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Dolphin
Dolphins are marine mammals that are closely related to whales and porpoises. There are almost forty species of dolphin in seventeen genus|genera. They vary in size from 1.2 metres (4 ft) and 40 kilograms (88 pound (unit of weight)|lb) (Maui's Dolphin), up to 9.5 m (30 ft) and ten tonnes (the Orca or Killer Whale). They are found worldwide, mostly in the shallower seas of the continental shelves, and are carnivores, mostly eating fish and squid. The Family (biology)|family Oceanic dolphin|Delphinidae is the largest in the Cetacea, and relatively recent: dolphins evolved about ten million years ago, during the Miocene. Dolphins are considered to be amongst the most intelligent of animals and their often friendly appearance and seemingly playful attitude have made them popular in human culture.
Origin of the name
The name is originally from Ancient Greek (''delphís''; "dolphin"), which was related to the Greek (''delphys''; "womb"). The animal's name can therefore be interpreted as meaning "a 'fish' with a womb".[The American Heritage Dictionary of the English Language, Fourth Edition, online entry at Dictionary.com, retrieved December 17 2006.] The name was transmitted via the Latin ''delphinus'', Middle Latin ''dolfinus'' and the Old French ''daulphin'', which reintroduced the ''ph'' into the word.
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),
- Used casually as a synonym for Bottlenose Dolphin, the most common and familiar species of dolphin.
In this article, the second definition is used. Porpoises (suborder Odontoceti, family Phocoenidae) are thus not dolphins in this sense. Orcas and some closely related species belong to the Delphinidae family and therefore qualify as dolphins, even though they are called whales in common language. A group of dolphins can be called a "school" or a "pod". Male dolphins are called "bulls", females "cows" and young dolphins are called "calves".[Dictionary.com - Style guide, animal names, page retrieved November 4 2007.]
Taxonomy
- Suborder Odontoceti, toothed whales
- Family Delphinidae, oceanic dolphins
- * Genus ''Delphinus''
- ** Long-Beaked Common Dolphin, ''Delphinus capensis''
- ** Short-Beaked Common Dolphin, ''Delphinus delphis''
- * Genus ''Tursiops ''
- ** Bottlenose Dolphin, ''Tursiops truncatus''
- ** Indo-Pacific Bottlenose Dolphin, ''Tursiops aduncus''
- * Genus ''Lissodelphis''
- ** Northern Rightwhale Dolphin, ''Lissodelphis borealis''
- ** Southern Rightwhale Dolphin, ''Lissiodelphis peronii''
- * Genus ''Sotalia''
- ** Tucuxi, ''Sotalia fluviatilis''
- ** Costero, ''Sotalia guianensis''
- * Genus ''Sousa''
- ** Indo-Pacific Hump-backed Dolphin, ''Sousa chinensis''
- *** Chinese White Dolphin (the Chinese variant), ''Sousa chinensis chinensis''
- ** Atlantic Humpbacked Dolphin, ''Sousa teuszii''
- * Genus ''Stenella''
- ** Atlantic Spotted Dolphin, ''Stenella frontalis''
- ** Clymene Dolphin, ''Stenella clymene''
- ** Pantropical Spotted Dolphin, ''Stenella attenuata''
- ** Spinner Dolphin, ''Stenella longirostris''
- ** Striped Dolphin, ''Stenella coeruleoalba''
- * Genus ''Steno''
- ** Rough-Toothed Dolphin, ''Steno bredanensis''
- * Genus ''Cephalorynchus''
- ** Chilean Dolphin, ''Cephalorhynchus eutropia''
- ** Commerson's Dolphin, ''Cephalorhynchus commersonii''
- ** Heaviside's Dolphin, ''Cephalorhynchus heavisidii''
- ** Hector's Dolphin, ''Cephalorhynchus hectori''
- * Genus ''Grampus''
