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]
- Pertaining to rorquals.
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.
CharacteristicsRorquals 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.
Taxonomyright|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.
- [http://www.wdcs.org:"Whale and Dolphin Conservation Society"]
rorqual in Min Nan: Balaenopteridae
rorqual in German: Furchenwale
rorqual in Estonian: Vaguvaallased
rorqual in Spanish: Balaenopteridae
rorqual in Basque: Zere
rorqual in French: Balaenopteridae
rorqual in Croatian: Brazdeni kitovi
rorqual in Indonesian: Rorqual
rorqual in Italian: Balaenopteridae
rorqual in Hebrew: לווייתני ענק
rorqual in Georgian: ზოლიანი ვეშაპისებრნი
rorqual in Lithuanian: Raukšlėtieji banginiai
rorqual in Limburgan: Vinvèsse
rorqual in Dutch: Vinvissen
rorqual in Norwegian: Finnhvaler
rorqual in Occitan (post 1500): Balaenopteridae
rorqual in Polish: Fałdowce
rorqual in Portuguese: Balaenopteridae
rorqual in Russian: Полосатиковые
rorqual in Finnish: Uurteisvalaat
rorqual in Swedish: Fenvalar
rorqual in Chinese: 须鲸科