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{{Sprotect|small=yes}}
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{{Taxobox
| name = '''Blue whale'''<ref name=msw3>{{MSW3 Mead
| pages = 725}}</ref>
| status = EN
| status_system = iucn3.1
| status_ref =<ref name="iucn">{{IUCN2008
|assessors=Reilly, S.B., Bannister, J.L., Best, P.B., Brown, M., Brownell Jr., R.L., Butterworth, D.S., Clapham, P.J., Cooke, J., Donovan, G.P., Urbán, J. & Zerbini, A.N.
|year=2008
|id=2477
|title=Balaenoptera musculus
|downloaded=7 October 2008}}</ref>
| image = Bluewhale877.jpg
| image_caption = Adult blue whale from the eastern Pacific Ocean
| image2 = Blue_whale_size.svg
| image2_caption = Size comparison against an average human
| regnum = ]ia
| phylum = ]
| classis = ]ia
| ordo = ]
| subordo = ]
| familia = ]
| genus = '']''
| species = '''''B. musculus '''''
| binomial = ''Balaenoptera musculus''
| binomial_authority = (], 1758)
| subdivision_ranks = ]
| subdivision =
*'']'' <small>Ichihara, 1966</small>
*?''B. m. indica'' <small>Blyth, 1859</small>
*''B. m. intermedia'' <small>Burmeister, 1871</small>
*''B. m. musculus'' <small>Linnaeus, 1758</small>
| range_map = cetacea_range_map_Blue_Whale.PNG
| range_map_caption = Blue whale range (in blue)
}}

The '''Blue whale''' ('''''Balaenoptera musculus''''') is a ] belonging to the suborder of ]s (called ]).<ref name="factsheet" /> Blue Whales can reach up to {{convert|33|m|ft}} in length and {{convert|180|metric ton|short ton|lk=on}}<ref>{{Cite web
| url=http://nationalzoo.si.edu/Animals/AnimalRecords/
| title=Animal Records
| publisher=Smithsonian National Zoological Park
| accessdate=2007-05-29 }}</ref> or more in weight. In volume, it is the ] ever known to have existed.<ref>{{cite web
| url=http://science.howstuffworks.com/question687.htm
| title=What is the biggest animal ever to exist on Earth?
| publisher=How Stuff Works
| accessdate=2007-05-29}}</ref>

Long and slender, the blue whale's body can be various shades of bluish-grey dorsally and somewhat lighter underneath.<ref> Fisheries and Aquaculture Department, Food and Agriculture Organization.</ref> There are at least three distinct ]: ''B. m. musculus'' of the North Atlantic and North Pacific, ''B. m. intermedia'' of the ] and ''B. m. brevicauda'' (also known as the ]) found in the ] and ]. ''B. m. indica'', found in the Indian Ocean, may be another subspecies. As with other baleen whales, its diet consists almost exclusively of small ]s known as ].<ref name="wheelock">{{cite web
|url=http://whale.wheelock.edu/bwcontaminants/welcome.html
|title=Contaminant analysis of organochlorines in blubber biopsies from blue whales in the St Lawrence
|publisher=Trent University
|author=Jason de Koning and Geoff Wild
|year=1997
| accessdate = 2007-06-29}}</ref>

Blue whales were abundant in nearly all the oceans until the beginning of the twentieth century. For over 40 years, they were hunted almost to ] by ] until protected by the international community in 1966. A 2002 report estimated there were 5,000 to 12,000 blue whales worldwide<ref name=pop>{{cite web
|url=http://www.sararegistry.gc.ca/virtual_sara/files/cosewic/sr_blue_whale_e.pdf
|publisher=Committee on the Status of Endangered Wildlife in Canada
|year=2002
|title=Assessment and Update Status Report on the Blue Whale ''Balaenoptera musculus''
| accessdate = 2007-04-19
|format=PDF}}</ref>, located in at least five groups. More recent research into the Pygmy subspecies suggests this may be an underestimate.<ref name=BBC_pop>{{Cite web
| author=Alex Kirby|work= BBC News
| year=2003
| title=Science seeks clues to pygmy whale
| url=http://news.bbc.co.uk/2/hi/science/nature/3003564.stm
| accessdate=April 21, 2006 | date=2003-06-19}}</ref> Before whaling, the largest population was in the Antarctic, numbering approximately 239,000 (range 202,000 to 311,000).<ref name = Ant>{{cite journal
| title = Evidence for increases in Antarctic blue whales based on Bayesian modelling
| author = T.A. Branch, K. Matsuoka and T. Miyashita
| journal = Marine Mammal Science
| volume = 20
| pages = 726–754
|year = 2004
| doi = 10.1111/j.1748-7692.2004.tb01190.x}}</ref> There remain only much smaller (around 2,000) concentrations in each of the North-East ], ], and ] groups. There are two more groups in the North ], and at least two in the ].

==Taxonomy==
{{See also|Evolution of cetaceans}}
Blue whales are ] (family ]), a family that includes the ], the ], ], the ] and the ].<ref name="factsheet" /> The family ] is believed to have diverged from the other families of the suborder ] as long ago as the middle ]. However, it is not known when the members of those families diverged from each other.

