Rorquals are the largest group of
baleen whaleThe baleen whales, also called whalebone whales or great whales, form the Mysticeti, one of two suborders of the Cetacea . Baleen whales are characterized by having baleen plates for filtering food from water, rather than having teeth. This distinguishes them from the other suborder of cetaceans,...
s, with nine
speciesIn biology, a species is:* a taxonomic rank or* a unit at that rank ....
in two
generaIn biology, a genus is a taxonomic unit used in the classification of living and fossil organisms. The term comes from Latin genus "descent, family, type, gender" , cognate with – genos, "race, stock, kin" ..In addition, genus is a taxonomic rank in the hierarchy In biology, a genus (plural:...
. They include the largest animal that has ever lived, the
Blue WhaleThe Blue Whale is a marine mammal belonging to the suborder of baleen whales . At up to in length and or more in weight, it is the largest animal ever known to have existed....
, which can reach , and two others that easily pass ; even the smallest of the group, the Northern Minke Whale, reaches .
Rorquals take their name from the
NorwegianNorwegian is a North Germanic language spoken primarily in Norway, where it is an official language. Together with Swedish and Danish, Norwegian forms a continuum of more or less mutually intelligible local and regional variants ...
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 WhaleThe Sei Whale , Balaenoptera borealis, is a baleen whale, the third-largest rorqual after the Blue Whale and the Fin Whale. It can be found worldwide in all oceans and adjoining seas, and prefers deep off-shore waters. It tends to avoid polar and tropical waters and semi-enclosed bodies of water...
, which has shorter grooves).
Rorquals are the largest group of
baleen whaleThe baleen whales, also called whalebone whales or great whales, form the Mysticeti, one of two suborders of the Cetacea . Baleen whales are characterized by having baleen plates for filtering food from water, rather than having teeth. This distinguishes them from the other suborder of cetaceans,...
s, with nine
speciesIn biology, a species is:* a taxonomic rank or* a unit at that rank ....
in two
generaIn biology, a genus is a taxonomic unit used in the classification of living and fossil organisms. The term comes from Latin genus "descent, family, type, gender" , cognate with – genos, "race, stock, kin" ..In addition, genus is a taxonomic rank in the hierarchy In biology, a genus (plural:...
. They include the largest animal that has ever lived, the
Blue WhaleThe Blue Whale is a marine mammal belonging to the suborder of baleen whales . At up to in length and or more in weight, it is the largest animal ever known to have existed....
, which can reach , and two others that easily pass ; even the smallest of the group, the Northern Minke Whale, reaches .
Characteristics
Rorquals take their name from the
NorwegianNorwegian is a North Germanic language spoken primarily in Norway, where it is an official language. Together with Swedish and Danish, Norwegian forms a continuum of more or less mutually intelligible local and regional variants ...
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 WhaleThe Sei Whale , Balaenoptera borealis, is a baleen whale, the third-largest rorqual after the Blue Whale and the Fin Whale. It can be found worldwide in all oceans and adjoining seas, and prefers deep off-shore waters. It tends to avoid polar and tropical waters and semi-enclosed bodies of water...
, which has shorter grooves). These are understood to allow the mouth to expand immensely when feeding. The "Minke" is allegedly named after a
NorwegianNorway , officially the Kingdom of Norway, is a country in Northern Europe occupying the western portion of the Scandinavian Peninsula, as well as Jan Mayen and the Arctic archipelago of Svalbard under the Spitsbergen Treaty...
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 whaleRight whales are the species of large baleen whales belonging to the genus Eubalaena. Three right whale species are recognized in this genus. They are closely related genetically to the larger, arctic Bowhead Whale, which is currently placed in its own genus, Balaena...
s, 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
baleenBaleen or whalebone enables baleen whales to feed. These whales do not have teeth, but instead have rows of baleen plates in the upper jaw – flat, flexible plates with frayed edges, arranged in two parallel rows, looking like combs of thick hair. Baleen is not bone, but is composed of...
plates with their tongue. They feed on crustaceans, such as
krillKrill is a type of shrimp-like marine invertebrate animal. These small crustaceans are important organisms of the zooplankton, particularly as food for baleen whales, manta rays, whale sharks, crabeater seals, and other seals, and a few seabird species that feed almost exclusively on them. Another...
, but also on various fish, such as
herringHerring are relatively small oily fish of the genus Clupea found in the shallow, temperate waters of the North Pacific and the North Atlantic oceans, including the Baltic Sea. Two species of Clupea are currently recognized, the Atlantic herring and the Pacific herring , each of which may be...
s and
sardineSardines, or pilchards, are a group of several types of small, oily fish related to herrings, family Clupeidae. Sardines were named after the Mediterranean island of Sardinia, where they were once in abundance....
s.
GestationGestation is the carrying of an embryo or fetus inside a female viviparous animal. Mammals duringpregnancy can have one or more gestations at the same time ....
