The photo is not one I took myself but copied from a Facebook group I belong to. They have some stunning photos. I have seen dolphins at Sea World perform and thought they were quite smart. I also took a day cruise in Hawaii and was privileged to see spinner dolphins. They jump in the air and spin around before diving back into the water. It is quite a sight to see. The guide said scientists don’t know why they spin around in the air except to play which goes to show that dolphins can experience unfettered joy just like humans can. Haven’t you ever felt so excited or happy that you wanted to jump in the air and spin around? Maybe on the day you proposed to your spouse, and he/she said yes or the day your first child was born? I think most of us have life-changing experiences that make us want to jump for joy — and yes, spin around too. And, of course, if you’re as old as me, you remember the TV series “Flipper” that was about a dolphin. According to Wikipedia, “Flipper” was an American television program broadcast on NBC from September 19, 1964, until April 15, 1967. Flipper, a bottlenose dolphin, was the pet of Porter Ricks, chief warden at Coral Key Park and Marine Preserve — a fictional version of John Pennekamp Coral Reef State Park in Key Largo, Florida, and his two young sons, Sandy and Bud. The show has been dubbed an "aquatic Lassie," and a considerable amount of children's merchandise inspired by the show was produced during its first run.
According to Wikipedia, dolphin is the common name of aquatic mammals within the infraorder Cetacea. The term dolphin usually refers to the extant families Delphinidae (the oceanic dolphins); Platanistidae (the Indian river dolphins), named Iniidae (the New World river dolphins); Pontoporiidae (the brackish dolphins); and the extinct Lipotidae (baiji or Chinese river dolphin). There are 40 extant species named as dolphins.
Dolphins range in size from the relatively small 5 feet 7 inches long and 110-pound bodied Māui dolphin to the 31 feet 2 inches and 11-short-ton killer whale. Dolphins can sometimes leap about 30 feet. Several species of dolphins exhibit sexual dimorphism, in that the males are larger than females. They have streamlined bodies and two limbs that are modified into flippers. Though not quite as flexible as seals, some dolphins can travel at speeds up to 18 miles per hour for short distances. Dolphins use their conical-shaped teeth to capture fast-moving prey. They have well-developed hearing which is adapted for both air and water and is so well developed that some can survive even if they are blind. Some species are well-adapted for diving to great depths. They have a layer of fat — or blubber — under the skin to keep warm in the cold water.
Although dolphins are widespread, most species of them prefer the warmer waters of the tropic zones, but some, like the right whale dolphin, prefer colder climates. Dolphins feed largely on fish and squid, but a few, like the killer whale, feed on large mammals, like seals. Male dolphins typically mate with multiple females every year, but females only mate every two to three years. Calves are typically born in the spring and summer months and females bear all the responsibility for raising them. Mothers of some species fast and nurse their young for a relatively long period of time. Dolphins produce a variety of vocalizations, usually in the form of clicks and whistles.
Dolphins are sometimes hunted in places such as Japan, in an activity known as dolphin drive hunting. Besides drive hunting, they also face threats from bycatch or unintentional catches, habitat loss and marine pollution. Dolphins have been depicted in various cultures worldwide. Dolphins occasionally feature in literature and film, as in the film series “Free Willy.” Dolphins are sometimes kept in captivity and trained to perform tricks. The most common dolphin species in captivity is the bottlenose dolphin, while there are around 60 killer whales in captivity.
Etymology
The name is originally from Greek “delphís” or "dolphin," which was related to the Greek “delphus” or "womb." The animal's name can therefore be interpreted as meaning "a 'fish' with a womb." The term “mereswine” or "sea pig" has also historically been used.
