123-463: See text Porpoises ( / ˈ p ɔː r p ə s ɪ z / ) are small dolphin -like cetaceans classified under the family Phocoenidae . Although similar in appearance to dolphins , they are more closely related to narwhals and belugas than to the true dolphins . There are eight extant species of porpoise, all among the smallest of the toothed whales . Porpoises are distinguished from dolphins by their flattened, spade-shaped teeth distinct from
246-530: A dolphinarium . Bottlenose dolphins are the most common species of dolphin kept in dolphinariums as they are relatively easy to train, have a long lifespan in captivity and have a friendly appearance. Hundreds if not thousands of bottlenose dolphins live in captivity across the world, though exact numbers are hard to determine. Other species kept in captivity are spotted dolphins , false killer whales and common dolphins , Commerson's dolphins , as well as rough-toothed dolphins , but all in much lower numbers than
369-447: A dorsal fin to prevent themselves from involuntarily spinning in the water. The oceanic dolphin ear is specifically adapted 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
492-401: A beached Vaquita showed remains of squid and grunts . Nothing is known about the diet of the spectacled porpoise. The tube in the head, through which this kind fish takes its breath and spitting water, located in front of the brain and ends outwardly in a simple hole, but inside it is divided by a downward bony septum, as if it were two nostrils; but underneath it opens up again in the mouth in
615-679: A dolphin in his coat of arms as King of Naples and Sicily. In contemporary days, a dolphin is still used in the coat of arms of many cities, as well as 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 . Cardinal Angelo Amato , prefect of the Congregation of the Causes of Saints , a dolphin in his coat of arms, as well as Cardinal Godfried Danneels , former Metropolitan Archbishop of Mechelen-Brussels . Dall%27s porpoise Dall's porpoise ( Phocoenoides dalli )
738-421: A dolphin-friendly way. The earliest campaigns with "Dolphin safe" labels were initiated in the 1980s as a result of cooperation between marine activists and the major tuna companies, and involved decreasing incidental dolphin kills by up to 50% by changing the type of nets used to catch tuna. The dolphins are netted only while fishermen are in pursuit of smaller tuna. Albacore are not netted this way, making albacore
861-513: A few days after their rescue. Porpoises and other smaller cetaceans have traditionally been hunted in many areas, at least in Asia, Europe and North America, for their meat and blubber. A dominant hunting technique is drive hunting, where a pod of animals is driven together with boats and usually into a bay or onto a beach. Their escape is prevented by closing off the route to the ocean with other boats or nets. This type of fishery for harbour porpoises
984-411: A few, like the orca, 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, and females bear all the responsibility for raising them. Mothers of some species fast and nurse their young for relatively long times. Dolphins produce a variety of vocalizations, usually in
1107-677: A flavor very similar to beef liver . Dolphin meat is high in mercury, and may pose a health danger to humans when consumed. The Faroe Islands population was exposed to methylmercury largely from contaminated pilot whale meat, which contained very high levels of about 2 mg methylmercury/kg. However, the Faroe Islands populations also eat significant amounts of fish. The study of about 900 Faroese children showed that prenatal exposure to methylmercury resulted in neuropsychological deficits at 7 years of age – World Health Organization There have been human health concerns associated with
1230-508: A good degree of eyesight. As well as this, the eyes of a porpoise are placed on the sides of its head, so their vision consists of two fields, rather than a binocular view like humans have. When porpoises surface, their lens and cornea correct the nearsightedness that results from the refraction of light; their eyes contain both rod and cone cells, meaning they can see in both dim and bright light. Porpoises do, however, lack short wavelength sensitive visual pigments in their cone cells indicating
1353-486: A good sense of taste, as their taste buds are atrophied or missing altogether. However, some have preferences between different kinds of fish, indicating some sort of attachment to taste. Unlike most animals, porpoises are conscious breathers. All mammals sleep, but porpoises cannot afford to become unconscious for long because they may drown. While knowledge of sleep in wild cetaceans is limited, porpoises in captivity have been recorded to sleep with one side of their brain at
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#17327724848301476-399: A known predator, with at least one documented case on the eastern North Pacific Ocean. Dall's porpoises are highly active swimmers. Rapid swimming at the surface creates a characteristic spray called a "rooster tail". They are commonly seen approaching boats to bowride, and they will also ride on the waves formed at the heads of larger swimming whales. Abundance throughout their range and
1599-451: 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 ; 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
1722-514: A more limited capacity for colour vision than most mammals. Most porpoises have slightly flattened eyeballs, enlarged pupils (which shrink as they surface to prevent damage), slightly flattened corneas and a tapetum lucidum ; these adaptations allow for large amounts of light to pass through the eye and, therefore, they are able to form a very clear image of the surrounding area. The olfactory lobes are absent in porpoises, suggesting that they have no sense of smell. Porpoises are not thought to have
1845-403: A newborn calf's mouth does not allow it to obtain a seal around the nipple—instead of the calf sucking milk, the mother squirts milk into the calf's mouth. This milk contains high amounts of fat, which aids in the development of blubber; it contains so much fat that it has the consistency of toothpaste. The calves are weaned at about 11 months of age. Males play no part in rearing calves. The calf
