Toothed whale

Toothed whales Fossil range: Latest Eocene - Recent
Bottlenose Dolphin
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Mammalia Order: Cetacea Suborder: Odontoceti Flower, 1869
Diversity
Around 73; see List of cetaceans or below.
Families
See text.

Cetaceans Portal

The toothed whales (systematic name Odontoceti) form a suborder of the cetaceans, including sperm whales, beaked whales, orca, dolphins, and others. As the name suggests, the suborder is characterized by having teeth, rather than baleen as do animals in the other suborder of cetaceans, Mysticeti. However, fossils indicate that early Baleen whales had teeth as well before evolving baleen, so defining the Odontoceti on teeth alone is problematic, and paleontologists have instead identified other features uniting fossil and modern odontocetes that are not shared by mysticetes. Toothed whales are active hunters, feeding on fish, squid, and in some cases marine mammals.

Baleen whales comprise the Mysticeti, one of two suborders of the mammalian order Cetacea, the other suborder being the Odontoceti, or toothed whales (dolphins, porpoises, and various whales). Baleen whales are characterized by having baleen plates for filtering food from water, rather than having teeth. They also differ from toothed whales in that they have two blowholes rather than one. Baleen whales also are known as whalebone whales or great whales.

Overview and description

Whales are members of the order Cetacea, which also includes dolphins and porpoises. Whales are the largest mammals, the largest vertebrates, and the largest known animals in the world. Like all mammals, whales breathe air into lungs, are warm-blooded, breast-feed their young, and have hair (although very little). Unlike fish, which breathe air using gills, whales breathe air through blowholes that lead into their lungs.

Cetaceans are divided into two suborders:

• The baleen whales (Mysticeti) are characterized by baleen, a sieve-like structure in the upper jaw made of the tough, structural protein keratin. The baleen is used to filter plankton from the water. Baleen whales are also characterized by two blowholes. Living Mysticeti species have teeth only during the embryonal phase. Fossil Mysticeti had teeth before baleen evolved.

• The toothed whales (Odontoceti) have teeth and prey on fish, squid, marine mammals, and so forth. This suborder includes dolphins and porpoises as well as whales. An outstanding ability of this group is to sense their surrounding environment through echolocation. Toothed whales have only one blowhole. In addition to numerous species of dolphins and porpoises, this suborder includes the Beluga whale and the sperm whale, which may be the largest toothed animals to ever inhabit Earth.

Toothed whales have a single blowhole on the top of the head (while the baleen whales possess two of them). The nostrils are not fused; one of them has become dominant over the other.

Toothed whales, as all whales, develop as an embryo in the womb, they are then born as calves, grow into juveniles and finally become adults.

As an adaptation for their echolocation, toothed whale skulls have become asymmetric. Their brains are relatively big, although real growth didn't occur before their echolocation started to evolve. Toothed whales' brains have a poor connection between the two hemispheres and an organ called a melon on their heads is used as a lens to focus sound waves. 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 saliva glands.

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. 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.

Behaviour

Vocalizations

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 kHz), while other employ more narrow band high frequency sounds (porpoises, Cephalorhynchus species like Hector's dolphin). Most dolphin species use very broad band clicks.

Movement

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.

Human impact

The Sperm Whale has been hunted commercially for a long time (see whaling). While small whales like the Pilot Whale today are still being pursued, the main threat for most species is accidental capture in fishing nets.

Keeping small whales (mostly Bottlenose Dolphins, Orcas, 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.

Taxonomy

• ORDER CETACEA

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• Suborder Odontoceti: toothed whales

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• Family Delphinidae: oceanic dolphins

• Template:Cephalorhynchus taxonomy
• Template:Steno taxonomy
• Template:Sousa taxonomy
• Template:Sotalia taxonomy
• Template:Tursiops taxonomy
• Template:Stenella taxonomy
• Template:Delphinus taxonomy
• Template:Lagenodelphis taxonomy
• Template:Lagenorhynchus taxonomy
• Template:Lissodelphis taxonomy
• Template:Grampus taxonomy
• Template:Peponocephala taxonomy
• Template:Feresa taxonomy
• Template:Pseudorca taxonomy
• Template:Orcinus taxonomy
• Template:Globicephala taxonomy
• Template:Orcaella taxonomy

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• Family Monodontidae

• Template:Monodon taxonomy
• Template:Delphinapterus taxonomy

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• Family Phocoenidae: Porpoises

• Template:Neophocaena taxonomy
• Template:Phocoena taxonomy
• Template:Phocoenoides taxonomy

Template:Physeteridae taxonomy

Template:Kogiidae taxonomy

Template:Ziphidae taxonomy

Template:Platanistoidea taxonomy

References

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