- ** Risso's Dolphin, ''Grampus griseus''
- * Genus ''Lagenodelphis''
- ** Fraser's Dolphin, ''Lagenodelphis hosei''
- * Genus ''Lagenorhyncus''
- ** Atlantic White-Sided Dolphin, ''Lagenorhynchus acutus''
- ** Dusky Dolphin, ''Lagenorhynchus obscurus''
- ** Hourglass Dolphin, ''Lagenorhynchus cruciger''
- ** Pacific White-Sided Dolphin, ''Lagenorhynchus obliquidens''
- ** Peale's Dolphin, ''Lagenorhynchus australis''
- ** White-Beaked Dolphin, ''Lagenorhynchus albirostris''
- * Genus ''Orcaella''
- ** Australian Snubfin Dolphin, ''Orcaella heinsohni''
- ** Irrawaddy Dolphin, ''Orcaella brevirostris''
- * Genus ''Peponocephala''
- ** Melon-headed Whale, ''Peponocephala electra''
- * Genus ''Orcinus''
- ** Killer Whale (Orca), ''Orcinus orca''
- * Genus ''Feresa''
- ** Pygmy Killer Whale, ''Feresa attenuata''
- * Genus ''Pseudorca''
- ** False Killer Whale, ''Pseudorca crassidens''
- * Genus ''Globicephala''
- ** Long-finned Pilot Whale, ''Globicephala melas''
- ** Short-finned Pilot Whale, ''Globicephala macrorhynchus''
- Family Platanistoidea, river dolphins
- * Genus ''Inia''
- ** Amazon River Dolphin (Boto), ''Inia geoffrensis''
- * Genus ''Lipotes''
- ** Chinese River Dolphin (Baiji), ''Lipotes vexillifer'' (considered functionally extinct)
- * Genus ''Platanista''
- ** Ganges River Dolphin, ''Platanista gangetica''
- ** Indus River Dolphin, ''Platanista minor''
- * Genus ''Pontoporia''
- ** La Plata Dolphin (Franciscana), ''Pontoporia blainvillei''
Six species in the family Delphinidae are commonly called "whales" but are strictly speaking dolphins. They are sometimes called "blackfish".
- Melon-headed Whale, ''Peponocephala electra''
- Killer Whale (Orca), ''Orcinus orca''
- Pygmy Killer Whale, ''Feresa attenuata''
- False Killer Whale, ''Psudorca crassidens''
- Long-finned Pilot Whale, ''Globicephala melas''
- Short-finned Pilot Whale, ''Globicephala macrorhynchus''
Hybrid dolphins
In 1933, three abnormal dolphins were beached off the Ireland|Irish coast; these appeared to be Hybrid (biology)|hybrids between Risso's Dolphin and the Bottlenose Dolphin.[Dolphin Safari (2006) sightings log, page retrieved December 17 2006.] This mating has since been repeated in captivity and a hybrid calf was born. In captivity, a Bottlenose Dolphin and a Rough-toothed Dolphin produced hybrid offspring.[Texas Tech University (1997), Mammals of Texas - Rough-toothed Dolphin, article retrieved December 8 2006.] A Common-Bottlenose hybrid lives at SeaWorld California [Robin's Island Dolphins at SeaWorld California, page retrieved December 17 2006.] Various other dolphin hybrids live in captivity around the world or have been reported the wild, such as a Bottlenose-Atlantic Spotted hybrid.[Denise L. Herzing, Kelly Moewe and Barbara J. Brunnick (2003), Interspecies interactions between Atlantic spotted dolphins, Stenella frontalis and bottlenose dolphins, Tursiops truncatus, on Great Bahama Bank, Bahamas, article retrieved on December 17 2006.] The best known hybrid however is the Wolphin, a False Killer Whale-Bottlenose Dolphin hybrid. The Wolphin is a fertile hybrid, and two such Wolphins currently live at the Sea Life Park in Hawaii, the first having been born in 1985 from a male False Killer Whale and a female Bottlenose. Wolphins have also been observed in the wild.[Louis Herman, interviewed for Associated Press, article by Jeanette J. Lee (2005), Livescience.com - Whale-Dolphin Hybrid Has Baby Wholphin, article retrieved April 26 2007.]