The blue whale is usually classified as one of eight species in the genus ''Balaenoptera''; one authority places it in a separate monotypic genus, ''Sibbaldus'',<ref>{{cite book
| author= Barnes LG, McLeod SA.
|editor= Jones ML et al.
|title= The Gray Whale
|year= 1984
|publisher= Academic Press
|location= Orlando, Florida
| isbn = 0123891809
|pages=3–32
|chapter= The fossil record and phyletic relationships of gray whales.}}</ref> but this is not accepted elsewhere.<ref name=msw3/> ] sequencing analysis indicates that the blue whale is ] closer to the ] (''Balaenoptera borealis'') and ] (''Balaenoptera brydei'') than to other ''Balaenoptera'' species, and closer to the ] (''Megaptera'') and the ] (''Eschrichtius'') than to the ]s (''Balaenoptera acutorostrata'' and ''Balaenoptera bonaerensis'').<ref>{{cite journal
|title=Cetacean mitochondrial DNA control region: sequences of all extant baleen whales and two sperm whale species
|author=Arnason, U., Gullberg A. & Widegren, B.
|journal=Molecular Biology and Evolution
|volume=10
|pages=960–970
|date= September 1, 1993 |url=http://mbe.oxfordjournals.org/cgi/content/abstract/10/5/960
|accessdate=2009-01-25
|pmid=8412655
|issue=5
}}</ref><ref>{{cite journal
|title=Mitochondrial Phylogenetics and Evolution of Mysticete Whales
|author=Sasaki, T
|journal=Systematic Biology
|volume=54
|issue=1
|pages=77–90
|date=February 23, 2005
|doi=10.1080/10635150590905939
|url=http://www.informaworld.com/smpp/content~content=a716097098~db=all
|accessdate=2009-01-25
|pmid=15805012
|last2=Nikaido
|first2=M
|last3=Hamilton
|first3=H
|last4=Goto
|first4=M
|last5=Kato
|first5=H
|last6=Kanda
|first6=N
|last7=Pastene
|first7=L
|last8=Cao
|first8=Y
|last9=Fordyce
|first9=R}}</ref> If further research confirms these relationships, it will be necessary to reclassify the rorquals.

There have been at least 11 documented cases of blue/] hybrid adults in the wild. Arnason and Gullberg describe the genetic distance between a Blue and a Fin as about the same as that between a human and a gorilla.<ref>{{cite journal
| author = A. Arnason and A. Gullberg
| title = Comparison between the complete mtDNA sequences of the blue and fin whale, two species that can hybridize in nature
| journal = Journal of Molecular Ecology
| year = 1993
| volume = 37
|pages = 312–322}}</ref> Researchers working off of Fiji believe they photographed a hybrid ]/blue whale.<ref>. Whale Center of New England (WCNE). Retrieved on 2008-02-27.</ref>

The specific name ''musculus'' is ] and could mean "muscular", but it can also be interpreted as "little mouse".<ref>{{cite book
| last = Simpson
| first = D.P.
| title = Cassell's Latin Dictionary
| publisher = Cassell Ltd.
| year = 1979
| edition = 5
| location = London
| page = 883
| isbn = 0-304-52257-0}}</ref> ], who named the species in his seminal '']'' of 1758,<ref>{{la icon}} {{cite book
| last=Linnaeus
| first=C
| authorlink=Carolus Linnaeus
| title=Systema naturae per regna tria naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata.
| publisher=Holmiae. (Laurentii Salvii).
| year=1758
| page=824
| url= }}</ref> would have known this and may have intended the ironic ].<ref>{{cite web
|url=http://www.dec.ny.gov/animals/9367.html
|title=Blue Whale Fact Sheet
|publisher=New York State Department of Environmental Conservation
| accessdate = 2007-06-29}}</ref> ] called this species '''sulphur-bottom''' in his novel '']'' due to an orange-brown or yellow tinge on the underparts from ] films on the skin. Other common names for the blue whale have included the '''Sibbald's rorqual''' (after ]), the '''great blue whale''' and the '''great northern rorqual'''. These names have now fallen into disuse.

Authorities classify the species into three or four subspecies: ''B. m. musculus'', the ] consisting of the North Atlantic and North Pacific populations, ''B. m. intermedia'', the ] of the ], ''B. m. brevicauda'', the ] found in the Indian Ocean and South Pacific,<ref>Ichihara T. (1966). The pygmy blue whale ''B. m. brevicauda'', a new subspecies from the Antarctic in ''Whales, dolphins and porpoises'' Page(s) 79-113.</ref> and the more problematic ''B. m. indica'', the ], which is also found in the Indian Ocean and, although described earlier, may be the same subspecies as ''B. m. brevicauda''.<ref name=msw3/>

==Description and behaviour==
]
]
]
] of this blue whale is just visible on the far left.]]

The blue whale has a long tapering body that appears stretched in comparison with the stockier build of other whales.<ref name="des" /> The head is flat and ''U''-shaped and has a prominent ridge running from the ] to the top of the upper lip.<ref name="des" /> The front part of the mouth is thick with ] plates; around 300 plates (each around one metre (3.2&nbsp;ft) long)<ref name="des" /> hang from the upper jaw, running 0.5&nbsp;m (1.6&nbsp;ft) back into the mouth. Between 60 and 90 grooves (called ventral pleats) run along the throat parallel to the body length. These pleats assist with evacuating water from the mouth after lunge feeding (see feeding below).

