Toothed Whales
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The toothed whales (systematic name Odontoceti) form a suborder of the cetaceans. As the name suggests, the suborder is characterized by having teeth (rather than baleen as do animals in the other suborder of cetaceans, mysticeti). Toothed whales are active hunters, feeding on fish, squid, and in some cases marine mammals.
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Anatomy
Toothed whales have a single blowhole on the top of the head (while the baleen whales possess two of them). Except for the sperm whale, most toothed whales are smaller than the baleen whales. The teeth differ considerably between the species. They may be numerous, with some dolphins bearing over 100 teeth in their jaws. The other extremum are the Narwhal with its 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 is likely to use its teeth for aggression and showmanship.
Behaviour
Vocals
Vocalizations are of great importance for toothed whales. They maintain a broad variety of calls to communicate, but also are capable of using ultrasound for echolocation.
Movement
Most toothed whales swim rapidly. The smaller species occasionally ride waves, like the bow waves of ships. Most frequently can dolphins be encountered this way. They are also famous for their acrobatic breaching from the water, e.g. the Spinner Dolphin.
Social behaviour
Generally toothed whales live in groups of up to a dozen animals. These so-called schools occasionally can join, forming bigger aggregations up to thousands of whales. Toothed whales are capable of complex interactions, e.g. cooperative hunting. In captivity some species display a high potential for learning; for this reason they are considered being among the most intelligent animals.
Human Impact
The Sperm Whale has been hunted commercially for long times (see whaling). While small whales like the Pilot Whale today are still being pursued, the main threat for most species is bycatch. Especially during the tuna fishery thousands of dolphins drown each year.
Keeping small whales (mostly Bottlenose Dolphins, Orca or Belugas) in captivity is a great attraction for ocean parks and zoos. However, it is controversial because of the marine mammals' need for large spaces.