Evolution and anatomy
Evolution
Dolphins, along with whales and porpoises, are descendants of terrestrial mammals, most likely of the Artiodactyl order (biology)|order. The ancestors of the modern day dolphins entered the water roughly fifty million years ago, in the Eocene epoch.
Modern dolphin skeletons have two small, rod-shaped pelvic bones thought to be vestigial hind legs. In October 2006 an unusual Bottlenose Dolphin was captured in Japan; it had small fins on each side of its genital slit which scientists believe to be a more pronounced development of these vestigial hind legs.[Associated Press / FOX news (2006), Japanese Researchers Find Dolphin With 'Remains of Legs', article retrieved November 6 2006.]
Anatomy
Dolphins have a streamlined fusiform body, adapted for fast swimming. The tail fin, called the fluke, is used for propulsion, while the pectoral fins together with the entire tail section provide directional control. The dorsal fin, in those species that have one, provides stability while swimming.
Though it varies per species, basic colouration patterns are shades of grey usually with a lighter underside. It is often combined with lines and patches of different hue and contrast.
The head contains the melon (whale)|melon, a round organ used for animal echolocation|echolocation. In many species, the jaws are elongated, forming a distinct beak; for some species like the Bottlenose, there is a curved mouth which looks like a fixed smile. Teeth can be very numerous (up to two hundred and fifty) in several species. Dolphins breathe through a blowhole (biology)|blowhole located on top of their head, with the Vertebrate trachea|trachea being anterior to the brain. The dolphin brain is large and highly complex and is different in structure from most land mammals.
Unlike most mammals, dolphins do not have hair, but they are born with a few hairs around the tip of their rostrum (anatomy)|rostrum which they lose shortly after birth, in some cases even before they are born.[The Institute for Marine Mammal Studies (IMMS), Dolphin Frequently Asked Questions: Why is a dolphin a mammal and not a fish?, article retrieved February 21 2008.] The only exception to this is the Boto river dolphin, which does have some small hairs on the rostrum.[VirtualExplorers.org, All About Dolphins - Amazon River Dolphin fact sheet, article retrieved February 21 2008.]
Their reproductive organs are located on the underside of the body. Males have two slits, one concealing the penis and one further behind for the anus. The female has one genital slit, housing the vagina and the anus. A Mammary gland|mammary slit is positioned on either side of the female's genital slit.
Senses
Most dolphins have acute eyesight, both in and out of the water, and their sense of Hearing (sense)|hearing is superior to that of humans. Though they have a small ear opening on each side of their head, it is believed that hearing underwater is also if not exclusively done with the lower jaw which conducts the sound vibrations to the middle ear via a fat-filled cavity in the lower jaw bone. Hearing is also used for Animal echolocation|echolocation, which seems to be an ability all dolphins have. It is believed that their teeth are arranged in a way that works as an array or antenna to receive the incoming sound and make it easier for them to pinpoint the exact location of an object.[Goodson, A.D. and M. Klinowska. "A Proposed Echolocation Receptor for the Bottlenose Dolphin (''Tursiops truncatus''): Modelling the Receive Directivity from Tooth and Lower Jaw Geometry", in Thomas and Kastelein, eds, ''NATO ASI Series A: Sensory Abilities of Cetaceans'', vi.196:255-267 (Plenum NY, 1990) ISBN 0-30-643695-7] The dolphin's sense of touch is also well-developed, with free nerve endings being densely packed in the skin, especially around the snout, pectoral fins and genital area. However, dolphins lack an olfactory nerve and lobes and thus are believed to have no sense of smell,[SeaWorld, Bottlenose Dolphins - Senses, article retrieved December 17 2006.] but they can taste and do show preferences for certain kinds of fish. Since dolphins spend most of their time below the surface normally, just tasting the water could act in a manner analogous to a sense of smell.
