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The toothed whales (systematic name Odontoceti) form a parvorder of the artiodactyl infraorder Cetacea, including sperm whales, beaked whales, dolphins, and others. As the name suggests, the parvorder is characterized by the presence of teeth rather than the baleen of other whales.
Toothed whales have a single blowhole on the tops of their heads (while the baleen whales possess two of them).[1] The nostrils are not fused; one has evolved to generate the clicks which the whales use for their echolocation, while the other has become the dominant blowhole.[2]
As an adaptation for their echolocation, toothed whale skulls have become mostly asymmetric. Their brains are relatively large, although more significant growth did not occur before their echolocation started to evolve. Toothed whales' brains have a poor connection between the two hemispheres. The fatty organ called a melon on their heads is used like a lens to focus sound waves for echolocation. Vocal cords are not present; their sounds are produced in the blowhole system, instead. Toothed whales have lost their sense of smell, as well as their salivary glands.
Except for the sperm whale, most toothed whales are smaller than the baleen whales. The teeth differ considerably among the species. They may be numerous, with some dolphins bearing over 100 teeth in their jaws. At the other extreme are the narwhal with its single long tusk and the almost toothless beaked whales with bizarre teeth only in males. Not all species are believed to use their teeth for feeding. For instance, the sperm whale likely uses its teeth for aggression and showmanship.
Vocalizations are of great importance to toothed whales. While many species also maintain a broad variety of calls to communicate, all species investigated so far use short click sounds for purposes of echolocation. Sperm whales use low frequencies (a few to perhaps 50 Hz), while others employ more narrow-band, high-frequency sounds (porpoises, Cephalorhynchus species such as Hector's dolphin). Most dolphin species use very broad-band clicks.
Most toothed whales swim rapidly. The smaller species occasionally ride waves, such as the bow waves of ships. Dolphins can be frequently encountered this way. They are also famous for their acrobatic breaching from the water, e.g. the spinner dolphin.
Small whales are beset by a variety of anthropogenic threats, including hunting, bycatch (entanglement in fishing gear), competition with fisheries, ship strikes, tourism (whale watching and "dolphin-assisted" therapy), live capture for display and research, habitat loss and degradation, industrial and military operations, chemical pollution, disease and biotoxins (e.g., from dinoflagellates), ozone depletion, and climate change.[3]
Keeping some cetaceans (such as bottlenose dolphins, killer whales, belugas, pilot whales, or common dolphins) in captivity can be an attraction for ocean parks and zoos. Bottlenose dolphins are often used by the US Navy as "military dolphins" along with California sea lions and beluga whales. [4]
The sperm whale has been hunted commercially for a long time. While hunters still pursue small whales such as the pilot whale, the main threat for most species is accidental capture in fishing nets.
Currently, no international convention gives universal coverage to all small whales, although the International Whaling Commission has attempted to extend its jurisdiction over them. ASCOBANS was negotiated to protect all small whales in the North and Baltic Seas and in the northeast Atlantic. ACCOBAMS protects all whales in the Mediterranean and Black Seas. The global UNEP Convention on Migratory Species currently covers seven toothed whale species or populations on its Appendix I, and 37 species or populations on Appendix II. All whales (great and small) are listed in CITES appendices, meaning international trade in them and products derived from them is very limited.
Spade-toothed whale, ref to man
Pilot whale spy hopping
File:Narwhals breached
Mother and baby sperm whale
Sperm whale on beach
Killer whales, also known as Orcas
Orca size to a man
Short-beaked common dolphin
Long beaked common dolphin
Common dolphin
Bottlenose dolphin
Spotted Dolphin
Atlantic Spotted Dolphin
Commerson's Dolphin
Dusky Dolphin
Boto also called Amazon River Dolphin
Animal, Gray whale, Humpback whale, Whale, Fish
Cnidaria, Sponge, Bacteria, Fungus, Biological classification
Cetacea, Moby-Dick, Herman Melville, New Zealand, Animal
Silurian, Carboniferous, Paleogene, Neogene, Cambrian
Carboniferous, Devonian, Triassic, Paleogene, Neogene
Hudson Bay, Russia, Canada, Cetacea, Greenland
Cetacea, Pinyin, Animal, Finless porpoise, Chinese language
Animal, Cetacea, IUCN Red List, Florida, Africa
Animal, England, Turkey, Massachusetts, Faroe Islands