1968-414: A polygynous mating system in which males compete for females. During the mating season, a male will select a fertile female and guard her to ensure paternity. While guarding, males may sacrifice opportunities to forage on deep dives. Births usually take place in the summer after a gestation period of 11 to 12 months. Females generally give birth every 3 years, depending on their condition. Life expectancy
2091-468: A range of tens to hundreds of square kilometres. Some pods have a loose social structure, with individuals frequently joining or leaving, but others seem to be more permanent, perhaps dominated by a male and a harem of females. Individuals communicate by sound, producing low-frequency whistles, and also produce high-frequency broadband clicks of 80–220 kHz, which are primarily used for echolocation . Gestation lasts from 10 to 18 months, and results in
2214-406: A signature whistle of an individual they have not encountered for over twenty 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. Oceanic dolphins frequently leap above the water surface, this being done for various reasons. When travelling, jumping can save
2337-404: A smaller number of squid and small crustaceans, but some species specialise in eating squid, or, in the case of the orca, also eat marine mammals and birds. All, however, are purely carnivorous . They typically have between 100 and 200 teeth, although a few species have considerably fewer. Delphinids travel in large pods, which may number a thousand individuals in some species. Each pod forages over
2460-424: A thick layer from the milk, which has a very high fat content. Porpoises have two flippers on the front and a tail fin. Their flippers contain four digits. Although porpoises do not possess fully developed hind limbs, they possess discrete rudimentary appendages, which may contain feet and digits. Porpoises are fast swimmers in comparison to seals, which typically cruise at 9–28 km/h (5–15 kn). The fusing of
2583-411: A time, so that they may swim, breathe consciously, and avoid both predators and social contact during their period of rest. Porpoises are fully aquatic creatures. Females deliver a single calf after a gestation period lasting about a year. Calving takes place entirely under water, with the foetus positioned for tail-first delivery to help prevent drowning. Females have mammary glands, but the shape of
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#17327724848302706-607: A variety of surface and mid-water species. Common prey are mesopelagic fish, such as myctophids , and gonatid squid. Stomach content analyses have also found cases of crustacean consumption, including krill and shrimp, but this is abnormal and likely not an important part of their diet. A previous study revealed that tagged Dall's porpoises spent most of their time within 10 m of the surface, but have been recorded diving to depths of up to 94 m. Dall's porpoises live in small, fluid groups of two to ten individuals, but aggregations of hundreds have been reported. They have
2829-416: A void. –John Ray, 1671, the earliest description of cetacean airways In Aristotle 's time, the 4th century BCE, porpoises were regarded as fish due to their superficial similarity. Aristotle, however, could already see many physiological and anatomical similarities with the terrestrial vertebrates, such as blood (circulation), lungs, uterus and fin anatomy. His detailed descriptions were assimilated by
2952-870: A white belly patch that extends farther forward across the body than that of the dalli type. Dall's porpoises are limited to the North Pacific: in the east from California to the Bering Sea and Okhotsk Sea , and in the west down to the Sea of Japan . They have been sighted as far south as Scammon's Lagoon in Baja California when water temperature was unseasonably cold. Dall's porpoises generally prefer cold waters less than 18 °C (64 °F). Although mostly an offshore species, they do occur in deeper coastal waters, near submarine canyons or in fjords . Dall's porpoises are opportunistic, hunting
3075-412: A wide range of colors and patterns. Oceanic dolphins have a torpedo-shaped, muscular body with an inflexible neck, limbs modified into flippers, nonexistent external ear flaps, a large tail fin, and a bulbous head. A dolphin skull has small eye orbits, a long snout, but not as long as its river dolphin counterpart, and eyes placed on the sides of its head. Several species exhibit sexual dimorphism, with
3198-789: A zoo in Germany. At least 150 harbour porpoises have been kept worldwide, but only about 20 were actively caught for captivity. The captive history is best documented from Denmark where about 100 harbour porpoises have been kept, most in the 1960s and 1970s. All but two were incidental catches in fishing nets or strandings. Nearly half of these died within a month of diseases caught before they were captured or from damage sustained during capture. Up until 1984, none lived for more than 14 months. Attempts to rehabilitate seven rescued individuals in 1986 only resulted in three that could be released 6 months later. Very few have been brought into captivity later, but they have lived considerably longer. In recent decades,
3321-451: Is Dall's porpoise. Odontocetes possess teeth with cementum cells overlying dentine cells. Unlike human teeth, which are composed mostly of enamel on the portion of the tooth outside of the gum, whale teeth have cementum outside the gum. Porpoises have a three-chambered stomach, including a fore-stomach and fundic and pyloric chambers. Porpoises, like other odontocetes, possess only one blowhole. Breathing involves expelling stale air from
3444-487: Is a species of porpoise endemic to the North Pacific . It is the largest of porpoises and the only member of the genus Phocoenoides . The species is named after American naturalist W. H. Dall . Dall's porpoise is the only member of the genus Phocoenoides . The dalli and truei types were initially described as separate species in 1911, but later studies determined that the available evidence only supported
3567-513: Is a serious problem for marine mammals. Heavy metals and plastic waste are not biodegradable, and sometimes cetaceans consume these hazardous materials, mistaking them for food items. As a result, the animals are more susceptible to diseases and have fewer offspring. Harbour porpoises from the English Channel were found to have accumulated heavy metals. The military and geologists employ strong sonar and produce an increases in noise in
