Dolphins are
marine mammalMarine mammals, which include seals, whales, dolphins, and walruses, form a diverse group of 128 species that rely on the ocean for their existence. They do not represent a distinct biological grouping, but rather are unified by their reliance on the marine environment for feeding. The level of...
s that are closely related to
whaleWhale 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
porpoisePorpoises 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. There are almost forty species of dolphin in 17
generaIn 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...
. They vary in size from 1.2 m (3.9 ft) and 40 kg (88.2 lb) (
Maui's dolphinMaui's dolphin is the world's smallest known species of dolphin. They are a sub-species of the Hector's dolphin....
), up to 9.5 m (31.2 ft) and 10 tonne (the orca or killer whale). They are found worldwide, mostly in the shallower seas of the continental shelves, and are carnivores, mostly eating
fishFish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
and
squidSquid are cephalopods of the order Teuthida, which comprises around 300 species. Like all other cephalopods, squid have a distinct head, bilateral symmetry, a mantle, and arms. Squid, like cuttlefish, have eight arms arranged in pairs and two, usually longer, tentacles...
. The
familyIn biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
DelphinidaeOceanic dolphins are the members of the Delphinidae family of cetaceans. These marine mammals are related to whales and porpoises. They are found worldwide, mostly in the shallower seas of the continental shelves...
is the largest in the
CetaceaThe 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...
n order, and evolved relatively recently, about ten million years ago, during the
MioceneThe Miocene is a geological epoch of the Neogene Period and extends from about . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene...
. Dolphins are among the most intelligent animals, and their often friendly appearance and seemingly playful attitude have made them popular in human culture.
Etymology
The name is originally from
GreekGreek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
(delphís), "dolphin", which was related to the Greek (delphus), "womb". The animal's name can therefore be interpreted as meaning "a 'fish' with a womb". The name was transmitted via the
LatinLatin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
delphinus (the
romanizationIn linguistics, romanization or latinization is the representation of a written word or spoken speech with the Roman script, or a system for doing so, where the original word or language uses a different writing system . Methods of romanization include transliteration, for representing written...
of the later Greek δελφῖνος - delphinos), which in Middle Latin became dolfinus and in
Old FrenchOld French was the Romance dialect continuum spoken in territories that span roughly the northern half of modern France and parts of modern Belgium and Switzerland from the 9th century to the 14th century...
daulphin, which reintroduced the ph into the word. The term
mereswine (that is, "sea pig") has also historically been used.
The word is used in a few different ways. It can mean:
- any member of the family Delphinidae (oceanic dolphins),
- any member of the families Delphinidae and Platanistoidea (oceanic and river dolphins),
- any member of the suborder Odontoceti (toothed whales; these include the above families and some others),
- and is used casually as a synonym for bottlenose dolphin
Bottlenose dolphins, the genus Tursiops, are the most common and well-known members of the family Delphinidae, the family of oceanic dolphins. Recent molecular studies show the genus contains two species, the common bottlenose dolphin and the Indo-Pacific bottlenose dolphin , instead of one...
, the most common and familiar species of dolphin.
This article uses the second definition and does not describe
porpoisePorpoises 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 (suborder Odontoceti, family Phocoenidae).
OrcaThe 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...
s and some closely related species belong to the Delphinidae family and therefore qualify as dolphins, even though they are called
whaleWhale 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 in common language. A group of dolphins is called a "school" or a "pod". Male dolphins are called "bulls", females "cows" and young dolphins are called "calves".
Taxonomy
- Suborder Odontoceti, toothed whales
- Family Delphinidae, oceanic dolphin
Oceanic dolphins are the members of the Delphinidae family of cetaceans. These marine mammals are related to whales and porpoises. They are found worldwide, mostly in the shallower seas of the continental shelves...
s
- Genus Delphinus
- Long-Beaked Common Dolphin
The 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 Dolphin
The 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
- Genus Tursiops
- Common Bottlenose Dolphin
Tursiops 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 Dolphin
The 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 Dolphin
The 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, a new discovered species from sea around MelbourneMelbourne is the capital and most populous city in the state of Victoria, and the second most populous city in Australia. The Melbourne City Centre is the hub of the greater metropolitan area and the Census statistical division—of which "Melbourne" is the common name. As of June 2009, the greater...
in September 2011.
- Genus Lissodelphis
- Northern Rightwhale Dolphin, Lissodelphis borealis
- Southern Rightwhale Dolphin, Lissodelphis peronii
- Genus Sotalia
- Tucuxi
The 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
- Costero
The 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
- Genus Sousa
- Indo-Pacific Hump-backed Dolphin, Sousa chinensis
- Chinese White Dolphin
The Chinese white dolphin is a humpback dolphin species, one of eighty cetacean species. An adult is white or pink and may appear as an albino dolphin to some. Uniquely, the population along the Chinese coast has pink skin. Pink skin is not pigment, but blood vessels for thermoregulation...
(the Chinese variant), Sousa chinensis chinensis
- Atlantic Humpbacked Dolphin, Sousa teuszii
- Genus 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...
- Atlantic Spotted Dolphin
The 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 Dolphin
The 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 Dolphin
The 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 Dolphin
The 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 Dolphin
The Striped Dolphin is an extensively studied dolphin that is found in temperate and tropical waters of all the world's oceans.-Taxonomy:...
, Stenella coeruleoalba
- Genus Steno
- Rough-Toothed Dolphin
The 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
- Genus Cephalorhynchus
Cephalorhynchus 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 Dolphin
The 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 Dolphin
Commerson'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 Dolphin
The 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 Dolphin
Hector'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
- Genus Grampus
- Risso's Dolphin
Risso'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
- Genus Lagenodelphis
- Fraser's Dolphin
Fraser'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
- Genus Lagenorhynchus
Lagenorhynchus 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 Dolphin
The 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 Dolphin
The 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 Dolphin
The hourglass dolphin is a small dolphin in the family Delphinidae that inhabits Antarctic and sub-Antarctic waters....
, Lagenorhynchus cruciger
- Pacific White-Sided Dolphin
The 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 Dolphin
Peale'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 Dolphin
The White-beaked dolphin is a marine mammal belonging to the family Delphinidae in the suborder Odontoceti .-Taxonomy:...
, Lagenorhynchus albirostris
- Genus Orcaella
The 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...
- Australian Snubfin Dolphin
The 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
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:...
, Orcaella brevirostris
- Genus Peponocephala
- 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...
, Peponocephala electra
- Genus Orcinus
- Killer Whale (Orca), Orcinus orca
- Genus Feresa
- 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...
, Feresa attenuata
- Genus Pseudorca
- 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...
, Pseudorca crassidens
- Genus Globicephala
- Long-finned Pilot Whale
The 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 Whale
The 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
- Genus †Australodelphis
Australodelphis 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
Australodelphis 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...
- Family Platanistidae
- Ganges and Indus River Dolphin
The South Asian River Dolphin is a freshwater or river dolphin found in India, Nepal and Pakistan which is split into two sub-species, the Ganges River Dolphin and Indus River Dolphin...
, Platanista gangetica with two subspecies
- Ganges River Dolphin (or Susu), Platanista gangetica gangetica
- Indus River Dolphin
The Indus River dolphin is a sub-species of freshwater or river dolphin found in the Indus River of Pakistan...
(or Bhulan), Platanista gangetica minor
- Family Iniidae
Iniidae is a family of river dolphins containing one living and three extinct genera.-Taxonomy:The family was described by John Edward Gray in 1846.Current classifications include a single living genera, Inia, with one species and three subspecies...
