Editing Blue whale (section)

== Taxonomy ==
{{See also|Evolution of cetaceans}}

=== Nomenclature ===
The genus name, ''[[Balaenoptera]]'', means ''winged whale,''<ref name=Reeves_etal_2002/> while the species name, ''musculus'', could mean "muscle" or a diminutive form of "mouse", possibly a pun by [[Carl Linnaeus]]<ref name=Reeves_etal_2002/><ref name=Calamb_Steig_1997/> when he named the species in ''[[Systema Naturae]]''.<ref name=Linnaeus_1758>{{cite book | last=Linnaeus | first=Carl | date=1758 | title=Systema Naturae per regna tria naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis | location=Stockholm, Holmia | publisher=Laurentius Salvius | page=824 | author-link=Carl Linnaeus}}</ref> One of the first published descriptions of a blue whale comes from [[Robert Sibbald]]'s ''Phalainologia Nova'',<ref name=Sibbald_1692>{{cite journal | author1=Sibbald, Robert | title=Phalainologia Nova | journal=Blue Whale ("Balaenoptera Musculus") | pages=675–678 | date=1692 | author-link=Robert Sibbald}}</ref> after Sibbald found a stranded whale in the estuary of the [[Firth of Forth]], Scotland, in 1692. The name "blue whale" was derived from the Norwegian ''blåhval'', coined by [[Svend Foyn]] shortly after he had perfected the harpoon gun. The Norwegian scientist [[G. O. Sars]] adopted it as the common name in 1874.<ref name=Bortolotti_2008>{{cite book|author1=Bortolotti, D.|title=Wild Blue: A Natural History of the World's Largest Animal | publisher=[[St. Martin's Press]]|location=New York|date=2008}}</ref>

Blue whales were referred to as "Sibbald's rorqual", after Robert Sibbald, who first described the species.<ref name=Sibbald_1692/> Whalers sometimes referred to them as "sulphur bottom" whales, as the bellies of some individuals are tinged with yellow.<ref name=":0">{{Cite journal |last=Bennett |first=A G |date=1920 |title=On the occurrence of diatoms on the skin of whales |url=https://royalsocietypublishing.org/doi/10.1098/rspb.1920.0021 |journal=Proc. R. Soc. Lond. B |volume=91 |issue=641 |pages=352–357|doi=10.1098/rspb.1920.0021 }}</ref> This tinge is due to a coating of huge numbers of [[diatoms]].<ref name=":0" /> ([[Herman Melville]] briefly refers to "sulphur bottom" whales in his novel ''[[Moby-Dick]]''.<ref name="Melville_1851" />)

===Evolution===
{{cladogram |align=right
|caption=<small>A [[phylogenetic tree]] of six baleen whale species<ref name=Arnason_etal_2018/></small>
|clades={{clade|style=font-size:75%;line-height:75%;width:350px;
|label1=[[Balaenopteridae]]
|1={{clade
   |1=[[Minke whale]]
   |2={{clade
      |1={{clade
         |1='''''B. musculus''''' ('''blue whale''')
         |2=''B. borealis'' ([[sei whale]])
       }}
      |2={{clade 
         |1=''Eschrichtius robustus'' ([[gray whale]])
         |2={{clade
            |1=''B. physalus'' ([[fin whale]])
            |2=''Megaptera novaeangliae'' ([[humpback whale]])
          }}
       }}
    }}
 }}
}}
}}
Blue whales are [[rorquals]] in the family [[Balaenopteridae]]. A 2018 analysis estimates that the Balaenopteridae family diverged from other families in between 10.48 and 4.98&nbsp;million years ago during the late [[Miocene]].<ref name=Arnason_etal_2018>{{cite journal | author1=Árnason, U. | author2=Lammers, F. | author3=Kumar, V. | author4=Nilsson, M. A. | author5=Janke, A. | title=Whole-genome sequencing of the blue whale and other rorquals finds signatures for introgressive gene flow | journal=[[Science Advances]] | volume=4 | issue = 4 | pages=eaap9873 | date=2018| bibcode=2018SciA....4.9873A | doi=10.1126/sciadv.aap9873 | pmid=29632892 | pmc=5884691}}</ref> The earliest discovered anatomically modern blue whale is a partial skull fossil from southern [[Italy]] identified as ''B.'' cf. ''musculus'', dating to the Early [[Pleistocene]], roughly 1.5–1.25&nbsp;million years ago.<ref name=Bianucci_etal_2019>{{cite journal | author1=Bianucci, G. | author2=Marx, F. G. | author3=Collareta, A. | author4=Di Stefano, A. | author5=Landini, W. | author6=Morigi, C. | author7=Varola, A. | title=Rise of the titans: baleen whales became giants earlier than thought | journal=[[Biology Letters]] | volume=15 | issue = 5 | page=20190175 | date=2019| doi=10.1098/rsbl.2019.0175 | pmid=31039728 | pmc=6548731}}</ref> The Australian [[pygmy blue whale]] diverged during the [[Last Glacial Maximum]]. Their more recent divergence has resulted in the subspecies having a relatively low genetic diversity,<ref name=Attard_etal_2015>{{cite journal | author1=Attard, C. R. M. | author2=Beheregaray, L. B. | author3=Jenner, K. C. S. | author4=Gill, P. C. | author5=Jenner, M.-N. M. | author6=Morrice, M. G. | author7=Teske, P. R. | author8=Moller, L. M. | title=Low genetic diversity in pygmy blue whales is due to climate-induced diversification rather than anthropogenic impacts | journal=Biology Letters | volume=11 | issue=5 | page=20141037 | date=2015| doi=10.1098/rsbl.2014.1037 | pmid=25948571 | pmc=4455730}}</ref> and New Zealand blue whales have an even lower genetic diversity.<ref name=Barlow_etal_2018>{{cite journal | author1=Barlow, D. R. | author2=Torres, L. G. | author3=Hodge, K. B. | author4=Steel, D. | author5=Baker, C. S. | author6=Chandler, T. E. | author7=Bott, N. | author8=Constantine, R. | author9=Double, M. C. | author10=Gill, P. | author11=Glasgow, D. | author12=Hamner, R. M. | author13=Lilley, C. | author14=Ogle, M. | author15=Olson, P. A. | title=Documentation of a New Zealand blue whale population based on multiple lines of evidence | journal=Endangered Species Research | volume=36 | pages=27–40 | date=2018| doi=10.3354/esr00891 | doi-access=free}}</ref>