Though most dolphins do not have any hair, they do still have hair follicles and it is believed these might still perform some sensory function, though it is unclear what exactly this may be.[Bjorn Mauck, Ulf Eysel and Guide Dehnhardt (2000), Selective heating of vibrissal follicles in seals (Phoca Vitulina) and dolphins (Sotalia Fluviatilis Guianensis), article retrieved March 11, 2007.] The small hairs on the rostrum of the Boto river dolphin are believed to function as a somatosensory system|tactile sense however, possibly to compensate for the Boto's poor eyesight.[Laurie Stepanek (1998), Amazon River Dolphin (Inia geoffrensis), article retrieved March 11, 2007.]
Behaviour
Dolphins are often regarded as one of Earth's most intelligent animals, though it is hard to say just how intelligent dolphins are, as comparisons of species' relative intelligence are complicated by differences in sensory apparatus, response modes, and nature of cognition. Furthermore, the difficulty and expense of doing experimental work with large aquatics means that some tests which could yield meaningful results still have not been carried out, or have been carried out with inadequate sample size and methodology. Dolphin behaviour has been studied extensively by humans however, both in captivity and in the wild. See the cetacean intelligence article for more details.
Social behaviour
Dolphins are social, living in pods (also called "schools") of up to a dozen individuals. In places with a high abundance of food, pods can join temporarily, forming an aggregation called a ''superpod''; such groupings may exceed a thousand dolphins. The individuals communicate using a variety of clicks, whistles and other vocalizations. They also use ultrasonic sounds for echolocation. Membership in pods is not rigid; interchange is common. However, the cetaceans can establish strong bonds between each other. This leads to them staying with injured or ill individuals, even actively helping them to breathe by bringing them to the surface if needed.[Davidson College, biology department (2001) Bottlenose Dolphins - Altruism, article retrieved March 12 2008.] This altruism|altruistic behaviour does not appear to be limited to their own species however. A dolphin in New Zealand that goes by the name of ''Moko'' has been observed to seemingly help guide a female Pygmy Sperm Whale together with her calf out of shallow water where they had stranded several times.[Ray Lilley for Associated Press (2008), Dolphin Appears to Guide Whales to Sea, article retrieved March 12 2008.] They have also been known to seemingly protect swimmers from sharks by swimming circles around the swimmers[CBC News (2004), Dolphins save swimmers from shark, article retrieved March 11, 2007.][Rowan Hooper for New Scientist (2005), Dolphins teach their children to use sponges, article retrieved December 17 2006.] Another such behaviour was discovered amongst river dolphins in Brazil, where some male dolphins apparently use objects such as weeds and sticks as part of a sexual display.[Nic Fleming, Science correspondent for the Telegraph (2008), Dolphins woo females with bunches of weeds, article retrieved February 11 2008.]
Dolphins are known to engage in acts of aggression towards each other. The older a male dolphin is, the more likely his body is covered with scars ranging in depth from teeth marks made by other dolphins. It is suggested that male dolphins engage in such acts of aggression for the same reasons as humans: disputes between companions or even competition for other females. Acts of aggression can become so intense that targeted dolphins are known to go into exile, leaving their communities as a result of losing a fight with other dolphins.
Male Bottlenose Dolphins have been known to engage in infanticide (zoology)|infanticide. Dolphins have also been known to kill porpoises for reasons which are not fully understood, as porpoises generally do not share the same fish diet as dolphins and are therefore not competitors for food supplies.[Dr. George Johnson (date unknown), Is Flipper A Senseless Killer?, article retrieved December 17 2006.]
Reproduction and sexuality
Dolphin copulation happens belly to belly and though many species engage in lengthy foreplay, the actual act is usually only brief, but may be repeated several times within a short timespan. The gestation period varies per 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 maturity. The age at which sexual maturity is reached varies per species and gender.