- Amazon River Dolphin (or Boto), Inia geoffrensis
- Family Lipotidae
- Baiji
Baiji may refer to:* The Baiji or Yangtze River Dolphin * Baiji, Iraq, a city of northern Iraq.* "Baiji" is the pinyin Romanization for Baekje....
(or Chinese River Dolphin), Lipotes vexillifer (possibly extinct, since December 2006)
- Family Pontoporiidae
- La Plata Dolphin
The La Plata Dolphin or Franciscana is found in coastal Atlantic waters of southeastern South America. Taxonomically it is a member of the river dolphin group and the only one that actually lives in the ocean and saltwater estuaries, rather than inhabiting exclusively freshwater...
(or Franciscana), Pontoporia blainvillei
Six species in the family Delphinidae are commonly called "whales", but genetically are dolphins. They are sometimes called blackfish.
- 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...
, Peponocephala electra
- Killer Whale (Orca), Orcinus orca
- 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...
, Feresa attenuata
- 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...
, Pseudorca crassidens
- Long-finned Pilot Whale
The 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 Whale
The 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
Hybridization
In 1933, three strange dolphins beached off the
IrishIreland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...
coast; they appeared to be hybrids between
Risso'sRisso'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...
and bottlenose dolphins. This mating was later repeated in captivity, producing a hybrid calf. In captivity, a bottlenose and a
rough-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...
produced hybrid offspring. A common-bottlenose hybrid lives at
SeaWorldSeaWorld is a United States chain of marine mammal parks, oceanariums, and animal theme parks owned by SeaWorld Parks & Entertainment. The parks feature captive orca, sea lion, and dolphin shows and zoological displays featuring various other marine animals. There are operations in Orlando,...
California. Other dolphin hybrids live in captivity around the world or have been reported in the wild, such as a bottlenose-
Atlantic spottedThe 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:...
hybrid. The best known hybrid is the
wolphinA Wholphin or Wolphin is a rare hybrid, born from a mating of a female Bottlenose Dolphin with a male false killer whale . The name implies a hybrid of whale and dolphin, although taxonomically, both are within the "oceanic dolphin" family, which is within the "toothed whale" suborder...
, a false killer whale-bottlenose dolphin hybrid. The wolphin is a fertile hybrid. Two wolphins currently live at the Sea Life Park in
HawaiiHawaii is the newest of the 50 U.S. states , and is the only U.S. state made up entirely of islands. It is the northernmost island group in Polynesia, occupying most of an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of...
; the first was born in 1985 from a male false killer whale and a female bottlenose. Wolphins have also been observed in the wild.
Evolution and anatomy
Evolution
Dolphins, along with whales and porpoises, are descendants of terrestrial mammals, most likely of the Artiodactyl
orderIn scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
. The ancestors of the modern day dolphins entered the water roughly 50 million years ago, in the
EoceneThe Eocene Epoch, lasting from about 56 to 34 million years ago , is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era. The Eocene spans the time from the end of the Palaeocene Epoch to the beginning of the Oligocene Epoch. The start of the...
epoch.
Modern dolphin
skeletonThe skeleton is the body part that forms the supporting structure of an organism. There are two different skeletal types: the exoskeleton, which is the stable outer shell of an organism, and the endoskeleton, which forms the support structure inside the body.In a figurative sense, skeleton can...
s have two small, rod-shaped pelvic bones thought to be vestigial hind limbs. In October 2006, an unusual bottlenose dolphin was captured in
JapanJapan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
; it had small
finA fin is a surface used for stability and/or to produce lift and thrust or to steer while traveling in water, air, or other fluid media, . The first use of the word was for the limbs of fish, but has been extended to include other animal limbs and man-made devices...
s on each side of its genital slit, which scientists believe to be a more pronounced development of these vestigial hind limbs.
Anatomy
Dolphins have a streamlined fusiform body, adapted for fast swimming. The tail fin, called the fluke, is used for
propulsionAnimal locomotion, which is the act of self-propulsion by an animal, has many manifestations, including running, swimming, jumping and flying. Animals move for a variety of reasons, such as to find food, a mate, or a suitable microhabitat, and to escape predators...
, while the pectoral fins together with the entire tail section provide directional control. The
dorsal finA dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...
, in those species that have one, provides stability while swimming. Though it varies by species, basic coloration patterns are shades of grey, usually with a lighter underside, often with lines and patches of different hue and contrast.
The head contains the
melonThe 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....
, a round organ used for
echolocationEcholocation, 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...
. In many species, elongated jaws form a distinct beak; species such as the bottlenose have a curved mouth which looks like a fixed smile. Some species have up to 250 teeth. Dolphins breathe through a
blowholeIn biology, a blowhole is the hole at the top of a cetacean's head through which the animal breathes air. It is homologous with the nostril of other mammals. As whales reach the water surface to breathe, they will forcefully expel air through the blowhole. Not only is air expelled, but mucus and...
on top of their head. The
tracheaIn tetrapod anatomy the trachea, or windpipe, is a tube that connects the pharynx or larynx to the lungs, allowing the passage of air. It is lined with pseudostratified ciliated columnar epithelium cells with goblet cells that produce mucus...
is anterior to the brain. The dolphin brain is large and highly complex, and is different in structure from that of most land mammals.
Unlike most mammals, dolphins do not have hair, except for a few hairs around the tip of their
rostrumThe term rostrum is used for a number of unrelated structures in different groups of animals:*In crustaceans, the rostrum is the forward extension of the carapace in front of the eyes....
which they lose shortly before or after birth. The only exception to this is the
Boto river dolphinThe Amazon river dolphin, alternatively Bufeo, Bufeo Colorado, Boto Cor de Rosa, Boutu, Nay, Tonina, or Pink Dolphin , is a freshwater river dolphin endemic to the Orinoco, Amazon and Araguaia/Tocantins River systems of Brazil, Bolivia, Peru, Ecuador, Colombia and Venezuela...
, which has persistent small hairs on the rostrum.
Dolphins' reproductive organs are located on the underside of the body. Males have two slits, one concealing the
penisThe penis is a biological feature of male animals including both vertebrates and invertebrates...
and one further behind for the
anusThe anus is an opening at the opposite end of an animal's digestive tract from the mouth. Its function is to control the expulsion of feces, unwanted semi-solid matter produced during digestion, which, depending on the type of animal, may be one or more of: matter which the animal cannot digest,...
. The female has one genital slit, housing the
vaginaThe vagina is a fibromuscular tubular tract leading from the uterus to the exterior of the body in female placental mammals and marsupials, or to the cloaca in female birds, monotremes, and some reptiles. Female insects and other invertebrates also have a vagina, which is the terminal part of the...
and the
anusThe anus is an opening at the opposite end of an animal's digestive tract from the mouth. Its function is to control the expulsion of feces, unwanted semi-solid matter produced during digestion, which, depending on the type of animal, may be one or more of: matter which the animal cannot digest,...
. Two
mammary slitsA mammary gland is an organ in mammals that produces milk to feed young offspring. Mammals get their name from the word "mammary". In ruminants such as cows, goats, and deer, the mammary glands are contained in their udders...
are positioned on either side of the female's genital slit.
Though the exact methods used to achieve this are not known, dolphins can tolerate and recover from extreme injuries, such as
sharkSharks are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 420 million years ago....
bites. The
healingPhysiological healing is the restoration of damaged living tissue, organs and biological system to normal function. It is the process by which the cells in the body regenerate and repair to reduce the size of a damaged or necrotic area....
process is rapid and even very deep wounds do not cause dolphins to hemorrhage to death. Furthermore, even gaping wounds restore in such a way that the animal's body
contourContour may refer to:* an outline or silhouette* a contour line on a contour map, or the corresponding line on the ground or sea bed* Contour , a phonetic sound* Pitch contour , a melody shape...
is restored, and
infectionAn infection is the colonization of a host organism by parasite species. Infecting parasites seek to use the host's resources to reproduce, often resulting in disease...
of such large wounds seems rare.
