Oceanic dolphin
Encyclopedia
Oceanic dolphins are the members of the Delphinidae family of cetacea
ns. These marine mammals are related to whale
s and porpoise
s. They are found worldwide, mostly in the shallower seas of the continental shelves. As the name implies, these dolphin
s tend to be found in the open seas, unlike the river dolphin
s, although a few species such as the Irrawaddy dolphin
are coastal or riverine.
Six of the larger species in the Delphinidae, the Orca
and the Pilot
, Melon-headed
, Pygmy Killer
and False Killer
Whales, are commonly called whales, rather than dolphins; they are also sometimes collectively known as "blackfish".
, although there are exceptions to all of these rules. They have a wide range of colors and patterns.
Most delphinids primarily eat fish, along with a smaller number of squid and small crustaceans, but some species specialise in eating squid, or, in the case of the Orca, also eat marine mammals. All, however, are purely carnivorous
. They typically have between 100 and 200 teeth, although a few species have considerably fewer.
Delphinids travel in large pods, which may number a thousand individuals in some species. Each pod forages over a range of a few dozen to a few hundred square miles. Some pods have a loose social structure, with individuals frequently joining or leaving, but others seem to be more permanent, perhaps dominated by a male and a 'harem' of females. Individuals communicate by sound, producing low frequency whistles, and also produce high frequency broadband clicks of 80-220 kHz
, which are primarily used for echolocation
. Gestation
lasts from ten to twelve months, and results in the birth of a single calf.
Recent molecular
analyses indicate that several delphinid genera
(especially Stenella
and Lagenorhynchus
) are not monophyletic
as currently recognized. Thus, the coming years will likely see significant taxonomic revisions within the family.
Cetacea
The order Cetacea includes the marine mammals commonly known as whales, dolphins, and porpoises. Cetus is Latin and is used in biological names to mean "whale"; its original meaning, "large sea animal", was more general. It comes from Ancient Greek , meaning "whale" or "any huge fish or sea...
ns. These marine mammals are related to whale
Whale
Whale is the common name for various marine mammals of the order Cetacea. The term whale sometimes refers to all cetaceans, but more often it excludes dolphins and porpoises, which belong to suborder Odontoceti . This suborder also includes the sperm whale, killer whale, pilot whale, and beluga...
s and porpoise
Porpoise
Porpoises are small cetaceans of the family Phocoenidae; they are related to whales and dolphins. They are distinct from dolphins, although the word "porpoise" has been used to refer to any small dolphin, especially by sailors and fishermen...
s. They are found worldwide, mostly in the shallower seas of the continental shelves. As the name implies, these dolphin
Dolphin
Dolphins are marine mammals that are closely related to whales and porpoises. There are almost forty species of dolphin in 17 genera. They vary in size from and , up to and . They are found worldwide, mostly in the shallower seas of the continental shelves, and are carnivores, mostly eating...
s tend to be found in the open seas, unlike the river dolphin
River dolphin
River dolphins are the four living species of dolphin that reside in freshwater rivers and estuaries. River dolphins inhabit areas of Asia and South America. They are classed in the Platanistoidea superfamily of cetaceans. Three species live in fresh water rivers. The fourth species, the La Plata...
s, although a few species such as the Irrawaddy dolphin
Irrawaddy dolphin
The Irrawaddy dolphin is a euryhaline species of oceanic dolphin found in discontinuous subpopulations near sea coasts and in estuaries and rivers in parts of the Bay of Bengal and Southeast Asia.-Etymology and taxonomic history:...
are coastal or riverine.
Six of the larger species in the Delphinidae, the Orca
Orca
The killer whale , commonly referred to as the orca, and less commonly as the blackfish, is a toothed whale belonging to the oceanic dolphin family. Killer whales are found in all oceans, from the frigid Arctic and Antarctic regions to tropical seas...
and the Pilot
Pilot whale
Pilot whales are cetaceans belonging to the genus Globicephala. There are two extant species, the long-finned pilot whale and the short-finned pilot whale . The two are not readily distinguished at sea and analysis of the skulls is the best way to tell the difference between them...
, Melon-headed
Melon-headed Whale
The melon-headed whale is a cetacean of the oceanic dolphin family . It is closely related to the pygmy killer whale and pilot whale, and collectively these dolphin species are known by the common name blackfish. It is also related to the false killer whale...