Dolphins are known to have sex for reasons other than reproduction, sometimes also engaging in acts of a homosexual nature.[Herzing D.L., Rogers C.A., for the Wild Dolphin Project, Directionality of sexual aggression in mixed-species encounters between Atlantic Spotted dolphins and Bottlenose dolphins in the Bahamas (2005), article retrieved September 18 2007.] Various dolphin species have been known to engage in sexual behaviour with other dolphin species,[Scott et. al,Aggression in bottlenose dolphins: evidence for sexual coercion, male-male competition, and female tolerance through analysis of tooth-rake marks and behaviour (2005), article retrieved September 18 2007.] Occasionally, dolphins will also show sexual behaviour towards other animals, including humans.[Amy Samuels, Lars Bejder, Rochelle Constantine and Sonja Heinrich (2003), Marine Mammals: Fisheries, Tourism and Management Issues, chapter 15, pages 266 to 268, Cetaceans that are typically lonely and seek human company. Retrieved December 17 2006.]
Feeding
Various methods of feeding exist, not just between species but also within a species. Various methods may be employed, some techniques being used by only a single dolphin population. Fish and squid are the main source of food for most dolphin species, but the False Killer Whale and the Killer Whale also feed on other marine mammals.
One feeding method employed by many species is herding, where a pod will control a school of fish while individual members take turns plowing through the school, feeding. The tightly packed school of fish is commonly known as a bait ball. Coralling is a method where fish are chased to shallow water where they are more easily captured. In South Carolina, the Atlantic Bottlenose Dolphin takes this one step further with what has become known as strand feeding, where the fish are driven onto mud banks and retrieved from there.["Coastal Stock(s) of Atlantic Bottlenose Dolphin: Status Review and Management," Proceedings and Recommendations from a Workshop held in Beaufort, North Carolina, 13 September 1993 – 14 September 1993. U.S. Department of Commerce, National Oceanic and Atmospheric Administration, National Marine Fisheries Service. pp. 56–57.] In some places, Orcas will also come up to the beach to capture sea lions. Some species also whack fish with their fluke, stunning them and sometimes sending fish clear out of the water.
Reports of cooperative human-dolphin fisheries date back to the ancient Rome|ancient Roman author and natural philosophy|natural philosopher Pliny the Elder.[M.B. Santos, R. Fernández, A. López, J.A. Martínez and G.J. Pierce (2007), Variability in the diet of bottlenose dolphin, Tursiops truncatus, in Galician waters, north-western Spain, 1990 – 2005 (.pdf), article retrieved April 3 2007.] A modern human-dolphin fishery still takes place in Laguna, Brazil|Laguna, Santa Catarina (state)|Santa Catarina, Brazil. Here, dolphins drive fish towards fishermen waiting along the shore and give them a signal when they can cast their nets. The dolphins then feed off the fish that manage to escape the nets.[The Telegraph (2006), Brazil's sexiest secret, article retrieved March 11, 2007.][Dr. Moti Nissani (2007) Bottlenose Dolphins in Laguna Requesting a Throw Net (video). Supporting material for Dr. Nissani's presentation at the 2007 International Ethological Conference. Video retrieved February 13 2008.]
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 however; frequency modulated sounds which are usually just called whistles; burst-pulsed sounds and clicks. Whistles are used by dolphins to communicate, though the nature and extent of their ability to communicate in this way is not known. Research has shown however that at least some dolphin species are capable of sending identity information to each other using a signature whistle; a whistle that refers specifically to the identity of a certain dolphin. The burst-pulsed sounds are also used for communication, but again the nature and extent of communication possible this way is not known.[Atlantic Spotted Dolphin vocalizations, chapter Delphinid vocalizations., the dolphin communication project, article retrieved August 7 2007.] The clicks are directional and used by dolphins for echolocation and are often in a short series called a click train, the rate increasing when approaching an object of interest. Dolphin echolocation clicks are amongst the Whale song#Toothed Whale Sound Levels|loudest sounds made by animals in the sea.[W. W. L. Au, The Sonar of Dolphins (Springer, NY, 1993).]
