toothed whale

Toothed whales Fossil range: Eocene–Recent PreЄ Є O S D C P T J K Pg N
Bottlenose Dolphin
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Cetacea
Suborder:	Odontoceti Flower, 1869
Families
See text.
Diversity
Around 73; see List of cetaceans or below.

Cetaceans portal

The toothed whales (systematic name Odontoceti) form a suborder of the cetaceans, including sperm whales, beaked whales, orca^[1], 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.

Anatomy

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.

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 Hz), while others 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

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.^[2]

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.

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.

Currently there is no international convention that 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. All whales (great and small) are listed in CITES Appendices, meaning that international trade in them and products derived from them is very limited.

Taxonomy

• ORDER CETACEA
  • Suborder Odontoceti: toothed whales
    • Superfamily Delphinoidea
      • Family Delphinidae: oceanic dolphins
        • Subfamily Delphininae(syn. Eudelphinus)
          • 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 Sousa
            • Atlantic Humpback Dolphin, Sousa teuszi
            • Indian Humpback Dolphin, Sousa plumbea
            • Chinese White Dolphin, Sousa chinensis
          • Genus Stenella(syn. Clymenia, Micropia, Fretidelphis, Prodelphinus)
            • Pantropical Spotted Dolphin, Stenella attenuata
            • Atlantic Spotted Dolphin, Stenella frontalis
            • Spinner Dolphin, Stenella longirostris
            • Clymene Dolphin, Stenella clymene
            • Striped Dolphin, Stenella coeruleoalba
          • Genus Tursiops
            • Bottlenose Dolphin, Tursiops truncatus
            • Indian Ocean Bottlenose Dolphin, Tursiops aduncus
        • Subfamily Lissodelphininae
          • Genus Cephalorhynchus(syn. Eutropia)
            • Commerson's Dolphin, Cephalorhynchus commersonii
            • Chilean Dolphin, Cephalorhynchus eutropia
            • Heaviside's Dolphin, Cephalorhynchus heavisidii
            • Hector's Dolphin, Cephalorhynchus hectori
          • Genus Lissodelphis(syn. Tursio, Leucorhamphus)
            • Northern Right Whale Dolphin, Lissodelphis borealis
            • Southern Right Whale Dolphin, Lissodelphis peronii
        • Subfamily Orcininae
          • Genus Feresa
            • Pygmy Killer Whale, Feresa attenuata
          • Genus Globicephala (syn. Sphaerocephalus, Globiceps, Globicephalus)
            • Long-finned Pilot Whale, Globicephala melas
            • Short-finned Pilot Whale, Globicephala macrorhyncus
          • Genus Grampus (syn. Grampidelphis, Grayius)
            • Risso's Dolphin, Grampus griseus
          • Genus Orcaella
            • Irrawaddy Dolphin, Orcaella brevirostris
            • Australian Snubfin Dolphin, Orcaella heinsohni
          • Genus Orcinus (syn. Orca, Ophysia, Gladiator)
            • Orca (Killer Whale), Orcinus orca
          • Genus Peponocephala
            • Melon-headed Whale, Peponocephala electra
          • Genus Pseudorca(syn. Neorca)
            • False Killer Whale, Pseudorca crassidens
        • Subfamily Stenoninae
          • Genus Sotalia (syn. Tucuxa)
            • Tucuxi, Sotalia fluviatilis
          • Genus Steno(syn. Glyphidelphis, Stenopontistes)
            • Rough-toothed Dolphin, Steno bredanensis
        • Subfamily incertae sedis
          • 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
      • Family Monodontidae
        • Subfamily Delphinapterinae
          • Genus Delphinapterus
            • Beluga, Delphinapterus leucas
        • Subfamily Monodontinae
          • Genus Monodon
            • Narwhal, Monodon monoceros
      • Family Phocoenidae: Porpoises
        • Subfamily Phocoeninae
          • Genus Neophocaena (syn. Meomeris)
            • Finless Porpoise, Neophocaena phocaenoides
          • Genus Phocoena (syn. Australophocaena, Acanthodelphis)
            • Harbour Porpoise, Phocoena phocaena
            • Vaquita, Phocoena sinus
            • Spectacled Porpoise, Phocoena dioptrica
            • Burmeister's Porpoise, Phocoena spinipinnis
        • Subfamily Phocoenoidinae
          • Genus Phocoenoides
            • Dall's Porpoise, Phocoenoides dalli
    • Superfamily Inioidea
      • Family Iniidae
        • Genus Inia
          • Bolivian River Dolphin, Inia boliviensis
          • Amazon River Dolphin, Inia geoffrensis
      • Family Pontoporiidae
        • Genus Pontoporia
          • La Plata Dolphin, Pontoporia blainvillei
    • Superfamily Lipotoidea
      • Family Lipotidae
        • Genus Lipotes
          • Chinese River Dolphin, Lipotes vexillifer
    • Superfamily Physeteroidea
      • Family Kogiidae
        • Genus Kogia
          • Dwarf Sperm Whale, Kogia sima
          • Pygmy Sperm Whale, Kogia breviceps
      • Family Physeteridae: sperm whale family
        • Genus Physeter
          • Sperm Whale, Physeter macrocephalus
    • Superfamily Platanistoidea: river dolphins
      • Family Platanistidae
        • Genus Platanista
          • Ganges and Indus River Dolphin, Platanista gangetica
    • Superfamily Ziphioidea
      • Family Ziphidae, beaked whales
        • Subfamily Berardiinae
          • Genus Berardius, giant beaked whales
            • Arnoux's Beaked Whale, Berardius arnuxii
            • Baird's Beaked Whale (North Pacific Bottlenose Whale), Berardius bairdii
        • Subfamily Hyperoodontinae
          • Genus Hyperoodon
            • Northern Bottlenose Whale, Hyperoodon ampullatus
            • Southern Bottlenose Whale, Hyperoodon planifrons
          • Genus Indopacetus
            • Indo-Pacific Beaked Whale (Longman's Beaked Whale), Indopacetus pacificus
          • 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
        • Subfamily Ziphiinae
          • Genus Tasmacetus
            • Tasman Beaked Whale (Shepherd's Beaked Whale), Tasmacetus shepherdi
          • Genus Ziphius
            • Cuvier's Beaked Whale, Ziphius cavirostris

References