3690-488: Is about 15 to 20 years, but a lot about their mortality is unknown. Dall's porpoises are prey to transient killer whales . They have, however, been observed in association with resident killer whales, engaging in apparent play behaviors with their calves, and swimming with them. One recognizable Dall's porpoise was observed travelling with the AB pod of resident orca from May through October 1984. Great white sharks are also
3813-454: Is apparent in body size and shape, with mature males being larger, developing a deeper caudal peduncle, and having a dorsal fin that is significantly angled forward in comparison to a female's. Dall's porpoise calves have a greyish coloration with no frosting on flippers and flukes. Calves measure about 100 cm at birth. Growth rates are similar at first, but at about two years old males begin to grow faster than females. Externally, maturity
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3936-635: Is best documented from the Danish straits , where it occurred until the end of the 19th century (it was banned in 1899), and again during the shortages in World War I and World War II . The Inuit in the Arctic hunt harbour porpoises by shooting and drive hunt for Dall's porpoise still takes place in Japan. The number of individuals taken each year is in the thousands, although a quota of around 17,000 per year
4059-414: Is consumed. Atlantic porpoises are thought to follow the seasonal migration of bait fish , like herring , and their diet varies between seasons. The stomach contents of Dall's porpoises reveal that they mainly feed on cephalopods and bait fish, like capelin and sardines . Their stomachs also contained some deep-sea benthic organisms. The finless porpoise is known to also follow seasonal migrations. It
4182-470: Is dependent for one to two years, and maturity occurs after seven to ten years, all varying between species. This mode of reproduction produces few offspring, but increases the probability of each one surviving. Porpoises eat a wide variety of creatures. The stomach contents of harbour porpoises suggests that they mainly feed on benthic fish , and sometimes pelagic fish . They may also eat benthic invertebrates. In rare cases, algae, such as Ulva lactuca ,
4305-441: Is estimated to be over one million, but current population trends are unknown. Surveys along the coasts of California, Oregon, and Washington between 2008 and 2014 estimated a population abundance of 25,800. Alaska's population is estimated to be 83,400. Abundance in coastal British Columbia is nearly 5,000 individuals. Populations in the western North Pacific are divided by both subspecies and migratory patterns. Abundance of
4428-494: Is herding, where a pod squeezes a school of fish into 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. Orca 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
4551-472: Is in effect today making it the largest direct hunt of any cetacean species in the world and the sustainability of the hunt has been questioned. Porpoises are highly affected by bycatch . Many porpoises, mainly the vaquita , are subject to great mortality due to gillnetting . Although it is the world's most endangered marine cetacean, the vaquita continues to be caught in small-mesh gillnet fisheries throughout much of its range. Incidental mortality caused by
4674-489: Is known that populations in the mouth of the Indus River migrate to the sea from April through October to feed on the annual spawning of prawns . In Japan, sightings of small pods of them herding sand lance onto shore are common year-round. Little is known about the diets of other species of porpoises. A dissection of three Burmeister's porpoises shows that they consume shrimp and euphausiids (krill). A dissection of
4797-595: Is listed as Least Concern on the IUCN Red List . Levels of both bycatch and commercial hunting are likely underestimates because they account only for reported data; however, there is no evidence for a range-wide decline of the species. The species is also listed on Appendix II of the Convention on the Conservation of Migratory Species of Wild Animals (CMS), and, like all other marine mammal species,
4920-443: Is located in a layer of blubber between the meat and the skin. When dolphin meat is eaten in Japan, it is often cut into thin strips and eaten raw as sashimi , garnished with onion and either horseradish or grated garlic , much as with sashimi of whale or horse meat ( basashi ). When cooked, dolphin meat is cut into bite-size cubes and then batter-fried or simmered in a miso sauce with vegetables. Cooked dolphin meat has
5043-403: Is measured by length which is usually attained at 3–5 years. Sizes vary between populations, but on average females reach a maximum size of 210 cm and males grow to about 220 cm, except in the southern Okhotsk Sea where males can grow as long as 239 cm. Two colormorphs have been identified: the dalli type and truei type. The truei type, found only in the western Pacific, has
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5166-450: Is nearly extinct due to bycatch in gill nets, with a predicted population of fewer than a dozen individuals. Since the extinction of the baiji , the vaquita is considered the most endangered cetacean. Some species of porpoises have been and are kept in captivity and trained for research, education and public display. Porpoises, along with whales and dolphins , are descendants of land-living ungulates (hoofed animals) that first entered
5289-458: Is rapidly declining because of bycatch in gillnets), there have been attempts of transferring some to captivity. The first and only caught for captivity were two females in 2017. Both became distressed and were rapidly released, but one of them died in the process. Soon after the project was abandoned. Only a single Burmeister's porpoise and a single spectacled porpoise have been kept in captivity. Both were stranded individuals that only survived
5412-552: 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. Dolphins do, however, lack short wavelength sensitive visual pigments in their cone cells indicating
5535-419: Is seen, by some, to be a sign of highly developed, abstract thinking. Self-awareness, though not well-defined scientifically, is believed to be the precursor to more advanced processes like meta-cognitive reasoning (thinking about thinking) that are typical of humans. Research in this field has suggested that cetaceans, among others, possess self-awareness. The most widely used test for self-awareness in animals