, Pygmy Killer
Pygmy Killer Whale
The pygmy killer whale is a small, rarely seen cetacean of the oceanic dolphin family . It derives its common name from sharing some physical characteristics with the orca It is the smallest species that has "whale" in its common name. In fact, "killer" may be more apt in the case of the pygmy...
and False Killer
False Killer Whale
The False Killer Whale is a cetacean, and the third largest member of the oceanic dolphin family . It lives in temperate and tropical waters throughout the world. As its name implies, the False Killer Whale shares characteristics, such as appearance, with the more widely known Orca...
Whales, are commonly called whales, rather than dolphins; they are also sometimes collectively known as "blackfish".
Characteristics
The Delphinidae are the most diverse of the cetacean families, with numerous variations between species. They range in size from 1.2 metres (3.9 ft) and 40 kilograms (88.2 lb) (Haviside's dolphin), up to 9 metres (29.5 ft) and 10 tonnes (the Orca). Most species weigh between approximately 50 and 200 kg (110.2 and 440.9 lb). They typically have a curved dorsal fin, a clear 'beak' at the front of the head, and a forehead melonMelon (whale)
The melon is an ovoid-shaped, fatty organ found in the forehead of all toothed whales , including dolphins and porpoises and believed to be used in echolocation....
, although there are exceptions to all of these rules. They have a wide range of colors and patterns.
Most delphinids primarily eat fish, along with a smaller number of squid and small crustaceans, but some species specialise in eating squid, or, in the case of the Orca, also eat marine mammals. All, however, are purely carnivorous
Carnivore
A carnivore meaning 'meat eater' is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of animal tissue, whether through predation or scavenging...
. They typically have between 100 and 200 teeth, although a few species have considerably fewer.
Delphinids travel in large pods, which may number a thousand individuals in some species. Each pod forages over a range of a few dozen to a few hundred square miles. Some pods have a loose social structure, with individuals frequently joining or leaving, but others seem to be more permanent, perhaps dominated by a male and a 'harem' of females. Individuals communicate by sound, producing low frequency whistles, and also produce high frequency broadband clicks of 80-220 kHz
Hertz
The hertz is the SI unit of frequency defined as the number of cycles per second of a periodic phenomenon. One of its most common uses is the description of the sine wave, particularly those used in radio and audio applications....
, which are primarily used for echolocation
Animal echolocation
Echolocation, also called biosonar, is the biological sonar used by several kinds of animals.Echolocating animals emit calls out to the environment and listen to the echoes of those calls that return from various objects near them. They use these echoes to locate and identify the objects...
. Gestation
Gestation
Gestation is the carrying of an embryo or fetus inside a female viviparous animal. Mammals during pregnancy can have one or more gestations at the same time ....
lasts from ten to twelve months, and results in the birth of a single calf.
Taxonomy
- Suborder Odontoceti
- Superfamily DelphinoideaDelphinoideaDelphinoidea is the largest group of toothed whales with 66 genera in 6 families. The largest living member of the superfamily is the killer whale, which can reach 6 tonnes, while the smallest, Commerson's Dolphin, is also the smallest living cetacean....
- Family Delphinidae
- Genus Peponocephala
- Melon-headed whaleMelon-headed WhaleThe melon-headed whale is a cetacean of the oceanic dolphin family . It is closely related to the pygmy killer whale and pilot whale, and collectively these dolphin species are known by the common name blackfish. It is also related to the false killer whale...
, Peponocephala electra
- Melon-headed whale
- Genus Orcinus
- OrcaOrcaThe killer whale , commonly referred to as the orca, and less commonly as the blackfish, is a toothed whale belonging to the oceanic dolphin family. Killer whales are found in all oceans, from the frigid Arctic and Antarctic regions to tropical seas...
(killer whale), Orcinus orca - Orcinus citoniensisOrcinus citoniensisOrcinus citoniensis is an extinct species of whale belonging to the family Delphinidae that lived from in the Pliocene.The species was related to the modern killer whale. Was described based on an incomplete skull found in Italy, which lacks the rear and left side, but had the back side. Had 14...
†
- Orca
- Genus Feresa
- Pygmy killer whalePygmy Killer WhaleThe pygmy killer whale is a small, rarely seen cetacean of the oceanic dolphin family . It derives its common name from sharing some physical characteristics with the orca It is the smallest species that has "whale" in its common name. In fact, "killer" may be more apt in the case of the pygmy...
