Portal:Cetaceans
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Cetaceans evolved from land mammals that adapted to marine life about 50 million years ago. Over a period of a few millions of years during the Eocene, the cetaceans returned to the sea. Their body is fusiform (spindle-shaped), the forelimbs are modified into flippers, the tiny hindlimbs are vestigial and the tail has horizontal flukes. Cetaceans are nearly hairless, and are insulated by a thick layer of blubber.
Cetaceans inhabit all of the world's oceans, as well as some freshwater lakes and rivers in South America, North America, and Asia. Some species, like the Orca, or Killer Whale, can be found across the globe.
Cetology is the branch of marine science associated with the study of cetaceans.
The 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. The Sei Whale migrates annually from cool and subpolar waters in summer to temperate and subtropical waters for winter, although in most areas the exact migration routes are not well known.
The whales reach lengths of up to 20 metres (66 ft) long and weigh up to 45 tonnes (50 tons). It consumes an average of 900 kilograms (2,000 lb) of food each day, primarily copepods and krill, and other zooplankton. It is among the fastest of all cetaceans, and can reach speeds of up to 50 kilometres per hour (31 mi/hr, 27 knots) over short distances.
Following large-scale commercial hunting of the species between the late-nineteenth and late-twentieth centuries when over 238,000 individuals were taken, the Sei Whale is now an internationally protected species, although limited hunting still occurs under controversial research programmes conducted by Iceland and Japan. As of 2006, the worldwide population of the Sei Whale was about 54,000, about a fifth of its pre-whaling population.
More on the Sei Whale
--~72.15.87.190 (talk)--72.15.87.190 (talk) 12:05, 12 June 2008 (UTC)
- 19 May - Iceland's commercial whaling hunt begins with a lower quota of 40 Minke Whales, despite whalers hopes for 100. Read more...
- 8 March - A survey conducted by Greenpeace suggests that most stores and sushi restaurants in Japan are not selling whale meat. Read more...
- 20 February - Sperm Whales are filmed sleeping for the first time. Read more...
- 16 February - Anti-whaling protester Sophie Wyness and her father Martin speak against the decision to drop charges against them in court for their trespass at the Japanese Embassy in London. Read more...
- 7 February - Photographs portraying slaughter of whales, including that of an alleged mother and calf, are released in Australian media; Japanese authorities claim that the whales in the picture are not related. Read more...
- 26 January - President George W. Bush exempts the United States Navy from a law against high-power sonar, a decision met with criticism. Read more...
[[Media:]]
- ...the Orca, is the fastest swimmer of all the cetaceans and can reach speeds of more than 50km/h while hunting.
- ...some cetaceans can dive to depths of more than a kilometre and stay there for more than an hour.
- ...newborn cetacean calves do not have the skills to swim for long periods or to accelerate away from danger, so they swim in the slipstream of their mothers, enabling the mother to protect her calf.
- ...all cetaceans have a blubber layer — a layer of fat under the skin. In most dolphins, this layer is about one quarter to one third of the total body weight, but in southern right whales nearly half of its weight (up to 50 tons) will be blubber.
- ...most whales and dolphins live long lives. Wild bottlenose dolphins live well into their forties, while some of the larger whales live in excess of 80 years!
Subcategories of Cetaceans:
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Baleen makes up baleen plates, which are arranged in two parallel rows that look like combs of thick hair; they are attached to the upper jaws of baleen whales. It is composed of keratin, which is the same substance that makes up human hair and nails. Whales use these combs for filter feeding. Whales are the only vertebrate group to use this method of feeding in great abundance (flamingos and crabeater seals use similar methods, but do not have baleen), and it has allowed them to grow to immense sizes. The Blue Whale, the largest animal ever to live, is a baleen whale.
More on baleen
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A Blue Whale song Recorded in the South Pacific Humpback Whale Song Made by the National Oceanic and Atmospheric Administration - Problems playing the files? See media help.
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