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A Sperm Whale fluke

Cetaceans (from Latin: cetus, lit. 'whale', from Ancient Greek: , romanizedk?tos, 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 fifteen species divided into three families, and include the blue whale, right whale, bowhead whale, rorqual, 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 been enabled by unique evolutionary adaptations in their physiology and anatomy. 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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Idealized dolphin head showing the regions involved in sound production.

Whale song is the sound made by whales to communicate. The word "song" is used in particular to describe the pattern of regular and predictable sounds made by some species of whales (notably the humpback) in a way that is reminiscent of human singing.

The mechanisms used to produce sound vary from one family of cetaceans to another. Marine mammals, such as whales, dolphins, and porpoises, are much more dependent on sound for communication and sensation than land mammals are , as other senses are of limited effectiveness in water. Sight is limited for marine mammals because of the way water absorbs light. Smell is also limited, as molecules diffuse more slowly in water than air, which makes smelling less effective. In addition, the speed of sound in water is roughly four times that in the atmosphere at sea level. Because sea-mammals are so dependent on hearing to communicate and feed, environmentalists and cetologists are concerned that they are being harmed by the increased ambient noise in the world's oceans caused by ships and marine seismic surveys.

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A Fin Whale from above.
Photo credit: Protected Resources Division, Southwest Fisheries Science Center, La Jolla, California

The Fin Whale, at 27 metres long, is the second largest whale and animal after the Blue Whale. It is found in all the world's major oceans, and in waters ranging from the polar to the tropical. It is absent only from waters close to the ice pack at both the north and south poles and relatively small areas of water away from the large oceans.

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A dead Atlantic Northern Right Whale after colliding with a ship propeller.
  • ...the leading cause of death in North Atlantic Right Whales is injury sustained from colliding with ships.
  • ...the Spade Toothed Whale is the rarest, and probably the most poorly known large mammalian species.
  • ...the ear bone 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.
  • ...from its discovery by John Edward Gray in 1850 until a re-assessment in 1981, the Clymene Dolphin was regarded as sub-species of the Spinner Dolphin.
  • ...the Australian Snubfin Dolphin (Orcaella heinsohni) is a recently recognised species of dolphin first described in 2005.


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See also Wikispecies, a Wikimedia project dedicated to the classification of species.

Cetacean articles

Whale species

Andrews' Beaked Whale o Balaenoptera omurai o Beluga o Blainville's Beaked Whale o Blue Whale Cscr-featured.svg o Bottlenose Whale o Bowhead Whale o Bryde's Whale o Cuvier's Beaked Whale o Dwarf Sperm Whale o Fin Whale Cscr-featured.svg o Gervais' Beaked Whale o Giant beaked whale o Ginkgo-toothed Beaked Whale o Gray Whale o Gray's Beaked Whale o Hector's Beaked Whale o Hubbs' Beaked Whale o Humpback Whale Cscr-featured.svg o Layard's Beaked Whale o Longman's Beaked Whale o Melon-headed Whale o Minke Whale o Narwhal o Perrin's Beaked Whale o Pygmy Beaked Whale o Pygmy Killer Whale o Pygmy Right Whale o Pygmy Sperm Whale o Right Whale Cscr-featured.svg o Sei Whale Cscr-featured.svg o Shepherd's Beaked Whale o Sowerby's Beaked Whale o Spade Toothed Whale o Sperm Whale Symbol support vote.svg o Stejneger's Beaked Whale o True's Beaked Whale

Dolphin species

Atlantic Spotted Dolphin o Atlantic White-sided Dolphin o Australian Snubfin Dolphin o Baiji o Boto o Chilean Dolphin o Clymene Dolphin o Commerson's Dolphin o Common Bottlenose Dolphin o Dusky Dolphin Symbol support vote.svg o False Killer Whale o Fraser's Dolphin o Ganges and Indus River Dolphin o Heaviside's Dolphin o Hector's Dolphin o Hourglass Dolphin o Humpback dolphin o Indo-Pacific Bottlenose Dolphin o Irrawaddy Dolphin o Killer Whale Cscr-featured.svg o La Plata Dolphin o Long-beaked Common Dolphin o Long-finned pilot whale o Pacific White-sided Dolphin o Pantropical Spotted Dolphin o Peale's Dolphin o Pygmy Killer Whale o Right whale dolphin o Risso's Dolphin o Rough-toothed Dolphin o Short-beaked Common Dolphin o Short-finned pilot whale o Spinner Dolphin o Striped Dolphin o Tucuxi o White-beaked Dolphin

Porpoise species

Burmeister's Porpoise o Dall's Porpoise o Finless Porpoise o Harbour Porpoise o Spectacled Porpoise o Vaquita

Other articles

Aboriginal whaling o Ambergris o Animal echolocation o Archaeoceti o Baleen o Baleen whale o Beached whale o Beaked Whale o Blowhole (biology) o Blubber o Bottlenose dolphin Symbol support vote.svg o Callosity o Cephalorhynchus o Cetacea o Cetacean intelligence o Cetology o Cetology of Moby-Dick o Common dolphin o Cumberland Sound Beluga o Dolphin o Dolphinarium Symbol support vote.svg o Dolphin drive hunting Symbol support vote.svg o Evolution of cetaceans o Exploding whale o Harpoon o History of whaling o Human-animal communication o Institute of Cetacean Research o International Whaling Commission o Lagenorhynchus o Melon (whale) o Mesoplodont Whale o Military dolphin o Moby-Dick o Mocha Dick o Monodontidae o Oceanic dolphin o Orcaella o Pilot Whale Symbol support vote.svg o Porpoise o River dolphin o River Thames Whale o Rorquals o Sperm whale family o Sperm whaling o Spermaceti o Stenella o Tay Whale o The Marine Mammal Center o Toothed Whale o U.S. Navy Marine Mammal Program o Whale Symbol support vote.svg o Whaling o Whale and Dolphin Conservation Society o Whale surfacing behaviour o Whale oil o Whale louse o Whale song o Whale watching o Wolphin

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Cetaceans News



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]



  • 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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