[[Whole genome sequencing]] suggests that blue whales are most closely related to [[sei whale]]s with gray whales as a [[sister group]]. This study also found significant [[gene flow]] between minke whales and the ancestors of the blue and sei whale. Blue whales also displayed high genetic diversity.<ref name=Arnason_etal_2018/>

====Hybridization====
Blue whales are known to [[interbreed]] with [[fin whale]]s.<ref>This may have already been known to Icelanders in the 17th century, see {{cite book |last=Lindquist |first=Ole |date=1997 |title=Peasant fisherman whaling in the Northeast Atlantic area, ca 900-1900 AD |url=https://www.fishernet.is/images/stories/peasant_fisherman_whaling.pdf |location=Akureyri |publisher=Háskólinn á Akureyri |page=27 |isbn=9979-834-10-2 |access-date=2025-04-16}}</ref> The earliest description of a possible hybrid between a blue whale and a fin whale was a {{cvt|20|m}} anomalous female whale with the features of both the blue and the fin whales taken in the North Pacific.<ref name=Doroshenko_1970>{{cite journal | author1=Doroshenko, V. N. | title=A whale with features of the fin and the blue whale | journal=Izvestia TINRO | volume=70 | pages=255–257 | date=1970}}</ref> A whale captured off northwestern Spain in 1984, was found to have been the product of a blue whale mother and a fin whale father.<ref name=Berube_Aguilar_1998>{{cite journal | author1=Bérubé, M. | author2=Aguilar, A. | title=A new hybrid between a blue whale, ''Balaenoptera Musculus'', and a fin whale, "B. Physalus:" frequency and implications of hybridization | journal=Marine Mammal Science | volume=14 | issue=1 | pages=82–98 | date=1998| doi=10.1111/j.1748-7692.1998.tb00692.x| bibcode=1998MMamS..14...82B }}</ref>