The ] is small,<ref name="des" /> visible only briefly during the dive sequence. Located around three-quarters of the way along the length of the body, it varies in shape from one individual to another; some only have a barely perceptible lump, but others may have prominent and ] dorsals. When surfacing to breathe, the blue whale raises its shoulder and blowhole out of the water to a greater extent than other large whales such as the ] or ]. Observers can use this trait to differentiate between species at sea. Some blue whales in the North Atlantic and North Pacific raise their tail fluke when diving. When breathing, the whale emits a spectacular vertical single-column spout up to {{convert|12|m|ft}}, typically {{convert|9|m|ft}}. Its ] capacity is 5,000 litres (1320 U.S. gallons). Blue whales have twin blowholes shielded by a large splashguard.<ref name="des" />

The flippers are {{convert|3|-|4|m|ft}} long. The upper sides are grey with a thin white border. The lower sides are white. The head and tail fluke are generally uniformly grey. The whale's upper parts, and sometimes the flippers, are usually mottled. The degree of mottling varies substantially from individual to individual. Some may have a uniform slate-grey color, but others demonstrate a considerable variation of dark blues, greys and blacks, all tightly mottled.<ref name="factsheet">{{citeweb
|url=http://www.acsonline.org/factpack/bluewhl.htm
|title=American Cetacean Society Fact Sheet - Blue Whales
|accessdate=20 June 2007
|dateformat=dmy}}</ref>

Blue whales can reach speeds of {{convert|50|km/h|mph}} over short bursts, usually when interacting with other whales, but {{convert|20|km/h|mph}} is a more typical traveling speed.<ref name="factsheet" /> When feeding, they slow down to {{convert|5|km/h|mph}}.

Blue whales most commonly live alone or with one other individual. It is not known how long traveling pairs stay together. In locations where there is a high concentration of food, as many as 50 blue whales have been seen scattered over a small area. However, they do not form the large close-knit groups seen in other baleen species.

===Size===
] in the collections of the ].]]
Blue whales are difficult to weigh because of their size. Most blue whales killed by whalers were not weighed whole, but cut up into manageable pieces first. This caused an underestimate of the total weight of the whale, due to the loss of blood and other fluids. Nevertheless, measurements between {{convert|150|-|170|metric ton |short ton}} were recorded of animals up to {{convert|27|m|ft}} in length. The weight of a {{convert|30|m|ft}} individual is believed by the American ] (NMML) to be in excess of {{convert|180|metric ton|short ton}}. The largest blue whale accurately weighed by NMML scientists to date was a female that weighed {{convert|177|metric ton|short ton}}.<ref name=pop />

The blue whale is the largest animal ever known to have lived.<ref name="des">{{citeweb
|url=http://www.wdcs.org/dan/publishing.nsf/allweb/F8FE8974A62E12F88025696D004A8EE9
|title=Size and Description of the Blue Whale Species
|accessdate=15 June 2007
|dateformat=dmy}}</ref> The largest known ] of the ] Era was the '']'',<ref>{{es icon}} {{cite journal
|author= Bonaparte J, Coria R
|year= 1993
|title=Un nuevo y gigantesco sauropodo titanosaurio de la Formacion Rio Limay (Albiano-Cenomaniano) de la Provincia del Neuquen, Argentina
|journal= Ameghiniana
|volume=30
|issue= 3
|pages=271–282}}</ref> which is estimated to have weighed up to {{convert|90|metric ton|short ton}}, though a controversial vertebra of ''] fragillimus'' may indicate an animal of up to {{convert|122|metric ton|short ton}} and {{convert|40|-|60|m|ft}}.<ref name="carpenter2006">Carpenter, K. (2006). "Biggest of the big: a critical re-evaluation of the mega-sauropod ''Amphicoelias fragillimus''." In Foster, J.R. and Lucas, S.G., eds., 2006, ''Paleontology and Geology of the Upper Jurassic Morrison Formation.'' New Mexico Museum of Natural History and Science Bulletin '''36''': 131-138.</ref> Furthermore, there are weight estimates for the very poorly known '']'' ranging from {{convert|140|-|220|metric ton|short ton}}, besides length estimates up to about {{convert|45|m|ft}}. The extinct fish ] may have approached its size.<ref>{{cite web
|url=http://news.nationalgeographic.com/news/2003/10/1001_031001_biggestfish.html
|title=&quot;Biggest Fish Ever Found&quot; Unearthed in U.K
|publisher=News.nationalgeographic.com
|date=October 1, 2003
|accessdate=2008-11-03}}</ref> However, complete fossils are difficult to come by, making size comparisons difficult. All these animals are considered to be smaller than the blue whale.