5658-467: Is still harvested for meat in Japan. The number of individuals taken each year increased following the 1980s moratorium on whaling of larger cetacean species. In 1988, more than 45,000 Dall's porpoises were harpooned. In 1990, after international attention was drawn to the issue, the Japanese government introduced a reduction on take. A quota of over 17,000 a year is in effect today (9,000 dalli type in
5781-411: Is the bottlenose dolphin , and less than 50 orca were found in oceanariums in 2012. Delphinids, especially bottlenose dolphins, are able to hybridize with a wide variety of other delphinid species; wholphins are just one of many possible hybrids. Six species, sometimes referred to as "blackfish", are dolphins commonly called whales: the orca , the melon-headed whale , the pygmy killer whale ,
5904-537: Is the mirror test in which a temporary dye is placed on an animal's body, and the animal is then presented with a mirror; they then see if the animal shows signs of self-recognition. In 1995, Marten and Psarakos used television to test dolphin self-awareness. They showed dolphins real-time footage of themselves, recorded footage, and another dolphin. They concluded that their evidence suggested self-awareness rather than social behavior. While this particular study has not been repeated since then, dolphins have since passed
6027-704: The Convention on the Conservation of Migratory Species of Wild Animals (CMS). In addition, the Harbour porpoise is covered by the Agreement on the Conservation of Small Cetaceans of the Baltic, North East Atlantic, Irish and North Seas (ASCOBANS), the Agreement on the Conservation of Cetaceans in the Black Sea, Mediterranean Sea and Contiguous Atlantic Area (ACCOBAMS) and the Memorandum of Understanding Concerning
6150-690: The Dauphin de Viennois (later Dauphin of France ) through which it passed to the Counts of Forez , Albon and other French families, as well as several branches of the Bourbon family ( Count of Montpensier , Count of Beaujolais , among others) the Pandolfini of Florence, and the Delfini of Venice and Rome also used the dolphin as their "canting" armories. In the 19th century, Joseph Bonaparte adopted
6273-1105: The Dolfinarium Harderwijk , the Netherlands. In addition to the few kept in Europe, harbour porpoise were displayed at the Vancouver Aquarium (Canada) until recently. This was a female that had beached herself onto Horseshoe Bay in 2008 and a male that had done the same in 2011. They died in 2017 and 2016 respectively. Finless porpoises have commonly been kept in Japan, as well as China and Indonesia. As of 1984, ninety-four in total had been in captivity in Japan, eleven in China, and at least two in Indonesia. As of 1986, three establishments in Japan had bred them, and there had been five recorded births. Three calves died moments after their birth, but two survived for several years. This breeding success, combined with
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#17327724848306396-634: The Globicephalinae (round-headed whales, which include the false killer whale and pilot whale ). Delphinidae is a family within the superfamily Delphinoidea , which also includes the porpoises (Phocoenidae) and the Monodontidae ( beluga whale and narwhal ). River dolphins are relatives of the Delphinoidea. Oceanic dolphins range in size from the 1.7-metre-long (5 ft 7 in) and 50-kilogram (110-pound) Maui's dolphin to
6519-478: 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 dolphins in heraldry still may take after this notion, sometimes showing the dolphin skin covered with fish scales . In the Middle Ages , the dolphin became an important heraldic element in the coats of arms of several European noble families, the most noticeable being those of
6642-754: The United Nations issued a moratorium in the 1990s. Before the moratorium went into effect, 8,000 Dall's porpoises are estimated to have been bycaught in one year alone (1989–1990). Smaller numbers, from several hundred to a few thousand, are estimated to have been bycaught in Japanese salmon fisheries in US waters and in the Bering Sea from 1981 to 1987. Driftnet and trawl fisheries still operate in some areas throughout their range, with particularly high levels of bycatch in Russian waters. The Dall's porpoise
6765-628: The World Wildlife Fund to ensure the future for this subspecies, and have placed five porpoises in another well-protected area, the He-wang-miao oxbow. Five protected natural reserves have been established in areas of the highest population density and mortality rates with measures being taken to ban patrolling and harmful fishing gear in those areas. There have also been efforts to study porpoise biology to help specialize conservation through captivation breeding. The Baiji Dolphinarium,
6888-412: The blowhole , forming an upward, steamy spout, followed by inhaling fresh air into the lungs. All porpoises have a thick layer of blubber . This blubber can help with insulation from the harsh underwater climate, protection to some extent as predators would have a hard time getting through a thick layer of fat, and energy for leaner times. Calves are born with only a thin layer of blubber, but rapidly gain
7011-512: The false killer whale , and the two species of pilot whales , but they are classified under the family Delphinidae . Recent molecular analyses indicate that several delphinid genera (especially Stenella and Lagenorhynchus ) are not monophyletic as currently recognized. Thus, significant taxonomic revisions within the family are likely. Extinct taxon, according to the Paleobiology Database. The Delphinidae are
7134-861: The 1960s resulted in the appearance of many dolphinaria around the world, making dolphins accessible to the public. Criticism and animal welfare laws forced many to close, although hundreds still exist around the world. In the United States , the best known are the SeaWorld marine mammal parks . In the Middle East the best known are Dolphin Bay at Atlantis, The Palm and the Dubai Dolphinarium . Various species of dolphins are kept in captivity. These small cetaceans are more often than not kept in theme parks, such as SeaWorld , commonly known as
7257-432: The 9.4-metre (31 ft) and 10-metric-ton (11-short-ton) orca , the largest known dolphin. Several species exhibit sexual dimorphism ; the males are larger than females. They have streamlined muscular bodies and two limbs that are modified into flippers. Though not quite as flexible as seals , some dolphins can travel at speeds 29 km/h (18 mph) for short distances. Most delphinids primarily eat fish, along with