A study at the U.S. National Marine Mammal Foundation revealed that dolphins, like humans, develop a natural form of
type 2 diabetesDiabetes mellitus, often simply referred to as diabetes, is a group of metabolic diseases in which a person has high blood sugar, either because the body does not produce enough insulin, or because cells do not respond to the insulin that is produced...
, which may lead to a better understanding of the disease and new treatments for both humans and dolphins.
Senses
Most dolphins have acute eyesight, both in and out of the water, and they can hear frequencies ten times or more above the upper limit of adult human hearing. Though they have a small ear opening on each side of their head, it is believed hearing underwater is also, if not exclusively, done with the lower jaw, which conducts sound to the
middle earThe middle ear is the portion of the ear internal to the eardrum, and external to the oval window of the cochlea. The mammalian middle ear contains three ossicles, which couple vibration of the eardrum into waves in the fluid and membranes of the inner ear. The hollow space of the middle ear has...
via a fat-filled cavity in the lower jaw bone. Hearing is also used for
echolocationEcholocation, 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...
, which all dolphins have. Dolphin teeth are believed to function as antennae to receive incoming sound and to pinpoint the exact location of an object. Beyond locating an object, echolocation also provides the animal with an idea on the object's shape and size, though how exactly this works is not yet understood.
The dolphin's sense of touch is also well-developed, with free nerve endings densely packed in the skin, especially around the snout, pectoral fins and genital area. However, dolphins lack an
olfactory nerveThe olfactory nerve, or cranial nerve I, is the first of twelve cranial nerves. It is instrumental in the sense of smell. Derived from the embryonic nasal placode, the olfactory nerve is capable of regeneration.-Anatomy:...
and lobes, and thus are believed to have no sense of smell. They do have a sense of
tasteTaste is one of the traditional five senses. It refers to the ability to detect the flavor of substances such as food, certain minerals, and poisons, etc....
and show preferences for certain kinds of fish. Since dolphins spend most of their time below the surface, tasting the water could function like smelling, in that substances in the water can signal the presence of objects that are not in the dolphin’s mouth.
Though most dolphins do not have hair, they do have
hair follicleA hair follicle is a skin organ that produces hair. Hair production occurs in phases, including a growth phase , and cessation phase , and a rest phase . Stem cells are principally responsible for the production of hair....
s that may perform some sensory function. The small hairs on the rostrum of the Boto river dolphin are believed to function as a
tactile senseThe somatosensory system is a diverse sensory system composed of the receptors and processing centres to produce the sensory modalities such as touch, temperature, proprioception , and nociception . The sensory receptors cover the skin and epithelia, skeletal muscles, bones and joints, internal...
possibly to compensate for the Boto's poor eyesight.
Behavior
Dolphins are often regarded as one of Earth's most intelligent animals, though it is hard to say just how intelligent. Comparing species' relative intelligence is complicated by differences in sensory apparatus, response modes, and nature of cognition. Furthermore, the difficulty and expense of experimental work with large aquatic animals has so far prevented some tests and limited sample size and rigor in others. Compared to many other species, however, dolphin behavior has been studied extensively, both in captivity and in the wild. See
cetacean intelligenceCetacean intelligence denotes the cognitive capabilities of the Cetacea order of mammals, which includes whales, porpoises, and dolphins.-Brain size:...
for more details.
Social behavior
Dolphins are social, living in pods of up to a dozen individuals. In places with a high abundance of food, pods can merge temporarily, forming a
superpod; such groupings may exceed 1,000 dolphins. Individuals communicate using a variety of clicks, whistles-like sounds and other vocalizations. Membership in pods is not rigid; interchange is common. However, dolphins can establish strong social bonds; they will stay with injured or ill individuals, even helping them to breathe by bringing them to the surface if needed. This
altruismAltruism is a concern for the welfare of others. It is a traditional virtue in many cultures, and a core aspect of various religious traditions, though the concept of 'others' toward whom concern should be directed can vary among cultures and religions. Altruism is the opposite of...
does not appear to be limited to their own species however. The dolphin
MokoMoko was a male bottlenose dolphin who associated with humans on the east coast of the North Island of New Zealand from 2007 to 2010.Moko, short for Mokotahi, a headland on Mahia Peninsula, was three-years-old as of July 2009. He resided at Mahia Beach for two and a half years from 2007 to...
in
New ZealandNew Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
has been observed guiding a female
Pygmy Sperm WhaleThe Pygmy Sperm Whale is one of three species of toothed whale in the sperm whale family. They are not often sighted at sea, and most of what is known about them comes from the examination of stranded specimens.-Taxonomy:...
together with her calf out of shallow water where they had stranded several times. They have also been seen protecting swimmers from sharks by swimming circles around the swimmers or charging the sharks to make them go away.
Dolphins also display
cultureCulture is a term that has many different inter-related meanings. For example, in 1952, Alfred Kroeber and Clyde Kluckhohn compiled a list of 164 definitions of "culture" in Culture: A Critical Review of Concepts and Definitions...
, something long believed to be unique to humans (and possibly other
primateA primate is a mammal of the order Primates , which contains prosimians and simians. Primates arose from ancestors that lived in the trees of tropical forests; many primate characteristics represent adaptations to life in this challenging three-dimensional environment...
species). In May 2005, a discovery in Australia found
Indo-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...
s (Tursiops aduncus) teaching their young to use tools. They cover their
snoutThe snout, or muzzle, is the protruding portion of an animal's face, consisting of its nose, mouth, and jaw.-Terminology:The term "muzzle", used as a noun, can be ambiguous...
s with
spongesSponges are animals of the phylum Porifera . Their bodies consist of jelly-like mesohyl sandwiched between two thin layers of cells. While all animals have unspecialized cells that can transform into specialized cells, sponges are unique in having some specialized cells, but can also have...
to protect them while foraging. This knowledge is mostly transferred by mothers to daughters, unlike
simianThe simians are the "higher primates" familiar to most people: the Old World monkeys and apes, including humans, , and the New World monkeys or platyrrhines. Simians tend to be larger than the "lower primates" or prosimians.- Classification and evolution :The simians are split into three groups...
primates, where knowledge is generally passed on to both sexes. Using sponges as mouth protection is a learned behavior. Another learned behavior was discovered among river dolphins in Brazil, where some male dolphins use weeds and sticks as part of a sexual display.
Dolphins engage in acts of aggression towards each other. The older a male dolphin is, the more likely his body is to be covered with bite scars. Male dolphins engage in such acts of aggression apparently for the same reasons as humans: disputes between companions and competition for females. Acts of aggression can become so intense that targeted dolphins sometimes go into exile as a result of losing a fight.
Male bottlenose dolphins have been known to engage in
infanticideIn animals, infanticide involves the killing of young offspring by a mature animal of its own species, and is studied in zoology, specifically in the field of ethology. Ovicide is the analogous destruction of eggs. Although human infanticide has been widely studied, the practice has been observed...
. Dolphins have also been known to kill porpoises for reasons which are not fully understood, as porpoises generally do not share the same diet as dolphins, and are therefore not competitors for food supplies.
Reproduction and sexuality
Dolphin copulation happens belly to belly; though many species engage in lengthy
foreplayIn human sexual behavior, foreplay is a set of intimate psychological and physically intimate acts between two or more people meant to create desire for sexual activity and sexual arousal. Either or any of the sexual partners may initiate the foreplay, and they may not be the active partner during...
