Editing Steller's sea cow (section)

===Extinction===
Genetic evidence suggests the Steller's sea cows around the Commander Islands were the last of a much more ubiquitous population dispersed across the North Pacific coastal zones. They had the same [[genetic diversity]] as the last and rather [[inbred]] population of [[woolly mammoth]]s on [[Wrangel Island]]. During glacial periods and reduction in sea levels and temperatures, suitable habitat substantially regressed, fragmenting the population. By the time sea levels stabilized around 5,000 years ago, the population had already plummeted. Together, these indicate that even without human influence, the Steller's sea cow would have still been a [[Extinction debt|dead clade walking]], with the vast majority of the population having already gone extinct from natural climatic and sea level shifts, with the tiny remaining population at major risk from a genetic [[extinction vortex]].<ref name=Sharko2021/>

[[File:Sea otter with sea urchin.jpg|thumb|The [[sea otter]] is a [[keystone species]] and keeps [[sea urchin]] populations in check. Its depopulation in the Aleutian Islands may have led to the decline of [[kelp forest|kelp]] and subsequently of sea cows.<ref name=kelp/>|alt=A sea otter swimming on its back, holding a sea urchin and smashing a rock against it]]
The presence of Steller's sea cows in the Aleutian Islands may have caused the Aleut people to migrate westward to hunt them. This possibly led to the sea cow's extirpation in that area, assuming it had not already happened yet, but the archaeological evidence is inconclusive.<ref name=whitmore/><ref name="domning2007" /><ref name=":1" /> One factor potentially leading to extinction of Steller's sea cow, specifically off the coast of St. Lawrence Island, was the [[Siberian Yupik people]] who have inhabited St. Lawrence island for 2,000 years. They may have hunted the sea cows into extinction, as the natives have a dietary culture heavily dependent upon [[marine mammal]]s. The onset of the [[Medieval Warm Period]], which reduced the availability of kelp, may have also been the cause for their [[local extinction]] in that area.<ref name=crerar/> It has also been argued that the decline of Steller's sea cow may have been an indirect effect of the harvesting of sea otters by the area's aboriginal people. With the otter population reduced, the [[sea urchin]] population would have increased, in turn reducing the stock of kelp, its principal food.<ref name=kelp>{{cite journal |last1=Estes |first1=James A. |last2=Burdin |first2=Alexander |last3=Doak |first3=Daniel F. |year=2016 |title=Sea otters, kelp forests, and the extinction of Steller's sea cow |journal=[[Proceedings of the National Academy of Sciences of the United States of America]] |doi=10.1073/pnas.1502552112 |pmc=4743786 |pmid=26504217 |bibcode=2016PNAS..113..880E |volume=113 |issue=4 |pages=880–885|doi-access=free }}</ref><ref name=Anderson/> In historic times, though, aboriginal hunting had depleted sea otter populations only in localized areas,<ref name=Anderson/> and as the sea cow would have been easy prey for aboriginal hunters, accessible populations may have been exterminated with or without simultaneous otter hunting. In any event, the range of the sea cow was limited to coastal areas off uninhabited islands by the time Bering arrived, and the animal was already [[endangered species|endangered]].<ref>{{cite book |last=Ellis |first=Richard |author-link=Richard Ellis (biologist) |title=No Turning Back: The Life and Death of Animal Species |url=https://archive.org/details/noturningbacklif00elli |url-access=registration |publisher=[[Harper Perennial]] |year=2004 |location=New York, New York |isbn=978-0-06-055804-8 |oclc=961898476 |page=[https://archive.org/details/noturningbacklif00elli/page/134 134]}}</ref><ref name=turvey2006>{{cite journal |last1=Turvey |first1=S. T. |last2=Risley |first2=C. L. |year=2006 |title=Modelling the extinction of Steller's sea cow |journal=Biology Letters |pmid=17148336 |doi=10.1098/rsbl.2005.0415 |pmc=1617197 |volume=2 |issue=1 |pages=94–97}}</ref>

