Temporal range: 55–0 Ma Early Eocene – Present
|Around 88 species.|
Cetacea is a widely distributed and diverse infraorder of fully aquatic marine mammals. There are 88 extant species of cetaceans. The two suborders of cetaceans, Mysticeti and Odontoceti, are thought to have split up around 34 million years ago. Whales and dolphins, the paraphyletic groups of Cetacea, as well as porpoises, belong to the clade Cetartiodactyla with even-toed ungulates; their closest living relatives are the hippopotamuses which diverged about 40 million years ago.
Cetaceans range in size from the 4.5 feet (1.4 m) and 120 pounds (54 kg) vaquita to the 110 feet (34 m) and 210 short tons (190 t) blue whale, which is also the largest creature on earth. Several species of mysticetes exhibit sexual dimorphism, in that the females are larger than males. They have streamlined bodies and two limbs that are modified into flippers. Some cetaceans can travel at up to 20 knots. Balaenopterids use throat pleats to expand their mouths in order to take in gulps of water. Balaenids have heads that can make up 40% of their body mass. Odontocetes have conical teeth designed for catching fish or squid. Mysticetes have a well developed sense of "smell", whereas odontocetes have well-developed hearing − so well adapted for both air and water 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.
Cetaceans are widespread, but some, as with the mysticetes, specialize in certain environments. Most mysticetes prefer the colder waters of the Northern and Southern Hemispheres, and migrate to the equator to give birth. Odontocetes feed largely on fish and squid, but a few, like the killer whale, feed on mammals, such as pinnipeds. Grey whales are specialized for feeding on bottom-dwelling mollusks. Males 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. Some whales produce a variety of vocalizations, notably the songs of the humpback whale. Many species, mainly dolphins, are highly sociable, with some pods reaching over a thousand individuals.
Once relentlessly hunted for their products, whales are now protected by international law. Some species are attributed with high levels of intelligence. At the 2012 meeting of the American Association for the Advancement of Science, support was reiterated for a cetacean bill of rights, listing cetaceans as non-human persons. The North Atlantic right whales nearly became extinct in the twentieth century, with a population low of 450, and is considered functionally extinct by cetologists, and the Baiji is also considered functionally extinct by the IUCN with the last sighting in 2004. Besides whaling, they also face threats from bycatch and marine pollution. The meat, blubber and baleen of whales have traditionally been used by indigenous peoples of the Arctic. Whales occasionally feature in literature and film, as in the great white whale of Herman Melville's Moby Dick. Small cetaceans, mainly dolphins, are kept in captivity and trained to perform tricks, but breeding success has been poor. Whale watching has become a form of tourism around the world.
- 1 Biology
- 2 Distribution and habitat
- 3 Lifestyle
- 4 Evolution
- 5 Classification
- 6 Interactions with humans
- 6.1 Research history
- 6.2 Threats
- 6.3 Cultural significance
- 6.4 In captivity
- 7 See also
- 8 References
- 9 External links
Cetaceans are fully aquatic marine mammals. They are not able to survive on land. If cetaceans are stranded, their body weight compresses their lungs or breaks their ribs, as they sometimes can weigh 90 metric tons (99 short tons). Smaller whales can die of heatstroke because of their well-developed thermal insulation. The build of cetaceans is well adapted to their habitat, yet they still share essential characteristics with all other higher mammals (Eutheria):
- Cetaceans have lungs, meaning they're air-breathers. The amount of time an individual can last without a breath varies from a few minutes to over two hours depending on the species.
- Cetaceans have especially powerful hearts. Likewise, the oxygen in the blood is distributed very effectively throughout the body.
- Cetaceans are warm-blooded animals, i.e., they hold, as opposed to the cold-blooded animals, a nearly constant, independent body temperature.
- Cetaceans give birth to fully developed calves and nurse them with an extremely high-fat milk from specific mammary glands. The embryonic development takes place in the body of the mother. During this time, the embryo is fed by a special nutritive tissue, the placenta.
Cetaceans, mainly whales, include the largest animals that ever lived. The blue whale (Balaenoptera musculus) can grow to a length of 33.5 metres (110 ft) and weigh up to 180 metric tons (200 short tons), making it the largest known creature ever. The sperm whale (Physeter macrocephalus) is the largest predatory animal on Earth. By contrast, the smallest of cetacean species can only reach a maximum body length of about 1.5 metres (4.9 ft), such as the La Plata dolphin, Hector's dolphin and the vacquita.
Among cetaceans, whales are also distinguished by an unusual longevity compared to other higher mammals. Some species, such as the bowhead whale (Balaena mysticetus), can reach an age of over 200 years. Based on the annual rings of the bony otic capsule, the age of the oldest known specimen is a male determined to be 211 years at the time of death.
The body shape of cetaceans is similar to that of fish generally, which can be attributed to their lifestyle and the special conditions of the habitat. They have a streamlined shape, and their forelimbs are transformed into flippers. Almost all have a dorsal fin on their back which can take on many forms depending on the species. In a few species it is completely absent, like, for example, the beluga whale. Both the flipper and the fin are for stabilization and steering in the water. They have a cartilaginous fluke at the end of their tail which is used for propulsion. The fluke is set horizontally instead of vertically on the body, as opposed to fish, which have vertical tails.
The hind legs are completely missing in cetaceans, as well as any other external body attachments that could hinder the streamline shape, like the pinna and the hair. The male genitals and mammary glands of females are sunk into the body.
All whales have an elongated head, especially in baleen whales due to the wide overhanging jaw which takes to extreme proportions. Their nostril(s) make up the blowhole, with one in toothed whales, and two in baleen whales. They lie on the top of the head, so that the rest of the body can remain submerged while surfacing for air. When the stale air, warmed from the lungs, is exhaled, it condenses as it meets colder external air. As with a terrestrial mammal breathing out on a cold day, a small cloud of 'steam' appears. This is called the 'spout' and varies between species in terms of shape, angle, and height. Species can be identified at a distance using this characteristic. In toothed whales, a connective tissue exists in the melon as a head buckle. This is filled with air sacs and fat which aids in buoyancy and biosonar. The sperm whales have a particularly pronounced melon; this is called the spermaceti organ and contains the eponymous spermaceti, hence the name "sperm whale". Even the long tusk of the narwhal is a vice-formed tooth. The baleen, which consists of long, fibrous strands of keratin, of baleen whales sit in place of the teeth and are used to seethe the water for plankton and krill among others.
The body is wrapped in a thick layer of fat known as blubber. This blubber is used for thermal insulation and gives cetaceans their smooth, streamlined body shape. In larger species, it can reach a thickness up to half a meter (1.6 ft). The very specific structure of the skin above the fat layer ensures a phenomenon known as Gray's Paradox: the body, especially for the faster swimmers, has in reality far better flow properties, than at a solids equal to the form in this case. This is attributed to the damping properties of the skin, interfering with mitigated vortices. To this end, the dermis forms a seam with the overlying epidermis and are interlocked. The papillae are seated on slats, which are largely transverse to the longitudinal axis of the body and thus also provide to the flow direction. The papillae are used for excretory ducts of sweat glands. Today, however, we know its real function and also know that cetaceans possess no skin glands except for the mammary glands. In addition to these structures, damping the skin has a microscopically fine relief pattern. Based on the results of physiological experiments, an active response of the skin is assumed. The optimization of the flow properties could be readjusted in experiments with artificial whale skin.
The cetacean skeleton is largely made up of compact bone, as it stabilizes in the water. For this reason, the usual terrestrial compact bones, which are finely woven through cancellous bone, are replaced with lighter and more elastic bones. In many places, bone elements are replaced by cartilage and even fat, thereby improving their hydrostatic qualities. The ear and the muzzle contain a bone shape that is exclusive to cetaceans with an extremely high density, which on recalls porcelain. This has special acoustic properties and conducts sound better than other bones, which aids with biosonar. In many toothed whales, the depression in their skull is due to the formation of a large melon and multiple air bags which are formed asymmetrically.
The skull of all cetaceans is extended, which can be clearly seen in baleen whales. The nostrils are located on top of the head above the eyes. The back of the skull is significantly shortened and deformed. By shifting the nostrils to the top of the head, the nasal passages extend perpendicularly through the skull. The teeth or baleen in the upper jaw sit exclusively on the maxilla. The braincase is concentrated through the nasal passage to the front and is correspondingly higher, with individual cranial bones that overlap (Teleskoping). The bony otic capsule, the petrosal, is only cartilaginous when connected to the skull, so that they can swing independently.
The number of vertebrae that make up the spine varies between species, anywhere between 40 and 93 individual vertebrae. The cervical spine, found in all mammals, consists of seven vertebrae which, however, are greatly reduced in most cetaceans or are fused together, which gives stability during swimming at the expense of mobility. The fins are carried by the thoracic vertebrae, ranging from 9 to 17 individual vertebrae. The sternum is regressed and is only cartilaginous, but nonetheless is strong. The last two to three pairs of ribs are not connected at all and hang freely in the body wall. This is followed by the stable lumbar and tail part of the spine which includes all other vertebrate. Below the caudal vertebrae is the chevron bone; the vortex developed provides additional attachment points for the tail musculature.