Jumping and playing
Dolphins occasionally leap above the water surface, sometimes performing acrobatic figures (e.g. the Spinner Dolphin). Scientists are not always quite certain about the purpose of this behaviour and the reason for it may vary; it could be to locate schools of fish by looking at above-water signs like feeding birds, they could be communicating to other dolphins to join a hunt, attempting to dislodge parasites, or simply doing it for fun.
Play is a fairly important part of dolphins' lives, and they can be observed playing with seaweed or play-fighting with other dolphins. At times they also harass other local creatures, like seabirds and turtles. Dolphins also seem to enjoy riding waves and frequently 'surf' coastal swells and the bow waves of boats. Occasionally, they're also willing to playfully interact with human swimmers.
Sleeping
Because dolphins need to come up to the surface to breathe and have to be alert for possible predators, they do not sleep in the same way land mammals do. Generally, dolphins sleep with only one brain Cerebral hemisphere|hemisphere in slow-wave sleep at a time, thus maintaining some amount of consciousness required to breathe and keeping one eye open to keep a watch out for possible threats. The earlier stages of sleep can be observed in both hemispheres of the brain, however.[Dallas Grasby (1994) Excerpts from "Sleep in marine mammals", L.M. Mukhametov, Experimental Brain Research Supplement 8, article retrieved February 11 2008.]
However, in captivity, dolphins have been observed to seemingly enter a fully asleep state where both eyes are closed and the animal does not respond to mild external stimuli, respiration being automatic with a tail kick reflex keeping the blowhole above the water. If not needed to keep the blowhole above the water, the tail kick reflex may subside. Dolphins kept unconscious using anesthesia|anesthetics initially show a similar tail kick reflex.[James G. McCormick (PhD), Department of Anesthesiology, Wake Forest University School of Medicine, Winston-Salem, North Carolina (2007), Behavioral Observations of Sleep and Anesthesia in the Dolphin: Implications for Bispectral Index Monitoring of Unihemispheric Effects in Dolphins, article retrieved February 11 2008.] Though a similar state has been observed with wild Sperm Whales, it is not known if this state is ever reached in the wild amongst any dolphin species.[BBC (2008), Sperm whales caught 'cat napping', article retrieved April 9 2008.]
Threats to dolphins
Natural threats to dolphins
Except for humans (discussed below), dolphins have few natural enemies, some species or specific populations having none at all making them apex predators. For most smaller species of dolphins, only a few larger species of shark such as the bull shark, dusky shark, tiger shark and great white shark are a potential risk, especially for calves. Some of the larger dolphin species such as Orcas may also prey on some of the smaller dolphin species, but this seems rare. Dolphins may also suffer from a wide variety of diseases and parasites.
Human threats to dolphins
Some dolphin species face an uncertain future, especially some of the river dolphin species such as the Amazon River Dolphin, and the Ganges and Baiji|Yangtze River Dolphin, all of which are critically or seriously endangered. A 2006 survey found no individuals of the Yangtze River Dolphin, leading to the conclusion that the species is now functionally extinct.[Douglas Williams for Shanghai Daily (2006), Yangtze dolphin may be extinct. Article retrieved December 9 2006.]
Contamination of environment - the oceans, seas, and rivers - is an issue of concern, especially pesticides, heavy metals, plastics, and other industrial and agricultural pollutants which do not disintegrate rapidly in the environment are reducing dolphin populations, and resulting in dolphins building up unusually high levels of contaminants. Injuries or deaths due to collisions with boats, especially their propellers, are also common.