, the actual act is usually brief, but may be repeated several times within a short timespan. The
gestation periodFor mammals the gestation period is the time in which a fetus develops, beginning with fertilization and ending at birth. The duration of this period varies between species.-Duration:...
varies with species; for the small Tucuxi dolphin, this period is around 11 to 12 months, while for the orca, the gestation period is around 17 months. They usually become sexually active at a young age, even before reaching
sexual maturitySexual maturity is the age or stage when an organism can reproduce. It is sometimes considered synonymous with adulthood, though the two are distinct...
. The age of sexual maturity varies by species and gender.
Dolphins are known to have sex for reasons other than reproduction, sometimes also engaging in homosexual behavior. Various species sometimes engage in sexual behavior including copulation with other dolphin species. Sexual encounters may be violent, with male dolphins sometimes showing aggressive behavior towards both females and other males. Occasionally, dolphins behave sexually towards other animals, including humans.
Feeding
Various methods of feeding exist among and within species, some apparently exclusive to a single population. Fish and squid are the main food, but the false killer whale and the orca also feed on other marine mammals.
One common feeding method is herding, where a pod squeezes a school of fish into a small volume, known as a
bait ballA bait ball, or baitball, occurs when small fish swarm in a tightly packed spherical formation about a common centre. It is a last ditch defensive measure adopted by small schooling fish when they are threatened by predators...
. Individual members then take turns plowing through the ball, feeding on the stunned fish. Coralling is a method where dolphins chase fish into shallow water to more easily catch them. In
South CarolinaSouth Carolina is a state in the Deep South of the United States that borders Georgia to the south, North Carolina to the north, and the Atlantic Ocean to the east. Originally part of the Province of Carolina, the Province of South Carolina was one of the 13 colonies that declared independence...
, the Atlantic bottlenose dolphin takes this further with "strand feeding", driving prey onto mud banks for easy access. In some places, orcas come to the beach to capture
sea lionSea lions are pinnipeds characterized by external ear-flaps, long fore-flippers, the ability to walk on all fours, and short thick hair. Together with the fur seal, they comprise the family Otariidae, or eared seals. There are six extant and one extinct species in five genera...
s. Some species also whack fish with their flukes, stunning them and sometimes knocking them out of the water.
Reports of cooperative human-dolphin fishing date back to the
ancient RomanAncient Rome was a thriving civilization that grew on the Italian Peninsula as early as the 8th century BC. Located along the Mediterranean Sea and centered on the city of Rome, it expanded to one of the largest empires in the ancient world....
author and
natural philosopherNatural philosophy or the philosophy of nature , is a term applied to the study of nature and the physical universe that was dominant before the development of modern science...
Pliny the ElderGaius Plinius Secundus , better known as Pliny the Elder, was a Roman author, naturalist, and natural philosopher, as well as naval and army commander of the early Roman Empire, and personal friend of the emperor Vespasian...
. A modern human-dolphin partnership currently operates in Laguna,
Santa CatarinaSanta Catarina is a state in southern Brazil with one of the highest standards of living in Latin America. Its capital is Florianópolis, which mostly lies on the Santa Catarina Island. Neighbouring states are Rio Grande do Sul to the south and Paraná to the north. It is bounded on the east by...
,
BrazilBrazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
. Here, dolphins drive fish towards fishermen waiting along the shore and signal the men to cast their nets. The dolphins’ reward is the fish that escape the nets.
Vocalizations
Dolphins are capable of making a broad range of sounds using nasal airsacs located just below the blowhole. Roughly three categories of sounds can be identified: frequency modulated whistles, burst-pulsed sounds and clicks. Dolphins communicate with whistle-like sounds produced by vibrating connective tissue, similar to how human vocal cords function, and through burst-pulsed sounds, though the nature and extent of that ability is not known. The clicks are directional and are for echolocation, often occurring in a short series called a click train. The click rate increases when approaching an object of interest. Dolphin echolocation clicks are amongst the loudest sounds made by marine animals.
Jumping and playing
Dolphins occasionally leap above the water surface, and sometimes perform acrobatic figures (for example, the
spinner 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:...
). Scientists are not certain about the purpose(s) of the acrobatics. Possibilities include locating schools of fish by looking at above-water signs like feeding birds, communicating with other dolphins, dislodging parasites or simple amusement.
Play is an important part of dolphin culture. Dolphins play with
seaweedSeaweed is a loose, colloquial term encompassing macroscopic, multicellular, benthic marine algae. The term includes some members of the red, brown and green algae...
and play-fight with other dolphins. At times they harass other local creatures, like
seabirdSeabirds are birds that have adapted to life within the marine environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent evolution, as the same environmental problems and feeding niches have resulted in similar adaptations...
s and
turtleTurtles are reptiles of the order Testudines , characterised by a special bony or cartilaginous shell developed from their ribs that acts as a shield...
s. Dolphins enjoy riding waves and frequently surf coastal swells and the
bow waveA bow wave is the wave that forms at the bow of a ship when it moves through the water. As the bow wave spreads out, it defines the outer limits of a ship's wake. A large bow wave slows the ship down, poses a risk to smaller boats, and in a harbor can cause damage to shore facilities and moored ships...
s of boats, at times “leaping” between the dual bow waves of a moving catamaran. Occasionally, they playfully interact with swimmers. Captive dolphins have been observed in aquariums engaging in complex play behavior which involves the creation and manipulation of
bubble ringA bubble ring, or ring bubble, is an underwater ring vortex where an air bubble occupies the core of the vortex, forming a ring shape. The ring of air as well as the nearby water spins poloidally as it travels through the water, much like a flexible bracelet might spin when it is rolled on to a...
s.
Sleeping
Generally, dolphins sleep with only one brain
hemisphereA cerebral hemisphere is one of the two regions of the eutherian brain that are delineated by the median plane, . The brain can thus be described as being divided into left and right cerebral hemispheres. Each of these hemispheres has an outer layer of grey matter called the cerebral cortex that is...
in
slow-wave sleepSlow-wave sleep , often referred to as deep sleep, consists of stages 3 and 4 of non-rapid eye movement sleep, according to the Rechtschaffen & Kales standard of 1968. As of 2008, the American Academy of Sleep Medicine has discontinued the use of stage 4, such that the previous stages 3 and 4 now...
at a time, thus maintaining enough consciousness to breathe and to watch for possible predators and other threats. Earlier sleep stages can occur simultaneously in both hemispheres.
In captivity, dolphins seemingly enter a fully asleep state where both eyes are closed and there is no response to mild external stimuli. In this case respiration is automatic; a tail kick
reflexA reflex action, also known as a reflex, is an involuntary and nearly instantaneous movement in response to a stimulus. A true reflex is a behavior which is mediated via the reflex arc; this does not apply to casual uses of the term 'reflex'.-See also:...
keeps the blowhole above the water if necessary.
AnesthetizedAnesthesia, or anaesthesia , traditionally meant the condition of having sensation blocked or temporarily taken away...
dolphins initially show a tail kick reflex. Though a similar state has been observed with wild
Sperm WhaleThe sperm whale, Physeter macrocephalus, is a marine mammal species, order Cetacea, a toothed whale having the largest brain of any animal. The name comes from the milky-white waxy substance, spermaceti, found in the animal's head. The sperm whale is the only living member of genus Physeter...
s, it is not known if dolphins in the wild reach this state. The
Indus river dolphinThe Indus River dolphin is a sub-species of freshwater or river dolphin found in the Indus River of Pakistan...
has a different sleep method from other dolphin species. Living in water with strong currents and potentially dangerous floating debris, it must swim continuously to avoid injury. As a result, this species sleeps in very short bursts which last between 4 and 60 seconds.