, Feresa attenuata
- Pygmy killer whale
- Genus Pseudorca
- False killer whaleFalse Killer WhaleThe False Killer Whale is a cetacean, and the third largest member of the oceanic dolphin family . It lives in temperate and tropical waters throughout the world. As its name implies, the False Killer Whale shares characteristics, such as appearance, with the more widely known Orca...
, Pseudorca crassidens
- False killer whale
- Genus Globicephala
- Long-finned pilot whaleLong-finned Pilot WhaleThe long-finned pilot whale is one of the two species of cetacean in the genus Globicephala. It belongs to the oceanic dolphin family , though its behavior is closer to that of the larger whales.-Description:...
, Globicephala melas - Short-finned pilot whaleShort-finned Pilot WhaleThe Short-finned Pilot Whale is one of the two species of cetacean in the genus Globicephala. It is part of the oceanic dolphin family , though its behaviour is closer to that of the larger whales....
, Globicephala macrorhynchus
- Long-finned pilot whale
- Genus Delphinus
- Long-beaked common dolphinLong-beaked Common DolphinThe Long-beaked Common Dolphin is a species of common dolphin. It has a more restricted range than the Short-beaked Common Dolphin . It has a disjointed range in coastal areas in tropical and warmer temperate oceans...
, Delphinus capensis - Short-beaked common dolphinShort-beaked Common DolphinThe short-beaked common dolphin is a species of common dolphin. It has a larger range than the long-beaked common dolphin , occurring throughout warm-temperate and tropical oceans, with the possible exception of the Indian Ocean...
, Delphinus delphis
- Long-beaked common dolphin
- Genus Lissodelphis
- Northern right whale dolphinNorthern Right Whale DolphinThe Northern right whale dolphin is a small and slender species of marine mammal found in the North Pacific Ocean. The Northern right whale dolphin travels in groups of up to 2000, often with other cetaceans, in deep waters of the North Pacific...
, Lissodelphis borealis - Southern right whale dolphinSouthern Right Whale DolphinThe southern right whale dolphin, Lissodelphis peronii, is a small and slender species of mammal found in cool waters of the southern hemisphere...
, Lissodelphis peronii
- Northern right whale dolphin
- Genus SotaliaSotalia (genus)The genus Sotalia now is considered to have two member species with the classification of Sotalia guianensis as a distinct species from Sotalia fluviatilis in 2007...
- TucuxiTucuxiThe Tucuxi , alternately bufeo gris or bufeo negro is a dolphin found in the rivers of the Amazon Basin. The word "tucuxi" is derived from the Tupi language word tuchuchi-ana and has now been adopted as the species' common name...
, Sotalia fluviatilis - CosteroCosteroThe Costero is found in the coastal waters to the north and east of South America. The common name "costero" has been suggested by Caballero and colleagues due to the species' affinity for coastal habitats. The Costero is a member of the oceanic dolphin family . Physically it resembles the...
, Sotalia guianensis
- Tucuxi
- Genus Sousa
- Pacific humpback dolphin, Sousa chinensis
- Indian humpback dolphin, Sousa plumbea
- Atlantic humpback dolphin, Sousa teuszii
- Genus StenellaStenellaStenella is a genus of aquatic mammals in Delphinidae, the family informally known as the oceanic dolphins.Currently five species are recognised in this genus:*Pantropical Spotted Dolphin, S. attenuata*Atlantic Spotted Dolphin, S. frontalis...
- Atlantic spotted dolphinAtlantic Spotted DolphinThe Atlantic Spotted Dolphin is a dolphin found in the Gulf Stream of the North Atlantic Ocean. Older members of the species have a very distinctive spotted coloration all over their body.-Taxonomy:...
, Stenella frontalis - Clymene dolphinClymene DolphinThe Clymene dolphin , in older texts known as the Short-snouted spinner dolphin, is a dolphin endemic to the Atlantic Ocean.- Taxonomy :...
, Stenella clymene - Pantropical spotted dolphinPantropical Spotted DolphinThe Pantropical Spotted Dolphin is a species of dolphin found in all the world's temperate and tropical oceans. The species was beginning to come under threat due to the killing of millions of individuals in tuna purse seines...
, Stenella attenuata - Spinner dolphinSpinner DolphinThe Spinner Dolphin is a small dolphin found in off-shore tropical waters around the world. It is famous for its acrobatic displays in which they spin longitudinally along their axis as they leap through the air.-Taxonomy:...
, Stenella longirostris - Striped dolphinStriped DolphinThe Striped Dolphin is an extensively studied dolphin that is found in temperate and tropical waters of all the world's oceans.-Taxonomy:...
, Stenella coeruleoalba
- Atlantic spotted dolphin
- Genus Steno
- Rough-toothed dolphinRough-toothed DolphinThe Rough-toothed dolphin is species of dolphin that can be found in deep warm and tropical waters around the world.The species was first described by Georges Cuvier in 1823...
, Steno bredanensis
- Rough-toothed dolphin
- Genus Tursiops
- Common bottlenose dolphinCommon Bottlenose DolphinTursiops truncatus, commonly known as the Common Bottlenose Dolphin, is the most well-known species from the family Delphinidae.Common bottlenose dolphins are the most familiar dolphins due to the wide exposure they receive in captivity in marine parks, dolphinarias, in movies, and television...
, Tursiops truncatus - Indo-Pacific bottlenose dolphinIndo-Pacific Bottlenose DolphinThe Indo-Pacific bottlenose dolphin is a species of bottlenose dolphin. The Indo-Pacific bottlenose dolphin grows to long, and weigh up to . It lives in the waters around India, northern Australia, South China, the Red Sea, and the eastern coast of Africa. Its back is dark grey and its belly...
, Tursiops aduncus - Burrunan dolphinBurrunan dolphinThe Burrunan dolphin is a recently-described species of bottlenose dolphin found in parts of Victoria, Australia. By size, the Burrunan dolphin is between the other two species of bottlenose dolphin and only around 150 individuals have been found in two locations.-Taxonomy:The species was formally...
, Tursiops australis
- Common bottlenose dolphin
- Genus CephalorhynchusCephalorhynchusCephalorhynchus is a genus in the dolphin family Delphinidae. It consists of four species:*Commerson's Dolphin, Cephalorhyncus commersonii*Chilean Dolphin, Cephalorhyncus eutropia*Heaviside's Dolphin, Cephalorhyncus heavisidii...
- Chilean dolphinChilean DolphinThe Chilean Dolphin , also known as the Black Dolphin, is one of four dolphins in the Cephalorhynchus genus. The dolphin is only found off the coast of Chile, it is commonly referred to in the country as Tunina....
, Cephalorhynchus eutropia - Commerson's dolphinCommerson's DolphinCommerson's Dolphin is one of four dolphins in the Cephalorhynchus genus. The species has also the common names Skunk Dolphin, Piebald Dolphin and Panda Dolphin...
, Cephalorhynchus commersonii - Heaviside's dolphinHeaviside's DolphinThe Haviside's Dolphin , or mistakenly the Heaviside's Dolphin, is a small dolphin that is found off the coast of Namibia and the west coast of South Africa...
, Cephalorhynchus heavisidii - Hector's dolphinHector's DolphinHector's dolphin is the best-known of the four dolphins in the genus Cephalorhynchus and is found only in New Zealand. At about 1.4 m in length, it is one of the smallest cetaceans....
, Cephalorhynchus hectori
- Chilean dolphin
- Genus Grampus
- Risso's dolphinRisso's DolphinRisso's dolphin is the only species of dolphin in the genus Grampus.-Taxonomy:Risso's dolphin is named after Antoine Risso, whose description formed the basis of the first public description of the animal, by Georges Cuvier, in 1812...
, Grampus griseus
- Risso's dolphin
- Genus Lagenodelphis
- Fraser's dolphinFraser's DolphinFraser's Dolphin or Sarawak Dolphin is a cetacean in the family Delphinidae found in deep waters in the Pacific Ocean and to a lesser extent in the Indian and Atlantic Oceans.-Taxonomy:...
, Lagenodelphis hosei
- Fraser's dolphin
- Genus LagenorhynchusLagenorhynchusLagenorhynchus is a genus in the order Cetacea, traditionally containing six species:* white-beaked dolphin, Lagenorhynchus albirostris* Atlantic white-sided dolphin, Lagenorhynchus acutus...
- Atlantic white-sided dolphinAtlantic White-sided DolphinThe Atlantic White-sided Dolphin is a distinctively coloured dolphin found in the cool to temperate waters of the North Atlantic Ocean.-Taxonomy:...
