Rorqual
Encyclopedia
Rorquals are the largest group of baleen whale
Baleen whale
The 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 species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 in two genera
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

. They include the largest animal that has ever lived, the Blue Whale
Blue Whale
The blue whale is a marine mammal belonging to the suborder of baleen whales . At in length and or more in weight, it is the largest known animal to have ever existed....

, which can reach 150 tonnes (165.3 ST), and another that easily reaches 50 tonnes (55.1 ST); even the smallest of the group, the Northern Minke Whale, reaches 9 tonnes (9.9 ST).

Characteristics

Rorquals take their name from French rorqual, which itself derives from the Norwegian
Norwegian language
Norwegian is a North Germanic language spoken primarily in Norway, where it is the official language. Together with Swedish and Danish, Norwegian forms a continuum of more or less mutually intelligible local and regional variants .These Scandinavian languages together with the Faroese language...

 word røyrkval, 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
Sei Whale
The sei whale , Balaenoptera borealis, is a baleen whale, the third-largest rorqual after the blue whale and the fin whale. It inhabits most oceans and adjoining seas, and prefers deep offshore waters. It avoids 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 Norwegian
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...

 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 whale
Right whale
Right whales are three species of large baleen whales consisting of two genera in the family Balaenidae of order Cetacea. Their bodies are very dark gray or black and rotund....

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 baleen
Baleen
Baleen or whalebone is a filter-feeder system inside the mouths of baleen whales. The baleen system works when a whale opens its mouth underwater and then water pours into the whale's mouth. The whale then pushes the water out, and animals such as krill are filtered by the baleen and remain as food...

 plates with their tongue. They feed on crustaceans, such as krill
Krill
Krill is the common name given to the order Euphausiacea of shrimp-like marine crustaceans. Also known as euphausiids, these small invertebrates are found in all oceans of the world...

, but also on various fish, such as herring
Herring
Herring is an 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. Three species of Clupea are recognized. The main taxa, the Atlantic herring and the Pacific herring may each be divided into subspecies...

s and sardine
Sardine
Sardines, or pilchards, are several types of small, oily fish related to herrings, family Clupeidae. Sardines are named after the Mediterranean island of Sardinia, around which they were once abundant....

s.

Gestation
Gestation
Gestation is the carrying of an embryo or fetus inside a female viviparous animal. Mammals during pregnancy 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 weaned
Weaning
Weaning 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 Whale
Bryde's Whale
Bryde's whales are baleen whales, one of the "great whales" or rorquals. They prefer tropical and temperate waters over the polar seas that other whales in their family frequent. They are largely coastal rather than pelagic. Bryde's whales are very similar in appearance to sei whales and almost as...

 and Eden's Whale occur in the Atlantic
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...

, Pacific, and Indian
Indian Ocean
The Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded on the north by the Indian Subcontinent and Arabian Peninsula ; on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and...

 oceans, being absent only from the cold waters of the Arctic
Arctic
The Arctic is a region located at the northern-most part of the Earth. The Arctic consists of the Arctic Ocean and parts of Canada, Russia, Greenland, the United States, Norway, Sweden, Finland, and Iceland. The Arctic region consists of a vast, ice-covered ocean, surrounded by treeless permafrost...

 and Antarctic
Antarctic
The 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 Whale
Bryde's Whale
Bryde's whales are baleen whales, one of the "great whales" or rorquals. They prefer tropical and temperate waters over the polar seas that other whales in their family frequent. They are largely coastal rather than pelagic. Bryde's whales are very similar in appearance to sei whales and almost as...

 and Eden's Whale (which are usually found close to shore all year round) and the Humpback Whale
Humpback Whale
The humpback whale is a species of 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...

 (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 current
Ocean current
An ocean current is a continuous, directed movement of ocean water generated by the forces acting upon this mean flow, such as breaking waves, wind, Coriolis effect, cabbeling, 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 plankton
Plankton
Plankton are any drifting organisms that inhabit the pelagic zone of oceans, seas, or bodies of fresh water. That is, plankton are defined by their ecological niche rather than phylogenetic or taxonomic classification...

 and krill for the short polar summer.

Feeding habits

As well as other methods, rorqual whales obtain prey by lunge feeding on bait ball
Bait ball
A bait ball, or baitball, occurs when small fish swarm in a tightly packed spherical formation about a common centre. It is a last ditch defensive measure adopted by small schooling fish when they are threatened by predators...

s. Lunge feeding is an extreme feeding method, where the whale accelerates to a high velocity and then opens its mouths to a large gape angle. This generates the water pressure required to expand its mouth and engulf and filter a huge amount of water and fish. According to Potvin and Goldbogen, lunge feeding in rorqual whales represents the largest biomechanical
Biomechanical
Biomechanical may refer to:*Biomechanics, the application of mechanical principles to living organisms*Biomechanics , system of actor training developed by Vsevolod Meyerhold*Biomechanical Art, the style of H. R...

 event on Earth.

Taxonomy

Formerly the rorqual family Balaenopteridae was split into two subfamilies, Balaenopterinae and Megapterinae, with each subfamily contained one genus, Balaenoptera
Balaenoptera
Balaenoptera is a genus of Balaenopteridae, the Rorqual whales, and contains eight species. The species Balaenoptera omurai was published in 2003...

and Megaptera
Humpback Whale
The humpback whale is a species of 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...

respectively. However, the phylogeny of the various rorqual species shows the current division is paraphyletic, and in 2005 the division into subfamilies was dropped.

The discovery of a new species in Balaenopteridae, Omura's whale (Balaenoptera omurai), was announced in November 2003, which looks similar to, if smaller than, the Fin Whale
Fin Whale
The fin whale , also called the finback whale, razorback, or common rorqual, is a marine mammal belonging to the suborder of baleen whales. It is the second longest whale and the sixth largest living animal after the blue whale, bowhead whale, and right whales, growing to nearly 27 metres long...

were found in Indo-Pacific waters.
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