There is some uncertainty about the biggest blue whale ever found, as most data comes from blue whales killed in ] waters during the first half of the twentieth century and was collected by whalers not well-versed in standard zoological measurement techniques. The longest whales ever recorded were two females measuring {{convert|33.6|-|33.3|m|ft}} respectively.<ref name = "SearsCal02">{{cite paper
| author = Sears R, Calambokidis J
| title = Update COSEWIC status report on the blue whale Balaenoptera musculus in Canada.
| publisher = Committee on the Status of Endangered Wildlife in Canada, Ottawa.
| year = 2002
| pages = 32}}</ref> The longest whale measured by ]s at the NMML was {{convert|29.9|m|ft}}.<ref name=pop />

A blue whale's ] weighs around {{convert|2.7|metric ton|short ton}}<ref name="SM">{{cite book
|title=The Scientific Monthly
|publisher=American Association for
the Advancement of Science
|year=1915
|page=21}}</ref> and, when fully expanded, its mouth is large enough to hold up to {{convert|90|metric ton|short ton}} of food and water.<ref name="wheelock" /> Despite the size of its mouth, the dimensions of its throat are such that a blue whale cannot swallow an object wider than a beach ball.<ref>Blue Planet: Frozen seas (BBC documentary)</ref> Its ] weighs {{convert|600|kg|lb}} and is the ] known in any animal.<ref name="SM" /> A blue whale's ] is about {{convert|23|cm|in}} in diameter.<ref>{{cite web
|url=http://www2.ucsc.edu/seymourcenter/PDF/2.%20Ms.%20B%20measurements.pdf
|title=Ms. Blue's Measurements
|author=Caspar, Dave
|year=2001
| month=April
|accessdate=2006-09-01
|publisher=Seymour Center, University of California, Santa Cruz.
|format=PDF}}</ref> During the first seven months of its life, a blue whale calf drinks approximately 400 litres (100 U.S. gallons) of milk every day. Blue whale calves gain ] quickly, as much as {{convert|90|kg|lb}} every 24 hours. Even at birth, they weigh up to {{convert|2700|kg|lb}}—the same as a fully grown ].<ref name="factsheet" />

===Feeding===
Blue whales feed almost exclusively on ], though they also take small numbers of ].<ref name="afsc">{{cite web
|url=http://www.afsc.noaa.gov/nmml/education/cetaceans/blue.php
|title=Detailed Information about Blue Whales
|publisher=Alaska Fisheries Science Center
|year=2004
| accessdate = 2007-06-14}}</ref> The species of this ] eaten by blue whales varies from ocean to ocean. In the North Atlantic, '']'', '']'', '']'' and '']'' are the usual food;<ref>{{cite journal
|author= Hjort J, Ruud JT
|year=1929
|title=Whaling and fishing in the North Atlantic
|journal= Rapp. Proc. Verb. Conseil int. Explor. Mer
|volume= 56
|issue=
|pages= }}</ref><ref>{{cite journal
|author=Christensen I, Haug T, Øien N
|year=1992
|title= A review of feeding and reproduction in large baleen whales (Mysticeti) and sperm whales ''Physeter macrocephalus'' in Norwegian and adjacent waters
|journal= Fauna Norvegica Series a
|volume= 13
|issue=
|pages=39–48}}</ref><ref>{{cite journal
|author= Sears R, Wenzel FW, Williamson JM
|year=1987
|title=The Blue Whale: A Catalogue of Individuals from the Western North Atlantic (Gulf of St. Lawrence)
|journal=Mingan Island Cetacean Study, St. Lambert, Quebec.
|pages=27}}</ref> in the North Pacific, '']'', '']'', '']'', '']'', '']'' and '']'';<ref>{{cite journal
|last=Sears
|first=R
|year=1990
|title= The Cortez blues
|journal= Whalewatcher
|volume=24
|issue=2
|pages=12–15}}</ref><ref>{{cite journal
|last=Kawamura
|first=A
|year= 1980
|title= A review of food of balaenopterid whales
|journal= Sci. Rep. Whales Res. Inst.
|volume=32
|issue=
|pages=155–197}}</ref><ref>{{cite book
|author=Yochem PK, Leatherwood S
|editor=Ridgway SH, Harrison R
|title= Handbook of Marine Mammals, Vol. 3:The Sirenians and Baleen Whales.
|edition=
|year=1980
|publisher=Academic Press
|location=London
|isbn=
|oclc=
|doi=
|id=
|pages= 193–240
|chapter= Blue whale ''Balaenoptera musculus'' (Linnaeus, 1758)}}</ref> and in the Antarctic, '']'', '']'' and '']''.

An adult blue whale can eat up to 40 million krill in a day.<ref></ref> The whales always feed in the areas with the highest concentration of krill, sometimes eating up to {{convert|3600|kg|lb}} of krill in a single day.<ref name="afsc" /> This daily calorie requirement of an adult blue whale is in the region of 1.5 million.<ref>] (2007), ''Extraordinary Animals: An Encyclopedia of Curious and Unusual Animals'', ].</ref>

Because krill move, blue whales typically feed at depths of more than {{convert|100|m|ft}} during the day and only surface-feed at night. Dive times are typically 10 minutes when feeding, though dives of up to 20 minutes are common. The longest recorded dive is 36 minutes<ref name=Sears98>(Sears 1998)</ref>. The whale feeds by lunging forward at groups of krill, taking the animals and a large quantity of water into its mouth. The water is then squeezed out through the baleen plates by pressure from the ventral pouch and tongue. Once the mouth is clear of water, the remaining krill, unable to pass through the plates, are swallowed. The blue whale also incidentally consumes small fish, crustaceans and squid caught up with krill.<ref>{{cite journal
|author= Nemoto T
|year=1957
|title=Foods of baleen whales in the northern Pacific
|journal= Sci. Rep. Whales Res. Inst.
|volume=12
|pages=33–89}}</ref><ref>{{cite journal
|author=Nemoto T, Kawamura A
|year=1977
|title= Characteristics of food habits and distribution of baleen whales with special reference to the abundance of North Pacific sei and Bryde’s whales
|journal=Rep. Int. Whal. Commn
|volume= 1
|issue=Special Issue
|pages=80–87}}</ref>