7380-588: The Conservation of the Manatee and Small Cetaceans of Western Africa and Macaronesia. Their conservation statuses are either at least concern or data deficient . As of 2014, only 505 Yangtze finless porpoises remained in the main section of the Yangtze, with an alarming population density in Ezhou and Zhenjiang. While many threatened species decline rate slows after their classification, population decline rates of
7503-577: The European coasts and Southern Hemisphere only much later, during the Pliocene . Recently discovered hybrids between male harbour porpoises and female Dall's porpoises indicate the two species may actually be members of the same genus . Porpoises have a bulbous head, no external ear flaps, a non-flexible neck, a torpedo shaped body, limbs modified into flippers, and a tail fin. Their skull has small eye orbits, small, blunt snouts, and eyes placed on
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#17327724848307626-499: The Japan-southern Okhotsk Sea population; 8,700 from the truei -type population that migrates into the central Okhotsk Sea) making it the largest direct hunt of any cetacean species in the world. The hunt of Dall's porpoises has been criticized by scientific committees which question the sustainability of large quotas on regional populations. Assessments are outdated for these targeted populations, and given
7749-768: The Mexican government has created a nature reserve covering the upper part of the Gulf of California and the Colorado River delta . They have also placed a temporary ban on fishing, with compensation to those affected, that may pose a threat to the vaquita. Oceanic dolphin See text . Oceanic dolphins or Delphinidae are a widely distributed family of dolphins that live in the sea . Close to forty extant species are recognised. They include several big species whose common names contain "whale" rather than "dolphin", such as
7872-549: The Romans, but mixed with a more accurate knowledge of the dolphins, as mentioned by Pliny the Elder in his "Natural history". In the art of this and subsequent periods, porpoises are portrayed with a long snout (typical of dolphins) and a high-arched head. The harbour porpoise was one of the most accessible species for early cetologists , because it could be seen very close to land, inhabiting shallow coastal areas of Europe. Much of
7995-486: The assumption that they would fare better than their dolphin counterparts due to their smaller size and shallow-water habitats. Up until the 1980s, they were consistently short-lived. Harbour porpoises have a very long captive history, with poorly documented attempts as early as the 15th century, and better documented starting in the 1860s and 1870s in London Zoo , the now-closed Brighton Aquarium & Dolphinarium, and
8118-442: The birth of a single calf. 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 oceanic dolphins are widespread, most species prefer the warmer waters of the tropic zones, but some, like the right whale dolphin , prefer colder climates. Some have a global distribution, like the orca. Oceanic dolphins feed largely on fish and squid, but
8241-546: The bottlenose dolphin. There are also fewer than ten pilot whales , Amazon river dolphins , Risso's dolphins , spinner dolphins , or tucuxi in captivity. Two unusual and very rare hybrid dolphins, known as wholphins , are kept at the Sea Life Park in Hawaii , which is a cross between a bottlenose dolphin and a false killer whale . Also, two common /bottlenose hybrids reside in captivity: one at Discovery Cove and
8364-474: The brain that are homologous to where they are found in humans, suggesting that they perform a similar function. Brain size was previously considered a major indicator of the intelligence of an animal. Since most of the brain is used for maintaining bodily functions, greater ratios of brain to body mass may increase the amount of brain mass available for more complex cognitive tasks. Allometric analysis indicates that mammalian brain size scales at approximately
8487-508: The case of the orca, also eat marine mammals and birds. All, however, are purely carnivorous . They typically have between 100 and 200 teeth, although a few species have considerably fewer. Various methods of feeding exist among and within oceanic 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. Orca on occasion also hunt whales larger than themselves. One common feeding method
8610-575: The conical teeth of dolphins, and lack of a pronounced beak, although some dolphins (e.g. Hector's dolphin ) also lack a pronounced beak. Porpoises, and other cetaceans , belong to the clade Cetartiodactyla with even-toed ungulates . Porpoises range in size from the vaquita , at 1.4 metres (4 feet 7 inches) in length and 54 kilograms (119 pounds) in weight, to the Dall's porpoise , at 2.3 m (7 ft 7 in) and 220 kg (490 lb). Several species exhibit sexual dimorphism in that
8733-445: The consumption of dolphin meat in Japan after tests showed that dolphin meat contained high levels of mercury . There are no known cases of mercury poisoning as a result of consuming dolphin meat, though the government continues to monitor people in areas where dolphin meat consumption is high. The Japanese government recommends that children and pregnant women avoid eating dolphin meat on a regular basis. Similar concerns exist with
8856-780: The consumption of dolphin meat in the Faroe Islands , where prenatal exposure to methylmercury and PCBs primarily from the consumption of pilot whale meat has resulted in neuropsychological deficits amongst children. Legally consuming dolphin meat in the United States would be near impossible for most due to the Marine Mammal Protection Act , which forbids "...the act of hunting, killing, capture, and/or harassment of any marine mammal..." (Exceptions are made for certain groups of people, such as Alaska Natives .) Theoretically, one could only eat
8979-498: The cornea. The olfactory lobes are absent in oceanic dolphins, suggesting that they have no sense of smell. Oceanic dolphins are not thought to have a good sense of taste, as their taste buds are atrophied or missing altogether. However, some have preferences between different kinds of fish, indicating some sort of attachment to taste. Most delphinids primarily eat fish, along with a smaller number of squid and small crustaceans, but some species specialize in eating squid, or, in
