Editing Orca (section)

===Types===
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{{further information|Orca types and populations}}
The three to five types of orcas may be distinct enough to be considered different [[Race (biology)|races]],<ref name=baird>{{harv|Baird|2002}}. [http://courses.washington.edu/mb351/readings/baird.pdf Status of Killer Whales in Canada] {{Webarchive|url=https://web.archive.org/web/20111108150031/http://courses.washington.edu/mb351/readings/baird.pdf |date=November 8, 2011 }}. Contract report to the Committee on the Status of Endangered Wildlife in Canada, Ottawa, ON, Canada. Also published as [http://www.cascadiaresearch.org/robin/kwstatus2001.pdf Status of Killer Whales, ''Orcinus orca'', in Canada] {{Webarchive|url=https://web.archive.org/web/20100714010207/http://www.cascadiaresearch.org/robin/kwstatus2001.pdf |date=July 14, 2010 }} ''The Canadian Field-Naturalist'' '''115''' (4) (2001), 676–701. Retrieved January 26, 2010.</ref> [[subspecies]], or possibly even [[species]]<ref name="Pitman2003">{{cite journal |last1=Pitman|first1= Robert L. |last2=Ensor|first2= Paul |year=2003 |url=http://swfsc.noaa.gov/uploadedFiles/Divisions/PRD/Programs/Ecology/PitmanandEnsor2003JCRM.pdf |title=Three forms of killer whales (''Orcinus orca'') in Antarctic waters |journal=Journal of Cetacean Research and Management |volume=5 |issue=2 |pages=131–139 |doi= 10.47536/jcrm.v5i2.813 |s2cid= 52257732 |access-date=January 9, 2010 |archive-date=April 27, 2020 |archive-url=https://web.archive.org/web/20200427185038/https://swfsc.noaa.gov/uploadedFiles/Divisions/PRD/Programs/Ecology/PitmanandEnsor2003JCRM.pdf |url-status=live }}</ref> (see [[Species problem]]). The [[IUCN]] reported in 2008, "The [[taxonomy (biology)|taxonomy]] of this genus is clearly in need of review, and it is likely that ''O. orca'' will be split into a number of different species or at least subspecies over the next few years."<ref name="iucn status 19 November 2021" /> Although large variation in the ecological distinctiveness of different orca groups complicate simple differentiation into types,<ref name="de bruyn et al. 2013">{{Cite journal |last1=De Bruyn |first1=P. J. N. |last2=Tosh |first2=C. A. |last3=Terauds |first3=A. |doi=10.1111/j.1469-185X.2012.00239.x |title=Killer whale ecotypes: Is there a global model? |journal=[[Biological Reviews]] |volume=88 |issue=1 |pages=62–80 |year=2013 |pmid=22882545 |hdl=2263/21531|s2cid=6336624 |hdl-access=free }}</ref> research off the west coast of North America has identified fish-eating "residents", mammal-eating "transients" and "offshores".{{sfn|Ford|Ellis|Balcomb|2000|pp=16–21}} Other populations have not been as well studied, although specialized fish and mammal eating orcas have been distinguished elsewhere.<ref name="Jefferson et al. 1991">{{cite journal |doi=10.1111/j.1365-2907.1991.tb00291.x |last1=Jefferson |first1=T. A. |last2=Stacey |first2=P. J. |last3=Baird |first3=R. W. |year=1991 |url=http://swfsc.noaa.gov/uploadedFiles/Divisions/PRD/Publications/Jeffersonetal.1991(8).pdf |title=A review of killer whale interactions with other marine mammals: predation to co-existence |journal=[[Mammal Review]] |volume=21 |pages=151–180 |issue=4 |access-date=February 23, 2010 |archive-date=July 22, 2011 |archive-url=https://web.archive.org/web/20110722004728/http://swfsc.noaa.gov/uploadedFiles/Divisions/PRD/Publications/Jeffersonetal.1991(8).pdf |url-status=live }}</ref> Mammal-eating orcas in different regions were long thought likely to be closely related, but genetic testing has refuted this hypothesis.<ref name=Schrope>{{cite journal |title=Food chains: Killer in the kelp |journal=Nature |author=Schrope|first1= Mark |volume=445 |pages=703–705 |year=2007 |doi=10.1038/445703a |pmid=17301765 |issue=7129 |bibcode=2007Natur.445..703S |s2cid=4421362 |doi-access=free }}</ref><ref>{{Cite journal |author1=Josh D. McInnes |author2=Andrew W. Trites |author3=Chelsea R. Mathieson |author4=Marilyn E. Dahlheim |author5=Jeffrey E. Moore |author6=Paula A. Olson |author7=Kevin M. Lester |title=Evidence for an Oceanic Population of Killer Whales (Orcinus orca) in Offshore Waters of California and Oregon |url=https://www.aquaticmammalsjournal.org/article/evidence-for-an-oceanic-population-of-killer-whales-orcinus-orca-in-offshore-waters-of-california-and-oregon/ |journal=Aquatic Mammals |date=2024 |access-date=2024-03-22| volume= 50| issue= 2 }|pages=   93–106|language=en-US |doi=10.1578/am.50.2.2024.93}}</ref>