The front limbs are paddle-shaped with shortened arms and elongated finger bones, to support the movement. They are united by cartilage. It also leads to a proliferation of the finger members, a so-called Hyperphalangie, on the second and third fingers. The only functional joint is the shoulder joint in all cetaceans except for the Amazon river dolphin. The collarbone is completely absent. The movement of cetaceans on land is no longer necessary and no longer possible due to the body weight, which is mainly a problem for the larger variety, and the hindlimbs which are greatly atrophied and only a rudimentary internal appendage without connections to the spine.
Internal anatomy and physiology
The structure of the respiratory and circulatory systems are of particular importance for the life of marine mammals. The oxygen balance of cetaceans is highly effective. Each breath can replace up to 90 percent of the total volume of air in their lungs. For land mammals, in comparison, this value is usually about 15 percent. In the lungs, the inhaled air is about twice as much oxygen withdrawn by the lung tissue as a land mammal. The oxygen, like all mammals, is in the blood and the lungs, but in cetaceans they are also stored in various tissues, mainly in the muscles, in which the muscle pigment, myoglobin, provides an effective bond. This external oxygen storage is vital for deep diving since, from a depth of about 100 metres (330 ft), the lung tissue is almost completely compressed by the water pressure. In the dipping process, they massively reduce their oxygen consumption by lowering the heart activity and blood circulation; individual organs are not supplied with oxygen during this time. Some rorquals can dive for up to 40 minutes, sperm whales between 60 and 90 minutes, and bottlenose whales for even two hours. The diving depths lie at an average of about 100 metres (330 ft), but some, like sperm whales, can dive to 3,000 metres (9,800 ft) deep, but usually dive to 1,200 metres (3,900 ft).
The stomach consists of three chambers. The first region is formed by a loose gland and a very muscular forestomach (which in beaked whales is missing), which is then followed by the main stomach and the pylorus, both of which are equipped with glands to help digestion. A bowel adjoins the stomachs, whose individual sections can, only histologically, be distinguished. The liver is very large and unaccompanied by the gall bladder.
The kidneys are strongly flattened and very long. The salt concentration in their blood is lower than that in the seawater; the kidneys, therefore, are also used to excrete salt. This allows cetaceans to drink seawater.
Cetacean eyes are set on the sides rather than the front of the head. This means only cetaceans with pointed 'beaks' (such as dolphins) have good binocular vision forward and downward. Tear glands secrete greasy tears, which protect the eyes from the salt in the water. The lens is almost spherical, which is most efficient at focusing the minimal light that reaches deep water. Cetaceans make up for their generally poor vision (with the exception of the dolphin) with excellent hearing.
The external ear of cetaceans has lost the pinna (visible ear), but still retains an extremely narrow external auditory meatus. To register sounds, instead, the posterior part of the mandible has a thin lateral wall (the pan bone) behind which a concavity houses a large fat pad. The fat pad passes anteriorly into the greatly enlarged mandibular foramen to reach in under the teeth, and posteriorly to reach the thin lateral wall of the ectotympanic. The ectotympanic only offers a reduced attachment area for the tympanic membrane and the connection between this auditory complex and the rest of the skull is reduced in cetaceans — to a single, small cartilage in oceanic dolphins. In odontocetes, the complex is surrounded by spongy tissue filled with air spaces, while in mysticetes it is integrated into the skull similar to land mammals. In odontocetes, the tympanic membrane (or ligament) has the shape of a folded-in umbrella that stretches from the ectotympanic ring and narrows off to the malleus (quite unlike the flat, circular membrane found in land mammals.) In mysticetes, it also forms a large protrusion (known as the "glove finger"), which stretches into the external meatus, and the stapes are larger than in odontocetes. In some small sperm whales, the malleus is fused with the ectotympanic. The ear ossicles are pachyosteosclerotic (dense and compact) in cetaceans and very different in shape compared to land mammals (other aquatic mammals, such as sirenians and earless seals, have also lost their pinnae). In modern cetaceans, the semicircular canals are much smaller relative to body size than in other mammals.
In modern cetaceans, the auditory bulla is separated from the skull and composed of two compact and dense bones (the periotic and tympanic) referred to as the tympano-periotic complex. This complex is located in a cavity in the middle ear, which, in Mysticeti, is divided by a bony projection and compressed between the exoccipital and squamosal but, in Odontoceti, is large and completely surrounds the bulla (hence called "peribullar"), which is therefore not connected to the skull except in physeterids. In odontoceti, the cavity is filled with a dense foam in which the bulla hangs suspended in five or more sets of ligaments. The pterygoid and peribullar sinuses that form the cavity tend to be more developed in shallow water and riverine species than in pelagic mysticeti. In odontoceti, the composite auditory structure is thought to serve as an acoustic isolator, analogous to the lamellar construction found in the temporal bone in bats.
Odontoceti (toothed whales, which includes dolphins and porpoises) are generally capable of echolocation. From this, Odontoceti can discern the size, shape, surface characteristics, distance and movement of an object. With this ability, cetaceans can search for, chase and catch fast-swimming prey in total darkness. Echolocation is so advanced in most Odontoceti, they can distinguish between prey and nonprey (such as humans or boats); captive Odontoceti can be trained to distinguish between, for example, balls of different sizes or shapes. Mysticeti (baleen whales) have exceptionally thin, wide basilar membranes in their cochleae without stiffening agents, making their ears adapted for processing low to infrasonic frequencies. Echolocation clicks also contain characteristic details unique to each animal, which may suggest that toothed whales can discern between their own click and that of others.
Cetaceans also use sound to communicate, whether it be groans, moans, whistles, clicks, or the complex 'singing' of the humpback whale. Besides hearing and vision, at least one species, the tucuxi or Guiana dolphin, is able to use electroreception to sense prey.
Unlike most animals, cetaceans are conscious breathers. All animals sleep, but cetaceans cannot afford to become unconscious for long because they may drown. While knowledge of sleep in wild cetaceans is limited, toothed cetaceans in captivity have been recorded to exhibit unihemispheric slow-wave sleep (USWS), which means they sleep with one side of their brain at a time, so that they may swim, breathe consciously, and avoid both predators and social contact during their period of rest.
A 2008 study found that sperm whales sleep in vertical postures just under the surface in passive shallow 'drift-dives', generally during the day, during which whales do not respond to passing vessels unless they are in contact, leading to the suggestion that whales possibly sleep during such dives.
Similarities in the chromosome genetics
The initial karyotype of cetaceans includes a set of chromosomes from 2n = 44. They have four pairs telozentrischer chromosomes (chromosomes whose centromeres sitting at one of the telomeres), two to four pairs subtelozentrischer and one or two large pairs submetazentrischer chromosomes. The remaining chromosomes are metacentric - the centromere is approximately in the middle - and are rather small. The sperm whales (Physeteridae), the beaked whales (Ziphiidae) and the right whales (Balaenidae) converge to a reduction in the number of chromosomes to 2n = 42nd.
Distribution and habitat
Cetaceans are marine animals and are found in all oceans of the world. Some species also live in river deltas and even in rivers. In contrast, only a few species live exclusively in fresh water, the river dolphins. While many marine species of cetaceans, such as the blue whale, the humpback whale and the orca, have a distribution area that includes nearly the entire ocean, there are also some species which occur only locally or in broken populations. These include the vacquita, which inhabits a small part of the Gulf of California, and Hector's dolphin, which lives in some coastal waters in New Zealand. In the oceans, there are both species that prefer the deeper marine areas and species that live frequently or exclusively in coastal and shallow water areas.
The distribution of habitats arises normally along certain temperature limits in the oceans, which means many species exist along certain latitudes. Many species live accordingly in tropical or subtropical waters, such as the Bryde's whale or Risso's dolphin, while others are found only in the Southern Ocean, like the Southern right whale dolphin or the hourglass dolphin, or in the Arctic Ocean, like the narwhal and the beluga. This vertical expansion is interrupted primarily by land masses as natural barriers. There are many cosmopolitan species and individual populations in the Pacific, the Atlantic and the Indian Oceans. Some species, conversely, live only in one of those oceans or in small clusters. For example, Sowerby's beaked whale and the Clymene dolphin exist only in the Atlantic, and the Pacific white-sided dolphin and the Northern straight dolphin live only in the North Pacific. For migratory species, their reproductive sites often lie in tropics and their feeding grounds in polar regions, but the two populations, one in the Arctic and the other in the Antarctic, are genetically separated by their long distance apart from each other. In some species, this separation of the populations leads eventually to the formation of new species, such as the Southern right whale, North Pacific right whale, and North Atlantic right whale.
A total of 32 species of cetaceans are found in European waters, including 25 species of toothed whales and seven seven species of baleen whales
Most whales are extremely social animals with a highly developed social behavior. Only a few species live in pairs or have solitary lives. A group of cetaceans, known as a pod, usually consists of 10 to 50 animals but on certain occasions, such as mass occurrence of food or mating season, may also include more than a thousand individuals in the groups. Also, intraspecies socialization may occur.
Pods have a fixed hierarchy, with the priority positions determined by biting, pushing, or ramming. The behavior in the group is aggressive only in situations of extreme stress such as lack of food, but usually it is peaceful. This contact swimming, mutual fondling and nudging play a major role. The playful behavior of the animals, which is manifested in air jumps, somersaults, surfing or fin hitting, occurs more often than not in smaller cetaceans, such as dolphins and porpoises.