9102-859: The creation of the International Committee for the Recovery of the Vaquita (CIRVA), which has tried to prevent the accidental deaths of vaquitas by outlawing the use of fishing nets within the vaquita's habitat. CIRVA has worked together with the CITES , the Endangered Species Act , and the Marine Mammal Protection Act (MMPA) to nurse the vaquita population back to a point at which they can sustain themselves. CIRVA concluded in 2000 that between 39 and 84 individuals are killed each year by such gillnets. To try to prevent extinction,
9225-403: The depth of the body of water in which they are. Similar to the navy, some boats produce waves that attract porpoises, while others may repel them. The problem with the waves that attract is that the animal may be injured or even killed by being hit by the vessel or its propeller. The harbour porpoise, spectacled porpoise, Burmeister's porpoise, and Dall's porpoise are all listed on Appendix II of
9348-472: The dolphin energy as there is less friction while in the air. This type of travel is known as porpoising. Other reasons include orientation, social displays, fighting, non-verbal communication , entertainment and attempting to dislodge parasites . Dolphins show various types of playful behavior , often including objects, self-made bubble rings , other dolphins, or other animals. When playing with objects or small animals, common behavior includes carrying
9471-427: 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
9594-433: The existence of one species. Currently, these two color morphs are recognized as distinct subspecies , Dall's porpoise ( Phocoenoides dalli dalli ) and True's porpoise ( Phocoenoides dalli truei ). Dall's porpoises can be easily distinguished from other porpoises and cetacean species within their range. They have a wide, robust body, a comparatively tiny head, and no distinguished beak. Their flippers are positioned at
9717-733: The females are larger than males. They have streamlined bodies and two limbs that are modified into flippers. Porpoises use echolocation as their primary sensory system . Some species are well adapted for diving to great depths. As all cetaceans, they have a layer of fat, or blubber, under the skin to keep them warm in cold water. Porpoises are abundant and found in a multitude of environments, including rivers ( finless porpoise ), coastal and shelf waters ( harbour porpoise , vaquita ) and open ocean ( Dall's porpoise and spectacled porpoise ), covering all water temperatures from tropical ( Sea of Cortez , vaquita ) to polar ( Greenland , harbour porpoise ). Porpoises feed largely on fish and squid, much like
9840-542: The findings that apply to all cetaceans were first discovered in porpoises. One of the first anatomical descriptions of the airways of the whales on the basis of a harbor porpoise dates from 1671 by John Ray. It nevertheless referred to the porpoise as a fish, most likely not in the modern-day sense, where it refers to a zoological group, but the older reference as simply a creature of the sea (cf. for example star-fish , cuttle-fish , jelly-fish and whale-fish ). Harbour porpoises have historically been kept in captivity, under
9963-408: The first breeding happened in 2005. Small numbers of Dall's porpoises have been kept in captivity in both the United States and Japan, with the most recent being in the 1980s. The first recorded instance of a Dall's taken for an aquarium was in 1956 captured off Catalina Island in southern California. Dall's porpoises consistently failed to thrive in captivity. These animals often repeatedly ran into
10086-443: The fleet of El Golfo de Santa Clara was estimated to be at around 39 vaquitas per year, which is over 17% of the population size. Harbour porpoises also suffer drowning by gillnetting, but on a less threatening scale due to their high population; their mortality rate per year increases a mere 5% due to this. The fishing market, historically has always had a porpoise bycatch. Today, the Marine Mammal Protection Act of 1972 has enforced
10209-580: The form of clicks and whistles. Oceanic 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 , habitat loss, and marine pollution . Dolphins have been depicted in various cultures worldwide. They occasionally feature in literature and film, as in the Warner Bros film Free Willy . Dolphins are sometimes kept in captivity and trained to perform in shows. The most common species of dolphin in captivity
10332-431: The front of the body and a triangular dorsal fin sits mid-body. Patterns of coloration are highly variable, but Dall's porpoises are mostly black, have white to grey patches on the flank and belly, and frosting on the dorsal fin and trailing edge of the fluke. They are the largest porpoise species, growing up to 2.3 metres (7 ft 7 in) in length and weighing 130–220 kilograms (290–490 lb). Sexual dimorphism
10455-418: The level of annual reported take, there may be regional declines in abundance. Environmental contaminants, including dichlorodiphenyldichloroethylene (DDE) and polychlorinated biphenyls (PCBs), are another threat to Dall's porpoises. Pollutants accumulate in the blubber layer, and in high concentrations can reduce hormone levels, affect the reproductive system, and result in calf death. Dall's porpoise
10578-407: The males being larger than the females. Breathing involves expelling stale air from the blowhole , forming an upward, steamy spout, followed by inhaling fresh air into the lungs; a spout only occurs when the warm air from the lungs meets the cold external air, so it may only form in colder climates. All oceanic dolphins have a thick layer of blubber , the thickness of which depends on how far
10701-474: The meat of a dolphin which died of natural causes, which would likely be highly undesirable (and potentially dangerous). Various fishing methods, like seine fishing for tuna and the use of drift and gill nets , unintentionally kill many oceanic dolphins. Accidental bycatch in gill nets is common and poses a risk for mainly local dolphin populations. Dolphin safe labels attempt to reassure consumers that fish and other marine products have been caught in
10824-430: The mirror test. In some parts of the world, such as Taiji, Japan and the Faroe Islands , dolphins are traditionally considered as food, and are killed in harpoon or drive hunts . Dolphin meat is consumed in a small number of countries worldwide, which include Japan and Peru (where it is referred to as chancho marino , or "sea pork"). Dolphin meat is dense and such a dark shade of red as to appear black. Fat