The term “dolphin” can be used to refer to — under the parvorder Odontoceti — all the species in the family Delphinidae (oceanic dolphins) and the river dolphin families Iniidae (South American river dolphins), Pontoporiidae (La Plata dolphin), Lipotidae (Yangtze river dolphin) and Platanistidae (Ganges river dolphin and Indus river dolphin). This term has often been misused in the U.S., mainly in the fishing industry, where all small cetaceans — dolphins and porpoises — are considered porpoises, while the fish “dorado” is called “dolphin fish.” In common usage the term “whale” is used only for the larger cetacean species, while the smaller ones with a beaked or longer nose are considered “dolphins.” The name “dolphin” is used casually as a synonym for bottlenose dolphin, the most common and familiar species of dolphin. There are six species of dolphins commonly thought of as whales, collectively known as blackfish: killer whale, melon-headed whale, pygmy killer whale, false killer whale and the two species of pilot whales, all of which are classified under the family Delphinidae and qualify as dolphins. Though the terms “dolphin” and “porpoise” are sometimes used interchangeably, porpoises are not considered dolphins and have different physical features such as a shorter beak and spade-shaped teeth; they also differ in their behavior. Porpoises belong to the family Phocoenidae and share a common ancestry with the Delphinidae.
A group of dolphins is called a "school" or a "pod." Male dolphins are called "bulls," females called "cows," and young dolphins are called "calves."
In history and religion
Dolphins have long played a role in human culture. Dolphins are sometimes used as symbols, for instance in heraldry.
In Greek myths, dolphins were seen invariably as helpers of humankind. Dolphins also seem to have been important to the Minoans, judging by artistic evidence from the ruined palace at Knossos. During the 2009 excavations of a major Mycenaean city at Iklaina, a striking fragment of a wall painting came to light, depicting a ship with three human figures and dolphins. Dolphins are common in Greek mythology, and many coins from ancient Greece have been found which feature a man, a boy or a deity riding on the back of a dolphin. The Ancient Greeks welcomed dolphins; spotting dolphins riding in a ship's wake was considered a good omen. In both ancient and later art, Cupid is often shown riding a dolphin. A dolphin rescued the poet Arion from drowning and carried him safe to land, at Cape Matapan, a promontory forming the southernmost point of the Peloponnesus. There was a temple to Poseidon and a statue of Arion riding the dolphin.
The Greeks reimagined the Phoenician god Melqart as Melikertês or Melicertes and made him the son of Athamas and Ino. He drowned but was transfigured as the marine deity Palaemon, while his mother became Leucothea. At Corinth, he was so closely connected with the cult of Poseidon that the Isthmian Games — originally instituted in Poseidon's honor — came to be looked upon as the funeral games of Melicertes. Phalanthus was another legendary character brought safely to shore in Italy on the back of a dolphin, according to Pausanias.
Dionysus was once captured by Etruscan pirates who mistook him for a wealthy prince they could ransom. After the ship set sail Dionysus invoked his divine powers, causing vines to overgrow the ship where the mast and sails had been. He turned the oars into serpents, so terrifying the sailors that they jumped overboard, but Dionysus took pity on them and transformed them into dolphins so that they would spend their lives providing help for those in need. Dolphins were also the messengers of Poseidon and sometimes did errands for him as well. Dolphins were sacred to both Aphrodite and Apollo.
When heraldry developed in the Middle Ages, not much was known about the biology of the dolphin and it was often depicted as a sort of fish. Traditionally, the stylized dolphins in heraldry still may take after this notion, sometimes showing the dolphin skin covered with fish scales.
When heraldry developed in the Middle Ages, not much was known about the biology of the dolphin and it was often depicted as a sort of fish. Traditionally, the stylized dolphins in heraldry still may take after this notion, sometimes showing the dolphin skin covered with fish scales.
Dolphins are present in the coat of arms of Anguilla and the coat of arms of Romania and the coat of arms of Barbados has a dolphin supporter.
A well-known historical example of a dolphin in heraldry, was the arms for the former province of the Dauphiné in southern France, from which were derived the arms and the title of the Dauphin of France, the heir to the former throne of France. The title literally means "The Dolphin of France."
"Dolfin" was the name of an aristocratic family in the maritime Republic of Venice, whose most prominent member was the 13th Century Doge Giovanni Dolfin.