Data communication between the singing males gives similar tones and melodies, which can be heard for hundreds of kilometers in the water. This activity is known as whale song. Recent research has shown that probably every whale population developed its own typical singing. Sometimes, an individual can be identified by its distinctive vocals, such as the 52-hertz whale which sings at a higher frequency than other whales. Some whales are capable of generating up to 622 different sounds. Comparisons of older and more recent recordings show that the composition of the sounds over the years has developed significantly.
Pod groups also hunt, often with other species. There are many species of dolphins along with large tunas on hunting expeditions, followed by the large schools of fish. The killer whale hunts in pods and targets belugas and even larger whales. Humpback whales, among others, form in collaboration bubble carpets to herd krill or plankton into bait balls before lunging at them.
Cetaceans are known to teach, learn, cooperate, scheme, and grieve. The neocortex of many cetaceans 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 the brain that are homologous to where they are found in humans, suggesting that they perform a similar function. At the 2012 meeting of the American Association for the Advancement of Science, support was reiterated for a cetacean bill of rights, listing cetaceans as non-human persons.
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 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. Sperm whales have the largest brain mass of any animal on earth, averaging 8,000 cubic centimetres (490 in3) and 7.8 kilograms (17 lb) in mature males. The brain to body mass ratio in some odontocetes, such as belugas and narwhals, is second only to humans. In some whales, however, it is less than half that of humans: 0.9% versus 2.1%. This comparison seems more favorable if the large amount of blubber that some whales require for insulation is omitted.
Smaller cetaceans, such as dolphins and porpoises, are known to engage in complex play behavior, which includes such things as producing stable underwater toroidal air-core vortex rings or "bubble rings". There are two main methods of bubble ring production: rapid puffing of a burst of air into the water and allowing it to rise to the surface, forming a ring, or swimming repeatedly in a circle and then stopping to inject air into the helical vortex currents thus formed. They also appear to enjoy biting the vortex-rings, so that they burst into many separate bubbles and then rise quickly to the surface. Whales are also known to produce bubble-nets for the purpose of foraging.
Larger whales are also thought, to some degree, to engage in play. The southern right whale, for example, elevates their tail fluke above the water, remaining in the same position for a considerable amount of time. This is known as "sailing". It appears to be a form of play and is most commonly seen off the coast of Argentina and South Africa. Humpback whales, among others, are also known to display this behaviour.
Self-awareness 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 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.
Some disagree with these findings, arguing that the results of these tests are open to human interpretation and susceptible to the Clever Hans effect. This test is much less definitive than when used for primates, because primates can touch the mark or the mirror, while cetaceans cannot, making their alleged self-recognition behavior less certain. Skeptics argue that behaviors that are said to identify self-awareness resemble existing social behaviors, and so researchers could be misinterpreting self-awareness for social responses to another individual. The researchers counter-argue that the behaviors shown are evidence of self-awareness, as they are very different from normal responses to another individual. Whereas apes can merely touch the mark on themselves with their fingers, cetaceans show less definitive behavior of self-awareness; they can only twist and turn themselves to observe the mark.
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 the mirror test.
Reproduction and development
For most species, a seasonal reproductive cycle occurs, in which the ovulation of the females with the main activity of the testicles coincides with the males. This cycle is usually coupled with seasonal movements, which can be observed in many species. Most toothed whales have a no fixed bonds. In many species, the females have several partners during a season. The baleen whales are, on the other hand, largely monogamous within each reproductive period, but lasting bonds do not go as well.
The gestation period of cetaceans takes place between nine and 16 months, with the duration not necessarily dependent on the size. Porpoises wear as well as the huge blue whales about 11 months. Cetaceans usually bear only one calf; with the occurrence of twins, one usually dies because the mother cannot afford sufficient milk for both juveniles. The fetus is positioned for a tail-first delivery, so that the risk of drowning while being delivered is a minimal. After parturition, the young animal is transported quickly to the surface for their first breath, which, in many species, follows several acts of "midwives". The young animals have, at birth, about one-third of their adult height and tend to be independently active, comparable to the precocial birds or messenger boys of terrestrial mammals. When suckling, the mother splashes milk actively using the muscles of the mammary glands into the mouth of the calf, as it has no lips to suck. This milk usually has a very high fat content, ranging from 16 to 46 percent, which causes the calf to rapidly increase in size and weight.
The suckling is mostly long, in many small cetaceans it lasts about four months and often goes hand in hand with large species over a year, with a narrow bond of mother to her offspring. For the rearing of young animals alone, the dams are responsible for all cetaceans. In some species of cetaceans, there are so-called "aunts" who also occasionally suckle the pups. Most cetaceans mature late, typically at seven to ten years. This reproductive strategy provides few offspring that have a high survival rate. An exception to this is the La Plata Dolphin who is already sexually mature at two years, but lives to be only about 20 years old. The sperm whale reaches sexual maturity within about 20 years, but has a lifespan of between 50 and 100 years.
Upon death, whale carcasses fall to the deep ocean and provide a substantial habitat for marine life. Evidence of whale falls in present-day and fossil records shows that deep sea whale falls support a rich assemblage of creatures, with a global diversity of 407 species, comparable to other neritic biodiversity hotspots, such as cold seeps and hydrothermal vents.
Deterioration of whale carcasses happens though a series of three stages. Initially, moving organisms such as sharks and hagfish, scavenge the soft tissues at a rapid rate over a period of months, and as long as two years. This is followed by the colonisation of bones and surrounding sediments (which contain organic matter) by enrichment opportunists, such as crustaceans and polychaetes, throughout a period of years. Finally, sulfophilic bacteria reduce the bones releasing hydrogen sulfide enabling the growth of chemoautotrophic organisms, which in turn, support other organisms such as mussels, clams, limpets, and sea snails. This stage may last for decades and supports a rich assemblage of species, averaging 185 species per site.
Relationships and phylogenetic development
For a long time, paleontologists thought the ancestors of whales were the mesonychid, a group of carnivorous ungulates with a controversial systematic position, because of the similar nature of the skull and teeth. Later studies of molecular biology and immunology showed that cetaceans are phylogenetically closely related with the even-toed ungulates (Artiodactyla). The lineage of whales, therefore, began in the early Eocene, more than 50 million years ago, with early artiodactyls.
Fossil discoveries at the beginning of the 21st century have confirmed this. The most striking common feature of cetaceans and even-toed ungulates is the anklebone, a bone in the upper ankle joint. Early cetaceans, archaeocetes, show double castors which only occurs in even-toed ungulates. Corresponding findings are from deposits of Tethys Sea in northern India and Pakistan. The Tethys Sea extended, during this time, as a shallow sea between the Asian continent and northward-bound Indian plate.
Most molecular biological evidence suggests that hippos are the closest living relatives, a sister group basically, of cetaceans. Some common anatomical features include similarities in the morphology of the posterior molars. The fossil record, however, cannot provide evidence to this assumed relationship, because the hippo lineage only dates back about 15 million years. The oldest cetaceans, on other hand, date back to about 50 million years ago.
In 2007 a group led by paleontologist Hans Thewissen created an alternative pedigree. Accordingly, the sister group of archaeocetes were the Raoellidae, an extinct group of even-toed ungulates. Both taxa form accordingly together the sister group of the remaining artiodactyls including hippos:
The presumed close relationship based on characteristics according Thewissen are primarily the bony ring on the temporal bone (bulla), the involucre, a skull feature which was previously associated only with cetaceans, as well as other features of the premolars and the bone structure.
Use of the fossil record can trace the gradual transition from terrestrial life to aquatic life. The regression of the hind limbs allowed greater flexibility of the spine. This has made it possible for whales to move around with the vertical tail hitting the water. The front legs were transformed into flippers but they lost their original mobility on land.
The ears of today's cetaceans are no longer external; the nostrils moved from the snout upwards, and transformed into a blowhole so that ceraceans do not have to surface completely to breathe. While the teeth are divided into incisors, canines, and molars among the terrestrial archaeocetes, the teeth of the modern cetaceans are brought into line with each other, which can be seen among the fish-eating odontocetes (transition from heterodont to Homodontie). A special and relatively late development occurred in the mytsicetes: they evolved baleen to replace teeth, which are structures of a horn-like protein (keratin) around 25 million years ago.
The transition from land to sea
One of the oldest members of ancient cetaceans (Archaeoceti) is Pakicetus from the Middle Eocene 50 million years ago approximately. This animal is as big as a wolf, whose skeleton is known only partially, and still had functioning legs and lived near the shore. The well-trained Roll leg suggests that this was an archaeocete who could still move well on land. The long snout has a carnivorous dentition.
The important transitional form from land to sea life is considered to date to about 49 million years ago, discovered in Pakistan, to be Ambulocetus ("running whale"), which was up to 3 metres (9.8 ft) long. The limbs of this archaeocete were adapted to swimming, but terrestrial locomotion was still possible. It moved in stooping and probably crawled like a seal or crocodile. The snout was elongated with far overhead nostrils and eyes. The tail of the animal was very strong and supported movement through water. Ambulocetus probably lived in mangroves in brackish water and fed into the riparian zone as a predator of fish and other vertebrates.