10947-479: The most diverse of the cetacean families, with numerous variations between species. They range in size from 1.2 m (3 ft 11 in) and 40 kg (88 lb) ( Haviside's dolphin ), to 9 m (30 ft) and 10 tonnes (orca). Most species weigh between 50 and 200 kg (110 and 440 lb). They typically have curved dorsal fins, clear 'beaks' at the front of their heads, and forehead melons , although exceptions to all of these rules are found. They have
11070-503: 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. These whistles are used in order for dolphins to communicate with one another by identifying an individual. It can be seen as
11193-462: The neck vertebrae, while increasing stability when swimming at high speeds, decreases flexibility, making it impossible for them to turn their head. When swimming, they move their tail fin and lower body up and down, propelling themselves through vertical movement, while their flippers are mainly used for steering. Flipper movement is continuous. Some species log out of the water, which may allow them to travel faster, and sometimes they porpoise out of
11316-421: The neck vertebrae, while increasing stability when swimming at high speeds, decreases flexibility, which means they are unable to turn their heads. Oceanic 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
11439-406: The object or animal along using various parts of the body, passing it along to other members of the group or taking it from another member, or throwing it out of the water. Dolphins have also been observed harassing animals in other ways, for example by dragging birds underwater without showing any intent to eat them. Playful behaviour that involves another animal species with active participation of
11562-527: The oceans around 50 million years ago (Mya). During the Miocene (23 to 5 Mya ), mammals were fairly modern, meaning they seldom changed physiologically from the time. The cetaceans diversified, and fossil evidence suggests porpoises and dolphins diverged from their last common ancestor around 15 Mya. The oldest fossils are known from the shallow seas around the North Pacific, with animals spreading to
11685-486: The oceans. Marine mammals that make use of biosonar for orientation and communication are not only hindered by the extra noise, but may race to the surface in panic. This may lead to a bubbling out of blood gases, and the animal then dies because the blood vessels become blocked, so-called decompression sickness . This effect, of course, only occurs in porpoises that dive to great depths, such as Dall's porpoise. Additionally, civilian vessels produce sonar waves to measure
11808-547: The offshore dalli type is about 162,000. It is estimated that there are about 173,000 dalli type that travel between Japan and the southern Okhotsk Sea. The dalli type that migrates to the Okhotsk Sea in the summer is estimated at 111,000. The population of truei -type porpoises migrating between Japan and the central Okhotsk Sea number about 178,000. Dall's porpoises are vulnerable to fisheries bycatch. Thousands were killed in commercial driftnet fisheries until
11931-546: The only place keeping the species in Denmark is the Fjord & Bælt Centre, where three rescues have been kept, along with their offspring. Among the three rescues, one (father of world's first harbour porpoise born in captivity) lived for 20 years in captivity, another for 15 years, while the third (mother of first born in captivity) is the world's oldest known harbour porpoise, being 28 years old in 2023. The typical age reached in
12054-404: The only truly dolphin-safe tuna. Loud underwater noises, such as those resulting from naval sonar use, live firing exercises, and certain offshore construction projects such as wind farms , may be harmful to dolphins, increasing stress, damaging hearing, and causing decompression sickness by forcing them to surface too quickly to escape the noise. The renewed popularity of dolphins in
12177-583: The other animal can also be observed, however. Playful human interaction with dolphins is one example, but playful interactions have been observed in the wild with a number of other species as well, including humpback whales and dogs . Oceanic dolphins are known to teach, learn, cooperate, scheme, and grieve. The neocortex of many species is home to elongated spindle neurons that, prior to 2007, were known only in hominids. In humans, these cells are involved in social conduct, emotions, judgment, and theory of mind. Cetacean spindle neurons are found in areas of
12300-489: The other at SeaWorld San Diego . Orca are well known for their performances in shows, but the number of orcas kept in captivity is very small, especially when compared to the number of bottlenose dolphins, with only 44 captive orca being held in aquaria as of 2012. The orca's intelligence , trainability, striking appearance, playfulness in captivity and sheer size have made it a popular exhibit at aquaria and aquatic theme parks. From 1976 to 1997, 55 whales were taken from
12423-404: 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
12546-422: The outside air's low impedance and the cochlear fluid's high impedance. In whales, 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, porpoises receive sound through the throat, from which it passes through a low-impedance fat-filled cavity to the inner ear. The porpoise ear is acoustically isolated from
12669-479: 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. 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
12792-605: The porpoise are actually accelerating. While population decline tracked from 1994 to 2008 has been pegged at a rate of 6.06% annually, from 2006 to 2012, the porpoise population decreased by more than half. Finless porpoise population decrease of 69.8% in just a 22-year span from 1976 to 2000. 5.3%. A majority of factors of this population decline are being driven by the massive growth in Chinese industry since 1990 which caused increased shipping and pollution and ultimately environmental degradation . Some of these can be seen in damming of
12915-739: The rest of the odontocetes. Little is known about reproductive behaviour. Females may have one calf every year under favourable conditions. Calves are typically born in the spring and summer months and remain dependent on the female until the following spring. Porpoises produce ultrasonic clicks, which are used for both navigation ( echolocation ) and social communication. In contrast to many dolphin species, porpoises do not form large social groups. Porpoises were, and still are, hunted by some countries by means of drive hunting . Larger threats to porpoises include extensive bycatch in gill nets , competition for food from fisheries, and marine pollution , in particular heavy metals and organochlorides . The vaquita
