">{{cite journal |last1=Higgins |first1=Damien |last2=Marcus |first2=Alan |last3=Gray |first3=Rachael |title=Health assessment of free-ranging endangered Australian sea lion (''Neophoca cinerea'') pups: Effect of haematophagous parasites on haematological parameters |journal=Comparative Biochemistry and Physiology |date=2015 |volume=184 |pages=132–143 |doi=10.1016/j.cbpa.2015.02.017 |pmid=25724096 }}</ref> The same method was used for the sea pups as on the Galapagos Islands, but in addition, the researchers in Australia took blood samples. The pups in Australia were being affected by hookworms, but they were also coming out in large numbers with warmer temperatures.<ref name="ScienceDirect"/> New Zealand sea lion pups (''Phocarctos hookeri'') were also affected in really early ages by hookworms (Uncinaria). The difference is that in New Zealand researchers took the necessary steps and began treatment.<ref name="EffectsOfHookworms">{{cite journal |last1=Chilvers |first1=B. L. |last2=Duignan |first2=P. J. |last3=Robertson |first3=B. C. |last4=Castinel |first4=A. |last5=Wilkinson |first5=I. S. |title=Effects of hookworms (''Uncinaria'' sp.) on the early growth and survival of New Zealand sea lion (''Phocarctos hookeri'') pups |journal=Polar Biology |date=February 2009 |volume=32 |issue=2 |pages=295–302 |doi=10.1007/s00300-008-0559-0 |bibcode=2009PoBio..32..295C |s2cid=10260797 }}</ref> The treatment seemed to be effective on the pups who have taken it. They found no traces of this infection afterwards. However, the percentage of pups who do have it is still relatively high at about 75%.<ref name="EffectsOfHookworms" /> Those pups who were treated had much better growth rates than those who did not. Overall parasites and hookworms are killing off enough pups to place them in endangerment. Parasites affect sea pups in various areas of the world. Reproductive success reduces immensely, survival methods, changes in health and growth have also been affected.

Similarly, climate change has resulted in increased toxic algae blooms in the oceans. These toxins are ingested by sardines and other fish which are then eaten by the sea lions, causing neurological damage and diseases such as epilepsy.<ref>{{Cite news|last=Richtel|first=Matt|date=2020-10-08|title=Brain Surgery for a 'Sweet Boy': Saving Cronutt the Sea Lion|language=en-US|work=The New York Times|url=https://www.nytimes.com/2020/10/08/science/sea-lion-epilepsy-surgery-cronutt.html|access-date=2020-10-13|issn=0362-4331|archive-date=13 October 2020|archive-url=https://web.archive.org/web/20201013144514/https://www.nytimes.com/2020/10/08/science/sea-lion-epilepsy-surgery-cronutt.html|url-status=live}}</ref>

=== Gene expressions and diet ===
Gene expressions are being used more often to detect the physiological responses to nutrition, as well as other stressors. In a study done with four Steller sea lions (Eumetopias jubatus), three of the four sea lions underwent a 70-day trial which consisted of unrestricted food intake, acute nutritional stress, and chronic nutritional stress. Results showed that individuals under nutritional stress down-regulated some cellular processes within their immune response and [[oxidative stress]]. Nutritional stress was considered the most proximate cause of population decline in this species.<ref name=":2">{{Cite journal|title = A nutrigenomic approach to detect nutritional stress from gene expression in blood samples drawn from Steller sea lions|last1 = Spitz|first1 = Jerome|date = September 2015|journal = Comparative Biochemistry and Physiology A|doi = 10.1016/j.cbpa.2015.02.006|pmid = 25700740|last2 = Becquet|first2 = Vanessa|last3 = Rosen|first3 = David A.S|last4 = Trites|first4 = Andrew W.|volume=187|pages=214–223}}</ref> In New Zealand sea lions, north-to south gradients driven by temperature differences were shown to be key factors in the prey mix.<ref name=":3">{{Cite journal|title = Diet of New Zealand sea lions (''Phocarctos hookeri'') at their southern breeding limits|last1 = Roberts|first1 = J.|date = June 2015|journal = Polar Biology|doi = 10.1007/s00300-015-1710-3|last2 = Lalas|first2 = C.|volume=38|issue = 9|pages=1483–1491| bibcode=2015PoBio..38.1483R |s2cid = 7836909}}</ref> Adult California sea lions eat about 5% to 8% of their body weight per day ({{cvt|15|-|40|lb}}).{{cn|date=October 2022}}