Dated from about 45 million years were more species such as Indocetus, Kutchicetus, Rodhocetus and Andrewsiphius, all of which were clearly adapted to life in water. The hind limbs of these species were already highly regressed, and the body shape is reminiscent of that of modern whales. Rodhocetus, a member of the Protocetidae family, is considered the first fully aquatic cetacean. The body was streamlined and was delicate and developed extended hand and feet bones. The merged pelvic lumbar spine was still there from loose individual bones, which made it possible to support the floating movement of the tail. Therefore, it was a good swimmer, but on the other hand, could likely move only relatively clumsy on land, much like a seal.
Residents of the oceans
Since the late Eocene, about 40 million years ago, cetaceans populated the subtropical oceans of the world and had no connection to land anymore, such as the 18 metres (59 ft) long Basilosaurus, sometimes referred to as Zeuglodon. The transition from land to water was, therefore, completed within about 10 million years. In Egypt, within the Wadi Al-Hitan, "Whale Valley", are numerous skeletons of Basilosaurus as well as other marine vertebrates.
The direct ancestors of today's cetaceans are probably found within the subfamily Dorudontidae whose most famous member, Dorudon atrox, lived at the same time Basilosaurus lived. Both groups had already developed the typical anatomical features for today's whales, such as hearing; life in the water for a formally terrestrial creature required significant adjustments such as the fixed Bulla, which replaces the eardrum of land mammals, as well as sound-conducting elements for directional hearing under water. The wrists of these animals were stiffened and probably contributed to the typical build of flippers. The hind legs still existed, however, but significantly reduced in size and with a vestigial pelvis connected.
In the following millennia, many different species occurred. Today, about 1,000 species have been documented, of which the vast majority have disappeared, but their descendants today inhabit all oceans.
Baleen whales (Mysticeti) owe their name to their baleen, the comb-like, frayed structures at the ends of horny plates; the whales with these plates filter micro-organisms, such as plankton, from the seawater by taking a large amount of sea water into their mouth and squeezing it through the baleen. The plates of bowhead whales can be 4 metres (13 ft) long. This group includes the largest living animals. Toothed whales (Odontoceti), which include the dolphins and porpoises, have a number of conical teeth in both jaws, as with dolphins, or only in the lower jaw, for example, the sperm whale or the beaked whales. Porpoises, however, have spade-shaped teeth. Toothed whales are characterized by their ability perceive their environment through means of biosonar.
|Relationship of extinct and extant cetaceans:|
- ORDER CETACEA
- Suborder Mysticeti: baleen whales
- Superfamily Balaenoidea
- Family Balaenidae: Right whales
- Family Cetotheriidae 
- Genus Caperea
- Pygmy right whale, Caperea marginata
- Superfamily Balaenopteroidea
- Family Balaenopteridae: rorquals
- Subfamily Balaenopterinae
- Genus Balaenoptera: slender rorquals
- Subfamily Megapterinae
- Subfamily Balaenopterinae
- Family Eschrichtiidae
- Family Balaenopteridae: rorquals
- Superfamily Balaenoidea
- Suborder Odontoceti: toothed whales
- Superfamily Delphinoidea
- Family Delphinidae: Oceanic dolphins
- Genus Cephalorhynchus: blunt-nosed dolphins
- Genus Delphinus: common dolphins
- Genus Feresa
- Pygmy killer whale, Feresa attenuata
- Genus Globicephala: pilot whales
- Genus Grampus
- Risso's dolphin, Grampus griseus
- Genus Lagenodelphis
- Fraser's dolphin, Lagenodelphis hosei
- Genus Lagenorhynchus: false bottlenose dolphins
- Genus Lissodelphis: right whale dolphin
- Genus Orcaella: Irrawaddy dolphins
- Genus Orcinus
- Killer whale, Orcinus orca
- Genus Peponocephala
- Melon-headed whale, Peponocephala electra
- Genus Pseudorca
- False killer whale, Pseudorca crassidens
- Genus Sotalia: northern South American dolphins
- Tucuxi, Sotalia fluviatilis
- Guiana dolphin, Sotalia guianensis
- Genus Sousa: humpback dolphins
- Genus Stenella: spotted dolphins
- Genus Steno
- Rough-toothed dolphin, Steno bredanensis
- Genus Tursiops: true bottlenose dolphins
- Family Monodontidae: arctic whales
- Family Phocoenidae: Porpoises
- Family Delphinidae: Oceanic dolphins
- Superfamily Physeteroidea
- Superfamily Platanistoidea
- Superfamily Inioidea
- Superfamily Lipotoidea: River dolphins
- Superfamily Ziphioidea: Beaked whales
- Family Ziphidae,
- Genus Berardius: giant beaked whales
- Subfamily Hyperoodontidae
- Genus Hyperoodon: bottlenose whales
- Genus Indopacetus
- Indo-Pacific beaked whale (Longman's beaked whale), Indopacetus pacificus
- Genus Mesoplodon, Mesoplodont whale
- Sowerby's beaked whale, Mesoplodon bidens
- Andrews' beaked whale, Mesoplodon bowdoini
- Hubbs' beaked whale, Mesoplodon carlhubbsi
- Blainville's beaked whale, Mesoplodon densirostris
- Gervais' beaked whale, Mesoplodon europaeus
- Ginkgo-toothed beaked whale, Mesoplodon ginkgodens
- Gray's beaked whale, Mesoplodon grayi
- Hector's beaked whale, Mesoplodon hectori
- Strap-toothed whale, Mesoplodon layardii
- True's beaked whale, Mesoplodon mirus
- Perrin's beaked whale, Mesoplodon perrini
- Pygmy beaked whale, Mesoplodon peruvianus
- Stejneger's beaked whale, Mesoplodon stejnegeri
- Spade-toothed whale, Mesoplodon traversii
- Deraniyagala's beaked whale, Mesoplodon hotaula
- Genus Tasmacetus
- Shepherd's beaked whale, Tasmacetus shepherdi
- Genus Ziphius
- Cuvier's beaked whale, Ziphius cavirostris
- Family Ziphidae,
- Superfamily Delphinoidea
- Suborder Mysticeti: baleen whales
Interactions with humans
In Aristotle's time, 4th century B.C.E., the whales were allocated as fish because of their external appearance, though Aristotle already could see many physiological-anatomical similarities with the terrestrial vertebrates such as blood (circulation), lungs, uterus and fin anatomy. His detailed descriptions were taken over by the Romans, but the content was mixed with the knowledge of the dolphins. Pliny the Elder mentioned that when he wrote a comprehensive natural history. Also, in the art of this and subsequent periods there is this mixture again, so dolphins have since been presented with a high-arched head, typical of porpoises, and a long snout. The harbor porpoise, next to the dolphins, is one of the most accessible for early cetologists, because it could be seen very close to land, as it inhabitants the shallow coastal areas of Europe. Much of the findings that apply to all cetaceans were first discovered in the 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, which nevertheless referred to as the porpoise fish.
The primary threats to cetaceans come from people, both the direct threat of hunting by whaling or drive hunting and indirect threats from sources such as fisheries and pollution.
|This section does not cite any references or sources. (September 2015)|
Whaling is the practice of hunting whales, mainly baleen whales and sperm whales. This activity has gone on since the Stone Age.
In the Middle Ages, people had many reasons for whaling, including their huge amounts of meat, the oil usable as fuel, and the jawbone, which was used in house construction. At the end of the Middle Ages, whole whaling fleets, mainly aimed at baleen whales, such as the bowhead whales, were hunting. For example, in the 16th and 17th centuries, the Dutch fleet had about 300 whaling ships with 18,000 crewmen.
In the 18th and 19th centuries, whales, baleen whales especially, were hunted for their baleen, which was used in the place of plastic which had not been invented yet, or as a replacement for wood; they were used such products as corset and crinoline. In addition, the spermaceti found in the sperm whale was used as a lubricant for machinery and the ambergris as a base material for the pharmaceutical industry and the perfume industry. In the second half of the 19th century, the explosive harpoon was invented and used; there was a massive increase in the catch size.
Large ships were transformed into mother ships for the whale handlers, and were supplied by fleets with steam drive. In the first half of the 20th century, whales were of great importance as a supplier of raw materials for industries. Whales were intensively hunted during this time; in the 1930s, 30,000 whales were killed. A further increase to over 40,000 animals per year was made up in the 1960s, which especially collapsed the stocks of large baleen whales.
Most hunted whales are now threatened in their existence, with some great whale species populations that have been exploited to the brink of extinction. Today, some are decimated, but a slow increase is possible. The Atlantic and the Korean gray whale populations were already completely eradicated, and the North Atlantic right whales are expected today with a population of 300 to 600 animals, and the blue whale is probably around 14,000 animals.
The first efforts to protect whales was decided in 1931. In some particularly endangered species, such as the humpback whale, they numbered about 100 animals, and were placed under international protection, and the first protected areas were established. In 1946, the International Whaling Commission was established; they monitor and secure the stocks of whales. The killing of whales for commercial purposes was prohibited worldwide by this organization from 1985 to 2005. However, whales are still hunted today. Japanese whaling ships are allowed to hunt whales of different species for supposedly scientific purposes. Native Greenlandics and other indigenous peoples of the world still practice whaling for traditional reasons and is allowed to survive. Iceland and Norway do not recognize the ban, and operate an open commercial whaling. Countries like Norway and Japan are committed to ending the moratorium.
