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A Sperm Whale fluke

Cetaceans (/sɪˈtʃəns/) (from Latin: cetus, lit. 'whale', from Ancient Greek: κῆτος, romanizedkētos, lit. 'huge fish') are aquatic mammals constituting the infraorder Cetacea. There are around 89 living species, which are divided into two parvorders. The first is the Odontoceti, the toothed whales, which consist of around 70 species, including the dolphin (which includes killer whales), porpoise, beluga whale, narwhal, sperm whale, and beaked whale. The second is the Mysticeti, the baleen (from Latin: balæna, lit. 'whale') whales, which have a filter-feeder system, and consist of 15 species divided into 3 families, and include the right whale, bowhead whale, rorqual, pygmy right whale, and gray whale.

The ancient and extinct ancestors of modern whales (Archaeoceti) lived 53 to 45 million years ago. They diverged from even-toed ungulates; their closest living relatives are hippopotamuses and others such as cows and pigs. They were semiaquatic and evolved in the shallow waters that separated India from Asia. Around 30 species adapted to a fully oceanic life. Baleen whales split from toothed whales around 34 million years ago.

The smallest cetacean is Maui's dolphin, at 1 m (3 ft 3 in) and 50 kg (110 lb); the largest is the blue whale, at 29.9 m (98 ft) and 173 t (381,000 lb). Baleen whales have a tactile system in the short hairs (vibrissae) around their mouth; toothed whales do not have vibrissae. Cetaceans have well-developed senses—their eyesight and hearing are adapted for both air and water. They have a layer of fat, or blubber, under the skin to maintain body heat in cold water. Several species exhibit sexual dimorphism. Two external forelimbs are modified into flippers; two internal hindlimbs are vestigial. Cetaceans have streamlined bodies: they can swim very quickly, with the killer whale able to travel at 56 kilometres per hour (35 mph) in short bursts, the fin whale able to cruise at 48 kilometres per hour (30 mph), dolphins able to make very tight turns at high speeds, and some species diving to great depths.

Although cetaceans are widespread, most species prefer the colder waters of the Northern and Southern Hemispheres. They spend their lives in the water of seas and rivers; having to mate, give birth, molt or escape from predators, like killer whales, underwater. This has drastically affected their anatomy to be able to do so. They feed largely on fish and marine invertebrates; but a few, like the killer whale, feed on large mammals and birds, such as penguins and seals. Some baleen whales (mainly gray whales and right whales) are specialised for feeding on benthic creatures. Male cetaceans typically mate with more than one female (polygyny), although the degree of polygyny varies with the species. Cetaceans are not known to have pair bonds. Male cetacean strategies for reproductive success vary between herding females, defending potential mates from other males, or whale song which attracts mates. Calves are typically born in the fall and winter months, and females bear almost all the responsibility for raising them. Mothers of some species fast and nurse their young for a relatively short period of time, which is more typical of baleen whales as their main food source (invertebrates) aren't found in their breeding and calving grounds (tropics). Cetaceans produce a number of vocalizations, notably the clicks and whistles of dolphins and the moaning songs of the humpback whale. Read more...

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Right whales are baleen whales belonging to the genus Eubalaena. Three right whale species are recognised in this genus. Sometimes the family Balaenidae is considered to be the family of right whales. Bowhead Whale, which has its own genus, Balaena also belongs to the Balaenidae family, and so is sometimes considered a right whale.

Right whales can grow up to 18 m (60 ft) long and weigh up to 100 tonnes. Their rotund bodies are mostly black, with distinctive callosities (roughened patches of skin) on their heads. They are called "right whales" because whalers thought the whales were the "right" ones to hunt, as they float when killed and often swim within sight of the shore. Populations were vastly reduced by intensive harvesting during the active years of the whaling industry. Today, instead of hunting them, people often watch these acrobatic whales for pleasure.

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Blue Whale skeleton
Photo credit: Bronwen Lea, 14 May 2004

A Blue whale skeleton, outside the Long Marine Laboratory at the University of California, Santa Cruz.

Blue Whales are the largest animal ever to have existed. Hunting of Blue Whales has led to a severe decline in numbers across the globe.

Did you know...