In Hindu mythology the Ganges river dolphin is associated with Ganga, the deity of the Ganges river. The dolphin is said to be among the creatures which heralded the goddess' descent from the heavens and her mount, the Makara, is sometimes depicted as a dolphin.
The Boto — a species of river dolphin that resides in the Amazon River — are believed to be shapeshifters or encantados who are capable of having children with human women.
There are comparatively few surviving myths of dolphins in Polynesian cultures, in spite of their maritime traditions and relevance of other marine animals such as sharks and seabirds; unlike these, they are more often perceived as food than as totemic symbols. Dolphins are most clearly represented in Rapa Nui Rongorongo, and in the traditions of the Caroline Islands they are depicted similarly to the Boto, being sexually active shapeshifters.
Evolution
Dolphins are descendants of land-dwelling mammals of the artiodactyl order or even-toed ungulates. They are related to the Indohyus, an extinct chevrotain-like ungulate, from which they split approximately 48 million years ago.
The primitive cetaceans or archaeocetes first took to the sea approximately 49 million years ago and became fully aquatic by 5–10 million years later.
Archaeoceti is a parvorder comprising ancient whales. These ancient whales are the predecessors of modern whales, stretching back to their first ancestor that spent their lives near — rarely in — the water. Likewise, the archaeocetes can be anywhere from near fully terrestrial to semi-aquatic to fully aquatic, but what defines an archaeocete is the presence of visible legs or asymmetrical teeth. Their features became adapted for living in the marine environment. Major anatomical changes include the hearing setup that channeled vibrations from the jaw to the earbone which occurred with Ambulocetus 49 million years ago, a streamlining of the body and the growth of flukes on the tail which occurred around 43 million years ago with Protocetus, the migration of the nasal openings toward the top of the cranium and the modification of the forelimbs into flippers which occurred with Basilosaurus 35 million years ago and the shrinking and eventual disappearance of the hind limbs which took place with the first odontocetes and mysticetes 34 million years ago. The modern dolphin skeleton has two small, rod-shaped pelvic bones thought to be vestigial hind limbs. 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 an unusually pronounced development of these vestigial hind limbs.
Today, the closest living relatives of cetaceans are the hippopotamuses; these share a semi-aquatic ancestor that branched off from other artiodactyls some 60 million years ago. Around 40 million years ago, a common ancestor between the two branched off into cetacea and anthracotheres; anthracotheres became extinct at the end of the Pleistocene two-and-a-half million years ago, eventually leaving only one surviving lineage: the hippo.
Anatomy
Dolphins have torpedo-shaped bodies with generally non-flexible necks, limbs modified into flippers, a tail fin and bulbous heads. Dolphin skulls have small eye orbits, long snouts and eyes placed on the sides of its head; they lack external ear flaps. Dolphins range in size from the 5 feet 7 inches long and 110-lb Māui dolphin to the 31 feet 2 inches and 11-short-tons killer whale. Overall, they tend to be dwarfed by other Cetartiodactyls. Several species have female-biased sexual dimorphism, with the females being larger than the males.
Dolphins have conical teeth, as opposed to porpoises' spade-shaped teeth. These conical teeth are used to catch swift prey such as fish, squid or large mammals, such as seal.
Breathing involves expelling stale air from their blowhole, in an upward blast, which may be visible in cold air, followed by inhaling fresh air into the lungs. Dolphins have rather small, unidentifiable spouts.
All dolphins have a thick layer of blubber, thickness varying on climate. This blubber can help with buoyancy, protection to some extent as predators would have a hard time getting through a thick layer of fat and energy for leaner times; the primary usage for blubber is insulation from the harsh climate. Calves, generally, are born with a thin layer of blubber, which develops at different paces depending on the habitat.
Dolphins have a two-chambered stomach that is similar in structure to terrestrial carnivores. They have fundic and pyloric chambers.