13038-509: The results with harbour porpoise in Denmark and the Netherlands, proved that porpoises can be successfully bred in captivity, and this could open up new conservation options. The reopened Miyajima Public Aquarium (Japan) houses three finless porpoises. As part of an attempt of saving the narrow-ridged (or Yangtze) finless porpoise , several are kept in the Baiji Dolphinarium in China. After having been kept in captivity for 9 years,
13161-586: The river as well as illegal fishing activity. To protect the species, China's Ministry of Agriculture classified the species as being National First Grade Key Protected Wild Animal, the strictest classification by law, meaning it is illegal to bring harm to a porpoise. Protective measures in the Tian-e-Zhou Oxbow Nature Reserve has increased its population of porpoises from five to forty in 25 years. The Chinese Academy of Science 's Wuhan Institute of Hydrobiology has been working with
13284-453: The ruined palace at Knossos . 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
13407-512: 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 . Dolphins are sometimes used as symbols, for instance in heraldry. When heraldry developed in
13530-443: The sides of the head. Porpoises range in size from the 1.4 m (4 ft 7 in) and 54 kg (119 lb) vaquita to the 2.3 m (7 ft 7 in) and 220 kg (490 lb) Dall's porpoise . Overall, they tend to be dwarfed by other cetaceans. Almost all species have female-biased sexual dimorphism, with the females being larger than the males, although those physical differences are generally small; one exception
13653-424: The skull by air-filled sinus pockets, which allow for greater directional hearing underwater. Odontocetes 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. The large bulge on top of the porpoises head is caused by the melon. The porpoise eye is relatively small for its size, yet they do retain
13776-447: 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 eye of oceanic dolphins
13899-405: The species lives from the equator. This blubber also helps keep the animal warm providing insulation from the harsh climate or cold depths. It can also aid in protection to some extent as predators would have a hard time getting through a thick layer of fat. Calves are born with only a thin layer of blubber, but some species compensate for this with lanugos . Oceanic dolphins have two flippers on
14022-464: The underside toward the head, a dorsal fin , and a tail fin. These flippers contain four digits. Although oceanic dolphins do not possess fully developed hind limbs, some possess discrete rudimentary appendages, which may contain feet and digits. Oceanic dolphins are fast swimmers in comparison to seals who typically cruise at 11–27 km/h (7–17 mph); the orca, in comparison, can travel at speeds of up to 55.5 km/h (34.5 mph). The fusing of
14145-478: The use of safer fishing equipment to reduce bycatch. Porpoises are very sensitive to anthropogenic disturbances, and are keystone species , which can indicate the overall health of the marine environment. Populations of harbor porpoises in the North and Baltic Seas are under increasing pressure from anthropogenic causes such as offshore construction, ship traffic, fishing, and military exercises. Increasing pollution
14268-482: The walls of their enclosures, refused food, and exhibited skin sloughing . Almost all Dall's porpoises introduced to aquaria died shortly after, typically within days. Only two have lived for more than 60 days: a male reached 15 months at Marineland of the Pacific and another 21 months at a United States Navy facility . As part of last-ditch effort of saving the extremely rare vaquita (the tiny remaining population
14391-434: The water, meaning jump out of the water. Their skeletal anatomy allows them to be fast swimmers. They have a very well defined and triangular dorsal fin , allowing them to steer better in the water. Unlike their dolphin counterparts, they are adapted for coastal shores, bays, and estuaries. The porpoise ear has specific adaptations to the marine environment. In humans, the middle ear works as an impedance equaliser between
14514-423: The water. Oceanic 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
14637-453: The whistle development of each dolphin. Dolphins are able to 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 distinguishable. Bottlenose dolphins have a strong memory when it comes to these signature whistles, as they are able to relate to
14760-574: The wild in Iceland, 19 in Japan and three in Argentina. These figures exclude animals that died during capture. Live captures fell dramatically in the 1990s, and by 1999, about 40% of the 48 animals on display in the world were captive-born. In Greek myths , they were seen invariably as helpers of humankind. Dolphins also seem to have been important to the Minoans , judging by artistic evidence from
14883-442: The wild is 14 years or less. Very few harbour porpoises have been born in captivity. Historically, harbour porpoises were often kept singly and those who were together often were not mature or of the same sex. Disregarding one born more than 100 years ago that was the result of a pregnant female being brought into captivity, the world's first full captive breeding was in 2007 in the Fjord & Bælt Centre, followed by another in 2009 in
15006-428: The ⅔ or ¾ exponent of the body mass. Comparison of a particular animal's brain size with the expected brain size based on such allometric analysis provides an encephalization quotient that can be used as another indication of animal intelligence. Orca have the second largest brain mass of any animal on earth, next to the sperm whale . The brain to body mass ratio in some is second only to humans. Self-awareness
15129-575: Was established in 1992 at the Institute of Hydrobiology of the Chinese Academy of Sciences in Wuhan which allowing the study of behavioral and biological factors affecting the finless porpoise, specifically breeding biology like seasonal changes in reproductive hormones and breeding behavior. Because vaquitas are indigenous to the Gulf of California, Mexico is leading conservation efforts with
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