A 2024 study supported the elevation of Eastern North American resident and transient orcas as distinct species,  ''O. ater''  and ''O. rectipinnus'' respectively.<ref>{{cite journal|last1=Morin|first1=P. A.|last2=McCarthy|first2=M. L.|last3=Fung|first3=C. W.|last4=Durban|first4=J. W.|last5=Parsons|first5=K. M.|last6=Perrin|first6=W. F.|last7=Taylor|first7=B. L.|last8=Jefferson|first8=T. A.|last9=Archer|first9=F. I.|year=2024|title=Revised taxonomy of eastern North Pacific killer whales (Orcinus orca): Bigg's and resident ecotypes deserve species status|journal=Royal Society Open Science|volume=11|issue=3|doi=10.1098/rsos.231368|pmid=38545612 |pmc=10966402|bibcode=2024RSOS...1131368M }}</ref> The [[Society for Marine Mammalogy]] declined to recognize the two species, citing uncertainty as to whether the types constituted unique species or subspecies. "Pending a more complete global review and revision", the Society provisionally recognized them as subspecies ''Orcinus orca ater'' and ''O. o. rectipinnus'', with ''O. o. orca'' as the [[nominate subspecies]].<ref name="SMM">{{cite web |title=List of Marine Mammal Species and Subspecies |url=https://marinemammalscience.org/science-and-publications/list-marine-mammal-species-subspecies/ |website=MarineMammalScience.org |publisher=[[Society for Marine Mammalogy]] |date=June 2024}}</ref>

Four types have been documented in the [[Antarctic]], Types A–D. Two dwarf species, named ''[[Orca types and populations|Orcinus nanus]]'' and ''[[Orca types and populations|Orcinus glacialis]]'', were described during the 1980s by Soviet researchers, but most cetacean researchers are skeptical about their status.<ref name="Pitman2003"/> Complete [[DNA sequencing|mitochondrial sequencing]] indicates the two Antarctic groups (types B and C) should be recognized as distinct species, as should the North Pacific transients, leaving the others as subspecies pending additional data.<ref>{{cite journal |title=Complete mitochondrial genome phylogeographic analysis of killer whales (''Orcinus orca'') indicates multiple species |first1=Phillip A. |last1= Morin |first2=Frederick |last2= Archer |first3=Andrew D. |last3= Foote |first4=Julia |last4= Vilstrup |first5=Eric E. |last5= Allen |first6=Paul |last6= Wade |first7=John |last7= Durban |first8=Kim |last8= Parsons |first9=Robert |last9= Pitman|journal=Genome Research | doi=10.1101/gr.102954.109 |pmid=20413674 |volume=20 |pages=908–916 |year=2010 |issue=7 |pmc=2892092}}</ref> A 2019 study of Type D orcas also found them to be distinct from other populations and possibly even a unique species.<ref name="Pitman et al. 2010">{{cite journal |last1=Pitman |first1=Robert L. |last2=Durban |first2=John W. |last3=Greenfelder |first3=Michael |last4=Guinet |first4=Christophe |last5=Jorgensen |first5=Morton |last6=Olson |first6=Paula A. |last7=Plana |first7=Jordi |last8=Tixier |first8=Paul |last9=Towers |first9=Jared R. |title=Observations of a distinctive morphotype of killer whale (''Orcinus orca''), type D, from subantarctic waters |journal=Polar Biology |date=August 7, 2010 |volume=34 |issue=2 |pages=303–306 |doi=10.1007/s00300-010-0871-3 |s2cid=20734772 }}</ref>