Toothed whale

How to read a taxoboxToothed whales
Fossil range: Latest Eocene - Recent
Bottlenose Dolphin
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.

Toothed whale is the general term for any of the various aquatic mammals comprising the suborder Odontoceti, characterized in extant species by the presence of teeth, one blowhole, the ability to sense their environment through echolocation, and nostrils that are not fused and with one that is dominant over the other. Among toothed whales are included sperm whales, orcas (killer whales), dolphins, porpoises, narwhals, and belugas.

Odontoceti is one of two suborders of cetaceans, the other being the baleen whales comprising the Mysticeti. As the name suggests, members of the Odontoceti suborder are characterized by having teeth, rather than baleen as do extant animals in 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 offer important ecological, commercial, and recreational functions. Ecologically, they help in the control of prey species, such as fish and squid, and are themselves, particularly as young, the source of food for various large aquatic predators. Some have been of great commercial importance. In particular, the sperm whale has been hunted commercially for a long time, with its spermaceti much sought for such purposes as watch oil, automatic transmission fluid, cosmetics, additives in motor oils, and numerous other products. 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, this practice is controversial because of the marine mammals' need for large spaces.

Contents

Overview and description

The order Cetacea includes aquatic mammals known by the common names of whales, dolphins, and porpoises. Like all mammals, the aquatic cetaceans breast-feed their young, breathe air into lungs, are warm-blooded, and have hair (although very little). Unlike fish, which breathe air using gills, cetaceans breathe air through blowholes that lead into their lungs. Cetaceans have a fusiform (spindle-shaped) body with anterior limbs in the form of flippers, and a flat, notched tail with horizontal flukes that lacks bony support. The tiny hindlimbs are vestigial. Cetaceans have an exclusively aquatic life cycle from birth until death.

The flukes of a sperm whale

Two suborders of cetaceans are recognized: Odontoceti and Mysticeti. Members of the Odontoceti are known as "toothed whales" and include dolphins, porpoises, and those species of whales with a single blowhole on the top of the head and teeth in the adults. In addition, the nostrils are not fused; one of them has become dominant over the other. Having teeth, they prey on fish, squid, marine mammals, and so forth. Members of the Mysticeti are known as 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.

Killer whale (orca), the largest species of dolphin

.

Note that while the common term whale is more specifically considered as any cetacean that is neither a dolphin (that is, members of the families Delphinidae or Platanistoidea) nor porpoise (several families), the term toothed whale refers to any of the members of Odontoceti and includes the numerous species of dolphins and porpoises as well. This suborder also includes many species of whales, including the beluga whales, beaked whales, and sperm whales. The use of the common term whale can lead to some confusion because orcas ("killer whales") and pilot whales have "whale" in their name, but they are dolphins for the purpose of classification.

An outstanding ability of the Odontoceti is the ability to sense their surrounding environment through echolocation. 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.

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.

Except for the sperm whale, which may be the largest toothed animal to ever inhabit Earth, 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.

Behavior

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.

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, such as seen with the spinner dolphin.