===Life history===
]
Mating starts in late autumn and continues to the end of winter.<ref name="Art">{{citeweb
|url=http://www.articleworld.org/index.php/Blue_Whale
|title=Blue Whale - ArticleWorld
|accessdate=2 July 2007
}}</ref> Little is known about mating behaviour or breeding grounds. Females typically give birth once every two to three years at the start of the winter after a ] of ten to twelve months.<ref name="Art" /> The calf weighs about {{convert|2.5|metric ton|short ton}} and is around {{convert|7|m|ft}} in length. Blue whale calves drink 380&ndash;570 litres (100&ndash;150 U.S. gallons) of milk a day. ] takes place for about six months, by which time the calf has doubled in length. Sexual maturity is typically reached at eight to ten years, by which time males are at least {{convert|20|m|ft}} long (or more in the Southern Hemisphere). Females are larger still, reaching sexual maturity at around the age of five, by which they are about {{convert|21|m|ft}} long.

Scientists estimate that blue whales can live for at least 80 years;<ref name = "SearsCal02"/><ref name="Art" /><ref name="npca">{{citeweb
|url=http://www.npca.org/marine_and_coastal/marine_wildlife/bluewhale.html
|title=www.npca.org
|accessdate=21 June 21, 2007
}}</ref> however, since individual records do not date back into the whaling era, this will not be known with certainty for many years. The longest recorded study of a single individual is 34 years, in the north-east Pacific.<ref name=Sears98/> The whales' only natural predator is the ].<ref>{{cite journal
| title = Sightings and movements of blue whales off central California from 1986–88 from photo-identification of individuals
| author = J. Calambokidis, G. H. Steiger, J. C. Cubbage, K. C. Balcomb, C. Ewald, S. Kruse, R. Wells and R. Sears
| journal = Rep. Whal. Comm.
| volume = 12
| pages = 343–348
| year = 1990}}</ref> Studies report that as many as 25% of mature blue whales have scars resulting from Orca attacks.<ref name = "SearsCal02"/> The mortality rate of such attacks is unknown.

Blue whale strandings are extremely uncommon, and, because of the species' social structure, mass strandings are unheard of.<ref>William Perrin and Joseph Geraci. "Stranding" pp 1192–1197 in ''Encyclopedia of Marine Mammals'' (Perrin, Wursig and Thewissen eds)</ref> However, when strandings do occur, they can become the focus of public interest. In 1920, a blue whale washed up near ] on the ] in the ] of ]. It had been shot in the head by whalers, but the harpoon had failed to explode. As with other mammals, the fundamental instinct of the whale was to try to carry on breathing at all costs, even though this meant beaching to prevent itself from drowning. Two of the whale's bones were erected just off a main road on Lewis and remain a tourist attraction.<ref>{{cite web
| title=The Whale bone Arch
| work = Places to Visit around the Isle of Lewis
| url=http://www.isle-of-lewis.com/places-to-visit.htm
| accessdate = 2005-05-18}}</ref>

===Vocalizations===
{{See also|Whale song}}
{| class="infobox" style="" width="25%"
|- style="text-align: center;"
|'''Multimedia relating to the blue whale'''<br /><div class="small">''Note that the whale calls have been sped up 10x from their original speed.''</div>
|-
|{{listen
| filename = Blue whale atlantic1.ogg
| title = A blue whale song
| description = Recorded in the Atlantic (1)
| format = ]
| filename2 = Blue whale atlantic2.ogg
| title2 = A blue whale song
| description2 = Recorded in the Atlantic (2)
| format2 = ]
| filename3 = Blue whale atlantic3.ogg
| title3 = A blue whale song
| description3 = Recorded in the Atlantic (3)
| format3 = ]
| filename4 = Blue_Whale_NE_Pacific.ogg
| title4 = A blue whale song
| description4 = Recorded in North Eastern Pacific
| format4 = ]
| filename5 = Blue_Whale_South_Pacific.ogg
| title5 = A blue whale song
| description5 = Recorded in the South Pacific
| format5 = ]
| filename6 = Blue_Whale_West_Pacific.ogg
| title6 = A blue whale song
| description6 = Recorded in the West Pacific
| format6 = ]
}}
|}
Estimates made by Cummings and Thompson (1971) suggest that source level of sounds made by blue whales are between 155 and 188 ]s when measured relative to a reference pressure of one ] at one metre.<ref>{{cite journal
| title = Underwater sounds from the blue whale ''Balaenoptera musculus''
| author = W.C. Cummings and P.O. Thompson
| journal = Journal of the Acoustics Society of America
| volume = 50(4)
| pages = 1193–1198
| year = 1971
| doi = 10.1121/1.1912752}}</ref><ref>{{cite book
| author= W.J. Richardson, C.R. Greene, C.I. Malme and D.H. Thomson
| title = Marine mammals and noise
| publisher = Academic Press, Inc., San Diego, CA.
| year = 1995
| isbn = 0-12-588441-9}}</ref> All blue whale groups make calls at a ] of between 10 and 40 ]; the lowest frequency sound a human can typically perceive is 20&nbsp;Hz. Blue whale calls last between ten and thirty seconds. Blue whales off the coast of ] have been repeatedly recorded making "songs" of four notes duration lasting about two minutes each, reminiscent of the well-known ]. Researchers believe that as this phenomenon has not been seen in any other populations, it may be unique to the ''B. m. brevicauda'' (Pygmy) subspecies.