Dolphins and other smaller cetaceans are also hunted in an activity known as dolphin drive hunting. This is an accomplish by driving a pod 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. Dolphins are hunted this way in several places around the world, including the Solomon Islands, the Faroe Islands, Peru, and Japan, the most well-known practitioner of this method. By numbers, dolphins are mostly hunted for their meat, though some end up in dolphinariums. Despite the controversial nature of the hunt resulting in international criticism, and the possible health risk that the often polluted meat causes, thousands of dolphins are caught in drive hunts each year.
The cost of whaling uninteresting small cetaceans - especially some dolphin species - partly decimated. Dolphin pods often reside near large shoals of tuna. This is also known to fishermen, which is why they often look for dolphins to catch tuna. Dolphins are much easier to make out than tuna, since they have to take a breath at the surface regularly. The fishermen pull their nets hundreds of meters wide in a circle around the dolphin groups, in the expectation that they also include a tuna shoal. When the nets are pulled together, the dolphins become entangled under water and drown. Line fishery in larger rivers are threats especially to river dolphins.
A far greater threat than by-catch arises, however, for small cetaceans: targeted hunting. In Southeast Asia, they are sold in poorer countries as fish-replacement to the native population, since the actual edible fish of the region promise higher revenues from exports. In the Mediterranean, small cetaceans are pursued as competitors for food, since the metabolism of marine mammals has a disproportionately higher energy needs than in predatory fish, they are deliberately destroyed to maintain the population of edible fish without having to share with them.
A stranding is the unintentional emergence of a cetacean to beach itself. The best known are mass strandings of pilot whales and sperm whales. The causes of cetacean strandings are not clear. Possible reasons for mass beachings are:
- toxic contaminants in the food chain
- debilitating parasites in the respiratory tract, brain or middle ear
- bacterial or viral infections
- panic flight from predators (incl. humans)
- strong social bonds within a group, so that all individuals follow a stranded animal
- disturbance of their magnetic senses by natural anomalies in the Earth's magnetic field
- Underwater noise pollution by shipping traffic, seismic surveys and military sonar experiments.
In the last 15 years, whale strandings frequently occurred in the context of military sonar testing. In December 2001, the US Navy admitted partial responsibility for the beaching and the deaths of several marine mammals in March 2000. The co-author of her interim report concludes that the animals killed by the active sonar of some Navy ships were injured. Generally, underwater noise, which is still on the increase, is made increasingly responsible for strandings because it impairs communication and sense of direction of the animals.
Climate change also appears by influencing the major wind systems to lead the world and thus the course of ocean currents which lead to cetacean strandings. Mark Hindell and his team from the Tasmanian University in Hobart studied cetacean strandings on the coast of Tasmania from 1920-2002 and found that greater strandings occurred at certain time intervals. Years with a tenfold number of strandings was accompanied by the occurrence of severe storms, which initiated the cold water flows increasingly close to the coast. In nutrient-rich cold water, cetaceans find particularly large prey animals, so they followed the cold water currents and thus, in these exceptional meteorological years, came into shallower waters than usual, where the risk is higher for strandings. Since many whales and dolphins live in pods and follow or accompany the sick or debilitated animals into shallow water, mass stranding occur often at low tide. Once stranded, large whales are crushed by their own body weight, if they cannot get into deeper water. In addition, the regulation of body temperature is no longer guaranteed in a stranded whale and there is a risk of overheating for smaller whales.
The increasing pollution for the marine mammals is also a serious problem. Heavy metals, residues of many plant and insect venoms, and plastic waste Flotsam are not biodegradable. 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.
The destruction of the ozone layer affects baleen whales, because plankton is highly sensitive to radiation and multiplies less. This shrinks the food supply for many marine animals, but the baleen whales are most impacted by this. Even the Nekton is, in addition to the intensive exploitation, damaged by the intense UV irradiation and is limited in quantity and quality as a food source.
Similar effects can be, at least in a long-term sense, acidification of the oceans due to the increased uptake of carbon dioxide, an effect that global warming counteracts because it heats up the atmosphere while decreasing the amount of carbon. CO2 reacts with water to form carbonic acid. The acidic water interferes with the construction of the calcium carbonate skeletons of various algae and micro-organisms. This in turn decreases the amount of plankton that baleen whales depend on, as it represents the main food source for many species.
Above all, the military and the geology employ strong sonar and produce blasting operations along with vessel traffic which increases noise in the oceans. Marine mammals that are characterized for their use of biosonar for orientation and communication are not only hindered, but are also induced to panic surface. This leads to bubble out of bound in blood gases, and the animal then dies because the tubes are blocked, so-called decompression accidents (known in humans as a "serious diving accident").
Naval exercises with sonar regularly results in fallen cetaceans that are washed up, who have gas bubbles in the blood vessels. The sound is very extensive and develops its disastrous effects in more than 100 kilometres (62 mi) radius. Depending on the frequencies used, different species are more or less affected than others. It is charged on the requirement that prior corresponding expanded operations of sonar technology first, possibly to be with sonar, ruled also that many marine mammals in the area are located.
Cetaceans play a big role in the culture of residents near sea areas and islands. These are mainly small cetaceans such as dolphins and porpoises, which could be observed intensely and thus were able to enter into the mythology of these people. However, great whales were known primarily whale strandings (especially sperm whales) or they have been described by mariners.
Petroglyphs of the Stone Age, such as those in Roddoy and Reppa (Norway), show that the animals were known early in these cultures. Whale bones were used for numerous purposes. In the Neolithic settlement of Skara Brae on Orkney is made from vertebrae saucepans. Some of the vessels contain traces of color, Childe treated them as paint buckets. A shell of baleen comes from Foshigarry, Scotland.
|This section does not cite any references or sources. (September 2015)|
For the ancient Greeks, the whale was first mentioned by Homer. Here, it is called Ketos, a term which initially included all large marine animals. From this was derived the Roman word for whale, Cetus. Other names were phálaina (Aristotle, Latin form of ballaena) for the female and, with an ironic characteristic style, musculus (Mouse) for the male animal. North Sea whales were called Physeter, which was meant for the sperm whale Physter macrocephalus. Particular detailed whales described by Aristotle are Pliny and Ambrose. All mention both the Viviparie and the suckling of the pups. Pliny describes the problems associated with the lungs with spray tubes, and Ambrose even claimed that these large whales would take their young into their mouth to protect them.
In the Bible especially, the Leviathan plays a role as a sea monster. The essence, which features a giant crocodile or a dragon and a whale, was created according to the Bible by God (Psalm 104, 26) and should again be destroyed by him (Psalm 74.14 and Isaiah 27.1). In the Book of Job, the Leviathan is described in more detail (Job 40.25 to 41.26).
In Jonah 2.1 to 11 is a clearer, more recognizable description of a whale alongside the prophet Jonah, who, on his flight from the divine task, the city of Nineveh is spewed to prophesy the downfall, swallowed by a whale on the beach of Nineveh.
Dolphins are far more often than great whales mentioned in the ancient world. Aristotle devotes the sacred animals of the Greeks in his Historia Animalium and gives details of their role as aquatic animals. The Greeks admired the dolphin as a "king of the aquatic animals" and referred to them erroneously as fish. Its intellectual property is perceived both by its ability to escape from the nets of the fishermen as well as his collaboration with fishermen engaged in fishing operations.
River dolphins are known from the Ganges and - very erroneously - the Nile. The latter apparently also equating with sharks and catfish. Supposedly they attacked even crocodiles.
In Greek mythology, dolphins occupy some space. Because of their intelligence, they rescued multiple people from drowning. They were said to have a special love for music - probably not least because of their own song - they saved, in the legends, very famous musicians like Arion of Lesbos from Methymna or Kairanos from Miletus. Because of the mental faculties, dolphins were considered for the god Dionysus.
Dolphins belong to the retinue of Poseidon and led him to his wife Amphitrite. But dolphins are also associated with other gods, such as Apollo, Dionysus and Aphrodite. The Greeks paid tribute to both the whale and the dolphin with its own constellation. The constellation of the Whale (Ketos, lat. Cetus) is located south of the constellation of the Dolphin (Delphi, lat. Delphinus) north of the zodiac.
In ancient art, there are often dolphin representations. Even the Cretan Minoans represented them. Later they often found them on reliefs, gems, lamps, coins, mosaics, grave stones, etc. A particularly popular representation is that of Arion or the Taras riding on a dolphin. In early Christian art, the dolphin is a popular motif, not least because it was partially, next to the fish, used as a symbol of Christ.
Middle Ages to the 19th century
The Irish monk St. Brendan described in his travel story Navigatio Sancti Brendani an encounter with a whale, which he should have done in the years 565-573. He described how he and his companions entered a treeless island, which turned out to be a giant whale, which he called Jasconicus. He met this whale seven years later and rested on his back.
Most descriptions of large whales from this time to whaling era, starting in the 17th century, came from beached whales, however, which resembled by their corpulence and their appearance no other known animal. This was particularly true for the sperm whale, the most frequently stranded in larger groups. Raymond Gilmore in 1959 to 1723 documented 17 sperm whales in the estuary of the Elbe and in 1784 documented 31 animals on the coast of Great Britain. In 1827, a blue whale with a length of 28.5 metres (94 ft) beached itself off the coast of what was then still belonging to the Netherlands Ostend, whose bones were sent all through Europe for seven years. During this time, other whales have been shown around the world and were used as attractions from museums and traveling exhibitions.