Two live blue-fin whale [[Hybrid (biology)|hybrids]] have since been documented in the Gulf of St. Lawrence (Canada), and in the Azores (Portugal).<ref name=Berube_etal_2017>{{cite conference | author1=Berube, M. | author2=Oosting, T. | author3=Aguilar, A. | author4=Berrow, S. | author5=Hao, W. | author6=Heide-Jørgensen, M. P. | author7=Kovacs, K. M. | author8=Landry, S. | author9=Lydersen, C. | author10=Martin, V. | author11=Øien, N. | author12=Panigada, S. | author13=Prieto, R. | author14=Ramp, C. | author15=Robbins, J. | title=Are the "Bastards" coming back? Molecular identification of live blue and fin whale hybrids in the North Atlantic ocean | conference=22nd Biennial Conference on the Biology of Marine Mammals | location=Halifax, Nova Scotia, Canada | date=2017}}</ref> DNA tests done in Iceland on a blue whale killed in July 2018 by the Icelandic whaling company [[Hvalur hf.]], found that the whale was the offspring of a male fin whale and female blue whale;<ref>{{cite web |last=Kilvert|first=Nick|url=https://www.abc.net.au/news/science/2018-07-20/dna-shows-blue-whale-hybrid-iceland-institute-says/10017276 | title=DNA test shows slaughtered blue whale is a hybrid, Iceland marine institute says | date=20 July 2018 | publisher=[[Australian Broadcasting Corporation|ABC]] | access-date=21 December 2019}}</ref> however, the results are pending independent testing and verification of the samples. Because the International Whaling Commission classified blue whales as a "Protection Stock", trading their meat is illegal, and the kill is an infraction that must be reported.<ref>{{cite web |last=Fishman|first=Margie|url=https://awionline.org/press-releases/hybrid-blue-fin-whale-still-protected | title=Hybrid blue-fin whale is still protected | date=19 July 2018 | publisher=[[Animal Welfare Institute]] | access-date=21 December 2019}}</ref> Blue-fin hybrids have been detected from genetic analysis of whale meat samples taken from Japanese markets.<ref name=Palumbi_Cipriano_1998>{{cite journal | author1=Palumbi, S. R. | author2=Cipriano, F. | title=Species identification using genetic tools: the value of nuclear and mitochondrial gene sequences in whale conservation | journal=Journal of Heredity | volume=89 | issue=5 | pages=459–464 | date=1998| doi=10.1093/jhered/89.5.459 | pmid=9768497 | doi-access=free}}</ref> Blue-fin whale hybrids are capable of being fertile. Molecular tests on a {{cvt|70|ft|order=flip}} pregnant female whale caught off Iceland in 1986 found that it had a blue whale mother and a fin whale father, while its fetus was sired by a blue whale.<ref name=Spilliaert_etal_1991>{{cite journal | author1=Spilliaert, R. | author2=Vikingsson, G. | author3=Arnason, U. | author4=Palsdottir, A. | author5=Sigurjonsson, J. | author6=Arnason, A. | title=Species hybridization between a female blue whale (''Balaenoptera rnusctllus'') and a male fin whale ("B.pbysalus"): Molecular and morphological documentation | journal=[[Journal of Heredity]] | volume=82 | issue=4 | pages=269–274 | date=1991| doi=10.1093/oxfordjournals.jhered.a111085 | pmid=1679066}}</ref>

In 2024, a genome analysis of North Atlantic blue whales found evidence that approximately 3.5% of the blue whales' genome was derived from hybridization with fin whales. Gene flow was found to be unidirectional from fin whales to blue whales. Comparison with Antarctic blue whales showed that this hybridization began after the separation of the northern and southern populations. Despite their smaller size, fin whales have similar cruising and sprinting speeds to blue whales, which would allow fin males to complete courtship chases with blue females.<ref name=Jossey_et_al_2024>{{cite journal | author1=Jossey, Sushma | author2=Haddrath, O. | author3=Loureiro, L. | author4=Weir, J. | author5=Lim, B. | author6=Miller, J. | author7=Scherer, S. | author8=Goskøyr, A | author9=Lille-Langøy, R | author10=Kovacs, Kit | author11=Lyndersen, C | author12=Routti, H | author13=Engstrom, M | title=Population structure and history of North Atlantic Blue whales (''Balaenoptera musculus musculus'') inferred from whole genome sequence analysis | journal=[[Conservation Genetics]] | volume=Open access | date=6 January 2024 | issue=2 | pages=357–371 | doi=10.1007/s10592-023-01584-5| doi-access=free | bibcode=2024ConG...25..357J | hdl=11250/3164708 | hdl-access=free }}</ref>

There is a reference to a humpback–blue whale hybrid in the [[South Pacific Ocean|South Pacific]], attributed to marine biologist Michael Poole.<ref name=Reeves_etal_2002/><ref name=Hatch_etal_2006>{{cite journal | author1=Hatch, L. T. | author2=Dopman, E. B. | author3=Harrison, R. G. | title=Phylogenetic relationships among the baleen whales based on maternally and paternally inherited characters | journal=[[Molecular Phylogenetics and Evolution]] | volume=41 | issue=1 | pages=12–27 | date=2006| doi=10.1016/j.ympev.2006.05.023 | pmid=16843014| bibcode=2006MolPE..41...12H }}</ref><ref>{{cite web |title=Genomic analyses reveal an absence of contemporary introgressive admixture between fin whales and blue whales, despite known hybrids|url=https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0222004|date=25 September 2019|access-date=15 February 2025}}</ref>