The reason for vocalization is unknown. Richardson ''et al.'' (1995) discuss six possible reasons:<ref>{{cite web
| author = National Marine Fisheries Service
| year = 2002
| title = Endangered Species Act - Section 7 Consultation Biological Opinion
| url = http://www.nmfs.noaa.gov/prot_res/readingrm/ESAsec7/7pr_surtass-2020529.pdf
| format = PDF }}</ref>

# Maintenance of inter-individual distance
# Species and individual recognition
# Contextual information transmission (e.g., feeding, alarm, courtship)
# Maintenance of social organization (e.g., contact calls between females and males)
# Location of topographic features
# Location of prey resources

==Population and whaling==
===Hunting era===
{{Main|History of whaling}}
]

Blue whales are not easy to catch or kill. Their speed and power meant that they were rarely pursued by early whalers, who instead targeted ] and ]s.<ref>{{cite book
|author= Scammon CM
|title=The marine mammals of the northwestern coast of North America. Together with an account of the American whale-fishery
|year= 1874
|publisher=John H. Carmany and Co.
|location=San Francisco
|page=319
|isbn= }}</ref> In 1864, the Norwegian ] equipped a ] with ]s specifically designed for catching large whales.<ref name="factsheet" /> Although initially cumbersome and with a low success rate, Foyn perfected the harpoon gun, and soon several whaling stations were established on the coast of ] in northern ]. Because of disputes with the local fishermen, the last whaling station in Finnmark was closed down in 1904.

Soon, blue whales were being hunted in ] (1883), the ] (1894), ] (1898), and ] (1903). In 1904-05 the first blue whales were taken off ]. By 1925, with the advent of the stern slipway in factory ships and the use of steam-driven whale catchers, the catch of blue whales, and baleen whales as a whole, in the Antarctic and sub-Antarctic began to increase dramatically. Between 1930 and 1931, these ships killed 29,400 blue whales in the Antarctic alone. By the end of ], populations had been significantly depleted, and, in 1946, the first quotas restricting international trade in whales were introduced, but they were ineffective because of the lack of differentiation between species. Rare species could be hunted on an equal footing with those found in relative abundance.

Blue whale hunting was banned in the 1960s by the ],<ref>{{cite journal
|last=Gambell
|first=R
|year= 1979
|title=The blue whale
|journal= Biologist
|volume= 26
|pages=209–215}}</ref><ref>{{cite journal
|last=Best
|first=PB
|year=1993
|month=
|title=Increase rates in severely depleted stocks of baleen whales
|journal=ICES J. Mar. Sci.
|volume=50
|pages=169–186
|doi=10.1006/jmsc.1993.1018}}</ref> and illegal whaling by the USSR finally halted in the 1970s,<ref>{{cite journal
|last=Yablokov
|first=AV
|year=1994
|title=Validity of whaling data
|journal=Nature
|volume=367
|issue=
|pages=108
|doi=10.1038/367108a0}}</ref> by which time 330,000 blue whales had been killed in the Antarctic, 33,000 in the rest of the Southern Hemisphere, 8,200 in the North Pacific, and 7,000 in the North Atlantic. The largest original population, in the Antarctic, had been reduced to 0.15% of their initial numbers.<ref name=Ant/>

===Population and distribution today===
]]]
] in the background, August 2007]]

Since the introduction of the whaling ban, studies have failed to ascertain whether the ] global blue whale population is increasing or remaining stable. In the Antarctic, best estimates show a significant increase at 7.3% per year since the end of illegal Soviet whaling, but numbers remain at under 1% of their original levels.<ref name=Ant/> It has also been suggested that Icelandic and Californian populations are increasing but these increases are not statistically significant. The total world population was estimated to be between 5,000 and 12,000 in 2002, although there are high levels of uncertainty in available estimates for many areas.<ref name=pop/>

The ] counts the blue whale as "endangered" as it has since the list's inception. In the ], the ] lists them as endangered under the ].<ref>{{cite web
|url=http://www.nmfs.noaa.gov/pr/laws/esa/
|title=Endangered Species Act
}}</ref> The largest known concentration, consisting of about 2,000 individuals, is the North-East Pacific population of the Northern blue whale (''B. m. musculus'') subspecies that ranges from ] to ] but is most commonly seen from California in summer. Infrequently, this population visits the North-West Pacific between ] and the northern tip of Japan.

In the North Atlantic, two stocks of ''B. m. musculus'' are recognized. The first is found off ], ], ] and the ]. This group is estimated to total about 500. The second, more easterly group is spotted from the ] in spring to Iceland in July and August; it is presumed that the whales follow the ] between the two volcanic islands. Beyond Iceland, blue whales have been spotted as far north as ] and ], though such sightings are rare. Scientists do not know where these whales spend their winters. The total North Atlantic population is estimated to be between 600 and 1,500.