Above all, the sailors of the whaling fleets of the 17th to 19th century provided more concrete and more graphic representations of the free-living whales, and the tales of whale watching led to stories that, to a large extent, the yarn can be assigned. Although they knew that most whales represent harmless giants, they described especially the battles with the harpooned animals than slaughter. With the intensification of whaling, there were increasing descriptions of the sea monsters, which include huge whales, sharks, sea snakes, giant squid, and octopuses.
Among the first whalers who described their experiences on whaling trips was Captain William Scoresby from Great Britain, who published the book in 1820 Northern Whale Fishery and it described the hunt for the great baleen whales of the northern seas. This was followed by Thomas Beale, a British surgeon, with the book Some observations on the natural history of the sperm whale in 1835 and Frederick Debell Bennett's the tale of a whale hunt in 1840. Also, whale were described in narrative literature and paintings, most famously in the novels Moby Dick by Herman Melville and 20,000 Leagues Under the Sea by Jules Verne. In the 1882 children's book Adventures of Pinocchio: Story of a jumping jack of Carlo Collodi, however, no cetacean occurs, although this is generally assumed. The wooden figures Pinocchio and Geppettos' creators were swallowed up in the novel by a whale.
Even in historical times, baleen was used as raw materials. Individual vessel components made of baleen partly existed, like the bottom of a bucket in the Scottish National Museum Edinburgh. From Howmae comes a chair seat made from baleen. The Norse crafted ornamented plates from baleen, sometimes interpreted as ironing boards.
In the Canadian Arctic (east coast) were Pott baleen in Punuk - and Thule culture (1000-1600 C.E.)  It was used to construct houses. They served for lack of wood as roof support for the Winter houses, with half of buolding buried under the ground. The actual roof was probably made of skins, which were covered with soil and moss.
Unlike in the past centuries, whales have not been seen in the 20th century as sea monsters and dangerous beasts. With its increasing research, they are gradually more and more discovered to be as an intelligent and peaceful group of animals that are hunted and killed for no reason by people. Above all others, the dolphins in particular received this role, which is also reflected in films and novels of the 1960s and 1990s. For example, the protagonist of the series Flipper was a bottlenose dolphin; from 1962 alongside other animal heroes like Rin Tin Tin, Lassie and Fury to a symbol of animal intelligence. This design was also used in the series SeaQuest DSV (1993-1996), the Warner Bros. movie Free Willy, the movie Star Trek IV: The Voyage Home, and the book series The Hitchhiker's Guide to the Galaxy by Douglas Adams.
The prestige of the great whales, until then mainly known by Moby-Dick, also changed dramatically. The animals are, since the 20th century, partly glorified as "gentle giants" who peacefully roam the seas. Above all, the study of whale song also led to an increasingly strong position in the field of esotericism. Today, their songs are used as a relaxing meditation music .
Belugas were the first whales to be kept in captivity. Other species were too rare, too shy, or too big. The first beluga was shown at Barnum's Museum in New York City in 1861. For most of the 20th century, Canada was the predominant source of wild belugas. They were taken from the St. Lawrence River estuary until the late 1960s, after which they were predominately taken from the Churchill River estuary until capture was banned in 1992. Russia has become the largest provider since it had been banned in Canada. Belugas are caught in the Amur River delta and their eastern coast, and then are either transported domestically to aquariums or dolphinariums in Moscow, St. Petersburg, and Sochi, or exported to other countries, such as Canada. Most captive belugas are caught in the wild, since captive-breeding programs are not very successful.
As of 2006, 30 belugas were in Canada and 28 in the United States, and 42 deaths in captivity had been reported up to that time. A single specimen can reportedly fetch up to US$100,000 (UK£64,160) on the market. The beluga's popularity is due to its unique colour and its facial expressions. The latter is possible because while most cetacean "smiles" are fixed, the extra movement afforded by the beluga's unfused cervical vertebrae allows a greater range of apparent expression.
The killer whale'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 the wild in Iceland, 19 from Japan, and three from 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.
Organizations such as World Animal Protection and the Whale and Dolphin Conservation Society campaign against the practice of keeping them in captivity. In captivity, they often develop pathologies, such as the dorsal fin collapse seen in 60–90% of captive males. Captives have vastly reduced life expectancies, on average only living into their 20s, although there are examples of killer whales living longer, including several over 30 years old, and two captive orcas, Corky II and Lolita, are in their mid-40s. In the wild, females who survive infancy live 46 years on average, and up to 70–80 years in rare cases. Wild males who survive infancy live 31 years on average, and up to 50–60 years. Captivity usually bears little resemblance to wild habitat, and captive whales' social groups are foreign to those found in the wild. Critics claim captive life is stressful due to these factors and the requirement to perform circus tricks that are not part of wild killer whale behavior. Wild killer whales may travel up to 160 kilometres (100 mi) in a day, and critics say the animals are too big and intelligent to be suitable for captivity. Captives occasionally act aggressively towards themselves, their tankmates, or humans, which critics say is a result of stress. Between 1991 and 2010, the bull orca known as Tilikum was involved in the death of three people, and was featured in the critically acclaimed 2013 film, Blackfish. Tilikum has lived at SeaWorld since 1992.
In July 2015, the Journal of Mammalogy published a study comparing life-history parameters of free-ranging killer whale populations with orca managed in captive facilities by SeaWorld Parks. The article coauthored by staff at SeaWorld and the Minnesota Zoo, indicates that there is no significant difference in survivorship between free-ranging and captive killer whales. The authors speculate about the future utility of studying captive populations for the purposes of understanding orca biology and the implications of such research of captive animals in the overall health of both wild and marine park populations. Each country has their own tank requirements; in the US, the minimum enclosure size is set by the Code of Federal Regulations, 9 CFR E § 3.104, under the Specifications for the Humane Handling, Care, Treatment, and Transportation of Marine Mammals.
Various species of dolphins are kept in captivity as well as several other species of porpoise such as Harbour Porpoises and Finless Porpoises. These small cetaceans are more often than not kept in theme parks, such as SeaWorld, commonly known as 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. Orcas 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 orcas being held in aquaria as of 2012. 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 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 Wolphins, 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 the other at SeaWorld San Diego.
Aquariums have tried housing species of whales in captivity, besides the successful beluga whale. The success of belugas turned attention to maintaining their relative, the narwhal, in captivity. However, in repeated attempts in the 1960s and 1970s, all narwhals kept in captivity died within months. A breeding pair of pygmy right whales were retained in an enclosed area (with nets); they were eventually released in South Africa. Gigi was an orphaned gray whale calf that beached herself in 1971. She was kept at SeaWorld San Diego for a year, and was released back into the wild. She was the first baleen whale to be kept in captivity. JJ, another gray whale calf, was kept at SeaWorld San Diego. JJ was an orphaned calf that beached itself on April 1997, and was transported two miles to SeaWorld. The 680 kilograms (1,500 lb) calf was a popular attraction, and behaved normally, despite being separated from his mother. A year later, the 8,164.7 kilograms (18,000 lb) whale grew too big to keep in captivity, though smaller than average, and was released on April 1, 1998; he was the second and probably the last baleen whale to be kept in captivity. There is a captive Amazon river dolphin housed at Acuario de Valencia, and it is the only river dolphin in captivity. 
Organizations such as World Animal Protection and the Whale and Dolphin Conservation Society campaign against the captivity of dolphins and killer whales; SeaWorld, which holds most of the world's captive killer whales, is cited for its role.
Aggression among captive killer whales is common. In August 1989, a dominant female killer whale, Kandu V, attempted to rake a newcomer whale, Corky II, with her mouth during a live show, and smashed her head into a wall. Kandu V broke her jaw which severed an artery and then bled to death. In November 2006, a dominant female killer whale, Kasatka, repeatedly dragged experienced trainer, Ken Peters, to the bottom of the stadium pool during a show after hearing her calf crying for her in the back pools. In February 2010, an experienced female trainer at SeaWorld Orlando, Dawn Brancheau, was killed by killer whale Tilikum shortly after a show in Shamu Stadium. Tilikum had been associated with the deaths of two people previously. In May 2012 Occupational Safety and Health Administration administrative law judge Ken Welsch cited SeaWorld for two violations in the death of Dawn Brancheau and fined the company a total of $12,000. Trainers were banned from making close contact with the orcas. In April 2014 the US Court of Appeals for the District of Columbia denied an appeal by SeaWorld.
In 2013, SeaWorld's treatment of killer whales in captivity was the basis of the movie Blackfish, which documents the history of Tilikum, a killer whale captured by SeaLand of the Pacific, later transported to SeaWorld Orlando who has been involved in the deaths of three people. In the aftermath of the release of the film, Martina McBride, 38 Special, REO Speedwagon, Cheap Trick, Heart, Barenaked Ladies, Trisha Yearwood, and Willie Nelson canceled scheduled concerts at SeaWorld parks. SeaWorld disputes the accuracy of the film and in December 2013 released an ad countering the allegations and emphasizing its contributions to the study of cetaceans and their conservation.