Various fishing methods, most notably Seine (fishing)|purse seine fishing for tuna and the use of drift and gill nets, results in a large amounts of dolphins being killed inadvertently.[Clover, Charles. 2004. ''The End of the Line: How overfishing is changing the world and what we eat''. Ebury Press, London. ISBN 0-09-189780-7 ] Accidental by-catch in gillnets and incidental captures in antipredator nets used in marine fish farms are common and poses a risk for mainly local dolphin populations.[CBC news (2003), Navy sonar may be killing whales, dolphins, article retrieved October 27, 2008.][Npower renewables, Underwater noise & vibration, section 9.4. Study retrieved October 27, 2008.]
Human–dolphin relationships
Mythology
Dolphins have long played a role in human culture. Dolphins are common in Greek mythology and there are many coins from the time which feature a man or boy riding on the back of a dolphin. The Ancient Greece|Ancient Greeks treated them with welcome; a ship spotting dolphins riding in their wake was considered a good omen for a smooth voyage. In Hindu mythology, the Ganges River Dolphin is associated with Ganga in Hinduism|Ganga, the deity of the Ganges river.
Entertainment
In more recent times, the Flipper (1963 film)|1963 ''Flipper'' movie and the subsequent popular ''Flipper (1964 TV series)|Flipper television series'', contributed to the popularity of dolphins in Western World|Western society. The series, created by Ivan Tors, portrayed a dolphin in a friendly relationship with two boys, Sandy and Bud; a kind of seagoing ''Lassie (1954 TV series)|Lassie''. Flipper, a Bottlenose Dolphin, understood English commands unusually well and was a marked hero. A Flipper (1996 film)|second ''Flipper'' movie was made in 1996, which was based on the story of the original movie. A Bottlenose Dolphin also played a prominent role in the 1990s science fiction television series ''seaQuest DSV'' in which the animal, named Darwin, could communicate with English speakers using a vocoder, a fictional invention which translated the clicks and whistles to English and back.
More well known from this time period is probably the movie ''Free Willy'' however, which made famous the Orca playing Willy, Keiko (orca)|Keiko. The 1977 horror movie ''Orca (film)|Orca'' paints a less friendly picture of the animal. Here, a male Orca takes revenge on fishermen after the killing of his mate. In the 1973 movie ''The Day of the Dolphin'' trained dolphins are kidnapped and made to perform a naval military assassination using explosives.
The renewed popularity of dolphins in the 1960s resulted in the appearance of many dolphinariums around the world, which have made dolphins accessible to the public. Though criticism and more strict animal welfare laws have forced many dolphinariums to close their doors, hundreds still exist around the world attracting a large amount of visitors. In the United States, best known are the SeaWorld marine mammal parks, and their common Orca stage name ''Shamu'', which they have trademarked, has become well known. Southwest Airlines, an American airline, has painted three of their Boeing 737 aircraft in ''Shamu'' colours as an advertisement for the parks and have been flying with such a livery on various aircraft since 1988.
Ecco the Dolphin is a well known Ecco the Dolphin (series)| video game series. The games are named after their main character, Ecco, a young Bottlenose Dolphin. The ''Ecco the Dolphin'' games hinge on the idea that cetaceans are sapient beings and have their own underwater society. The science fiction roleplaying game Blue Planet (role-playing game)|Blue Planet includes genetically "uplifted" dolphins as playable characters.
Welfare
A number of organizations rescue and Wildlife rehabilitation|rehabilitate sick, wounded, stranded or orphaned dolphins, such as the Mote Marine Laboratory, or work on dolphin conservation and welfare, such as the Whale and Dolphin Conservation Society.