California sea lions feed mainly offshore in coastal areas. They eat a variety of prey—such as squid, anchovies, mackerel, rockfish, and sardines—found in upwelling areas. They also may take fish from commercial fishing gear, sport fishing lines, and fish passage facilities at dams and rivers.<ref>{{Cite web|title=California Sea Lion |language=en-US|website=[[NOAA]]|url=https://www.fisheries.noaa.gov/species/california-sea-lion/overview|access-date=2024-01-06}}</ref>

=== Geographic variation ===
{{Multiple image
 | align = right
 | image1=Neophoca cinerea.JPG
 | image2=Steller Sea Lions(Vancouver)02(js).jpg
 | footer=The [[Australian sea lion]] vs. the [[Steller sea lion]]
}}
Geographic variation for sea lions have been determined by the observations of skulls of several Otariidae species; a general change in size corresponds with a change in latitude and primary productivity. Skulls of Australian sea lions from Western Australia were generally smaller in length whereas the largest skulls are from cool temperate localities. Otariidae are in the process of species divergence, much of which may be driven by local factors, particularly latitude and resources.<ref name=":1">{{cite journal|title = Geographic variation in skull characters of fur seals and sea lions (family Otariidae)|journal = Australian Journal of Zoology|volume = 50|issue = 4|pages = 415|url = https://www.researchgate.net/publication/230822658|doi = 10.1071/ZO01056|year = 2002|last1 = Brunner|first1 = S.|last2 = Shaughnessy|first2 = P. D.|last3 = Bryden|first3 = M. M.}}</ref> Populations of a given species tend to be smaller in the tropics, increase in size with increasing latitude, and reach a maximum in sub-polar regions. In a cool climate and cold waters, there should be a selective advantage in the relative reduction of body surface area resulting from increased size, since the metabolic rate is related more closely to body surface area than to body weight.<ref name=":1" />

== Breeding and population ==

=== Breeding methods and habits ===
[[File:Two sea lions on the beach of Otago Peninsula.jpg|thumb|Two sea lions on the beach of Otago Peninsula, New Zealand]]
Sea lions, with three groups of pinnipeds, have multiple breeding methods and habits over their families but they remain relatively universal. Otariids, or eared sea lions, raise their young, mate, and rest in more earthly land or ice habitats. Their abundance and haul-out behavior have a direct effect on their on land breeding activity. Their seasonal abundance trend correlates with their breeding period between the austral summer of January to March. Their rookeries populate with newborn pups as well as male and female otariids that remain to defend their territories. At the end of the breeding period males disseminate for food and rest while females remain for nurturing. Other points in the year consist of a mix of ages and genders in the rookeries with haul-out patterns varying monthly.<ref>{{Cite journal|url = https://dialnet.unirioja.es/descarga/articulo/5232329.pdf|title = Annual, seasonal and daily variation in the abundance of the South American sea lion ''Otaria flavescens'' in two breeding colonies in northern Chile|last = Sepúlveda|first = Maritza|date = August 2015|journal = Revista de Biologia Marina y Oceanografia|doi = 10.4067/S0718-19572015000300001|issue = 2|volume = 50|pages = 205–220|doi-access = free|archive-date = 14 February 2024|access-date = 14 February 2024|archive-url = https://web.archive.org/web/20240214132913/https://dialnet.unirioja.es/descarga/articulo/5232329.pdf|url-status = live}}</ref>

Steller sea lions, living an average of 15 to 20 years, begin their breeding season when adult males establish territories along the rookeries in early May. Male sea lions reach sexual maturity from ages 5 to 7 and do not become territorial until around 9 to 13 years of age. The females arrive in late May bringing in an increase of territorial defense through fighting and boundary displays. After a week births consist most usually of one pup with a perinatal period of 3 to 13 days.