In August 2014, SeaWorld announced it was building new killer whale tanks that would be almost double the size of the existing ones to provide more space for its them, scheduled for completion in 2018. The company maintained the move was not in response to the release of the Blackfish documentary. Wild killer whales may travel up to 160 kilometres (100 mi) in a day, and critics say the animals are too big and intelligent to be suitable for captivity. A "larger prison is still a prison," was the response of PETA which opposes orcas being kept in captivity and has proposed the theme park operator base its orcas in seaside sanctuaries. The company also pledged $10 million in matching funds for killer whale research. In November 2014, SeaWorld announced that attendance at the parks had dropped 5.2% from the previous year and profits had fallen 28% over that quarter. As of November 2014, the company's stock was down 50% from the previous year.
- Mead, J.G.; Brownell, R.L., Jr. (2005). "Order Cetacea". Mammal Species of the World: A Taxonomic and Geographic Reference (3 ed.) (Johns Hopkins University Press): 723–743. ISBN 978-0-8018-8221-0. OCLC 62265494.
- Groves; Colin; Grubb, Peter (2011). "Ungulate taxonomy". JHU Press.
- Juan Cantu (22 January 2015). "Smallest cetacean on the brink of extinction in Mexico". Defenders of Wildlife. Retrieved 1 September 2015.
- John C George; Jeffrey Bada; Judith Zeh; Laura Scott; Stephen E Brown; Todd O'Hara; Robert Suydam (1999). "Age and growth estimates of bowhead whales (Balaena mysticetus) via aspartic acid racemization". Canadian Journal of Zoology 77. doi:10.1139/z99-015.
- J.G.M. Thewissen (11 November 2013). The Emergence of Whales: Evolutionary Patterns in the Origin of Cetacea. Springer Science & Business Media. pp. 383–. ISBN 978-1-4899-0159-0.
- Debra Lee Miller (6 January 2007). Reproductive Biology and Phylogeny of Cetacea: Whales, Porpoises and Dolphins. CRC Press. ISBN 978-1-4398-4257-7.
- Bruno Cozzi; Sandro Mazzariol; Michela Podestà; Alessandro Zott (2009). "Diving Adaptations of the Cetacean Skeleton" (PDF). The Open Zoology Journal. Retrieved 5 September 2015.
- Scholander, Per Fredrik (1940). "Experimental investigations on the respiratory function in diving mammals and birds". Hvalraadets Skrifter (Oslo: Norske Videnskaps-Akademi) 22.
- Bruno Cozzi; Paola Bagnoli; Fabio Acocella; Maria Laura Costantino (2005). "Structure and biomechanical properties of the trachea of the striped dolphin Stenella coeruleoalba: Evidence for evolutionary adaptations to diving". The Anatomical Record 284 (1): 500–510. doi:10.1002/ar.a.20182. Retrieved 5 September 2015.
- C. Edward Stevens; Ian D. Hume (1995). Comparative Physiology of the Vertebrate Digestive System. University of Cambridge. p. 51. ISBN 0-521-44418-7. Retrieved 5 September 2015.
- Clifford A. Hui (1981). "Seawater Consumption and Water Flux in the Common Dolphin Delphinus delphis". Chicago Journals (San Diego) 54: 430.
- Thewissen, J. g. m. (2002). "Hearing". In Perrin, William R.; Wiirsig, Bernd; Thewissen, J. G. M. Encyclopedia of Marine Mammals. Academic Press. pp. 570–2. ISBN 0-12-551340-2.
- Ketten, Darlene R. (1992). "The Marine Mammal Ear: Specializations for Aquatic Audition and Echolocation". In Webster, Douglas B.; Fay, Richard R.; Popper, Arthur N. The Evolutionary Biology of Hearing (PDF). Springer Verlag. pp. 717–50. Retrieved March 2013. Pages 725–7 used here.
- Hooker, Sascha K. (2009). Perrin, William F.; Wursig, Bernd; Thewissen, J. G. M., eds. Encyclopedia of Marine Mammals (2 ed.). 30 Corporate Drive, Burlington Ma. 01803: Academic Press. p. 1176. ISBN 978-0-12-373553-9.
- Sayigh, L.S. (2014). Cetacean Acoustic Communication. In: Witzany G (ed). Biocommunication of Animals. Springer. 275-297. ISBN 978-94-007-7413-1
- Ketten, Darlene R. (1997). "Structure and function in whale ears" (PDF). The International Journal of Animal Sound and its Recording 8 (1–2): 103–135. doi:10.1080/09524622.1997.9753356. Retrieved December 2013.
- de Obaldia, C., Simkus, G. & and Zölzer, U. (2015). "Estimating the number of sperm whale (Physeter macrocephalus) individuals based on grouping of corresponding clicks". 41. Jahrestagung für Akustik (DAGA 2015), Nürnberg. doi:10.13140/RG.2.1.3764.9765.
- Morell, Virginia (July 2011). "Guiana Dolphins Can Use Electric Signals to Locate Prey". Science. American Association for the Advancement of Science (AAAS). Retrieved December 2013.
- Sekiguchi, Yuske; Arai, Kazutoshi; Kohshima, Shiro (21 June 2006). "Sleep behaviour". Nature 441. Bibcode:2006Natur.441E...9S. doi:10.1038/nature04898.
- Miller, P. J. O.; Aoki, K.; Rendell, L. E.; Amano, M. (2008). "Stereotypical resting behavior of the sperm whale". Current Biology 18 (1): R21–R23. doi:10.1016/j.cub.2007.11.003. PMID 18177706.
- Ulfur Anarson (1974). "Comparative chromosome studies in Cetacea". Institute of Genetics (Sweden: University of Lund) 77 (1). Retrieved 5 September 2015.
- AR Hoelzel (1998). "Genetic structure of cetacean populations in sympatry, parapatry, and mixed assemblages: implications for conservation policy". Journal of Heredity (Oxford). doi:10.1093/jhered/89.5.451. Retrieved 5 September 2015.
- Janet Mann; Richard C. Connor; Peter L. Tyack; et al. (eds.). Cetacean Societies: Field Study of Dolphins and Whales. University of Chicago.
- Siebert, Charles (8 July 2009). "Watching Whales Watching Us". New York Times Magazine. Retrieved 29 August 2015.
- Watson, K.K.; Jones, T. K.; Allman, J. M. (2006). "Dendritic architecture of the Von Economo neurons". Neuroscience 141 (3): 1107–1112. doi:10.1016/j.neuroscience.2006.04.084. PMID 16797136.
- Allman, John M.; Watson, Karli K.; Tetreault, Nicole A.; Hakeem, Atiya Y. (2005). "Intuition and autism: a possible role for Von Economo neurons". Trends Cogn Sci 9 (8): 367–373. doi:10.1016/j.tics.2005.06.008. PMID 16002323.
- Hof, Patrick R.; Van Der Gucht, Estel (2007). "Structure of the cerebral cortex of the humpback whale, Megaptera novaeangliae (Cetacea, Mysticeti, Balaenopteridae)". The Anatomical Record 290 (1): 1–31. doi:10.1002/ar.20407. PMID 17441195.
- "Dolphins deserve same rights as humans, say scientists". BBC News Online. 21 Feb 2012. Retrieved 22 May 2012.
- Moore, Jim. "Allometry". University of California San Diego. Retrieved 9 August 2015.
- "Sperm Whales brain size". NOAA Fisheries – Office of Protected Resources. Retrieved 9 August 2015.
- Fields, R. Douglas. "Are whales smarter than we are?". Scientific American. Retrieved 9 August 2015.
- Wiley, David; et al. (2011). "Underwater components of humpback whale bubble-net feeding behaviour". Behaviour 148 (5): 575–602. doi:10.1163/000579511X570893.
- Carwardine, M. H.; Hoyt, E. (1998). "Whales, Dolphins and Porpoises". NSW: Reader's Digest. ISBN 0-86449-096-8.
- "Elephant Self-Awareness Mirrors Humans". Live Science. 30 October 2006. Retrieved 29 August 2015.
- Derr, Mark. "Mirror test". New York Times. Retrieved 3 August 2015.
- Marten, Ken; Psarakos, Suchi (June 1995). "Using Self-View Television to Distinguish between Self-Examination and Social Behavior in the Bottlenose Dolphin (Tursiops truncatus)". Consciousness and Cognition 4 (2).
- Smith, Craig R.; Baco, Amy R. (2003). "Ecology of Whale Falls at the Deep-Sea Floor" (PDF). Oceanography and Marine Biology: an Annual Review 41: 311–354. Retrieved 23 August 2014.
- Fujiwara, Yoshihiro; et al. (16 February 2007). "Three-year investigations into sperm whale-fall ecosystems in Japan". Marine Ecology 28 (1): 219-230.
- Gingerich PD; ul-Haq M; von Koenigswald W; WJ Sanders; Smith BH (2009). "New Protocetid Whale from the Middle Eocene of Pakistan: Birth on Land, Precocial Development, and sexual dimorphism". PLoS ONE. Bibcode:2009PLoSO...4.4366G. doi:10.1371/journal.pone.0004366.
- Thewissen, JGM; Cooper, LN; Clementz, MT; Bajpai, S; Tiwari, BN (2007). "Whales originated from aquatic artiodactyls in the Eocene epoch of India" (PDF). Nature 450 (7173): 1190–4. Bibcode:2007Natur.450.1190T. doi:10.1038/nature06343. PMID 18097400. Retrieved February 2013.
- Michael Benton (2007). Vertebrate paleontology. p. 360.
- Gatesy, J. (1 May 1997). "More DNA support for a Cetacea/Hippopotamidae clade: the blood-clotting protein gene gamma-fibrinogen" (PDF). Molecular Biology and Evolution 14 (5): 537–543. doi:10.1093/oxfordjournals.molbev.a025790. PMID 9159931.