When Europeans discovered them, there may have been only 2,000 individuals left.<ref name=Sharko2021/> This small population was quickly wiped out by [[fur trade]]rs, [[seal hunting|seal hunters]], and others who followed Vitus Bering's route past its habitat to [[Alaska]].<ref>{{cite book |last=Haycox |first=Stephen W. |year=2002 |title=Alaska: An American Colony |publisher=[[University of Washington Press]] |location=Seattle, Washington |isbn=978-0-295-98249-6 |oclc=49225731 |pages=55,144 |url={{Google books|plainurl=yes|id=8yu3pYpzLdUC|page=55}}|quote=Each year, one or more vessels left Okhotsk or Petropavlosk on Kamchatka for hunting trips to the [Aleutian] islands. Typically, the ships would sail to the Commander Islands, where they would spend some time slaughtering and preserving the mat of Steller's rhytina (a sea cow)...}}</ref> It was also hunted to collect its valuable [[subcutaneous tissue|subcutaneous fat]]. The animal was hunted and used by Ivan Krassilnikov in 1754 and Ivan Korovin 1762, but Dimitri Bragin, in 1772, and others later, did not see it. Brandt thus concluded that by 1768, twenty-seven years after it had been discovered by Europeans, the species was extinct.<ref name=iucn/><ref name=Anderson/><ref name=jones>{{cite journal |last=Jones |first=Ryan T. |date=September 2011 |title=A 'Havock Made among Them': Animals, Empire, and Extinction in the Russian North Pacific, 1741–1810 |journal=Environmental History |doi=10.1093/envhis/emr091 |jstor=23049853 |volume=16 |issue=4 |pages=585–609}}</ref> In 1887, Stejneger estimated that there had been fewer than 1,500 individuals remaining at the time of Steller's discovery, and argued there was already an immediate danger of the sea cow's extinction.<ref name=iucn/>

The first attempt to hunt the animal by Steller and the other crew members was unsuccessful due to its strength and thick hide. They had attempted to impale it and haul it to shore using a large hook and heavy cable, but the crew could not pierce its skin. In a second attempt a month later, a [[harpoon]]er speared an animal, and men on shore hauled it in while others repeatedly stabbed it with [[bayonet]]s. It was dragged into shallow waters, and the crew waited until the tide receded and it was beached to butcher it.<ref name=orcutt2003/> After this, they were hunted with relative ease, the challenge being in hauling the animal back to shore. This bounty inspired [[maritime fur trade]]rs to detour to the Commander Islands and restock their food supplies during North Pacific expeditions.<ref name=whitmore/>

==== Impact of extinction ====
While not a [[keystone species]], Steller's sea cows likely influenced the community composition of the [[kelp forest]]s they inhabited, and also boosted their [[Primary production|productivity]] and resilience to environmental stressors by allowing more light into kelp forests and more kelp to grow, and enhancing the [[Recruitment (biology)|recruitment]] and [[Biological dispersal|dispersal]] of kelp through their feeding behavior. In the modern day, the flow of nutrients from kelp forests to adjacent ecosystems is regulated by the seasons, with seasonal storms and currents being the primary factor. The Steller's sea cow may have allowed this flow to continue year-round, thus allowing for more productivity in adjacent habitats. The disturbance caused by the Steller's sea cow may have facilitated the dispersal of kelp, most notably ''[[Nereocystis]]'' species, to other habitats, allowing recruitment and [[Colonisation (biology)|colonization]] of new areas, and facilitating [[Gene flow|genetic exchange]]. Their presence may have also allowed [[sea otter]]s and large [[marine invertebrates]] to coexist, indicating a commonly-documented decline in marine invertebrate populations driven by sea otters (an example being in populations of the [[Katharina tunicata|black leather chiton]])<ref>{{Cite journal|last1=Salomon|first1=Anne K.|last2=Tanape|first2=Nick M.|last3=Huntington|first3=Henry P.|date=September 2007|title=Serial depletion of marine invertebrates leads to the decline of a strongly interacting grazer|journal=Ecological Applications|volume=17|issue=6|pages=1752–1770|doi=10.1890/06-1369.1|issn=1051-0761|pmid=17913138|bibcode=2007EcoAp..17.1752S }}</ref> may be due to lost ecosystem functions associated with the Steller's sea cow. This indicates that due to the sea cow's extinction, the ecosystem dynamics and resilience of North Pacific kelp forests may have already been compromised well before more well-known modern stressors like [[Overexploitation|overharvesting]] and [[climate change]].<ref>{{Cite thesis|last=Bullen|first=Cameron David|date=2020|title=A marine megafaunal extinction and its consequences for kelp forests of the North Pacific|url=https://open.library.ubc.ca/soa/cIRcle/collections/ubctheses/24/items/1.0391881|access-date=2021-08-19|website=open.library.ubc.ca|doi=10.14288/1.0391881}}</ref><ref name=":2" />