Dolphins' reproductive organs are located inside the body, with genital slits on the ventral or belly side. Males have two slits, one concealing the penis and one further behind for the anus. Females have one genital slit — housing the vagina and the anus — with a mammary slit on either side.
Locomotion
Dolphins have two pectoral flippers, containing four digits, a boneless dorsal fin for stability and a tail fin for propulsion. Although dolphins do not possess external hind limbs, some possess discrete rudimentary appendages, which may contain feet and digits. Dolphins are fast swimmers in comparison to seals which typically cruise at 5.6–17.4 mph; the killer whale or orca, in comparison, can travel at speeds up to 34.5 mph. The fusing of the neck vertebrae, while increasing stability when swimming at high speeds, decreases flexibility, which means they are unable to turn their heads. River dolphins have non-fused neck vertebrae and can turn their heads up to 90°. Dolphins swim by moving their tail fin and rear body vertically, while their flippers are mainly used for steering. Some species log out of the water, which may allow them to travel faster. Their skeletal anatomy allows them to be fast swimmers. All species have a dorsal fin to prevent themselves from involuntarily spinning in the water.
Some dolphins are adapted for diving to great depths. In addition to their streamlined bodies, some can selectively slow their heart rate to conserve oxygen. Some can also reroute blood from tissue tolerant of water pressure to the heart, brain and other organs.
Their hemoglobin and myoglobin store oxygen in body tissues, and they have twice the concentration of myoglobin than hemoglobin.
Sensory
The dolphin ear has specific adaptations to the marine environment. In humans, the middle ear works as an impedance equalizer between the outside air's low impedance and the cochlear fluid's high impedance. In dolphins, and other marine mammals, there is no great difference between the outer and inner environments. Instead of sound passing through the outer ear to the middle ear, dolphins receive sound through the throat, from which it passes through a low-impedance, fat-filled cavity to the inner ear. The dolphin ear is acoustically isolated from the skull by air-filled sinus pockets, which allow for greater directional hearing underwater. Dolphins send out high frequency clicks from an organ known as a melon. This melon consists of fat, and the skull of any such creature containing a melon will have a large depression. This allows dolphins to produce biosonar for orientation. Though most dolphins do not have hair, they do have hair follicles that may perform some sensory function. Beyond locating an object, echolocation also provides the animal with an idea on an object's shape and size, though how exactly this works is not yet understood. The small hairs on the rostrum of the boto are believed to function as a tactile sense, possibly to compensate for the boto's poor eyesight.
The dolphin eye is relatively small for its size, yet they do retain a good degree of eyesight. As well as this, the eyes of a dolphin are placed on the sides of its head, so their vision consists of two fields, rather than a binocular view like humans have. When dolphins surface, their lens and cornea correct the nearsightedness that results from the refraction of light; they contain both rod and cone cells, meaning they can see in both dim and bright light, but they have far more rod cells than they do cone cells. They lack short wavelength sensitive visual pigments in their cone cells, indicating a more limited capacity for color vision than most mammals. Most dolphins have slightly flattened eyeballs, enlarged pupils which shrink as they surface to prevent damage, slightly flattened corneas and a tapetum lucidum or layer of tissue; these adaptations allow for large amounts of light to pass through the eye and, therefore, a very clear image of the surrounding area. They also have glands on the eyelids and outer corneal layer that act as protection for the cornea.
The olfactory lobes and nerve are absent in dolphins, suggesting that they have no sense of smell.
Dolphins are not thought to have a good sense of taste, as their taste buds are atrophied or missing altogether. Some have preferences for different kinds of fish, indicating some taste.
Socialization
Dolphins are highly social animals, often living in pods of up to a dozen individuals, though pod sizes and structures vary greatly between species and locations. In places with a high abundance of food, pods can merge temporarily, forming a superpod; such groupings may exceed 1,000 dolphins. Membership in pods is not rigid; interchange is common. They establish strong social bonds and will stay with injured or ill members, helping them to breathe by bringing them to the surface if needed. This altruism does not appear to be limited to their own species. The dolphin Moko in New Zealand has been observed guiding a female pygmy sperm whale 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 communicate using a variety of clicks, whistle-like sounds and other vocalizations. Dolphins also use nonverbal communication by means of touch and posturing.