Taxonomy

Sperm whale
  • ORDER CETACEA
    • Suborder Odontoceti: toothed whales
      • Family Delphinidae: oceanic dolphins
        • Genus Cephalorhynchus
          • Commerson's dolphin, Cephalorhynchus commersonii
          • Chilean dolphin, Cephalorhynchus eutropia
          • Heaviside's dolphin, Cephalorhynchus heavisidii
          • Hector's dolphin, Cephalorhynchus hectori
        • Genus Steno
          • Rough-toothed dolphin, Steno bredanensis
        • Genus Sousa
          • Atlantic humpback dolphin, Sousa teuszi
          • Indian humpback dolphin, Sousa plumbea
          • Chinese white dolphin, Sousa chinensis
        • Genus Sotalia
          • Tucuxi, Sotalia fluviatilis
          • Costero, Sotalia guianensis
        • Genus Tursiops
          • Bottlenose dolphin, Tursiops truncatus
          • Indian Ocean bottlenose dolphin, Tursiops aduncus
        • Genus Stenella
          • Pantropical Spotted Dolphin, Stenella attenuata
          • Atlantic spotted dolphin, Stenella frontalis
          • Spinner dolphin, Stenella longirostris
          • Clymene dolphin, Stenella clymene
          • Striped dolphin, Stenella coeruleoalba
        • Genus Delphinus
          • Short-beaked common dolphin, Delphinus delphis
          • Long-beaked common dolphin, Delphinus capensis
          • (Arabian common dolphin, Delphinus tropicalis)
        • Genus Lagenodelphis
          • Fraser's dolphin, Lagenodelphis hosei
        • Genus Lagenorhynchus
          • White-beaked dolphin, Lagenorhynchus albirostris
          • Atlantic white-sided dolphin, Lagenorhynchus acutus
          • Pacific white-sided dolphin, Lagenorhynchus obliquidens
          • Dusky dolphin, Lagenorhynchus obscurus
          • Black-chinned dolphin, Lagenorhynchus australis
          • Hourglass dolphin, Lagenorhynchus cruciger
        • Genus Lissodelphis
          • Northern right whale dolphin, Lissodelphis borealis
          • Southern right whale dolphin, Lissodelphis peronii
        • Genus Grampus
          • Risso's dolphin, Grampus griseus
        • Genus Peponocephala
          • Melon-headed whale, Peponocephala electra
        • Genus Feresa
          • Pygmy killer whale, Feresa attenuata
        • Genus Pseudorca
          • False killer whale, Pseudorca crassidens
        • Genus Orcinus
          • Orca (killer whale), Orcinus orca
        • Genus Globicephala
          • Long-finned pilot whale, Globicephala melas
          • Short-finned pilot whale, Globicephala macrorhynchus
        • Genus Orcaella
          • Irrawaddy dolphin, Orcaella brevirostris
          • Australian snubfin dolphin, Orcaella heinsohni
      • Family Monodontidae
        • Genus Monodon
        • Genus Delphinapterus
          • Beluga, Delphinapterus leucas
      • Family Phocoenidae: Porpoises
        • Genus Neophocaena
          • Finless porpoise, Neophocaena phocaenoides
        • Genus Phocoena
          • Harbor porpoise, Phocoena phocaena
          • Vaquita, Phocoena sinus
          • Spectacled porpoise, Phocoena dioptrica
          • Burmeister's porpoise, Phocoena spinipinnis
        • Genus Phocoenoides
          • Dall's porpoise, Phocoenoides dalli
      • Family Physeteridae
      • Family Kogiidae
        • Genus Kogia
          • Dwarf sperm whale, Kogia sima
          • Pygmy sperm whale, Kogia breviceps
      • Family Ziphidae: Beaked whales
        • Genus Ziphius
          • Cuvier's beaked whale, Ziphius cavirostris
        • Genus Berardius, giant beaked whales
          • Arnoux's beaked whale, Berardius arnuxii
          • Baird's beaked whale (North Pacific bottlenose whale), Berardius bairdii
        • Genus Tasmacetus
          • Tasman beaked whale (Shepherd's beaked whale), Tasmacetus shepherdi
        • Sub-family Hyperoodontidae
          • Genus Indopacetus
            • Indo-Pacific beaked whale (Longman's beaked whale), Indopacetus pacificus
          • Genus Hyperoodon
            • Northern bottlenose whale, Hyperoodon ampullatus
            • Southern bottlenose whale, Hyperoodon planifrons
          • Genus Mesoplodon, mesoplodont whales
            • Hector's beaked whale, Mesoplodon hectori
            • True's beaked whale, Mesoplodon mirus
            • Gervais' beaked whale, Mesoplodon europaeus
            • Sowerby's beaked whale, Mesoplodon bidens
            • Gray's beaked whale, Mesoplodon grayi
            • Pygmy beaked whale, Mesoplodon peruvianus
            • Andrew's beaked whale, Mesoplodon bowdoini
            • Bahamonde's beaked whale, Mesoplodon bahamondi
            • Hubbs' beaked whale, Mesoplodon carlhubbsi
            • Ginko-toothed beaked whale, Mesoplodon ginkgodens
            • Stejneger's beaked whale, Mesoplodon stejnegeri
            • Layard's beaked whale, Mesoplodon layardii
            • Blainville's beaked whale, Mesoplodon densirostris
            • Perrin's beaked whale, Mesoplodon perrini
      • Super-family Platanistoidea: river dolphins
        • Family Iniidae
          • Genus Inia
            • Amazon river dolphin, Inia geoffrensis
        • Family Lipotidae
          • Genus Lipotes
            • Chinese river dolphin, Lipotes vexillifer
        • Family Platanistidae
          • Genus Platanista
            • Ganges and Indus river dolphin, Platanista gangetica
        • Family Pontoporiidae
          • Genus Pontoporia
            • La Plata dolphin, Pontoporia blainvillei

References

  • Clover, C. 2004. The End of the Line: How Overfishing is Changing the World and What We Eat. London: Ebury Press. ISBN 0091897807.
  • Grzimek, B., D. G. Kleiman, V. Geist, and M. C. McDade. 2004. Grzimek's Animal Life Encyclopedia. Detroit: Thomson-Gale. ISBN 0787657883.
  • Mead, J. G., and R. L. Brownell. 2005. Order Cetacea. In D. E. Wilson and D. M. Reeder (eds.), Mammal Species of the World, 3rd edition. Johns Hopkins University Press. ISBN 0801882214.
  • Read, A. 1999. Porpoises. Stillwater, MN: Voyageur Press. ISBN 0896584208
  • Rice, D. W. 1998. Marine Mammals of the World: Systematics and Distribution. Lawrence, KS: Society for Marine Mammalogy. ISBN 1891276034.
  • Wilson, D. E., and D. M. Reeder. 1993. Mammal Species of the World: A Taxonomic and Geographic Reference. Washington: Smithsonian Institution Press. ISBN 1560982179.


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