Steller sea lions have exhibited multiple competitive strategies for reproductive success. Sea lion mating is often polygamous as males usually mate with different females to increase fitness and success, leaving some males to not find a mate at all. Polygamous males rarely provide parental care towards the pup. Strategies used to monopolize females include the resource-defense polygyny, or occupying important female resources. This involves occupying and defending a territory with resources or features attractive to females during sexually receptive periods. Some of these factors may include pupping habitat and access to water. Other techniques include potentially limiting access of other males to females.<ref>{{Cite journal|title = A long-term study reveals multiple reproductive behavior strategies among territorial adult male Steller sea lions (''Eumetopias jubatus'')|last1 = Parker|first1 = Pamela|date = 20 March 2014|journal = Canadian Journal of Zoology|doi = 10.1139/cjz-2013-0099|issue = 5|volume = 92|pages = 405–415|last2 = Maniscalco|first2 = John, M.| bibcode=2014CaJZ...92..405P }}</ref>

=== Population ===
''Otaria flavescens'' (South American sea lion) lives along the Chilean coast with a population estimate of 165,000. According to the most recent surveys in northern and southern Chile the sealing period of the middle twentieth century that left a significant decline in sea lion population is recovering. The recovery is associated with less hunting, otariids rapid population growth, legislation on nature reserves, and new food resources. Haul-out patterns change the abundance of sea lions at particular times of the day, month, and year. Patterns in migration relate to temperature, solar radiation, and prey and water resources. Studies of South American sea lions and other otariids document maximum population on land during early afternoon, potentially due to haul-out during high air temperatures. Adult and subadult males do not show clear annual patterns, maximum abundance being found from October to January. Females and their pups hauled-out during austral winter months of June to September.<ref>{{Cite journal|url = https://dialnet.unirioja.es/descarga/articulo/5232329.pdf|title = Annual, seasonal and daily variation in the abundance of the South American sea lion ''Otaria flavescens'' in two breeding colonies in northern Chile|last = Sepulveda|first = Maritza|date = August 2015|journal = Revista de Biologia Marina y Oceanografia|doi = 10.4067/S0718-19572015000300001|access-date = 29 October 2015|volume = 50|issue = 2|pages = 205–220|doi-access = free|archive-date = 16 November 2023|archive-url = https://web.archive.org/web/20231116191539/https://dialnet.unirioja.es/descarga/articulo/5232329.pdf|url-status = live}}</ref>

== Interactions with humans ==
[[File:Sea lions entertaining crowd in Central Park Zoo, New York City 2.jpg|thumb|Sea lions entertain a crowd in [[Central Park Zoo]]]]South American sea lions have been greatly impacted by human exploitation. During the late [[Holocene]] period to the middle of the twentieth century, [[hunter-gatherers]] along the [[Beagle Channel]] and northern [[Patagonia]] had greatly reduced the number of sea lions due to their hunting of the species and exploitation of the species' environment.<ref name=":4">{{Cite journal|title = Shifting niches of marine predators due to human exploitation: the diet of the South American sea lion (''Otaria flavescens'') since the late Holocene as a case study|journal = Paleobiology|date = 1 June 2015|issn = 1938-5331|pages = 387–401|volume = 41|issue = 3|doi = 10.1017/pab.2015.9|first1 = Lisette|last1 = Zenteno|first2 = Florencia|last2 = Borella|first3 = Julieta Gómez|last3 = Otero|first4 = Ernesto|last4 = Piana|first5 = Juan Bautista|last5 = Belardi|first6 = Luis Alberto|last6 = Borrero|first7 = Fabiana|last7 = Saporiti|first8 = Luis|last8 = Cardona|first9 = Enrique|last9 = Crespo| bibcode=2015Pbio...41..387Z |s2cid = 86469393}}</ref> Although [[seal hunting|sealing]] has been put to a halt, in many countries, such as [[Uruguay]], the sea lion population continues to decline because of the drastic effects humans have on their ecosystems.<ref name=":4" /> As a result, South American sea lions have been foraging at higher tropical latitudes than they did prior to human exploitation.<ref name=":4" /> 

Fishermen play a key role in the endangerment of sea lions. Sea lions rely on fish, like pollock, as a food source and have to compete with fishermen for it.<ref name=":5">{{Cite journal|title = Why do People Care about Sea Lions? A Fishing Game to Study the Value of Endangered Species|journal = Environmental and Resource Economics|date = 12 December 2013|issn = 0924-6460|pages = 503–523|volume = 59|issue = 4|doi = 10.1007/s10640-013-9746-8|first1 = Min|last1 = Gong|first2 = Geoffrey|last2 = Heal|s2cid = 154083833}}</ref> When fishermen are successful at their job, they greatly reduce the sea lion's food source, which in turn endangers the species.<ref name=":5" /> Also, human presence and human recreational activities can cause sea lions to engage in violent and aggressive actions.<ref name=":6">{{cite web|title = Human impacts on Australian sea lions, Neophoca cinerea, hauled out on Carnac Island (Perth, Western Australia): implications for wildlife and tourism management|url = http://researchrepository.murdoch.edu.au/238/|website = researchrepository.murdoch.edu.au|date = 1 January 2004|access-date = 30 October 2015|first = Orsini|last = Jean-Paul}}</ref> When humans come closer than 15 meters of a sea lion, the sea lions' vigilance increases because of the disturbance of humans.<ref name=":6" /> These disturbances can potentially cause sea lions to have psychological stress responses that cause the sea lions to retreat, sometimes even abandon their locations, and decreases the amount of time sea lions spend hauling out.<ref name=":6" /> [[File:Cal Sea Lions on Pier 39.JPG|thumb|Hundreds of [[California sea lion]]s congregating at [[Pier 39]], [[San Francisco]]]]