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
weanedWeaning is the process of gradually introducing a mammal infant, either human or animal, to what will be its adult diet and withdrawing the supply of its mother's milk.The process takes place only in mammals, as only mammals produce milk...
after 6-12 months, depending on species. Of some species, adults live in small herds, or 'pods' of two to five individuals. For example, Humpback whales have a fluid social structure, often engaging behavioral practices in a pod, other times being solo - not necessarily living together.
Distribution and habitat
Distribution is worldwide: the Blue, Fin, Humpback, and the Sei Whales are found in all major oceans; the Common (Northern) and Antarctic (Southern) Minke Whale species are found in all the oceans of their respective hemispheres; and either of
Bryde's WhaleBryde’s Whales are the least-known and in many ways the most unusual of the rorquals. They are small by rorqual standards—no more than about 25 tonnes—prefer tropical and temperate waters to the polar seas that other whales in their family frequent; are largely coastal rather than...
and Eden's Whale occur in the
AtlanticThe Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about 106.4 million square kilometres , it covers approximately one-fifth of the Earth's surface and about one-quarter of its water surface area. The first part of its name refers to the Atlas of Greek...
, Pacific, and
IndianThe Indian Ocean is the third largest of the world's oceanic divisions, covering about 20% of the water on the Earth's surface. It is bounded on the north by South Asia ; on the west by Africa; on the east by Indochina, the Sunda Islands, and Australia; and on the south by the Southern Ocean...
oceans, being absent only from the cold waters of the
ArcticThe Arctic is the region around the Earth's North Pole, opposite the Antarctic region around the South Pole. The Arctic includes the Arctic Ocean and parts of Canada, Greenland , Russia, the United States , Iceland, Norway, Sweden and Finland.The word Arctic comes from the Greek αρκτικός , "near...
and
AntarcticThe Antarctic is the region around the Earth's South Pole, opposite the Arctic region around the North Pole. The Antarctic comprises the continent of Antarctica and the ice shelves, waters and island territories in the Southern Ocean situated south of the Antarctic Convergence...
.
Most rorquals are strictly oceanic: the exceptions are
Bryde's WhaleBryde’s Whales are the least-known and in many ways the most unusual of the rorquals. They are small by rorqual standards—no more than about 25 tonnes—prefer tropical and temperate waters to the polar seas that other whales in their family frequent; are largely coastal rather than...
and Eden's Whale (which are usually found close to shore all year round) and the
Humpback WhaleThe humpback whale is a baleen whale. One of the larger rorqual species, adults range in length from and weigh approximately . The humpback has a distinctive body shape, with unusually long pectoral fins and a knobbly head. It is an acrobatic animal, often breaching and slapping the water...
(which is oceanic but passes close to shore when migrating). It is the largest and the smallest types - the Blue Whale and Antarctic Minke Whale - that occupy the coldest waters in the extreme south; the Fin Whale tends not to approach so close to the ice shelf; the Sei Whale tends to stay further north again. (In the northern hemisphere, where the continents distort weather patterns and
ocean currentAn ocean current is a continuous, directed movement of ocean water generated by the forces acting upon the water, such as the wind, Coriolis force, temperature and salinity differences and tides caused by the gravitational pull of the Moon and the Sun...
s, 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
planktonPlankton consist of any drifting organisms that inhabit the pelagic zone of oceans, seas, or bodies of fresh water. Plankton are defined by their ecological niche rather than their phylogenetic or taxonomic classification...
and krill for the short polar summer.
Taxonomy
Taxonomically, the Balaenopteridae (rorqual) family is split into two subfamilies - Balaenopterinae and Megapterinae. Each subfamily contains one genus -
BalaenopteraBalaenoptera is a genus of Balaenopteridae, the Rorqual whales, and contains eight species. The species Balaenoptera omurai was published in 2003...
and
MegapteraThe humpback whale is a baleen whale. One of the larger rorqual species, adults range in length from and weigh approximately . The humpback has a distinctive body shape, with unusually long pectoral fins and a knobbly head. It is an acrobatic animal, often breaching and slapping the water...
respectively. However, the phylogeny of the various rorqual species shows the current division is paraphyletic, and may need to be adjusted.
The discovery of new member of the
Balaenopteridae family was announced in November 2003 - specimens of the
Balaenoptera omuraiBalaenoptera omurai is a species of whale about which almost nothing is known. The announcement of the discovery of this whale was made in the November 20, 2003, edition of Nature by three Japanese scientists Shiro Wada, Masayuki Oishi and Tadasu K...
, which looks similar to, if smaller than, the
Fin WhaleThe Fin Whale , also called the Finback Whale, Razorback, or Common Rorqual, is a marine mammal belonging to the suborder of baleen whales...
were found in Indo-Pacific waters.