- Boisserie, Jean-Renaud; Lihoreau, Fabrice and Brunet, Michel (2005). "The position of Hippopotamidae within Cetartiodactyla". Proceedings of the National Academy of Sciences 102 (5): 1537–1541. Bibcode:2005PNAS..102.1537B. doi:10.1073/pnas.0409518102. PMC 547867. PMID 15677331.
- "Scientists find missing link between the dolphin, whale and its closest relative, the hippo". Science News Daily. 2005-01-25. Retrieved 2011-01-08.
- "National Geographic – Hippo: Africa's River Beast". National Geographic. Retrieved 2007-07-18.
- JGM Thewissen; Lisa Noelle Cooper; Mark T. Clementz; Sunil Bajpai; BN Tiwari (2007). "Whales orginated from aquatic artiodactyls in the Eocene epoch of India". Nature 450: 1190–1194. Bibcode:2007Natur.450.1190T. doi:10.1038/nature06343.
- J.G.M. Thewissen (1994). "Phylogenetic aspects of Cetacean origins: A morphological perspective". Journal of Mammalian Evolution: 157–184.
- John Gatesy; Jonathan H. Geisler; Joseph Chang; Carl Buell; Annalisa Berta; Robert W. Meredith; Mark S. Springer; Michael R. McGowen (2012). "A phylogenetic blueprint for a modern whale" (PDF). Molecular Phylogenetics and Evolution 66 (2): 479–506. doi:10.1016/j.ympev.2012.10.012. Retrieved 4 September 2015.
- R. Ewan Fordyce; Felix G. Marx (February 2013). "The pygmy right whale Caperea marginata: The Last of the cetotheres". Proc. R. Soc 280. doi:10.1098/rspb.2012.2645.
- Aldemaro Romero (2012). "When whales Became mammals: The Scientific Journey of Cetaceans from fish to mammals in the history of science" (PDF). INTECH Open Access Publisher. doi:10.5772/50811.
- Conrad Gesner. Historiae animalium. Archived from the original on 6 September 2008. Retrieved 4 September 2015.
- J. Ray (1671). "An account of the dissection of a porpess". Philosophical Transactions of the Royal Society of London 6: 2274–2279. Bibcode:1671RSPT....6.2274R.
- Susanne Prahl (2007). "Studies for the construction of epicranialen airway when porpoise (Phocoena phocoena Linnaeus, 1758)". Dissertation for the Doctoral Degree of the Department of Biology of the Faculty of mathematics, computer science and natural sciences at the University of Hamburg (Hamburg): 6.
- Cara E. Miller (2007). Current State of Knowledge of Cetacean Threats, Diversity, and Habitats in the Pacific Islands Region (PDF). Whale and Dolphin Conservation Society. ISBN 978-0-646-47224-9. Retrieved 5 September 2015.
- Schrope, Mark. (2003). "Whale deaths caused by US Navy's sonar". Nature 415 (106). Bibcode:2002Natur.415..106S. doi:10.1038/415106a.
- M. Andre; T. Johansson; E. Delory; M. van der Schaar (2005). "Cetacean biosonar and noise pollution" 2. Oceans 2005–Europe. doi:10.1109/OCEANSE.2005.1513199. Retrieved 4 September 2015.
- Cunliffe, B.; Gosden, C.; Joyce, R. "The circumpolar zone". The Oxford Handbook of Archaeology (Oxford: Oxford University Press).
- J. Savelle (1997). "The Role of Architectural utility in the formation of archaeological Whale Bone Assemblages". Journal of Archaeological Science 24: 869–885.
- unknown. "Movie Retriever: Whales". movieretriever.com.
- "The Whales, New York Tribune, August 9, 1861". New York Tribune. 9 August 1861. Retrieved 5 December 2011.
- "Beluga Whales in Captivity: Hunted, Poisoned, Unprotected" (PDF). Special Report on Captivity 2006. Canadian Marine Environment Protection Society. 2006. Retrieved 26 December 2014.
- "Beluga (Delphinapterus leucas) Facts – Distribution – In the Zoo". World Association of Zoos and Aquariums. Retrieved 5 December 2011.
- Bonner, Nigel. Whales. Facts on File. pp. 17, 23–24. ISBN 0713708875.
- NMFS 2005, pp. 43–44.
- Rose, N. A. (2011). "Killer Controversy: Why Orcas Should No Longer Be Kept in Captivity" (PDF). Humane Society International and the Humane Society of the United States. Retrieved December 21, 2014.
- "Whale Attack Renews Captive Animal Debate". CBS News. March 1, 2010. Retrieved 6 September 2015.
- Susan Jean Armstrong. Animal Ethics Reader. ISBN 9780415275897.
- "Blackfish". Rotten Tomatoes. Retrieved November 23, 2013.
- Zimmerman, Tim (2011). "The Killer in the Pool". The Best American Sampler 2011. Houghton Mifflin Harcourt. p. 336.
- "Corpse Is Found on Whale". New York Times. July 7, 1999. Retrieved September 11, 2011.
- "SeaWorld trainer killed by killer whale". CNN. February 25, 2010. Retrieved March 11, 2010.
- Todd R. Robeck; Kevin Willis; Michael R. Scarpuzzi; Justine K. O’Brien (2015). "Comparisons of life-history parameters between free-ranging and captive killer whale (Orcinus orca) populations for application toward species management". Journal of Mammaology. doi:10.1093/jmammal/gyv113. Retrieved 6 September 2015.
- "Chapter I: Space requirements". Electronic Code of Federal Regulation 1. Retrieved 6 September 2015.
- "Orcas in Captivity - A look at killer whales in aquariums and parks]". 23 November 2009. Retrieved 6 September 2015.
- Klinowska, Margaret; Cooke, Justin (1991). Dolphins, Porpoises, and Whales of the World: the IUCN Red Data Book (PDF). Retrieved 6 September 2015.
- J. L. Sumich; T. Goff; W. L. Perryman (2001). "Growth of two gray whale calves" (PDF). Aquatic mammals (Grossmont College): 231–233. Retrieved 6 September 2015.
- Rose, Naomi A.; E.C.M. Parsons; Richard Farinato (2009). "The Case Against Marine Mammals in Captivity" (PDF). The Humane Society of the United States and World Animal Protection. Retrieved June 7, 2011.
- Parsons, E. C. M. (2012). "Killer Whale Killers". Tourism in Marine Environments 8 (3): 153–160. doi:10.3727/154427312X13491835451494.
- "Near Death At SeaWorld: Worldwide Exclusive Video". The Huffington Post. Retrieved July 12, 2015.
- "SeaWorld trainer killed by killer whale". CNN. February 25, 2010. Retrieved February 24, 2010.
- Garcia, Jason; Jacobson, Susan (February 25, 2010). "Animal trainer killed at SeaWorld". Los Angeles Times.
- "Secretary of Labor, Complainant v. SeaWorld of Florida - Decision and Order" (PDF). Archived from the original (PDF) on June 8, 2012. Retrieved June 13, 2012.
- Karlamangla, Soumya (November 13, 2013). "Killer whales: Court weighs lifting ban on trainer-orca contact". Los Angeles Times.
- SeaWorld appeal of OSHA citations denied
- Whiting, Candace Calloway. In the Wake of Blackfish -- Is it Time to Retire the Last Killer Whale Whose Capture Was Shown in the Film?", TheHuffingtonPost.com, Inc., October 29, 2013. Retrieved October 29, 2013.
- "Martina McBride, 38 Special, cancel SeaWorld gig over 'Blackfish' - CNN.com". CNN. December 16, 2013.
- Streisand, Elizabeth Durand, "Bands Back Out of SeaWorld Concerts Because of 'Blackfish'" Yahoo! News December 9, 2013
- Bazzle, Steph (December 20, 2013). "SeaWorld Tries to Combat Animal Abuse Allegations". Indyposted. Retrieved December 26, 2013.
- Pedicini, Sandra (Aug 15, 2014). "SeaWorld to expand killer-whale habitat at its parks". Orlando Sentinel. Retrieved 16 August 2014.
- CBS News (1 March 2010). "Whale Attack Renews Captive Animal Debate". Newsgroup: News CBS News Check
- "SeaWorld to redesign tank for Killer Whales amid public criticism". The Orlando News.Net. 16 August 2014. Retrieved 16 August 2014.
- Omberg, Emily, "SeaWorld's financial struggles from 'Blackfish' affecting Busch Gardens", Orlando Sun Times, 18 November 2014
- Omberg, Emily, "SeaWorld losing revenue, attendance and profit because of "Blackfish"", Orlando Sun Times, 12 November 2014
- Trigaux, Robert, "As SeaWorld suffers 'Blackfish' impact, Busch Gardens suffers, too", Tampa Bay Times, 17 November 2014
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- "Cetaceans". Encyclopedia of Earth. Retrieved February 2011.
- Scottish Cetacean Research & Rescue – see page on Taxonomy
- "Dolphin and Whale News". Science Daily. Retrieved March 2010.
- Futuyma, Douglas J. (1998). "Cetacea Evolution". Retrieved 2010.
- EIA Cetacean campaign[dead link]: Reports and latest info.
- EIA in USA[dead link]: reports etc.