rorqual n : any of several baleen whales of the family Balaenopteridae having longitudinal grooves on the throat and a small pointed dorsal fin [syn: razorback]

English

Etymology

From røyrkval (‘furrow whale’), from Old Norse reyðarhvalr.

Pronunciation

• /ˈrɒrkwəl/

Noun

1. Any whale with longitudinal skin folds running from below the mouth to the navel, allowing the capacity of the mouth to expand greatly when feeding.

Translations

• Dutch: vinvis
• Norwegian: finnhval

Adjective

rorqual

1. Pertaining to rorquals.

Quotations

• 1873 — Jules Verne, 20,000 Leagues Under the Sea, Ch. 1 (transl. by F. P. Walter)

  Now then, the biggest whales, those rorqual whales that frequent the waterways of the Aleutian Islands, have never exceeded a length of 56 meters--if they reach even that.

See also

• baleen

Rorquals are the largest group of baleen whales, with nine species in two genera. They include the largest animal that has ever lived, the Blue Whale, which can reach 150 tonnes, and two others that easily pass 50 tonnes; even the smallest of the group, the Northern Minke Whale, reaches 9 tonnes.

Characteristics

Rorquals take their name from the Norwegian word röyrkval, meaning "furrow whale". All members of the family have a series of longitudinal folds of skin running from below the mouth back to the navel (except the Sei Whale, which has shorter grooves). These are understood to allow the mouth to expand immensely when feeding. The "Minke" is allegedly named after a Norwegian whaler named Meincke, who mistook a Northern Minke Whale for a Blue Whale.

Rorquals are slender and streamlined in shape, compared with their relatives the right whales, and most have narrow, elongated flippers. They have a dorsal fin, situated far back on the body, near to the tail. Rorquals feed by gulping in water, and then pushing it out through the baleen plates with their tongue. They feed on crustaceans, such as krill, but also on various fish, such as herring and sardines.

Gestation in rorquals lasts 11-12 months, so that both mating and birthing occur at the same time of year. Mothers give birth to a single young, which is weaned after 6-12 months, depending on species. Adults live in small herds, or 'pods' of two to five individuals.

Distribution and habitat

Distribution is worldwide: the Blue, Fin, Humpback, Sei, and Minke Whales are found in all major oceans; and one or other of the two species of Bryde's Whale occurs in the Atlantic, Pacific, and Indian oceans, being absent only from the cold waters of the Arctic and Antarctic.

Most rorquals are fairly strictly oceanic: the exceptions are Bryde's Whales (which are usually found close to shore all year round) and Humpback Whales (which are oceanic but pass close to shore when migrating). It is the largest and the smallest types - Blue and Minke Whales - that occupy the coldest waters in the extreme south; Fin Whales tend not to approach so close to the ice shelf; Sei Whales tend to stay further north again. (In the northern hemisphere, where the continents distort weather patterns and ocean currents, these movements are less obvious, although still present.) Within each species, the largest individuals tend to approach the poles more closely, while the youngest and fittest ones tend to stay in warmer waters before leaving on their annual migration.

Most rorquals breed in temperate waters during the winter, then migrate back to the polar feeding grounds rich in plankton and krill for the short polar summer.

Taxonomy

right|thumb|300px|The rorquals' phylogenetic tree ascertained from DNA sequencingTaxonomically the Balaenopteridae (rorqual) family is split into two sub-families - Balaenopterinae and Megapterinae. Each sub-family contains one genus - Balaenoptera and Megaptera respectively. However, the phylogeny of the various rorqual species shows the current division is paraphyletic, and may need to be adjusted.

The discovery of an eighth member of the Balaenopteridae family was announced in November 2003 - specimens of the Balaenoptera omurai, which looks similar to, if smaller than, the Fin Whale were found in Indo-Pacific waters.

References

External links

• [http://www.wdcs.org:"Whale and Dolphin Conservation Society"]