Editing Steller sea lion (section)

== 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>