===Subspecies and stocks===
At least four subspecies of blue whale are traditionally recognized, some of which are divided into population stocks or "management units".<ref name=NOAA>{{cite report|first1=Chris W. |last1= Oliver|date=November 2020|title= Recovery Plan for the Blue Whale (''Balaenoptera musculus'') |publisher=National Oceanic and Atmospheric Administration |url=https://www.fisheries.noaa.gov/resource/document/recovery-plan-blue-whale-balaenoptera-musculus-0|access-date=12 April 2022}}</ref><ref name=SMM_2016>{{cite web|url=https://www.marinemammalscience.org/species-information/list-marine-mammal-species-subspecies/ |title=List of Marine Mammal Species and Subspecies |date=13 November 2016 | publisher=[[The Society for Marine Mammalogy]] |access-date=30 December 2019}}</ref> They have a worldwide distribution, but are mostly absent from the [[Arctic Ocean]] and the [[Mediterranean]], [[Sea of Okhotsk|Okhotsk]], and [[Bering Sea]].<ref name=NOAA/>
[[File:Blue Whale 001 body bw.jpg|thumb|right|alt=Aerial photograph of an adult blue whale showing its length |Aerial view of adult blue whale]]
*Northern subspecies (''B. m. musculus'')
**North Atlantic population – This population is mainly documented from [[New England]] along eastern Canada to Greenland, particularly in the [[Gulf of St. Lawrence]], during summer though some individuals may remain there all year. They also aggregate near Iceland and have increased their presence in the [[Norwegian Sea]]. They are reported to migrate south to the [[West Indies]], the [[Azores]] and northwest Africa.<ref name=NOAA/> 
**Eastern North Pacific population – Whales in this region mostly feed off California's coast from summer to fall and then Oregon, Washington State, the [[Alaska Current|Alaska Gyre]] and [[Aleutian Islands]] later in the fall. During winter and spring, blue whales migrate south to the waters of Mexico, mostly the [[Gulf of California]], and the [[Costa Rica Thermal Dome|Costa Rica Dome]], where they both feed and breed.<ref name=NOAA/>
**Central/Western Pacific population – This stock is documented around the [[Kamchatka Peninsula]] during the summer; some individuals may remain there year-round. They have been recorded wintering in Hawaiian waters, though some can be found in the [[Gulf of Alaska]] during fall and early winter.<ref name=NOAA/>
*Northern Indian Ocean subspecies (''B. m. indica'') – This subspecies can be found year-round in the northwestern Indian Ocean, though some individuals have recorded travelling to the [[Crozet Islands]] during between summer and fall.<ref name=NOAA/>
*Pygmy blue whale (''B. m. brevicauda'')
**Madagascar population – This population migrates between the [[Seychelles]] and [[Amirante Islands]] in the north and the [[Crozet Island]]s and [[Prince Edward Islands]] in the south were they feed, passing through the [[Mozambique Channel]].<ref name=NOAA/> 
**Australia/Indonesia population – Whales in this region appear to winter off Indonesia and migrate to their summer feeding grounds off the coast of Western Australia, with major concentrations at [[Perth Canyon]] and an area stretching from the [[Great Australian Bight]] and [[Bass Strait]].<ref name=NOAA/>
**Eastern Australia/New Zealand population – This stock may reside in the [[Tasman Sea]] and the [[Lau Basin]] in winter and feed mostly in the [[South Taranaki Bight]] and off the coast of eastern [[North Island]]. Blue whales have been detected around New Zealand throughout the year.<ref name=NOAA/>
*Antarctic subspecies (''B. m. intermedia'') – This subspecies includes all populations found around the Antarctic. They have been recorded to travel as far north as eastern tropical Pacific, the central Indian Ocean, and the waters of southwestern Australia and northern New Zealand.<ref name=NOAA/>