Natural threats
Except for humans (discussed below), dolphins have few natural enemies. Some species or specific populations have none, making them
apex predatorApex predators are predators that have no predators of their own, residing at the top of their food chain. Zoologists define predation as the killing and consumption of another organism...
s. For most of the smaller species of dolphins, only a few of the larger sharks, such as the
bull sharkThe bull shark, Carcharhinus leucas, also known as Zambezi shark or unofficially known as Zambi in Africa and Nicaragua shark in Nicaragua, is a shark common worldwide in warm, shallow waters along coasts and in rivers...
,
dusky sharkThe dusky shark is a species of requiem shark, family Carcharhinidae, occurring in tropical and warm-temperate continental seas worldwide. A generalist apex predator, the dusky shark can be found from the coast to the outer continental shelf and adjacent pelagic waters, and has been recorded from...
,
tiger sharkThe tiger sharks, Galeocerdo cuvier, is a species of requiem shark and the only member of the genus Galeocerdo. Commonly known as sea tigers, tiger sharks are relatively large macropredators, capable of attaining a length of over . It is found in many tropical and temperate waters, and is...
and
great white sharkThe great white shark, scientific name Carcharodon carcharias, also known as the great white, white pointer, white shark, or white death, is a large lamniform shark found in coastal surface waters in all major oceans. It is known for its size, with the largest individuals known to have approached...
are a potential risk, especially for calves. Some of the larger dolphinic species, especially orcas (killer whales), may also prey on smaller dolphins, but this seems rare. Dolphins also suffer from a wide variety of
diseaseA disease is an abnormal condition affecting the body of an organism. It is often construed to be a medical condition associated with specific symptoms and signs. It may be caused by external factors, such as infectious disease, or it may be caused by internal dysfunctions, such as autoimmune...
s and parasites.
Human threats
Some dolphin species face an uncertain future, especially some river dolphin species such as the Amazon river dolphin, and the Ganges and
Yangtze river dolphinBaiji may refer to:* The Baiji or Yangtze River Dolphin * Baiji, Iraq, a city of northern Iraq.* "Baiji" is the pinyin Romanization for Baekje....
, which are critically or seriously endangered. A 2006 survey found no individuals of the Yangtze river dolphin, which now appears to be functionally extinct.
Pesticides, heavy metals, plastics, and other industrial and agricultural pollutants that do not disintegrate rapidly in the environment concentrate in predators such as dolphins. Injuries or deaths due to collisions with boats, especially their
propellerA propeller is a type of fan that transmits power by converting rotational motion into thrust. A pressure difference is produced between the forward and rear surfaces of the airfoil-shaped blade, and a fluid is accelerated behind the blade. Propeller dynamics can be modeled by both Bernoulli's...
s, are also common.
Various fishing methods, most notably purse seine fishing for
tunaTuna is a salt water fish from the family Scombridae, mostly in the genus Thunnus. Tuna are fast swimmers, and some species are capable of speeds of . Unlike most fish, which have white flesh, the muscle tissue of tuna ranges from pink to dark red. The red coloration derives from myoglobin, an...
and the use of
driftDrift netting is a fishing technique where nets, called drift nets, are allowed to float freely at the surface of a sea or lake. Usually a drift net is a gill net with floats attached to a rope along the top of the net, and weights attached to another rope along the foot of the net to keep the net...
and gill nets, unintentionally kill many dolphins. Accidental
by-catchThe term “bycatch” is usually used for fish caught unintentionally in a fishery while intending to catch other fish. It may however also indicate untargeted catch in other forms of animal harvesting or collecting...
in gill nets and incidental captures in antipredator nets that protect marine fish farms are common and pose a risk for mainly local dolphin populations. In some parts of the world, such as
Taijiis a town located in Higashimuro District, Wakayama, Japan.As of 1 January 2011, the town has an estimated population of 3,225 and a population density of 541 persons per km². The total area is 5.96 km². Taiji is the smallest local government by area in Wakayama Prefecture because, unlike others,...
in Japan and the Faroe Islands, dolphins are traditionally considered as food, and are killed in
harpoonA harpoon is a long spear-like instrument used in fishing to catch fish or large marine mammals such as whales. It accomplishes this task by impaling the target animal, allowing the fishermen to use a rope or chain attached to the butt of the projectile to catch the animal...
or
drive huntsDolphin drive hunting, also called dolphin drive fishing, is a method of hunting dolphins and occasionally other small cetaceans by driving them together with boats and then usually into a bay or onto a beach. Their escape is prevented by closing off the route to the open sea or ocean with boats...
. Dolphin meat is high in mercury, and may thus pose a health danger to humans when consumed.
Dolphin safe labelThere are various dolphin safe labels used for canned tuna to imply that the fish has been caught without harming or killing dolphins. However, because there are various labels used, there are also various restrictions imposed on the capture of tuna in order for it to deserve the related dolphin...
s attempt to reassure consumers fish and other marine products have been caught in a dolphin-friendly way. The original deal with "Dolphin safe" labels was brokered in the 1980s between marine activists and the major tuna companies, and involved decreasing incidental dolphin kills by up to 50% by changing the type of nets being used to catch the tuna. It should be noted that the dolphins are only netted while fishermen are in pursuit of smaller tuna. Albacore are not netted this way, which makes albacore the only truly dolphin-safe tuna.
Loud underwater noises, such as those resulting from
navalA navy is the branch of a nation's armed forces principally designated for naval and amphibious warfare; namely, lake- or ocean-borne combat operations and related functions...
sonarSonar is a technique that uses sound propagation to navigate, communicate with or detect other vessels...
use, live firing exercises, or certain
offshore constructionOffshore construction is the installation of structures and facilities in a marine environment, usually for the production and transmission of electricity, oil, gas and other resources....
projects, such as
wind farmA wind farm is a group of wind turbines in the same location used to produce electric power. A large wind farm may consist of several hundred individual wind turbines, and cover an extended area of hundreds of square miles, but the land between the turbines may be used for agricultural or other...
s, may be harmful to dolphins, increasing stress, damaging hearing, and causing
decompression sicknessDecompression sickness describes a condition arising from dissolved gases coming out of solution into bubbles inside the body on depressurization...
by forcing them to surface too quickly to escape the noise.
Mythology
Dolphins have long played a role in human culture. Dolphins are common in
Greek mythologyGreek mythology is the body of myths and legends belonging to the ancient Greeks, concerning their gods and heroes, the nature of the world, and the origins and significance of their own cult and ritual practices. They were a part of religion in ancient Greece...
and there are many coins from ancient Greece which feature a man or boy or deity riding on the back of a dolphin. The
Ancient GreeksAncient Greece is a civilization belonging to a period of Greek history that lasted from the Archaic period of the 8th to 6th centuries BC to the end of antiquity. Immediately following this period was the beginning of the Early Middle Ages and the Byzantine era. Included in Ancient Greece is the...
welcomed dolphins; spotting dolphins riding in a ship’s wake was considered a good omen. In
Hindu mythologyHindu religious literature is the large body of traditional narratives related to Hinduism, notably as contained in Sanskrit literature, such as the Sanskrit epics and the Puranas. As such, it is a subset of Nepali and Indian culture...
, the Ganges River Dolphin is associated with
GangaIn Hinduism, the river Ganges - referred to as Gaṅgā in the Hindu context and India - is considered sacred. The river, personified as a goddess, is worshipped by Hindus, who believe that bathing in the river causes the remission of sins and facilitates liberation from the cycle of life and death...