New Zealand sea lions were also exploited from hunting and sealing, and as a result were [[Local extinction|extirpated]] from New Zealand's mainland for over 150 years, with their population being restricted to the subantarctic.<ref name=":11">{{Cite journal|last1=Childerhouse|first1=Simon|last2=Gales|first2=Nick|date=1998-01-01|title=Historical and modern distribution and abundance of the New Zealand sea lion Phocarctos hookeri|url=https://doi.org/10.1080/03014223.1998.9518131|journal=New Zealand Journal of Zoology|volume=25|issue=1|pages=1–16|doi=10.1080/03014223.1998.9518131|issn=0301-4223|url-access=subscription}}</ref> In 1993, a female New Zealand sea lion gave birth on the mainland for the first time, and since then, they have slowly been recolonizing.<ref name=":11" /> These sea lions are the only pinnipeds that regularly move up to {{Convert|2|km|mi}} inland into forests.<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> As consequence, they have been hit by cars on roads, deliberately killed, and been disturbed by dogs.<ref>{{Cite book|last=Roberts|first=Jim|url=https://www.doc.govt.nz/Documents/conservation/native-animals/marine-mammals/nz-sea-lion-tmp/reivew-sea-lion-threats-2015.pdf|title=Review of threats to the recovery of NZ sea lions and other otariid species|publisher=National Institute of Water & Atmospheric Research Ltd|year=2015|location=Wellington|pages=11–14|archive-date=3 November 2021|access-date=22 November 2021|archive-url=https://web.archive.org/web/20211103195039/https://www.doc.govt.nz/Documents/conservation/native-animals/marine-mammals/nz-sea-lion-tmp/reivew-sea-lion-threats-2015.pdf|url-status=live}}</ref> Females need to move inland as a way to protect their pups, so roads, fences, residential areas, and private lands can inhibit their dispersal and breeding success.<ref name=":12">{{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://publications.goettingen-research-online.de/bitstream/2/94362/1/Methods%20Ecol%20Evol%20-%202021%20-%20Frans%20-%20Integrated%20SDM%20database%20Enhancing%20the%20relevance%20and%20utility%20of%20species%20distribution.pdf|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|archive-date=6 January 2024|access-date=6 December 2023|archive-url=https://web.archive.org/web/20240106062405/https://publications.goettingen-research-online.de/bitstream/2/94362/1/Methods%20Ecol%20Evol%20-%202021%20-%20Frans%20-%20Integrated%20SDM%20database%20Enhancing%20the%20relevance%20and%20utility%20of%20species%20distribution.pdf|url-status=live}}</ref> They have also adapted to commercial pine forests,<ref name=":12" /> and have given birth or nursed pups in residents' backyards and on golf courses.<ref>{{Cite web|date=2021-01-14|title=New Zealand city closes busy road for weeks to protect sea lion mother and pup|url=http://www.theguardian.com/world/2021/jan/14/new-zealand-city-closes-busy-road-to-protect-sea-lion-mother-and-pup|access-date=2021-11-22|website=the Guardian|language=en}}</ref> As one of the world's rarest sea lions, and an endangered and endemic species, efforts are being made to facilitate coexistence between them and humans.<ref>{{Cite news|last=Graham-McLay|first=Charlotte|date=2021-11-09|title=New Zealand's Sea Lions Are Back, and Crashing Golf Courses and Soccer Matches|language=en-US|work=The New York Times|url=https://www.nytimes.com/2021/11/09/science/new-zealand-sea-lions.html |archive-url=https://ghostarchive.org/archive/20211228/https://www.nytimes.com/2021/11/09/science/new-zealand-sea-lions.html |archive-date=2021-12-28 |url-access=limited|access-date=2021-11-22|issn=0362-4331}}{{cbignore}}</ref><ref>{{Cite news|title='Cheeky' sea lions are returning to New Zealand's shores — and locals are learning to share the coast|language=en-US|newspaper=Washington Post|url=https://www.washingtonpost.com/world/2021/11/13/new-zealand-sealions-return-study/|access-date=2021-11-22|issn=0190-8286|archive-date=13 November 2021|archive-url=https://web.archive.org/web/20211113212521/https://www.washingtonpost.com/world/2021/11/13/new-zealand-sealions-return-study/|url-status=live}}</ref>