In the Southern Hemisphere, there appear to be two distinct subspecies, ''B. m. intermedia'', the Antarctic blue whale, and the little-studied pygmy blue whale, ''B. m. brevicauda'', found in Indian Ocean waters. The most recent surveys (midpoint 1998) provided an estimate of 2,280 blue whales in the Antarctic.<ref>{{cite journal
|last=Branch
|first=T.A.
|title=Abundance of Antarctic blue whales south of 60°S from three complete circumpolar sets of surveys
|journal=Journal of Cetacean Research and Management
|volume=9
|issue=3
|pages=87–96
|year=2007}}</ref>, of which fewer than 1% are likely to be pygmy blue whales<ref>{{cite journal
|author=T.A. Branch
|title=Separating southern blue whale subspecies based on length frequencies of sexually mature females
|journal=Marine Mammal Science
|volume=23
|issue=4
|pages=803–833
|year=2007
|doi=10.1111/j.1748-7692.2007.00137.x
|last2=Abubaker
|first2=E. M. N.
|last3=Mkango
|first3=S.
|last4=Butterworth
|first4=D. S.}}</ref> Estimates from a 1996 survey were that 424 pygmy blue whales were in a small area south of ] alone,<ref>{{cite journal
| title = The abundance of blue whales on the Madagascar Plateau, December 1996
| author = P.B. Best
| journal = Journal of Cetacean Research and Management
| volume = 5
| pages = 253–260
| year = 2003}}</ref> thus it is likely that numbers in the entire Indian Ocean are in the thousands. If this is true, the global numbers would be much higher than estimates predict.<ref name=BBC_pop/>

A fourth subspecies, ''B. m. indica'', was identified by ] in 1859 in the northern Indian Ocean, but difficulties in identifying distinguishing features for this subspecies led to it being used a synonym for ''B. m. brevicauda'', the pygmy blue whale. Records for Soviet catches seem to indicate that the female adult size is closer to that of the Pygmy Blue than ''B. m. musculus'', although the populations of ''B. m. indica'' and ''B. m. brevicauda'' appear to be discrete, and the breeding seasons differ by almost six months.<ref name = SHDistribution>{{cite journal
|title=Past and present distribution, densities and movements of blue whales ''Balaenoptera musculus'' in the Southern Hemisphere and northern Indian Ocean
|author=T. A. Branch, K. M. Stafford, D. M. Palacios
|journal = Mammal Review
|year=2007
| volume = 37
| pages = 116–175
|doi=10.1111/j.1365-2907.2007.00106.x}}</ref>

Migratory patterns of these subspecies are not well known. For example, pygmy blue whales have been recorded in the northern Indian Ocean (], ], ]), where they may form a distinct resident population.<ref name= SHDistribution /> In addition, the population of blue whales occurring off ] and ] may also be a distinct population. Some Antarctic blue whales approach the eastern South Atlantic coast in winter, and occasionally, their vocalizations are heard off Peru, Western Australia, and in the northern Indian Ocean.<ref name= SHDistribution /> In Chile, the ], with support from the ], is undertaking extensive research and conservation work on a recently discovered feeding aggregation of the species off the coast of ] in an area named "Golfo del Corcovado", where 326 blue whales were spotted in the summer of 2007.<ref>{{cite web
| title=Blue Whales in Chile: The Giants of Marine Conservation
| publisher=The Rufford Small Grants Foundation
| url=http://www.ruffordsmallgrants.org/files/2007%20Rufford%201st%20phase%20blue%20whale%20report%20Chile_CBA.pdf
|author=R. Hucke-Gaete, B. Carstens, A. Ruiz-Tagle y M. Bello
|format=PDF
| accessdate=2009-03-22}}</ref>

Efforts to calculate the blue whale population more accurately are supported by marine mammologists at ] who maintain the OBIS-SEAMAP (Ocean Biogeographic Information System—Spatial Ecological Analysis of Megavertebrate Populations), a collation of marine mammal sighting data from around 130 sources.<ref>The data for the blue whale, along with a species profile, may be found here </ref>

===Threats other than hunting===
], near Santa Barbara, CA]]
Due to their enormous size, power and speed, adult blue whales have virtually no natural predators. There is, however, one documented case in '']'' of a blue whale being attacked by ]s; although the Orcas were unable to kill the animal outright during their attack, the blue whale sustained massive wounds and probably died as a result of them shortly after the attack.<ref>{{cite journal
| author = Tarpy, C.
| title = Killer whale attack!
| journal = National Geographic
| year = 1979
| volume = 155
| issue = 4 (April)
| pages = 542–545 }}</ref>

Blue whales may be wounded, sometimes fatally, after colliding with ocean vessels as well as becoming trapped or entangled in fishing gear.<ref name="recplan98"/> The ever-increasing amount of ocean noise, including ], drowns out the vocalizations produced by whales, which may make it harder for them to communicate.<ref name="recplan98"/> Human threats to the potential recovery of blue whale populations also include accumulation of ] (PCB) chemicals within the whale's body.<ref name="wheelock" />