, the deity of the Ganges river.
Popular culture
In more recent times, the 1963 film
FlipperFlipper is an American feature film released on August 14, 1963 written by Ricou Browning and Jack Cowden. Produced by Ivan Tors and directed by James B. Clark, it portrays a 12-year old boy living with his parents on the Florida Keys, who befriends an injured wild dolphin...
and the subsequent 1964
television seriesFlipper, from Ivan Tors Films in association with Metro-Goldwyn-Mayer Television, is an American television program first broadcast on NBC from September 19, 1964, until April 15, 1967. Flipper, a bottlenose dolphin, is the companion animal of Porter Ricks, Chief Warden at fictional Coral Key Park...
popularized dolphins in
Western societyThe Western world, also known as the West and the Occident , is a term referring to the countries of Western Europe , the countries of the Americas, as well all countries of Northern and Central Europe, Australia and New Zealand...
. The series, created by
Ivan TorsIvan Tors was a Hungarian playwright, film director, screenwriter, and film and television producer with an emphasis on non-violent but exciting science fiction, underwater filmed television and films, and films about animals...
, portrayed a dolphin as a kind of seagoing version of
LassieLassie is an American television series that follows the adventures of a female Rough Collie named Lassie and her companions, human and animal. The show was the creation of producer Robert Maxwell and animal trainer Rudd Weatherwax and was televised from September 12, 1954, to March 24, 1973...
, the collie made popular in the 1950s TV series. Flipper was a Bottlenose Dolphin who understood commands and always behaved heroically.
FlipperFlipper is a 1996 remake of the 1963 film of the same name, starring Paul Hogan and Elijah Wood. The movie is about a boy who has to spend the summer with his uncle Porter , who lives in the Florida Keys...
was remade as a film in 1996.
The 1973 movie
The Day of the DolphinThe Day of the Dolphin is a 1973 American science-fiction thriller film directed by Mike Nichols and starring George C. Scott. Loosely based on the 1967 novel, Un animal doué de raison , by French writer Robert Merle, the screenplay was written by Buck Henry.-Plot:A brilliant and driven scientist,...
portrayed kidnapped dolphins performing a naval military
assassinationTo carry out an assassination is "to murder by a sudden and/or secret attack, often for political reasons." Alternatively, assassination may be defined as "the act of deliberately killing someone, especially a public figure, usually for hire or for political reasons."An assassination may be...
using explosives. This was also explored in the similarly named The Simpsons Treehouse of Horror episode, "Night of the Dolphin", where Lisa frees a dolphin at a aquarium exhibit and unwittingly initiates their plan to overthrow the land-dwellers and live in their place. The 1990s science fiction television series
seaQuest DSVseaQuest DSV is an American science fiction television series created by Rockne S. O'Bannon. It originally aired on NBC between 1993 and 1996. In its final season, it was renamed seaQuest 2032. Set in "the near future", seaQuest mixes high drama with realistic scientific fiction...
featured a bottle-nose named Darwin who could communicate using a
vocoderA vocoder is an analysis/synthesis system, mostly used for speech. In the encoder, the input is passed through a multiband filter, each band is passed through an envelope follower, and the control signals from the envelope followers are communicated to the decoder...
, a fictional invention which translated clicks and whistles to English and back.
In
The Hitchhiker's Guide to the GalaxyThe Hitchhiker's Guide to the Galaxy is a science fiction comedy series created by Douglas Adams. Originally a radio comedy broadcast on BBC Radio 4 in 1978, it was later adapted to other formats, and over several years it gradually became an international multi-media phenomenon...
book series, dolphins are the second most intelligent species on Earth (after mice).
Killer whales have also been portrayed in film, though to a lesser extent than bottlenosed dolphins. The 1977 horror movie
OrcaOrca is a 1977 horror film directed by Michael Anderson and produced by Dino De Laurentiis, starring Richard Harris, Charlotte Rampling, and Will Sampson. The film was poorly received by critics and audiences alike due in part to its similarities to the film Jaws released two years prior...
portrayed killer whales as intelligent and capable of pair-bonding and aggressive behavior. In the movie, a male killer whale takes revenge on fishermen after they kill his mate. The 1993 movie
Free WillyFree Willy is a 1993 family film directed by Simon Wincer, and released by Warner Bros. under its Family Entertainment label. The film stars Jason James Richter as a young boy who befriends an orca whale, named "Willy."...
made a star of the Orca playing Willy,
KeikoKeiko was a male orca / actor who starred in the film Free Willy and was perhaps the most famous of captive orcas.- History :...
.
Dolphinaria
The renewed popularity of dolphins in the 1960s resulted in the appearance of many
dolphinariaA dolphinarium is an aquarium for dolphins. The dolphins are usually kept in a large pool, though occasionally they may be kept in pens in the open sea, either for research or for public performances...
around the world, making dolphins accessible to the public. Criticism and
animal welfareAnimal welfare is the physical and psychological well-being of animals.The term animal welfare can also mean human concern for animal welfare or a position in a debate on animal ethics and animal rights...
laws forced many to close, although hundreds still exist around the world. In the
United StatesThe United States of America is a federal constitutional republic comprising fifty states and a federal district...
, the best known are the
SeaWorldSeaWorld is a United States chain of marine mammal parks, oceanariums, and animal theme parks owned by SeaWorld Parks & Entertainment. The parks feature captive orca, sea lion, and dolphin shows and zoological displays featuring various other marine animals. There are operations in Orlando,...
marine mammal parkA marine mammal park is a commercial theme park or aquarium where marine mammals such as dolphins, beluga whales and sea lions are kept within water tanks and displayed to the public in special shows. A marine mammal park is more elaborate than a dolphinarium, because it also features other marine...
s.
Welfare
Organizations such as the
Mote Marine LaboratoryMote Marine Laboratory is an independent not-for-profit marine research organization based on City Island in Sarasota, FL. The laboratory aims to advance the science of the sea, both through its marine and estuarine research labs and through the public Mote Aquarium and its affiliated educational...
rescue and
rehabilitateWildlife rehabilitation is the process of removing from the wild and caring for injured, orphaned, or sick wild animals. The goal of wildlife rehabilitation is to provide the food, housing and medical care of these animals, returning them to the wild after treatment.-Process:Rehabilitation begins...
sick, wounded, stranded or orphaned dolphins, while others, such as the
Whale and Dolphin Conservation Societythe Whale and Dolphin Conservation Society is a wildlife charity that is dedicated solely to the worldwide conservation and welfare of all whales, dolphins and porpoises...
and
Hong Kong Dolphin Conservation SocietyThe Hong Kong Dolphin Conservation Society is a non-governmental organization that is dedicated to the conservation of whales, and dolphins and porpoises in Hong Kong...
, work on dolphin conservation and welfare.
IndiaIndia , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
has declared the Dolphin as their national aquatic animal in an attempt to protect the
endangeredAn endangered species is a population of organisms which is at risk of becoming extinct because it is either few in numbers, or threatened by changing environmental or predation parameters...
Ganges River Dolphin. The
Vikramshila Gangetic Dolphin SanctuaryVikramshila Gangetic Dolphin Sanctuary is located in Bhagalpur District of Bihar, India. The sanctuary is a 50 km stretch of the Ganges River from Sultanganj to Kahalgaon. Designated in 1991, it is the only protected area for the endangered Gangetic dolphins in Asia...
has been created in the Ganges river for the protection of the animals.