Therapy
Dolphins are an increasingly popular choice of animal-assisted therapy for psychological problems and developmental disabilities. For example, a 2005 study with 30 participants found it was an effective treatment for mild to moderate clinical depression|depression.[Christian Antonioli and Michael A. Reveley, (2005), Randomised controlled trial of animal facilitated therapy with dolphins in the treatment of depression.] However, this study was criticized on several grounds; for example, it is not known whether dolphins are more effective than common pets.Military
A number of militaries have employed dolphins for various purposes from finding mines to rescuing lost or trapped humans. Such military dolphins, however, drew scrutiny during the Vietnam War when rumors circulated that dolphins were being trained by the United States Navy to kill Vietnamese divers.[PBS - Frontline, The Story of Navy dolphins., article retrieved June 8, 2008.] Dolphins are still being trained by the United States Navy however as part of the U.S. Navy Marine Mammal Program. 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 Navy had been sold to Iran.[BBC News (2000), Iran buys kamikaze dolphins, article retrieved June 7, 2008.]
Literature
Dolphins are also common in contemporary literature, especially science fiction novels. A military role for dolphins is found in William Gibson's short story ''Johnny Mnemonic'', in which cyborg dolphins are used in war-time by the military to find submarines and, after the war, by a group of revolutionaries to decode encrypted information. Dolphins play a role as sentient patrollers of the sea enhanced with a deeper empathy toward humans in Anne McCaffrey's ''Dragonriders of Pern|The Dragonriders of Pern'' series. In the ''Known Space'' universe of author Larry Niven, dolphins also play a significant role as fully-recognised "legal entities". More humorous is ''The Hitchhiker's Guide to the Galaxy'', in which dolphins are the second most intelligent creatures on Earth (after mice, and followed by humans) and tried in vain to warn humans of the impending destruction of the planet. However, their behaviour was misinterpreted as playful acrobatics. Their story is told in ''So Long, and Thanks for All the Fish''. Much more serious is their major role (along with chimpanzees) in David Brin's Uplift Universe|Uplift series. A talking Dolphin called "Howard" helps Hagbard Celine and his submarine crew fight the evil Illuminati in Robert Shea and Robert Anton Wilson's Illuminatus Trilogy.
Dolphins also appear frequently in non-science fiction literature however. In the book ''The Music of Dolphins'' by author Karen Hesse, a girl is raised by dolphins from the age of four until she is discovered by the coast guard. Fantasy author Ken Grimwood wrote dolphins into his 1995 novel ''Into the Deep'' about a marine biology|marine biologist struggling to crack the code of cetacean intelligence|dolphin intelligence, including entire chapters written from the viewpoint of his dolphin characters. In this book, humans and dolphins are capable of communicating via telepathy.
Art
Dolphins are a popular artistic motif, dating back ancient times. Examples include the Triton Fountain by Bernini and depictions of dolphins in the ruined Minoan palace at Knossos and on Minoan pottery.
References
External links
Dolphin conservation and research:
- The Whale & Dolphin Conservation Society (WDCS)
- The Dolphin Institute
- The Dolphin research center
- Digital Library of Dolphin Development, Cetacean origins, Thewissen Lab
- The Bottlenose Dolphin Research Institute
- The Oceania Project, Caring for Whales and Dolphins
Dolphin news:
- Tursiops.org: Current Cetacean-related news
Dolphin photos:
- Red Sea Spinner Dolphin - Photo gallery
- PBS NOVA: Dolphins: Close Encounters
- David's Dolphin Images
- Images of Wild Dolphins in the Red Sea
- National Geographic
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Related Images- The Anatomy of a Dolphin showing its skeleton, major organs and body shape.
- '''Hind Limb Buds on Dolphins''' An embryo of a Spotted Dolphin in the fifth week of development. The hind limbs are present as small bumps (hind limb buds) near the base of the tail. The pin is approximately 1 inch (~2,5 cm) long.
- Bottlenose Dolphin with vestigial hind flippers, captured 2006 in Japan.
- Pacific White-Sided Dolphins breaching
- The famous Orca Keiko from the Free Willy movies being prepared for transport.
Sources: StartLearningNow, Wikipedia | Usage license: GNU FDL
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