, Lagenorhynchus acutus - Dusky dolphinDusky DolphinThe dusky dolphin is a dolphin found in coastal waters in the Southern Hemisphere. Its specific epithet is Latin for "dark" or "dim". It is very closely genetically related to the Pacific white-sided dolphin, but current scientific consensus is that they are distinct species...
, Lagenorhynchus obscurus - Hourglass dolphinHourglass DolphinThe hourglass dolphin is a small dolphin in the family Delphinidae that inhabits Antarctic and sub-Antarctic waters....
, Lagenorhynchus cruciger - Pacific white-sided dolphinPacific White-sided DolphinThe Pacific White-sided Dolphin is a very active dolphin found in the cool to temperate waters of the North Pacific Ocean.-Taxonomy:...
, Lagenorhynchus obliquidens - Peale's dolphinPeale's DolphinPeale's Dolphin is a small dolphin found in the waters around Tierra del Fuego at the foot of South America. It is also commonly known as the Black-chinned Dolphin or even Peale's Black-chinned Dolphin...
, Lagenorhynchus australis - White-beaked dolphinWhite-beaked DolphinThe White-beaked dolphin is a marine mammal belonging to the family Delphinidae in the suborder Odontoceti .-Taxonomy:...
, Lagenorhynchus albirostris
- Atlantic white-sided dolphin
- Genus OrcaellaOrcaellaThe snubfin dolphins are a genus of dolphins containing two members: the Irrawaddy Dolphin and Australian Snubfin Dolphin. The genus was long believed to be monotypic with the only species being the Irrawaddy Dolphin; however, in 2005, genetic analysis showed that the Australian Snubfin Dolphin is...
- Irrawaddy dolphinIrrawaddy dolphinThe Irrawaddy dolphin is a euryhaline species of oceanic dolphin found in discontinuous subpopulations near sea coasts and in estuaries and rivers in parts of the Bay of Bengal and Southeast Asia.-Etymology and taxonomic history:...
, Orcaella brevirostris - Australian snubfin dolphinAustralian Snubfin DolphinThe Australian snubfin dolphin is a dolphin found off the northern coasts of Australia. It closely resembles the Irrawaddy dolphin and was not described as a separate species until 2005. The Australian snubfin is tri-coloured, while the Irrawaddy dolphin only has two colours on its skin...
, Orcaella heinsohni
- Irrawaddy dolphin
- Genus †AustralodelphisAustralodelphisAustralodelphis is an extinct Pliocene genus of dolphin with a single described species, Australodelphis mirus. The genus is known from fossils found in the Sørsdal Formation, Vestfold Hills, East Antarctica...
- †Australodelphis mirusAustralodelphisAustralodelphis is an extinct Pliocene genus of dolphin with a single described species, Australodelphis mirus. The genus is known from fossils found in the Sørsdal Formation, Vestfold Hills, East Antarctica...
- †Australodelphis mirus
- Genus †Etruridelphis
- †Etruridelphis giulii
- Genus Peponocephala
- Family Delphinidae
- Superfamily Delphinoidea
Recent molecular
Molecular phylogeny
Molecular phylogenetics is the analysis of hereditary molecular differences, mainly in DNA sequences, to gain information on an organism's evolutionary relationships. The result of a molecular phylogenetic analysis is expressed in a phylogenetic tree...
analyses indicate that several delphinid genera
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
(especially Stenella
Stenella
Stenella is a genus of aquatic mammals in Delphinidae, the family informally known as the oceanic dolphins.Currently five species are recognised in this genus:*Pantropical Spotted Dolphin, S. attenuata*Atlantic Spotted Dolphin, S. frontalis...
and Lagenorhynchus
Lagenorhynchus
Lagenorhynchus is a genus in the order Cetacea, traditionally containing six species:* white-beaked dolphin, Lagenorhynchus albirostris* Atlantic white-sided dolphin, Lagenorhynchus acutus...
) are not monophyletic
Monophyly
In common cladistic usage, a monophyletic group is a taxon which forms a clade, meaning that it contains all the descendants of the possibly hypothetical closest common ancestor of the members of the group. The term is synonymous with the uncommon term holophyly...
as currently recognized. Thus, the coming years will likely see significant taxonomic revisions within the family.