Various scientists to have researched Dolphin behaviour have proposed that their unusually high intelligence compared to other animals means that dolphins should be seen as non-human persons that should have their own specific rights, and that it is
morallyMorality is the differentiation among intentions, decisions, and actions between those that are good and bad . A moral code is a system of morality and a moral is any one practice or teaching within a moral code...
unacceptable to keep them captive for entertainment purposes, or to kill them; either intentionally for consumption or as by-catch.
Attack on humans
Although dolphins generally interact well with humans, some attacks have occurred, most of them with small injuries. The attacks can occur both in the wild and captivity.
OrcaThe 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...
s, the largest species of dolphin, have been involved in fatal
attacks on humansKiller whales are powerful predators capable of dispatching prey much larger than humans, such as leopard seals and great white sharks. They have also been recorded preying on usually terrestrial species such as moose swimming between islands...
in captivity. The record-holder of documented orca fatal attacks is a male named
TilikumTilikum , sometimes misspelled Tillikum, is a bull orca who lives in captivity at SeaWorld Orlando. He has sired many offspring, and has been involved in the deaths of three people. Following a year long hiatus after his last incident, Tilikum returned to performing at SeaWorld Orlando on 30 March...
, that belongs to
SeaWorldSeaWorld is a United States chain of marine mammal parks, oceanariums, and animal theme parks owned by SeaWorld Parks & Entertainment. The parks feature captive orca, sea lion, and dolphin shows and zoological displays featuring various other marine animals. There are operations in Orlando,...
and has played a role in the death of three people in three different incidents (1991, 1999 and 2010). There are documented incidents in the wild too, but none of them fatal.
Fatal attacks from other species are less common, but there is a registered occurrence in the coast of
BrazilBrazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
in 1994, when a man died after injuries suffered during a
bottlenose dolphinBottlenose dolphins, the genus Tursiops, are the most common and well-known members of the family Delphinidae, the family of oceanic dolphins. Recent molecular studies show the genus contains two species, the common bottlenose dolphin and the Indo-Pacific bottlenose dolphin , instead of one...
attack. Non-fatal incidents occur more frequently, both in wild and captivity.
While dolphin attacks are much rarer than other sea animal attacks, such as
shark onesA shark attack is an attack on a human by a shark. Every year around 60 shark attacks are reported worldwide, although death is quite unusual. Despite the relative rarity of shark attacks, the fear of sharks is a common phenomenon, having been fueled by the occasional instances of serial attacks,...
, some scientists are worried about the careless programs of human-dolphin interaction. Dr. Andrew J. Read, a biologist at the Duke University Marine Laboratory who studies dolphin attacks, points that dolphins are large and wild predators, so people should be more careful when they interact with them.
Therapy
Dolphins are an increasingly popular choice of
animal-assisted therapyAnimal-assisted therapy is a relatively new field of study, although the human-animal bond has existed for thousands of years. AAT is a type of therapy that involves animals as a form of treatment. The goal of AAT is to improve a patient’s social, emotional, or cognitive functioning...
for psychological problems and developmental disabilities. For example, a 2005 study found dolphins an effective treatment for mild to moderate
depressionMajor depressive disorder is a mental disorder characterized by an all-encompassing low mood accompanied by low self-esteem, and by loss of interest or pleasure in normally enjoyable activities...
. However, this study was criticized on several grounds. For example, it is not known whether dolphins are more effective than common pets.
ReviewA review is an evaluation of a publication, a product or a service, such as a movie , video game, musical composition , book ; a piece of hardware like a car, home appliance, or computer; or an event or performance, such as a live music concert, a play, musical theater show or dance show...
s of this and other published dolphin-assisted therapy (DAT) studies have found important methodological flaws and have concluded that there is no compelling scientific evidence that DAT is a legitimate therapy or that it affords more than fleeting mood improvement.
Military
A number of militaries have employed dolphins for various purposes from finding mines to rescuing lost or trapped humans. The military use of dolphins, however, drew scrutiny during the Vietnam War when rumors circulated that the
United States NavyThe United States Navy is the naval warfare service branch of the United States Armed Forces and one of the seven uniformed services of the United States. The U.S. Navy is the largest in the world; its battle fleet tonnage is greater than that of the next 13 largest navies combined. The U.S...
was training dolphins to kill Vietnamese divers. The United States Navy denies that at any point dolphins were trained for combat. Dolphins are still being trained by the United States Navy on other tasks as part of the
U.S. Navy Marine Mammal ProgramThe U.S. Navy Marine Mammal Program is a program administered by the U.S. Navy which studies the military use of marine mammals—principally Bottlenose Dolphins and California Sea Lions—and trains animals to perform tasks such as ship and harbor protection, mine detection and clearance, and...
. The Russian military is believed to have closed its marine mammal program in the early 1990s. In 2000 the press reported that dolphins trained to kill by the
Soviet NavyThe Soviet Navy was the naval arm of the Soviet Armed Forces. Often referred to as the Red Fleet, the Soviet Navy would have played an instrumental role in a Warsaw Pact war with NATO, where it would have attempted to prevent naval convoys from bringing reinforcements across the Atlantic Ocean...
had been sold to
IranIran , officially the Islamic Republic of Iran , is a country in Southern and Western Asia. The name "Iran" has been in use natively since the Sassanian era and came into use internationally in 1935, before which the country was known to the Western world as Persia...
.
Literature
Dolphins are also common in contemporary literature, especially science fiction novels. Dolphins play a military role in
William GibsonWilliam Gibson is an American-Canadian science fiction author.William Gibson may also refer to:-Association football:*Will Gibson , Scottish footballer...
's short story Johnny Mnemonic, in which
cyborgA cyborg is a being with both biological and artificial parts. The term was coined in 1960 when Manfred Clynes and Nathan S. Kline used it in an article about the advantages of self-regulating human-machine systems in outer space. D. S...
dolphins find submarines and decode encrypted information. Dolphins play a role as sentient patrollers of the sea enhanced with a deeper empathy toward humans in
Anne McCaffreyAnne Inez McCaffrey was an American-born Irish writer, best known for her Dragonriders of Pern series. Over the course of her 46 year career she won a Hugo Award and a Nebula Award...
's
The Dragonriders of PernDragonriders of Pern is a science fiction series written primarily by the late American-Irish author Anne McCaffrey, who initiated it in 1967. Beginning 2003, her middle child Todd McCaffrey has written Pern novels, both solo and jointly with Anne. The series comprises 22 novels and several short...
series. In the
Known SpaceKnown Space is the fictional setting of some dozen science fiction novels and several collections of short stories written by author Larry Niven. It has also in part been used as a shared universe in the Man-Kzin Wars spin-off anthologies sub-series....
universe of author
Larry NivenLaurence van Cott Niven / ˈlæri ˈnɪvən/ is an American science fiction author. His best-known work is Ringworld , which received Hugo, Locus, Ditmar, and Nebula awards. His work is primarily hard science fiction, using big science concepts and theoretical physics...
, dolphins play a significant role as fully recognised "legal entities". More humorous is
Douglas AdamsDouglas Noel Adams was an English writer and dramatist. He is best known as the author of The Hitchhiker's Guide to the Galaxy, which started life in 1978 as a BBC radio comedy before developing into a "trilogy" of five books that sold over 15 million copies in his lifetime, a television...