Sea lion attacks on humans are rare, but when humans come within approximately {{convert|2.5| meters|ft|0}}, it can be very unsafe.<ref name=":6" /> In a highly unusual attack in 2007 in [[Western Australia]], a sea lion leapt from the water and seriously mauled a 13-year-old girl surfing behind a speedboat. The sea lion appeared to be preparing for a second attack when the girl was rescued. An Australian marine biologist suggested that the sea lion may have viewed the girl "like a rag doll toy" to be played with.<ref>[https://news.bbc.co.uk/2/hi/asia-pacific/6556895.stm Sea lion attacks Australian girl] . BBC News (15 April 2007). Retrieved on 2016-05-09.</ref><ref>Hayward, Andrea (15 April 2007) [https://web.archive.org/web/20070519221540/http://www.news.com.au/story/0,23599,21560487-2,00.html Monster sea lion likely to be 'playing' with teen]. news.com.au</ref><ref>[https://web.archive.org/web/20071030001559/http://www.news.com.au/couriermail/story/0,,21557673-953,00.html Sea lion mauls girl]. News.com.au (15 April 2007).</ref> In [[San Francisco]], where an increasingly large population of [[California sea lion]]s crowds docks along San Francisco Bay, incidents have been reported in recent years of swimmers being bitten on the legs by large, aggressive males, possibly as [[territory (animal)|territorial acts]].<ref>{{cite news | url=http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2006/11/16/MNGMFMDVGC1.DTL&hw=sea+lion&sn=011&sc=518 | work=The San Francisco Chronicle | first=Jane | last=Kay | title=Rogue sea lion in S.F. menaces swimmers / Marauding mammal bites at least 14, chases 10 from Aquatic Park Lagoon | date=24 June 2011 | archive-date=21 October 2009 | access-date=22 March 2011 | archive-url=https://web.archive.org/web/20091021234747/http://www.sfgate.com/cgi-bin/article.cgi?f=%2Fc%2Fa%2F2006%2F11%2F16%2FMNGMFMDVGC1.DTL&hw=sea%20lion&sn=011&sc=518 | url-status=live }}</ref><ref>{{cite news |author=Harrell, Ashley |url=http://www.sfweekly.com/2009-10-07/news/too-cute-to-shoot/ |title=Too Cute to Shoot? – Page 1 – News – San Francisco |newspaper=SF Weekly |date=7 October 2009 |access-date=28 June 2012 |archive-date=10 August 2015 |archive-url=https://web.archive.org/web/20150810041018/http://www.sfweekly.com/2009-10-07/news/too-cute-to-shoot/ |url-status=dead }}</ref> In April 2015, a sea lion attacked a 62-year-old man who was boating with his wife in [[San Diego]]. The attack left the man with a punctured bone.<ref>{{cite web|title = Sea lion attacks San Diego man posing for photo, yanks him overboard|url = http://www.cbsnews.com/news/sea-lion-attacks-san-diego-man-posing-for-photo-yanks-him-overboard/|website = www.cbsnews.com|date = 30 April 2015|access-date = 30 October 2015|archive-date = 1 November 2015|archive-url = https://web.archive.org/web/20151101012913/http://www.cbsnews.com/news/sea-lion-attacks-san-diego-man-posing-for-photo-yanks-him-overboard/|url-status = live}}</ref> In May 2017, a sea lion grabbed and pulled a girl into the water by her dress before retreating.  The child was sitting on a pier side in [[British Columbia]] while tourists were illegally feeding the sea lions when the incident took place.<ref>{{Cite news|url=https://www.washingtonpost.com/news/animalia/wp/2017/05/21/video-shows-the-terrifying-moment-a-sea-lion-yanks-a-girl-into-the-water/|title=Video shows the terrifying moment a sea lion yanks a girl into the water|newspaper=Washington Post|access-date=2017-05-22}}</ref> She was pulled out of the water with minor injuries and received antibiotic prophylactic treatment for [[seal finger]] infection from the superficial bite injury.<ref>{{cite news |title=Steveston Sea Lion Video: Girl Grabbed By Animal Treated For Superficial Wound |url=http://www.huffingtonpost.ca/2017/05/23/residents-blame-sea-lion-incident-on-people-not-the-animal-or-harbour-authority_n_16775688.html |access-date=20 September 2018 |work=HuffPost Canada |date=23 May 2017 |archive-date=2 August 2018 |archive-url=https://web.archive.org/web/20180802101658/https://www.huffingtonpost.ca/2017/05/23/residents-blame-sea-lion-incident-on-people-not-the-animal-or-harbour-authority_n_16775688.html |url-status=live }}</ref><ref>{{Cite news|url=https://www.bbc.com/news/world-us-canada-40056576|title=Sea lion attack: Girl treated over 'seal finger' risk|date=2017-05-26|work=BBC News|access-date=2017-05-26|language=en-GB|archive-date=2 August 2018|archive-url=https://web.archive.org/web/20180802091338/https://www.bbc.com/news/world-us-canada-40056576|url-status=live}}</ref>

