Baleen whale
| Baleen whales
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 Humpback Whale breaching
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| Around 15 species; see list of cetaceans or below. | ||||||||||
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Balaenidae |
The baleen whales, also called whalebone whales or great whales, form the Mysticeti, one of two suborders of the Cetacea (whales, dolphins and porpoises). 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, the toothed whales or Odontoceti. Living Mysticeti species have teeth only during the embryonal phase. Fossil Mysticeti had teeth before baleen evolved.
The suborder contains four families and fourteen species. A list of species can be found below and at the Cetacea article. The scientific name derives from the Greek word mystax, which means "moustache".
Overview
Whales are members of the order Cetacea, which also includes dolphins and porpoises. Whales are the largest mammals, the largest vertebrates, and the largest known animals in the world. Like all mammals, whales breathe air into lungs, are warm-blooded, breast-feed their young, and have hair (although very little). Unlike fish, which breathe air using gills, whales breathe air through blowholes that lead into their lungs.
Cetaceans are divided into two suborders:
- The baleen whales (Mysticeti) are characterized by the baleen, a sieve-like structure in the upper jaw made of the tough, structural protein keratin. The baleen is used to filter plankton from the water. Baleen whales are the largest whales. They are characterized by two blowholes.
- The toothed whales (Odontoceti) have teeth and prey on fish, squid, or both. This suborder includes dolphins and porpoises as well as whales. An outstanding ability of this group is to sense their surrounding environment through echolocation. Toothed whales have only one blowhole. In addition to numerous species of dolphins and porpoises, this suborder includes the Beluga whale and the sperm whale, which may be the largest toothed animal to ever inhabit Earth.
Taxonomy of baleen whales
The families of baleen whales include the Balaenopteridae (humpback whales, fin whales, Sei Whale, and others), the Balaenidae (right and bowhead whales), the Eschrichtiidae (gray whale), and the Neobalaenidae (pygmy right whales), among others. The Balaenopteridae family (rorquals) also includes the Blue Whale, the world's largest animal, and perhaps the largest animal ever to roam the earth. It reaches 30 meters (93 feet) long and can weigh up to 180 tons.
Taxonomic listing
The classification here closely follows Rice (1998), Marine Mammals of the World: Systematics and Distribution (1998), which has become the standard taxonomy reference in the field. There is close agreement between this classification and that of Mammal Species of the World: 3rd Edition (Wilson and Reeder 2003). Any differences are noted using the abbreviations "Rice" and "MSW3" respectively. Further differences due to recent discoveries are also noted.
Discussion of synonyms and subspecies are relegated to the relevant genus and species articles.
- ORDER CETACEA
- Suborder Mysticeti: Baleen whales
- Family Balaenidae: Right whales and Bowhead Whale
- Genus Balaena
- Bowhead Whale, Balaena mysticetus
- Genus Eubalaena
- Atlantic Northern Right Whale, Eubalaena glacialis
- Pacific Northern Right Whale, Eubalaena japonica
- Southern Right Whale, Eubalaena australis
- Genus Balaena
- Family Balaenopteridae: Rorquals
- Subfamily Balaenopterinae
- Genus Balaenoptera
- Common Minke Whale, Balaenoptera acutorostrata
- Antarctic Minke Whale, Balaenoptera bonaerensis
- Sei Whale, Balaenoptera borealis
- Bryde's Whale, Balaenoptera brydei
- Eden's Whale Balaenoptera edeni - Rice lists this as a separate species, MSW3 does not
- Blue Whale, Balaenoptera musculus
- Fin Whale, Balaenoptera physalus
- Balaenoptera omurai, discovery announced November 2003. No common name yet in usage
- Genus Balaenoptera
- Subfamily Megapterinae
- Genus Megaptera
- Humpback Whale, Megaptera novaeangliae
- Genus Megaptera
- Subfamily Balaenopterinae
- † Genus Eobalaenoptera
- † Harrison's Whale, Eobalaenoptera harrisoni
- Family Eschrichtiidae
- Genus Eschrichtius
- Gray Whale, Eschrichtius robustus
- Genus Eschrichtius
- Family Neobalaenidae: Pygmy Right Whale
- Genus Caperea
- Pygmy Right Whale, Caperea marginata
- Genus Caperea
- Family Balaenidae: Right whales and Bowhead Whale
- Suborder Odontoceti: toothed whales
- Suborder Mysticeti: Baleen whales
Anatomy
Baleen whales are generally larger than toothed whales, and females are larger than males. This group comprises the largest living animal species, the Blue Whale. Baleen whales have two blowholes, causing a V-shaped blow. 400px
As in all whales, the body is fusiform, resembling the streamlined form of a fish. The forelimbs, also called flippers, are paddle-shaped. The end of the tail holds the fluke, or tail fins, which provide propulsion by vertical movement. Although whales generally do not possess hind limbs, baleen whales sometimes have rudimentary hind limbs; some even with feet and digits. Most species of whale bear a fin on their backs known as a dorsal fin.
Beneath the skin lies a layer of fat, the blubber. It serves as an energy reservoir and also as insulation. Whales have a four-chambered heart. The neck vertebrae are fused in most whales, which provides stability during swimming at the expense of flexibility.
The shapes of whales' spouts when exhaling from the blowholes after a dive, when seen from the right angle, differ between species. Whales have a unique respiratory system that lets them stay underwater for long periods of time without taking in oxygen. Some whales, such as the sperm whale, can stay underwater for up to two hours holding a single breath.
Ecology and life history
Behavioral ecology
Breaching
In spite of their enormous mass, baleen whales are able to leap completely out of the water. Particularly known for their acrobatics are the Humpback Whales, but other baleen whales also break through the water surface with their body or beat it loudly with their fins. The reason for these habits is not known for certain, and was identified in three separate sightings.
Vocalization
In contrast to toothed whales, baleen whales are unlikely to echo-locate. Instead they are able to produce high volume sounds in the infrasonic range. The calls of the largest whales can be heard several hundred kilometres away. Unique are the songs of the Humpback Whales, consisting of complex sequences that may slowly evolve over years. They are probably used for courting.
Importance to humans
From the 11th to the late 20th centuries, baleen whales were hunted commercially for their oil and baleen. Their oil can be made into margarine and cooking oils. Baleen was used to stiffen corsets, as parasol ribs and to crease paper.
Evolutionary history
Early baleen whales first appeared as far back as Early Oligocene, or perhaps the latest Eocene (39-29 million years ago). Early baleen whales did not have (or had very little) baleen, but still had teeth obtained from their ancestors. Among them was Janjucetus, a baleen whale with sharp teeth that hunted fishes, squid, and large prey such as sharks and probably dolphin-like cetaceans. This hints that early baleen whales were predatory and eventually evolved into the gentler, toothless whales known today. The first baleened, toothless baleen whales probably appeared in the Early or Middle Miocene, from a toothed ancestor that adapted to eat small fishes or other creatures and eventually to feed by filtering.
See also
| Cetaceans Portal |
- Baleen
- Toothed whale
- Cetacea
Bibliography
ReferencesISBN links support NWE through referral fees
- Wilson, D. E., and D. M. Reeder. 1993. Mammal Species of the World: A Taxonomic and Geographic Reference. Washington: Smithsonian Institution Press. ISBN 1560982179.
External links
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