Blue whales off the [[Chile]]an coast might be a separate subspecies based on their geographic separation, genetics, and unique song types.<ref name=LeDuc_etal_2007>{{cite journal | author1=LeDuc, R. G. | author2=Dizon, A. E. | author3=Goto, M. | author4=Pastene, L. A. | author5=Kato, H. | author6=Nishiwaki, S. | author7=LeDuc, C. A. | author8=Brownell, R. L. | title=Patterns of genetic variation in Southern Hemisphere blue whales, and the use of assignment test to detect mixing on the feeding grounds | journal=Journal of Cetacean Research and Management | volume=9 | pages=73–80 | date=2023| doi=10.47536/jcrm.v9i1.694 | s2cid=257136658 | doi-access=free }}</ref><ref name=Torres-Florez_etal_2015>{{cite journal | author1=Torres-Florez, J. P. | author2=Olson, P. A. | author3=Bedrinana-Romano, L. | author4=Rosenbaum, H. | author5=Ruiz, J. | author6=Leduc, R. | author7=Huck-Gaete, R. | title=First documented migratory destination for eastern South Pacific blue whales | journal=Marine Mammal Science | volume=31 | issue=4 | pages=1580–1586 | date=2015| doi=10.1111/mms.12239 | doi-access=free | bibcode=2015MMamS..31.1580T }}</ref><ref name=Buchan_etal_2010>{{cite journal | author1=Buchan, S. J. | author2=Rendell, L. E. | author3=Hucke-Gaete, R. | title=Preliminary recordings of blue whale (''Balaenoptera musculus'') vocalizations in the Gulf of Corcovado, northern Patagonia Chile | journal=Marine Mammal Science | volume=26 | issue=2 | pages=451–459 | date=2010| doi=10.1111/j.1748-7692.2009.00338.x | bibcode=2010MMamS..26..451B }}</ref> Chilean blue whales might overlap in the [[Eastern Tropical Pacific]] with [[Antarctica]] blue whales and Eastern North Pacific blue whales. Chilean blue whales are genetically differentiated from Antarctica blue whales such that [[interbreeding]] is unlikely. However, the genetic distinction is less between them and the Eastern North Pacific blue whale, hence there might be gene flow between the Southern and Northern Hemispheres.<ref name=LeDuc_etal_2016>{{cite journal | author1=LeDuc, R. G. | author2=Archer, E. I. | author3=Lang, A. R. | author4=Martien, K. K. | author5=Hancock-Hanser, B. | author6=Torres-Florez, J. P. | author7=Hucke-Gaete, R. | author8=Rosenbaum, H. R. | author9=Van Waerebeek, K. | author10=Brownell, R. L. Jr. | author11=Taylor, B. L. | title=Genetic variation in blue whales in the eastern Pacific: implication for taxonomy and use of common wintering grounds | journal=[[Molecular Ecology]] | volume=26 | issue=3 | pages=740–751 | date=2016| doi=10.1111/mec.13940 | pmid=27891694 | s2cid=206184206 }}</ref> A 2019 study by Luis Pastene, Jorge Acevedo and Trevor Branch provided new morphometric data from a survey of 60 Chilean blue whales, hoping to address the debate about the possible distinction of this population from others in the Southern Hemisphere. Data from this study, based on whales collected in the [[Whaling in Chile|1965/1966 whaling season]], shows that both the maximum and mean body length of Chilean blue whales lies between these values in pygmy and Antarctic blue whales. Data also indicates a potential difference in snout-eye measurements between the three, and a significant difference in fluke-anus length between the Chilean population and pygmy blue whales. This further confirms Chilean blue whales as a separate population, and implies that they do not fall under the same subspecies as the pygmy blue whale (''B. m. brevicauda'').<ref name=Pastene_etal_2019>{{Cite journal |last1=Pastene |first1=Luis A. |last2=Acevedo |first2=Jorge |last3=Branch |first3=Trevor A. |date=2019 |title=Morphometric analysis of Chilean blue whales and implications for their taxonomy |url=https://onlinelibrary.wiley.com/doi/10.1111/mms.12625 |journal=Marine Mammal Science |language=en |volume=36 |issue=1 |pages=116–135 |doi=10.1111/mms.12625 |issn=0824-0469}}</ref>

A 2024 genomic study of the global blue whale population found support for the subspecific status of Antarctic and Indo-western Pacific blue whales but not eastern Pacific blue whales. The study found "...divergence between the eastern North and eastern South Pacific, and among the eastern Indian Ocean, the western South Pacific and the northern Indian Ocean." and "no divergence within the Antarctic".<ref>{{cite journal|author1=Attard, C. R. M.|author2=Sandoval-Castillo, J|author3=Lang, A. R.|author4=Vernazzani, B. G.|author5=Torres, L. G.|author6=Baldwin, R|author7=Jenner, K. C. S.|author8=Gill, P. C.|author9=Burton, C. L. K.|author10=Barceló, A|author11=Sironi, M|author12=Jenner, M.-N. M.|author13=Morrice, M. G.|author14=Beheregaray, L. B.|author15=Möller, L. M.|year=2024|title=Global conservation genomics of blue whales calls into question subspecies taxonomy and refines knowledge of population structure|journal=Animal Conservation|volume=27|issue=5|pages=626–638|doi=10.1111/acv.12935|bibcode=2024AnCon..27..626A |doi-access=free}}</ref>