With ] causing glaciers and permafrost to melt rapidly and allowing a large amount of fresh water to flow into the oceans, there are concerns that if the amount of fresh water in the oceans reaches a critical point, there will be a disruption in the ].{{Citation needed|date=April 2010}} Considering the blue whale's migratory patterns are based on ocean temperature, a disruption in this circulation, which moves warm and cold water around the world, would be likely to have an effect on their migration.<ref>{{cite web
|url=http://www.bto.org/research/reports/researchrpt_complete/RR414_Climate%20change_&_migratory_species.pdf
|author=Robert A. Robinson, Jennifer A. Learmonth, Anthony M. Hutson, Colin D. Macleod, Tim H. Sparks, David I. Leech, Graham J. Pierce, Mark M. Rehfisch and Humphrey Q.P. Crick
|title=Climate Change and Migratory Species
|publisher=BTO
|month=August
| year=2005
| accessdate = 2007-07-09
|format=PDF}}</ref> The whales summer in the cool, high latitudes, where they feed in ]-abundant waters; they winter in warmer, low latitudes, where they mate and give birth.<ref>{{cite journal
| author = Hucke-Gaete, Rodrigo, Layla P. Osman, Carlos A. Moreno, Ken P. Findlay, and Don K. Ljungblad
| title = Discovery of a Blue Whale Feeding and Nursing Ground in Southern Chile
| journal = The Royal Society
| year = 2003
| pages = s170-s173
| url = http://www.pubmedcentral.nih.gov.oca.ucsc.edu/picrender.fcgi?artid=1810017&blobtype=pdf}}</ref>
The change in ocean temperature would also affect the blue whale's food supply. The warming trend and decreased salinity levels would cause a significant shift in krill location and abundance.<ref>{{cite journal
| author = Moline, Mark A., Herve Claustre, Thomas K. Frazer, Oscar Schofield, and Maria Vernet
| title = Alteration of the Food Web Along the Antarctic Peninsula in Response to a Regional Warming Trend
| journal = Global Change Biology
| volume = 10
| year = 2004
| pages = 1973–1980
| url = http://www.blackwell-synergy.com.oca.ucsc.edu/doi/abs/10.1111/j.1365-2486.2004.00825.x
| doi = 10.1111/j.1365-2486.2004.00825.x}}</ref>

== Museums ==
]]]
The ] in ] contains a famous mounted skeleton and life-size model of a blue whale, which were both the first of their kind in the world but have since been replicated at the ]. Similarly, the ] in ] has a full-size model in its Milstein Family Hall of Ocean Life.

The ] in ] features a life-size model of a mother blue whale with her calf suspended from the ceiling of its main hall.<ref>{{cite web
| title=Aquarium of the Pacific - Online Learning Center - Blue Whale
| url=http://www.aquariumofpacific.org/onlinelearningcenter/species/blue_whale/
| accessdate=2009-08-12}}</ref> The ] at ], Canada, is in the final stages of installing a housed display of a blue whale directly on the main campus boulevard.<ref>{{cite web|url=http://www.beatymuseum.ubc.ca/projblue01.html|title=The Blue Whale Project |date=2010|work=Beaty Biodiversity Museum|publisher=University of British Columbia|accessdate=2 May 2010|location= Vancouver, BC}}</ref>

== Whale-watching ==
Living blue whales may be encountered on ] cruises in the ]<ref>{{cite journal
|author= Wenzel FW, Mattila DK, Clapham PJ
|year=1988
|title=''Balaenoptera musculus'' in the Gulf of Maine
|journal= Mar. Mammal Sci.
|volume=4
|pages= 172–175
|doi=10.1111/j.1748-7692.1988.tb00198.x}}</ref> and are the main attractions along the north shore of the ] and in the Saint Lawrence estuary.<ref name="recplan98">{{Cite book
| author = Reeves RR, Clapham PJ, Brownell RL, Silber GK
| title =Recovery plan for the blue whale ''(Balaenoptera musculus)''
| year = 1998
| page = 42
| place = Silver Spring, MD
| publisher = National Marine Fisheries Service
| accessdate=2007-06-20
| url=http://www.nmfs.noaa.gov/pr/pdfs/recovery/whale_blue.pdf
|format=PDF}}</ref>

==Footnotes==
{{reflist|colwidth=30em}}

==References==
{{cetaceaportal}}
{{refbegin}}
*{{RefAudubonMarineMammals}} pp.&nbsp;89–93.
*{{cite book
| title = Blue Whales
| author = J. Calambokidis and G. Steiger
| year = 1998
| publisher = Voyageur Press
| isbn = 0-89658-338-4}}
*{{cite web
| title=Blue Whale
| work= ]
| url= http://www.acsonline.org/factpack/bluewhl.htm
| accessdate = 2005-01-07}}
*{{cite web
| title=Blue whale, ''Balaenoptera musculus''
| work = MarineBio.org
| url = http://marinebio.org/species.asp?id=41
| accessdate = 2006-04-21}}
* Blue whale biology & status
{{refend}}

==External links==
{{Commons
|Balaenoptera musculus}}
{{Wikispecies
|Balaenoptera musculus}}
{{Spoken Misplaced Pages|Blue whale.ogg|2006-04-13}}
*
* ] *<!--- Note the double-linking in the line above is a deliberate to keep the section looking neat -->
* - ] Lab of Ornithology—Bioacoustics Research Program
*
*

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Revision as of 20:34, 13 May 2010

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