There have also been documented events of sea lions assisting humans. One such notable instance of this is when [[Kevin Hines]] jumped off the [[Golden Gate Bridge]] in a suicide attempt and was helped to stay afloat by a sea lion until he was rescued by the [[Coast guard|Coast Guard]].<ref name="sealion">{{cite news |last=Bergeron |first=Ryan |date=2019-08-12 |title=He jumped off the Golden Gate Bridge and survived. Now, he's seeing his wish for a safety net come true |publisher=[[CNN]] |url=https://www.cnn.com/2019/08/09/health/turning-points-kevin-hines-golden-gate-bridge-suicide-survivor/ |accessdate=2019-08-17}}</ref>

Sea lions have also been a focus of tourism in Australia and New Zealand.<ref name=":6" /> One of the main sites to view sea lions is in the [[Carnac Island]] Nature Reserve near [[Perth]] in Western Australia. This tourist site receives over 100,000 visitors, many of whom are recreational boaters and tourists, who can watch the male sea lions haul out on to the shore.<ref name=":6" /> They have sometimes been called "the unofficial welcoming committee of the [[Galápagos Islands]]".<ref name="Bret Love">"In the Galapagos Islands they're so ubiquitous that they run the risk of being taken for granted. Here, you can find this unofficial welcoming committee almost everywhere"</ref>

==Gallery==
<gallery widths="250" heights="250">
Image:Zalophus californianus at Moss Landing 3.jpg|A gathering of more than 40 sea lions off the coast of Moss Landing, California
Image:GiGi sea lion 1984.jpg|GiGi, a sea lion trained by the U.S. Navy for underwater recovery, nuzzles merchant mariner Capt. Arne Willehag of the USNS ''Sioux'' during a 1983 training session.
Image:sea lion head.jpg|A sea lion at the [[Memphis Zoo]]
Image:Sea Lion Lounging.JPG|A sea lion pup sleeping at Pantai Inn
Image:Sea lion head by the ocean.jpg|A sea lion in [[Malibu, California|Malibu]], California
Image:Sealion052006.JPG|A sea lion at Monterey Breakwater
Image:Sea lion chillin'.jpg|A sea lion sleeps in the [[Ballestas Islands]], Peru
Image:Sea lions chillin'.jpg|A group of sea lions rest in the [[Ballestas Islands]], Peru
</gallery>

==See also==
*[[List of carnivorans by population]]

==References==
{{Reflist|30em}}

==Further reading==
{{Commons|Otariidae}}
{{Wikispecies|Otariidae}}
* Healy, Jack (March 2015). [https://www.nytimes.com/2015/03/13/us/starving-sea-lions-washing-ashore-by-the-hundreds-in-california.html?_r=0 Starving Sea Lions Washing Ashore by the Hundreds in California].  ''The New York Times''

{{Carnivora|C1.}}
{{Pan-Pinnipedia|O.|state=autocollapse}}
{{Taxonbar|from=Q3887135}}
{{Authority control}}

 [[Category:Otariinae|Sea lion]]
[[Category:Paraphyletic groups]]
[[Category:Mammal common names]]
[[Category:Fur trade]]