Dolphins also display culture, something long believed to be unique to humans and possibly other primate species. In May 2005, a discovery in Australia found Indo-Pacific bottlenose dolphins teaching their young to use tools. They cover their snouts with sponges to protect them while foraging. This knowledge is mostly transferred by mothers to daughters, unlike simian 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.
Forms of caregiving between fellows and even for members of different species are recorded in various species — such as trying to save weakened fellows or female pilot whales holding up dead calves for long periods.
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 can get into disputes over companions and females. Acts of aggression can become so intense that targeted dolphins sometimes go into exile after losing a fight.
Male bottlenose dolphins have been known to engage in infanticide. 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. The Cornwall Wildlife Trust records about one such death a year. Possible explanations include misdirected infanticide, misdirected sexual aggression or play behavior.
Feeding
There are various feeding methods 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. Orcas on occasion also hunt whale species larger than themselves. Different breeds of dolphins vary widely in the number of teeth they possess. The orca or killer whale usually carries 40-56 teeth while the popular bottlenose dolphin has anywhere from 72 to 116 conical teeth, and its smaller cousin the common dolphin has 188-268 teeth so that the number of teeth each breed carries varies widely between individuals. Hybrids between common and bottlenose bred in captivity had an intermediate amount of teeth.
One common feeding method is herding, where a pod squeezes a school of fish into a small volume, known as a bait ball. Individual members then take turns plowing through the ball, feeding on the stunned fish. Corralling is a method where dolphins chase fish into shallow water to catch them more easily. Orcas and bottlenose dolphins have also been known to drive their prey onto a beach to feed on it, a behavior known as beach or strand feeding. 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 Roman author and natural philosopher Pliny the Elder. A modern human-dolphin partnership currently operates in Laguna, Santa Catarina, Brazil. 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.
In Shark Bay, Australia, dolphins catch fish by trapping them in huge conch shells. In "shelling," a dolphin brings the shell to the surface and shakes it, so that fish sheltering within fall into the dolphin's mouth. From 2007 to 2018, in 5,278 encounters with dolphins, researchers observed 19 dolphins shelling 42 times. The behavior spreads mainly within generations, rather than being passed from mother to offspring.
Vocalization
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 the way 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.
Bottlenose dolphins have been found to have signature whistles, a whistle that is unique to a specific individual. These whistles are used in order for dolphins to communicate with one another by identifying an individual. It can be seen as the dolphin equivalent of a name for humans. These signature whistles are developed during a dolphin's first year; it continues to maintain the same sound throughout its lifetime. In order to obtain each individual whistle sound, dolphins undergo vocal production learning. This consists of an experience with other dolphins that modifies the signal structure of an existing whistle sound. An auditory experience influences the whistle development of each dolphin. Dolphins can communicate to one another by addressing another dolphin through mimicking their whistle. The signature whistle of a male bottlenose dolphin tends to be similar to that of his mother, while the signature whistle of a female bottlenose dolphin tends to be more distinguishing. Bottlenose dolphins have a strong memory when it comes to these signature whistles, as they are able to relate to a signature whistle of an individual they have not encountered for over 20 years. Research done on signature whistle usage by other dolphin species is relatively limited. The research on other species done so far has yielded varied outcomes and inconclusive results.
Because dolphins are generally associated in groups, communication is necessary. Signal masking is when other similar sounds or conspecific sounds interfere with the original acoustic sound. In larger groups, individual whistle sounds are less prominent. Dolphins tend to travel in pods, upon which there are groups of dolphins that range from a few to many. Although they are traveling in these pods, the dolphins do not necessarily swim right next to each other. Rather, they swim within the same general vicinity. To prevent losing one of their pod members, there are higher whistle rates. Because their group members were spread out, this was done to continue traveling together.
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