  • ...Qi Qi was the name of one of several captive Baijis held at the Wuhan Institute in China in an attempt to rescue the species.
  • ...the Beaked whales (genus Ziphidae) contain over twenty species of small whales, and are the least known of all cetaceans.
  • ...The ear bone called the hammer (malleus) in cetaceans is fused to the walls of the bone cavity where the ear bones are, making hearing in air nearly impossible. Instead sound is transmitted through their jaws and skull bones.
  • ...cetaceans with pointed beaks have good binocular vision, but others, such as the Sperm Whale cannot see directly in front or behind.
  • ...Migaloo is an albino Humpback Whale often spotted off the east coast of Australia.

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Cetacean articles

Whale species

Andrews' Beaked WhaleBalaenoptera omuraiBelugaBlainville's Beaked WhaleBlue Whale Cscr-featured.svgBottlenose WhaleBowhead WhaleBryde's WhaleCuvier's Beaked WhaleDwarf Sperm WhaleFin Whale Cscr-featured.svgGervais' Beaked WhaleGiant beaked whaleGinkgo-toothed Beaked WhaleGray WhaleGray's Beaked WhaleHector's Beaked WhaleHubbs' Beaked WhaleHumpback Whale Cscr-featured.svgLayard's Beaked WhaleLongman's Beaked WhaleMelon-headed WhaleMinke WhaleNarwhalPerrin's Beaked WhalePygmy Beaked WhalePygmy Killer WhalePygmy Right WhalePygmy Sperm WhaleRight Whale Cscr-featured.svgSei Whale Cscr-featured.svgShepherd's Beaked WhaleSowerby's Beaked WhaleSpade Toothed WhaleSperm Whale Symbol support vote.svgStejneger's Beaked WhaleTrue's Beaked Whale

Dolphin species

Atlantic Spotted DolphinAtlantic White-sided DolphinAustralian Snubfin DolphinBaijiBotoChilean DolphinClymene DolphinCommerson's DolphinCommon Bottlenose DolphinDusky Dolphin Symbol support vote.svgFalse Killer WhaleFraser's DolphinGanges and Indus River DolphinHeaviside's DolphinHector's DolphinHourglass DolphinHumpback dolphinIndo-Pacific Bottlenose DolphinIrrawaddy DolphinKiller Whale Cscr-featured.svgLa Plata DolphinLong-beaked Common DolphinLong-finned pilot whalePacific White-sided DolphinPantropical Spotted DolphinPeale's DolphinPygmy Killer WhaleRight whale dolphinRisso's DolphinRough-toothed DolphinShort-beaked Common DolphinShort-finned pilot whaleSpinner DolphinStriped DolphinTucuxiWhite-beaked Dolphin

Porpoise species

Burmeister's PorpoiseDall's PorpoiseFinless PorpoiseHarbour PorpoiseSpectacled PorpoiseVaquita

Other articles

Aboriginal whalingAmbergrisAnimal echolocationArchaeocetiBaleenBaleen whaleBeached whaleBeaked WhaleBlowhole (biology)BlubberBottlenose dolphin Symbol support vote.svgCallosityCephalorhynchusCetaceaCetacean intelligenceCetologyCetology of Moby-DickCommon dolphinCumberland Sound BelugaDolphinDolphinarium Symbol support vote.svgDolphin drive hunting Symbol support vote.svgEvolution of cetaceansExploding whaleHarpoonHistory of whalingHuman–animal communicationInstitute of Cetacean ResearchInternational Whaling CommissionLagenorhynchusMelon (whale)Mesoplodont WhaleMilitary dolphinMoby-DickMocha DickMonodontidaeOceanic dolphinOrcaellaPilot Whale Symbol support vote.svgPorpoiseRiver dolphinRiver Thames WhaleRorqualsSperm whale familySperm whalingSpermacetiStenellaTay WhaleThe Marine Mammal CenterToothed WhaleU.S. Navy Marine Mammal ProgramWhale Symbol support vote.svgWhalingWhale and Dolphin Conservation SocietyWhale surfacing behaviourWhale oilWhale louseWhale songWhale watchingWolphin

Cscr-featured.svg Represents a Featured article, Symbol support vote.svg Represents a Good article

Cetaceans News

2014

January

The clymene dolphin (Stenella clymene) became the first confirmed naturally occurring hybrid marine mammal species when DNA analysis showed it to be descended from the spinner dolphin and the striped dolphin. [1]

2009

February

  • 10 February - Filipino fishermen have rescued around 200 melon-headed whales which were stranded in shallow waters off the coast of Bataan. Only three dolphins were reported to have died. more

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2008

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