Blue whale: Difference between revisions

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Blue Whales were abundant in most oceans around the world until the beginning of the twentieth century. For the first 40 years of that century they were hunted by [[whaling|whalers]] almost to [[extinction]]. Hunting of the species was outlawed by the international community in 1966. A 2002 report estimated there were 5,000 to 12,000 Blue Whales worldwide<ref name=pop>Committee on the Status of Endangered Wildlife in Canada (2002) [http://www.wildwhales.org/cetaceans/blue/sr_blue_whale_e.pdf.pdf Assessment and Update Status Report on the Blue Whale ''Balaenoptera musculus''] Population size and trends, p5. URL accessed [[April 19]] [[2006]].</ref> located in at least five groups. More recent research into the Pygmy subspecies suggest this may be an under-estimate.<ref name=BBC_pop>{{Cite web| author = Alex Kirby, 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 | accessyear = 2006}}</ref> Before whaling the largest population 239,000 (range 202,000 to 311,000) was in the Antarctic<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}}</ref> but now there remain only much smaller (around 2,000) concentrations in each of the North-East [[Pacific Ocean|Pacific]], the Antarctic, and the Indian Ocean. There are two more groups in the North [[Atlantic Ocean|Atlantic]] and at least two in the Southern Hemisphere.

Thereblah haveblah been at least 11 documented cases of Blue/[[Fin Whale]] hybrid adults in the wild. Aranson and Gullberg (1983)<ref>{{cite journal | author= A. Arnason and A. Gullberg | title= Comparison betweenblahbetween 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> describe the genetic distance between a Blue and a Fin as about the same as that between a human and gorilla. Blue Whale/[[Humpback Whale]] hybrids are also known.

==Taxonomy and evolution==

Blue Whales are [[rorquals]] (family [[Balaenopteridae]]), a family that includes the [[Humpback Whale]], the [[Fin Whale]], the [[Bryde's Whale]], the [[Sei Whale]] and the [[Minke Whale]]. The family [[Balaenopteridae]] is believed to have diverged from the other families of the suborder Mysticeti as long ago as the middle [[Oligocene]]. However, it is not known when the members of these families diverged from each other.

The Blue Whale is usually classified as one of seven species of whale in the genus ''Balaenoptera''; however, DNA sequencing analysis indicates that Blue Whales are phylogenetically closer to the [[Humpback Whale|Humpback]] (''Megaptera'') and the [[Gray Whale]] (''Eschrichtius'') than to other ''Balaenoptera'' species; should further research corroborate these relationships, it will be necessary to recognize the separate genus ''Sibbaldus'' for the Blue Whale.

[[Image:Rorqual phylogenetic tree.PNG|left|thumbnail|250px|A [[phylogenetic tree]] of animals related to the Blue Whale]]

There have been at least 11 documented cases of Blue/[[Fin Whale]] hybrid adults in the wild. Aranson and Gullberg (1983)<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> describe the genetic distance between a Blue and a Fin as about the same as that between a human and gorilla. Blue Whale/[[Humpback Whale]] hybrids are also known.

The specific name ''musculus'' is [[Latin]] and could mean "muscular", but it can also be interpreted as "little mouse". [[Carolus Linnaeus|Linnaeus]], who named the species in his seminal work of 1758, would have known this and, given his sense of humour, may have intended the ironic [[double entendre|double meaning]]. Other common names for the Blue Whale have included the '''Sulphur-bottom''', '''Sibbald's Rorqual''', the '''Great Blue Whale''' and the '''Great Northern Rorqual'''. These names have fallen into disuse in recent decades.