’
The Hitchhiker's Guide to the GalaxyThe Hitchhiker's Guide to the Galaxy is a science fiction comedy series created by Douglas Adams. Originally a radio comedy broadcast on BBC Radio 4 in 1978, it was later adapted to other formats, and over several years it gradually became an international multi-media phenomenon...
series of picaresque novels, in which dolphins are the second most intelligent creatures on Earth (after mice, followed by humans) and try in vain to warn humans of Earth’s impending destruction. Their story is told in
So Long, and Thanks for All the FishSo Long, and Thanks for All the Fish is the fourth book of the Hitchhiker's Guide to the Galaxy "trilogy" written by Douglas Adams. Its title is the message left by the dolphins when they departed Planet Earth just before it was demolished to make way for a hyperspace bypass, as described in The...
. Much more serious is their major role in
David BrinGlen David Brin, Ph.D. is an American scientist and award-winning author of science fiction. He has received the Hugo, Locus, Campbell and Nebula Awards.-Biography:...
's
UpliftThe Uplift Universe is a fictional universe created by science fiction writer David Brin. A central feature in this universe is the process of biological uplift.His books which take place in this universe:* Sundiver...
series. A talking Dolphin named "Howard" helps
Hagbard CelineFreeman Hagbard Celine, H.M., S.H. is a central protagonist in the Illuminatus trilogy of books by Robert Shea and Robert Anton Wilson, named after the legendary Viking hero Hagbard who died for love. In the Schrödinger's Cat trilogy, the sequel to Illuminatus!, it is stated that 'Hagbard Celine'...
and his submarine crew fight the evil
IlluminatiThe Illuminati is a name given to several groups, both real and fictitious. Historically the name refers to the Bavarian Illuminati, an Enlightenment-era secret society founded on May 1, 1776...
in Robert Shea and
Robert Anton WilsonRobert Anton Wilson , known to friends as "Bob", was an American author and polymath who became at various times a novelist, philosopher, psychologist, essayist, editor, playwright, poet, futurist, civil libertarian and self-described agnostic mystic...
's Illuminatus Trilogy.
Dolphins appear frequently in non-science fiction literature. In the book
The Music of DolphinsThe Music of Dolphins, by Karen Hesse, is a children's book that follows the story of Mila , a feral child raised by a pod of dolphins around the Florida Keys and Caribbean....
by author
Karen HesseKaren Hesse is an American author of children's literature and literature for young adults, often with historical settings.-Life:...
, dolphins raise a girl from the age of four until the
coast guardA coast guard or coastguard is a national organization responsible for various services at sea. However the term implies widely different responsibilities in different countries, from being a heavily armed military force with customs and security duties to being a volunteer organization tasked with...
eventually discovers her. Fantasy author
Ken GrimwoodKenneth Milton Grimwood was an American author who was born in Dothan, Alabama. In his fantasy fiction Grimwood combined themes of life-affirmation and hope with metaphysical concepts, themes found in his best-known novel, the highly popular Replay...
wrote dolphins into his 1995 novel Into the Deep about a
marine biologistMarine biology is the scientific study of organisms in the ocean or other marine or brackish bodies of water. Given that in biology many phyla, families and genera have some species that live in the sea and others that live on land, marine biology classifies species based on the environment rather...
struggling to crack the code of
dolphin intelligenceCetacean intelligence denotes the cognitive capabilities of the Cetacea order of mammals, which includes whales, porpoises, and dolphins.-Brain size:...
, including chapters written from a dolphinian viewpoint.
Art
Dolphins are a popular artistic motif, dating back to ancient times. Examples include the
Triton FountainThe Triton Fountain is a seventeenth century fountain in Rome, by the well-known Baroque sculptor Gian Lorenzo Bernini...
by Bernini and depictions of dolphins in the ruined
MinoanThe Minoan civilization was a Bronze Age civilization that arose on the island of Crete and flourished from approximately the 27th century BC to the 15th century BC. It was rediscovered at the beginning of the 20th century through the work of the British archaeologist Arthur Evans...
palace at
KnossosKnossos , also known as Labyrinth, or Knossos Palace, is the largest Bronze Age archaeological site on Crete and probably the ceremonial and political centre of the Minoan civilization and culture. The palace appears as a maze of workrooms, living spaces, and store rooms close to a central square...
and on Minoan pottery.
Cuisine
Dolphin meat is consumed in a small number of countries world-wide, which include
JapanJapan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
and
PeruPeru , officially the Republic of Peru , is a country in western South America. It is bordered on the north by Ecuador and Colombia, on the east by Brazil, on the southeast by Bolivia, on the south by Chile, and on the west by the Pacific Ocean....
(where it is referred to as chancho marino, or "sea pork"). While Japan may be the best-known and most controversial example, only a very small minority of the population has ever sampled it.
Dolphin meat is dense and such a dark shade of red as to appear black. Fat is located in a layer of
blubberBlubber is a thick layer of vascularized adipose tissue found under the skin of all cetaceans, pinnipeds and sirenians.-Description:Lipid-rich, collagen fiber–laced blubber comprises the hypodermis and covers the whole body, except for parts of the appendages, strongly attached to the musculature...
between the meat and the skin. When dolphin meat is eaten in Japan, it is often cut into thin strips and eaten raw as
sashimiSashimi is a Japanese delicacy. It consists of very fresh raw meat, most commonly fish, sliced into thin pieces.-Origin:The word sashimi means "pierced body", i.e...
, garnished with onion and either
horseradishHorseradish is a perennial plant of the Brassicaceae family, which also includes mustard, wasabi, broccoli, and cabbages. The plant is probably native to south eastern Europe and the Arab World , but is popular around the world today...
or grated
garlicAllium sativum, commonly known as garlic, is a species in the onion genus, Allium. Its close relatives include the onion, shallot, leek, chive, and rakkyo. Dating back over 6,000 years, garlic is native to central Asia, and has long been a staple in the Mediterranean region, as well as a frequent...
, much as with sashimi of
whaleWhale meat is the flesh of whales used for consumption by humans or other animals. It is prepared in various ways, and is historically part of the diet and cuisine of various communities that live near an ocean, including those of Japan, Norway, Iceland, and the Arctic...
or
horse meatHorse meat is the culinary name for meat cut from a horse. It is a major meat in only a few countries, notably in Central Asia, but it forms a significant part of the culinary traditions of many others, from Europe to South America to Asia. The top eight countries consume about 4.7 million horses...
(basashi). When cooked, dolphin meat is cut into bite-size cubes and then batter-fried or simmered in a
misois a traditional Japanese seasoning produced by fermenting rice, barley and/or soybeans, with salt and the fungus , the most typical miso being made with soy. The result is a thick paste used for sauces and spreads, pickling vegetables or meats, and mixing with dashi soup stock to serve as miso...
sauce with vegetables. Cooked dolphin meat has a flavor very similar to beef liver.
See also
- Bottlenose Dolphin Research Institute
The 'Bottlenose Dolphin Research Institute' is a marine science and education center, committed toconserving the diversity and integrity of marine life to meet the needs of current and future generations...
- Dolphin Research Center
The Dolphin Research Center is a dolphinarium on Grassy Key, Florida. The series of saltwater lagoons carved out of the shoreline is home to a family of bottlenose dolphins and California sea lions...
- Environmental Investigation Agency
The Environmental Investigation Agency is an NGO founded in 1984 by Dave Currey, Jennifer Lonsdale and Allan Thornton, three environmental activists in the United Kingdom. Its stated goal is to investigate and expose crimes against wildlife and the environment...
Further reading
- Carwardine, M., Whales, Dolphins and Porpoises, Dorling Kindersley, 2000. ISBN 978-0-7513-2781-6
- Williams, Heathcote
Heathcote Williams is an English poet, actor and award-winning playwright. He is also an intermittent painter, sculptor and long-time conjuror...
, Whale Nation, New York, Harmony Books, 1988. ISBN 978-0-517-56932-0
External links
Conservation, research and news:
Photos: