Cetacea

Edit links
Source: Wikipedia, the free encyclopedia.

Cetacea
Temporal range: 53.5–0 
Ma
 Early Eocene – Present
Clockwise from top:
harbor porpoise
(Phocoena phocoena).
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Artiodactyla
Clade:
Cetaceamorpha
Infraorder: Cetacea
Brisson, 1762
Subgroups

(see text for families)

Diversity
Around 94 species

Cetacea (

carnivorous diet. They propel themselves through the water with powerful up-and-down movement of their tail which ends in a paddle-like fluke, using their flipper-shaped forelimbs to maneuver.[4]

While the majority of cetaceans live in marine environments, a small number reside solely in brackish water or fresh water. Having a cosmopolitan distribution, they can be found in some rivers and all of Earth's oceans, and many species inhabit vast ranges where they migrate with the changing of the seasons.

Cetaceans are famous for their high intelligence, complex social behaviour, and the enormous size of some of the group's members. For example, the blue whale reaches a maximum confirmed length of 29.9 meters (98 feet) and a weight of 173 tonnes (190 short tons), making it the largest animal known ever to have existed.[5][6][7]

There are approximately 89

even-toed ungulates, most closely related to hippopotamus within the clade Whippomorpha
.

Cetaceans have been extensively hunted for their meat, blubber and oil by commercial operations. Although the International Whaling Commission has agreed on putting a halt to commercial whaling, whale hunting is still going on, either under IWC quotas to assist the subsistence of Arctic native people or in the name of scientific research, although a large spectrum of non-lethal methods are now available to study marine mammals in the wild.[9] Cetaceans also face severe environmental hazards from underwater noise pollution, entanglement in abandoned ropes and nets, collisions with ships, plastic and heavy metals build-up, to accelerating climate change,[10][11] but how much they are affected varies widely from species to species, from minimally in the case of the southern bottlenose whale to the baiji (or Chinese river dolphin) which is considered to be functionally extinct due to human activity.[12]

Baleen whales and toothed whales

Skull of the North Atlantic right whale (Mysticeti)
Skull of the orca (Odontoceti)

The two parvorders, baleen whales (Mysticeti) and toothed whales (Odontoceti), are thought to have diverged around thirty-four million years ago.[13]

Baleen whales have bristles made of

bowhead whales
) have massive heads that can make up 40% of their body mass. Most mysticetes prefer the food-rich colder waters of the Northern and Southern Hemispheres, migrating to the Equator to give birth. During this process, they are capable of fasting for several months, relying on their fat reserves.

The parvorder of Odontocetes – the toothed whales – include sperm whales, beaked whales, orcas, dolphins and porpoises. Generally their teeth have evolved to catch fish, squid or other

pinnipeds
and other whales.

Toothed whales have well-developed senses – their eyesight and hearing are adapted for both air and water, and they have advanced sonar capabilities using their melon. Their hearing is so well-adapted for both air and water that some blind specimens can survive. Some species, such as sperm whales, are well adapted for diving to great depths. Several species of toothed whales show sexual dimorphism, in which the males differ from the females, usually for purposes of sexual display or aggression.

Anatomy

Dolphin anatomy

Cetacean bodies are generally similar to those of fish, which can be attributed to their lifestyle and the habitat conditions. Their body is well-adapted to their habitat, although they share essential characteristics with other higher mammals (Eutheria).[14]

They have a streamlined shape, and their forelimbs are flippers. Almost all have a dorsal fin on their backs, but this can take on many forms, depending on the species. A few species, such as the beluga whale, lack them. Both the flipper and the fin are for stabilization and steering in the water.

The male genitals and the mammary glands of females are sunken into the body.[15][16]

The body is wrapped in a thick layer of fat, known as blubber. This provides thermal insulation and gives cetaceans their smooth, streamlined body shape. In larger species, it can reach a thickness up to one-half meter (1.6 feet).

Sexual dimorphism evolved in many toothed whales. Sperm whales, narwhals, many members of the beaked whale family, several species of the porpoise family, orcas, pilot whales, eastern spinner dolphins and northern right whale dolphins show this characteristic.[17] Males in these species developed external features absent in females that are advantageous in combat or display. For example, male sperm whales are up to 63% percent larger than females, and many beaked whales possess tusks used in competition among males.[17][18] Hind legs are not present in cetaceans, nor are any other external body attachments such as a

pinna and hair.[19]

Head

Head profile of a beluga whale, featuring the large "melon" region
Close up of a feeding humpback whale, showing baleen

Whales have an elongated head, especially

baleen whales, due to the wide overhanging jaw. Bowhead whale plates can be 9 metres (30 ft) long. Their nostril(s) make up the blowhole, with one in toothed whales and two in baleen whales.[20]

The nostrils are located on top of the head above the eyes so that the rest of the body can remain submerged while surfacing for air. 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.[21] 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.

In toothed whales, connective tissue exists in the

biosonar. The sperm whale has 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. In many toothed whales, the depression in their skull is due to the formation of a large melon and multiple, asymmetric air bags.

River dolphins, unlike most other cetaceans, can turn their head 90°. Most other cetaceans have fused neck vertebrae and are unable to turn their head at all.

The baleen of baleen whales consists of long, fibrous strands of keratin. Located in place of the teeth, it has the appearance of a huge fringe and is used to sieve the water for plankton and krill.

Brain

Brain of the sperm whale, considered the largest brain in the world

Sperm whales have the largest brain mass of any animal on Earth, averaging 8,000 cm3 (490 in3) and 7.8 kg (17 lb) in mature males.

brain to body mass ratio in some odontocetes, such as belugas and narwhals, is second only to humans.[23]
In some whales, however, it is less than half that of humans: 0.9% versus 2.1%.

In cetaceans, evolution in the water has caused changes to the head that have modified brain shape such that the brain folds around the insula and expands more laterally than in terrestrial mammals. As a result, the cetacean prefrontal cortex (compared to that in humans) rather than frontal is laterally positioned.[24]

Allometric
analysis of the relationship between mammalian brain mass (weight) and body mass for different species of mammals shows that larger species generally have larger brains. However, this increase is not fully proportional. Typically the brain mass only increases in proportion to somewhere between the two-thirds power (or the square of the cube root) and the three-quarters power (or the cube of the fourth root) of the body mass. mbrain ∝ (mbody)k where k is between two-thirds and three-quarters. Thus if Species B is twice the size of Species A, its brain size will typically be somewhere between 60% and 70% higher.[25] Comparison of a particular animal's brain size with the expected brain size based on such an analysis provides an encephalization quotient that can be used as an indication of animal intelligence.

The

spindle neurons are found in areas of the brain homologous to where they are found in humans, suggesting they perform a similar function.[28]

Skeleton

Diagram featuring the typical skeletal of a toothed whale (top) and a baleen whale (bottom)

The cetacean skeleton is largely made up of

biosonar
.

The number of

chevron bone
.

The front limbs are paddle-shaped with shortened arms and elongated finger bones, to support movement. They are connected by cartilage. The second and third fingers display a proliferation of the finger members, a so-called hyperphalangy. The shoulder joint is the only functional joint in all cetaceans except for the

collarbone
is completely absent.

Fluke

Humpback whale fluke

Cetaceans have a

fluke is set horizontally on the body and used with vertical movements, unlike fish and ichthyosaurs, which have vertical tails which move horizontally.[29]

Physiology

Circulation

Cetaceans have powerful hearts. Blood oxygen is distributed effectively throughout the body. They are warm-blooded, i.e., they hold a nearly constant body temperature.

Respiration

Cetaceans have lungs, meaning they breathe air. An individual can last without a breath from a few minutes to over two hours depending on the species. Cetacea are deliberate breathers who must be awake to inhale and exhale. When 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 across species in shape, angle and height. Species can be identified at a distance using this characteristic.

The structure of the

marine mammals. The oxygen balance is effective. Each breath can replace up to 90% of the total lung volume. For land mammals, in comparison, this value is usually about 15%. During inhalation, about twice as much oxygen is absorbed by the lung tissue as in a land mammal. As with all mammals, the oxygen is stored in the blood and the lungs, but in cetaceans, it is also stored in various tissues, mainly in the muscles. The muscle pigment, myoglobin
, provides an effective bond. This additional oxygen storage is vital for deep diving, since beyond a depth around 100 m (330 ft), the lung tissue is almost completely compressed by the water pressure.

Abdominal organs

The stomach consists of three chambers. The first region is formed by a loose gland and a muscular forestomach (missing in beaked whales); this is followed by the main stomach and the

gall bladder.[30]

The kidneys are long and flattened. The salt concentration in cetacean blood is lower than that in seawater, requiring kidneys to excrete salt. This allows the animals to drink seawater.

testes are located internally, without an external scrotum.[33][34][35][36] The uterus is bicornuate.[34]

Senses

Cetacean eyes are set on the sides rather than the front of the head. This means only species 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. Odontocetes have little to no ability to taste or smell, while mysticetes are believed to have some ability to smell because of their reduced, but functional olfactory system.[37] Cetaceans are known to possess excellent hearing.[38]

At least one species, the

electroreception to sense prey.[39]

Ears

Biosonar

The external ear has lost the

pinna (visible ear), but still retains a narrow ear canal. The three small bones or ossicles that transmit sound within each ear are dense and compact, and differently shaped from those of land mammals. The semicircular canals are much smaller relative to body size than in other mammals.[40]

A bony structure of the middle and inner ear, the

auditory bulla, is composed of two compact and dense bones (the periotic and tympanic). It is housed in a cavity in the middle ear; in the Odontoceti (apart from in the physeterids, this cavity is filled with dense foam and completely surrounds the bulla, which is connected to the skull only by ligaments. This may isolate the ear from sounds transmitted through the bones of the skull, something that also happens in bats.[41]

Cetaceans use sound to communicate, using groans, moans, whistles, clicks or the 'singing' of the humpback whale.[39]

Echolocation

Odontoceti are generally capable of echolocation.[42] They can discern the size, shape, surface characteristics, distance and movement of an object. They can search for, chase and catch fast-swimming prey in total darkness. Most Odontoceti 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. 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.[43]

Mysticeti have exceptionally thin, wide basilar membranes in their

infrasonic frequencies.[44]

Chromosomes

The initial

telomeres), two to four pairs of subtelocentric and one or two large pairs of submetacentric chromosomes. The remaining chromosomes are metacentric—the centromere is approximately in the middle—and are rather small. All cetaceans have chromosomes 2n = 44, except the sperm whales and pygmy sperm whales, which have 2n = 42.[45]

Ecology

Range and habitat

See also: Cetaceans of the Caribbean

Cetaceans are found in many aquatic habitats. While many marine species, such as the blue whale, the humpback whale and the orca, have a distribution area that includes nearly the entire ocean, some species occur only locally or in broken populations. These include the vaquita, which inhabits a small part of the Gulf of California and Hector's dolphin, which lives in some coastal waters in New Zealand. River dolphin species live exclusively in fresh water.

Many species inhabit specific latitudes, often in tropical or subtropical waters, such as

northern straight dolphin
live only in the North Pacific.

Cosmopolitan species may be found in the Pacific, Atlantic and Indian Oceans. However, northern and southern populations become genetically separated over time. In some species, this separation leads eventually to a divergence of the species, such as produced the southern right whale, North Pacific right whale and North Atlantic right whale.[46] Migratory species' reproductive sites often lie in the tropics and their feeding grounds in polar regions.

Thirty-two species are found in European waters, including twenty-five toothed and seven baleen species.

Whale migration

Many species of whales migrate on a latitudinal basis to move between seasonal habitats. For example, the gray whale migrates 10,000 miles (16,000 km) round trip. The journey begins at winter birthing grounds in warm lagoons along Baja California, and traverses 5,000–7,000 miles (8,000–11,300 km) of coastline to summer feeding grounds in the Bering, Chuckchi and Beaufort seas off the coast of Alaska.[47]

Behaviour

Sleep

Conscious breathing cetaceans sleep but cannot afford to be 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.[48]

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.[49]

Diving

See also: Physiology of underwater diving § Mammals

While diving, the animals reduce their oxygen consumption by lowering the heart activity and blood circulation; individual organs receive no oxygen during this time. Some

sperm whales between 60 and 90 minutes and bottlenose whales for two hours. Diving depths average about 100 m (330 ft). Species such as sperm whales can dive to 3,000 m (9,800 ft), although more commonly 1,200 metres (3,900 ft).[50][51]

Social relations

Most cetaceans are social animals, although a few species live in pairs or are solitary. A group, known as a pod, usually consists of ten to fifty animals, but on occasion, such as mass availability of food or during mating season, groups may encompass more than one thousand individuals. Inter-species socialization can occur.[52]

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 stress such as lack of food, but usually it is peaceful. Contact swimming, mutual fondling and nudging are common. 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.[52]

Whale song

Males in some baleen species communicate via whale song, sequences of high pitched sounds. These "songs" can be heard for hundreds of kilometers. Each population generally shares a distinct song, which evolves over time. Sometimes, an individual can be identified by its distinctive vocals, such as the 52-hertz whale that sings at a higher frequency than other whales. Some individuals are capable of generating over 600 distinct sounds.[52] In baleen species such as humpbacks, blues and fins, male-specific song is believed to be used to attract and display fitness to females.[53]

Hunting

Pod groups also hunt, often with other species. Many species of dolphins accompany large tunas on hunting expeditions, following large schools of fish. The orca 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.[52]

Intelligence

Main article: Cetacean intelligence
Bubble net feeding

Cetacea are known to teach, learn, cooperate, scheme and grieve.[54]

Smaller cetaceans, such as dolphins and porpoises, engage in complex play behavior, including such things as producing stable underwater toroidal air-core vortex rings or "bubble rings". The two main methods of bubble ring production are rapid puffing 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 produce bubble nets to aid in herding prey.[55]

Killer whale porpoising

Larger whales are also thought to engage in play. The southern right whale elevates its tail fluke above the water, remaining in the same position for a considerable 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.[56] Humpback whales also display this behaviour.

Self-awareness appears to be a sign of abstract thinking. Self-awareness, although not well-defined, is believed to be a precursor to more advanced processes such as metacognitive reasoning (thinking about thinking) that humans exploit. Dolphins appear to possess self-awareness.[57] 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. Researchers then explore whether the animal shows signs of self-recognition.[58]

Critics claim that the results of these tests are susceptible to the

primates. Primates can touch the mark or the mirror, while dolphins cannot, making their alleged self-recognition behavior less certain. Skeptics argue that behaviors said to identify self-awareness resemble existing social behaviors, so researchers could be misinterpreting self-awareness for social responses. Advocates counter that the behaviors are different from normal responses to another individual. Dolphins show less definitive behavior of self-awareness, because they have no pointing ability.[58]

In 1995, Marten and Psarakos used video to test dolphin self-awareness.[59] 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 replicated, dolphins later "passed" the mirror test.[58]

Decision-making

Collective decisions are an important part of life as a cetacean for the many species that spend time in groups (whether these be temporary such as the fission-fusion dynamics of many smaller dolphin species or long-term stable associations as are seen in killer whale and sperm whale matrilines). [60] Little is known about how these decisions work, though studies have found evidence messy consensus decisions in groups of sperm whales and leadership in other species like bottlenose dolphins and killer whales.

Life history

Reproduction and brooding

Most cetaceans sexually mature at seven to 10 years. An exception to this is the La Plata dolphin, which is sexually mature at two years, but lives only to about 20. The sperm whale reaches sexual maturity within about 20 years and has a lifespan between 50 and 100 years.[52]

For most species, reproduction is seasonal.

monogamous
within each reproductive period.

Gestation ranges from 9 to 16 months. Duration is not necessarily a function of size. Porpoises and blue whales gestate for about 11 months. As with all mammals other than marsupials and monotremes, the embryo is fed by the placenta, an organ that draws nutrients from the mother's bloodstream. Mammals without placentas either lay minuscule eggs (monotremes) or bear minuscule offspring (marsupials).

Cetaceans usually bear one calf. In the case of twins, one usually dies, because the mother cannot produce sufficient milk for both. The fetus is positioned for a tail-first delivery, so that the risk of drowning during delivery is minimal. After birth, the mother carries the infant to the surface for its first breath. At birth, they are about one-third of their adult length and tend to be independently active, comparable to terrestrial

mammals
.

Suckling

Like other placental mammals, cetaceans give birth to well-developed calves and nurse them with milk from their

mammary glands. When suckling, the mother actively splashes milk into the mouth of the calf, using the muscles of her mammary glands, as the calf has no lips. This milk usually has a high-fat content, ranging from 16 to 46%, causing the calf to increase rapidly in size and weight.[52]

In many small cetaceans, suckling lasts for about four months. In large species, it lasts for over a year and involves a strong bond between mother and offspring.

The mother is solely responsible for brooding. In some species, so-called "aunts" occasionally suckle the young.

This reproductive strategy provides a few offspring that have a high survival rate.

Lifespan

Among cetaceans, whales are distinguished by an unusual longevity compared to other higher mammals. Some species, such as the

otic capsule, the age of the oldest known specimen is a male determined to be 211 years at the time of death.[61]

Death

Main article: Whale fall

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.[62]

Deterioration of whale carcasses happens through three stages. Initially, organisms such as

chemoautotrophic organisms, which in turn, support organisms such as mussels, clams, limpets and sea snails. This stage may last for decades and supports a rich assemblage of species, averaging 185 per site.[62][63]

Disease

cardiopathies, bone and skin lesions, strandings and death. Until 2008, no case had ever been reported in porpoises, but isolated populations have an increased risk and consequentially a high mortality rate.[64]

Evolution

Main article: Evolution of cetaceans

Fossil history

Origins

The direct ancestors of today's cetaceans are probably found within the

Dorudontidae whose most famous member, Dorudon, lived at the same time as Basilosaurus. Both groups had already developed some of the typical anatomical features of today's whales, such as the fixed bulla, which replaces the mammalian eardrum, as well as sound-conducting elements for submerged directional hearing. Their wrists were stiffened and probably contributed to the typical build of flippers. The hind legs existed, however, but were significantly reduced in size and with a vestigial pelvis connection.[65]

Transition from land to sea

Fossil of a Maiacetus (red, beige skull) with fetus (blue, red teeth) shortly before the end of gestation [66]

The fossil record traces the gradual transition from terrestrial to aquatic life. The regression of the hind limbs allowed greater flexibility of the spine. This made it possible for whales to move around with the vertical tail hitting the water. The front legs transformed into flippers, costing them their mobility on land.[citation needed]

One of the oldest members of ancient cetaceans (Archaeoceti) is Pakicetus from the Middle Eocene of Pakistan. This is an animal the size of a wolf, whose skeleton is known only partially. It had functioning legs and lived near the shore. This suggests the animal could still move on land. The long snout had carnivorous dentition.[65]

The transition from land to sea dates to about 49 million years ago, with the Ambulocetus ("running whale"), also discovered in Pakistan. It was up to 3 m (9.8 ft) long. The limbs of this archaeocete were leg-like, but it was already fully aquatic, indicating that a switch to a lifestyle independent from land happened extraordinarily quickly.[67] The snout was elongated with overhead nostrils and eyes. The tail was strong and supported movement through water. Ambulocetus probably lived in mangroves in brackish water and fed in the riparian zone as a predator of fish and other vertebrates.[68]

Dating from about 45 million years ago are species such as

lumbar spine was present, making it possible to support the floating movement of the tail. It was likely a good swimmer, but could probably move only clumsily on land, much like a modern seal.[65]

Marine animals

Since the late Eocene, about 40 million years ago, cetaceans populated the subtropical oceans and no longer emerged on land. An example is the 18 metre long

Wadi Al-Hitan ("Whale Valley") in Egypt contains numerous skeletons of Basilosaurus, as well as other marine vertebrates.[69]

External phylogeny

Tethys Sea deposits in northern India and Pakistan. The Tethys Sea was a shallow sea between the Asian continent and northward-bound Indian plate.[citation needed
]

aquatic reptiles
.

Molecular and morphological evidence suggests that

Artiodactyla can be represented in the following cladogram:[73][74][75][76][77]

Artiodactyla
 

Tylopoda (camels)

 Artiofabula 

 Suina (pigs)

 Cetruminantia 
 
Ruminantia
 (ruminants) 

 Tragulidae (mouse deer)

 Pecora (horn bearers)

 
Cetancodonta/Whippomorpha
 

 Hippopotamidae (hippopotamuses)

 Cetacea (whales)

54 mya

Internal phylogeny

Further information: List of cetaceans and List of extinct cetaceans

Within Cetacea, the two

Odontoceti), which have teeth shaped like cones, spades, pegs, or tusks, and can perceive their environment through biosonar
.

Relationship of extinct and extant cetaceans[78]:
 

 Raoellidae †

 Cetacea 

 Pakicetidae †

 Ambulocetidae †

 Remingtonocetidae †

 Rodhocetus †

 Dorudon †

 Basilosaurus †

 
Mysticeti
 
(
baleen whales
, 25 mya)
 
Odontoceti
 
 Kogiidae 

 Dwarf sperm whales

 
Physeteridae
 

 Sperm whales

 Platanistidae 

 South Asian river dolphins

 
Ziphiidae
 

 Beaked whales

 
Inioidea
 
 Lipotidae 

Yangtze river dolphin

(South American
river dolphins)
 Delphinoidea 
 
Delphinidae
 

 

Oceanic dolphins

("true" dolphins)
 Monodontidae 

 Belugas & Narwhals

 
Phocoenidae
 

 Porpoises

(
toothed whales
)
† Extinct taxa

The terms whale and dolphin are informal:

  • Mysticeti
    :
  • Odontoceti
    :

The term 'great whales' covers those currently regulated by the International Whaling Commission:[79] the Odontoceti families Physeteridae (sperm whales), Ziphiidae (beaked whales), and Kogiidae (pygmy and dwarf sperm whales); and Mysticeti families Balaenidae (right and bowhead whales), Cetotheriidae (pygmy right whales), Eschrichtiidae (grey whales), as well as part of the family Balaenopteridae (minke, Bryde's, sei, blue and fin; not Eden's and Omura's whales).[80]

Status

Threats

The primary threats to cetaceans come from people, both directly from whaling or drive hunting and indirect threats from fishing and pollution.[81]

Whaling

Main articles:
History of Whaling, and Dolphin drive hunting
Methods of
drive hunt in Hvalba on the Faroe Islands
being taken away with a forklift.

Whaling is the practice of hunting whales, mainly baleen and sperm whales. This activity has gone on since the Stone Age.

In the

bowheads
. In the 16th and 17th centuries, the Dutch fleet had about 300 whaling ships with 18,000 crewmen.

In the 18th and 19th centuries, baleen whales especially were hunted for their baleen, which was used as a replacement for wood, or in products requiring strength and flexibility such as corsets and crinoline skirts. In addition, the spermaceti found in the sperm whale was used as a machine lubricant and the ambergris as a material for pharmaceutical and perfume industries. In the second half of the 19th century, the explosive harpoon was invented, leading to a massive increase in the catch size.

Large ships were used as "mother" ships for the whale handlers. In the first half of the 20th century, whales were of great importance as a supplier of raw materials. Whales were intensively hunted during this time; in the 1930s, 30,000 whales were killed. This increased to over 40,000 animals per year up to the 1960s, when stocks of large baleen whales collapsed.

Most hunted whales are now threatened, with some great whale populations exploited to the brink of extinction. Atlantic and Korean

North Atlantic right whale population fell to some 300–600. The blue whale
population is estimated to be around 14,000.

The first efforts to protect whales came in 1931. Some particularly endangered species, such as the humpback whale (which then numbered about 100 animals),[citation needed] were placed under international protection and the first protected areas were established. In 1946, the International Whaling Commission (IWC) was established, to monitor and secure whale stocks. Whaling of 14 large species for commercial purposes was prohibited worldwide by this organization from 1985 to 2005, though some countries do not honor the prohibition.

Whales caught 2010–2014, by country

The stocks of species such as humpback and blue whales have recovered, though they are still threatened. The United States Congress passed the

Marine Mammal Protection Act of 1972
sustain the marine mammal population. It prohibits the taking of marine mammals except for several hundred per year taken in Alaska. Japanese whaling ships are allowed to hunt whales of different species for ostensibly scientific purposes.

Aboriginal whaling is still permitted. About 1,200 pilot whales were taken in the Faroe Islands in 2017,[82] and about 900 narwhals and 800 belugas per year are taken in Alaska, Canada, Greenland, and Siberia. About 150 minke are taken in Greenland per year, 120 gray whales in Siberia and 50 bowheads in Alaska, as aboriginal whaling, besides the 600 minke taken commercially by Norway, 300 minke and 100 sei taken by Japan and up to 100 fin whales taken by Iceland.[83] Iceland and Norway do not recognize the ban and operate commercial whaling. Norway and Japan are committed to ending the ban.

Dolphins and other smaller cetaceans are sometimes hunted in an activity known as dolphin drive hunting. This is accomplished by driving a pod together with boats, 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). Dolphins are mostly hunted for their meat, though some end up in dolphinaria. Despite the controversy thousands of dolphins are caught in drive hunts each year.

Fishing

See also: Cetacean bycatch
Dominoes made of baleen

Dolphin pods often reside near large tuna shoals. This is known to fishermen, who look for dolphins to catch tuna. Dolphins are much easier to spot from a distance than tuna, since they regularly breathe. The fishermen pull their nets hundreds of meters wide in a circle around the dolphin groups, in the expectation that they will net a tuna shoal. When the nets are pulled together, the dolphins become entangled under water and drown. Line fisheries in larger rivers are threats to

river dolphins
.

A greater threat than by-catch for small cetaceans is targeted hunting. In Southeast Asia, they are sold as fish-replacement to locals, since the region's edible fish promise higher revenues from exports. In the Mediterranean, small cetaceans are targeted to ease pressure on edible fish.[81]

Strandings

Main article: Cetacean stranding

A stranding is when a cetacean leaves the water to lie on a beach. In some cases, groups of whales strand together. The best known are mass strandings of pilot whales and sperm whales. Stranded cetaceans usually die, because their as much as 90 metric tons (99 short tons) body weight compresses their lungs or breaks their ribs. Smaller whales can die of heatstroke because of their thermal insulation.

Beached humpback whale

The causes are not clear. Possible reasons for mass beachings are:[81]

  • toxic contaminants
  • debilitating parasites (in the respiratory tract, brain or middle ear)
  • infections (bacterial or viral)
  • flight from predators (including humans)
  • social bonds within a group, so that the pod follows a stranded animal
  • disturbance of their magnetic senses by natural anomalies in the Earth's magnetic field
  • injuries
  • noise pollution by shipping traffic, seismic surveys and military sonar experiments

Since 2000, whale strandings frequently occurred following 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 coauthor of the interim report stated that animals killed by active sonar of some Navy ships were injured. Generally, underwater noise, which is still on the increase, is increasingly tied to strandings; because it impairs communication and sense of direction.[84]

Climate change influences the major wind systems and ocean currents, which also lead to cetacean strandings. Researchers studying strandings on the Tasmanian coast from 1920 to 2002 found that greater strandings occurred at certain time intervals. Years with increased strandings were associated with severe storms, which initiated cold water flows close to the coast. In nutrient-rich, cold water, cetaceans expect large prey animals, so they follow the cold water currents into shallower waters, where the risk is higher for strandings. Whales and dolphins who live in pods may accompany sick or debilitated pod members into shallow water, stranding them at low tide.[85]

Environmental hazards

See also: Marine mammals and sonar

Worldwide, use of active sonar has been linked to about 50 marine mammal strandings between 1996 and 2006. In all of these occurrences, there were other contributing factors, such as unusual (steep and complex) underwater geography, limited egress routes, and a specific species of marine mammal — beaked whales — that are suspected to be more sensitive to sound than other marine mammals.

—Rear Admiral Lawrence Rice

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 disease and have fewer offspring.[81]

Damage to the ozone layer reduces plankton reproduction because of its resulting radiation. This shrinks the food supply for many marine animals, but the filter-feeding baleen whales are most impacted. Even the Nekton is, in addition to intensive exploitation, damaged by the radiation.[81]

Food supplies are also reduced long-term by ocean acidification due to increased absorption of increased atmospheric carbon dioxide. The CO2 reacts with water to form carbonic acid, which reduces the construction of the calcium carbonate skeletons of food supplies for zooplankton that baleen whales depend on.[81]

The military and resource extraction industries operate strong

biosonar for orientation and communication. Severe instances can panic them, driving them to the surface. This leads to bubbles in blood gases and can cause decompression sickness.[87]
Naval exercises with sonar regularly results in fallen cetaceans that wash up with fatal decompression. Sounds can be disruptive at distances of more than 100 kilometres (62 mi). Damage varies across frequency and species.

Relationship to humans

Research history

See also: Cryptid whale and Whale § In myth, literature and art
A whale as depicted by Conrad Gesner, 1587, in Historiae animalium

In Aristotle's time, the fourth century BCE, whales were regarded as fish due to their superficial similarity. Aristotle, however, observed many physiological and anatomical similarities with the terrestrial vertebrates, such as blood (circulation), lungs, uterus and fin anatomy.[88] His detailed descriptions were assimilated by 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, dolphins are portrayed with a high-arched head (typical of porpoises) and a long snout. The harbour porpoise was one of the most accessible species for early cetologists; because it could be seen close to land, inhabiting shallow coastal areas of Europe. Much of the findings that apply to all cetaceans were first discovered in porpoises.[89] One of the first anatomical descriptions of the airways of a harbor porpoise dates from 1671 by John Ray. It nevertheless referred to the porpoise as a fish.[90][91]

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 a void.

— John Ray, 1671, the earliest description of cetacean airways

In the 10th edition of Systema Naturae (1758), Swedish biologist and taxonomist Carl Linnaeus asserted that cetaceans were mammals and not fish. His groundbreaking binomial system formed the basis of modern whale classification.

Culture

Cetaceans have played a role in human culture through history.

Prehistoric

petroglyphs, such as those in Roddoy and Reppa (Norway), and the Bangudae Petroglyphs in South Korea, depict them.[92][93] Whale bones were used for many purposes. In the Neolithic settlement of Skara Brae on Orkney
sauce pans were made from whale vertebrae.

Antiquity

"Destruction of Leviathan" engraving by Gustave Doré, 1865
Silver coin with Taras riding a dolphin

The whale was first mentioned in ancient Greece by Homer. There, it is called Ketos, a term that 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. North Sea whales were called Physeter, which was meant for the sperm whale Physter macrocephalus. Whales are described in particular by Aristotle, Pliny and Ambrose. All mention both live birth and suckling. Pliny describes the problems associated with the lungs with spray tubes and Ambrose claimed that 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[94] and should again be destroyed by him.[95][96] In the Book of Job, the leviathan is described in more detail.[97][98]

In Jonah there is a more recognizable description of a whale alongside the prophet Jonah, who, on his flight from the city of Nineveh is swallowed by a whale.

Dolphins are mentioned far more often than whales. Aristotle discusses 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 intelligence was apparent both in its ability to escape from fishnets and in its collaboration with fishermen.

River dolphins are known from the Ganges and – erroneously – the Nile. In the latter case it was equated with sharks and catfish. Supposedly they attacked even crocodiles.

Dolphins appear in Greek mythology. Because of their intelligence, they rescued multiple people from drowning. They were said to love music, probably because of their own song, and in the legends they saved famous musicians, such as Arion of Lesbos from Methymna
.

Constellation Cetus

Dolphins belong to the domain of Poseidon and led him to his wife Amphitrite. Dolphins are associated with other gods, such as Apollo, Dionysus and Aphrodite. The Greeks paid tribute to both whales and dolphins with their own constellation. The constellation of the Whale (Ketos, lat. Cetus) is located south of the Dolphin (Delphi, lat. Delphinus) north of the zodiac.

Ancient art often included dolphin representations, including the Cretan

Christ
.

Middle Ages to the 19th century

See also:
Cryptid whales

St. Brendan
described in his travel story Navigatio Sancti Brendani an encounter with a whale, between 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 until the whaling era, beginning in the 17th century, were of beached whales, which resembled no other animal. This was particularly true for the sperm whale, the most frequently stranded in larger groups. Raymond Gilmore documented seventeen sperm whales in the estuary of the Elbe from 1723 to 1959 and thirty-one animals on the coast of Great Britain in 1784. In 1827, a blue whale beached itself off the coast of Ostend. Whales were used as attractions in museums and traveling exhibitions.

Depiction of baleen whaling, 1840
Stranded sperm whale engraving, 1598

Whalers from the 17th to 19th centuries depicted whales in drawings and recounted tales of their occupation. Although they knew that whales were harmless giants, they described battles with harpooned animals. These included descriptions of sea monsters, including huge whales, sharks, sea snakes, giant squid and octopuses.

Among the first whalers who described their experiences on whaling trips was Captain

20,000 Leagues Under the Sea by Jules Verne
.

Baleen was used to make vessel components such as the bottom of a bucket in the Scottish National Museum. The Norsemen crafted ornamented plates from baleen, sometimes interpreted as ironing boards.

In the Canadian Arctic (east coast) in Punuk and Thule culture (1000–1600 C.E.),[99] baleen was used to construct houses in place of wood as roof support for winter houses, with half of the building buried under the ground. The actual roof was probably made of animal skins that were covered with soil and moss.[100]

Modern culture

Further information: Whale § Interactions with humans
Sea World show featuring bottlenose dolphins and false killer whales

In the 20th century perceptions of cetaceans changed. They transformed from monsters into creatures of wonder, as science revealed them to be intelligent and peaceful animals. Hunting was replaced by whale and dolphin tourism. This change is reflected in films and novels. For example, the protagonist of the series Flipper was a bottle-nose dolphin. The TV series SeaQuest DSV (1993–1996), the movies Free Willy, Star Trek IV: The Voyage Home and the book series The Hitchhiker's Guide to the Galaxy by Douglas Adams are examples.[101]

The study of whale song also produced a popular album, Songs of the Humpback Whale.

Captivity

Whales and dolphins have been kept in captivity for use in education, research and entertainment since the 19th century.

Belugas

Main article: Beluga whale § Captivity

St. Petersburg and Sochi, or exported to countries such as Canada.[103] They have not been domesticated.[104]

As of 2006, 30 belugas lived in Canada and 28 in the United States. 42 deaths in captivity had been reported.

£64,160). The beluga's popularity is due to its unique color 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.[105]

Orcas

Main article:
Captive killer whales
See also: SeaWorld § Criticism and resulting impact, and Incidents at SeaWorld parks
Ulises the orca, 2009

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, fifty-five whales were taken from the wild in Iceland, nineteen 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 forty-eight animals on display in the world were captive-born.[106]

Organizations such as World Animal Protection and the Whale and Dolphin Conservation 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 reduced life expectancy, on average only living into their 20s, although some live longer, including several over 30 years old and two, Corky II and Lolita, in their mid-40s. In the wild, females who survive infancy live 46 years on average and up to 70–80 years. Wild males who survive infancy live 31 years on average and can reach 50–60 years.[107]

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 orca behavior. Wild orca 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.

stress.[109] Orcas are well known for their performances in shows, but the number of orcas kept in captivity is small, especially when compared to the number of bottlenose dolphins, with only forty-four captive orcas being held in aquaria as of 2012.[110]

Each country has its 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.[111]

Dawn Brancheau doing a show four years before the incident

Aggression among captive orcas is common. They attack each other and their trainers as well. In 2013, SeaWorld's treatment of orcas in captivity was the basis of the movie Blackfish, which documents the history of Tilikum, an orca at SeaWorld Orlando, who had been involved in the deaths of three people.[112] The film led to proposals by some lawmakers to ban captivity of cetaceans, and led SeaWorld to announce in 2016 that it would phase out its orca program after various unsuccessful attempts to restore its revenues, reputation, and stock price.[113]

Others

SeaWorld pilot whale with trainers

Dolphins and porpoises are kept in captivity.

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 at Discovery Cove and SeaWorld San Diego
.

In repeated attempts in the 1960s and 1970s,

Acuario de Valencia is the only trained river dolphin in captivity.[114][115]

Here is a list of all the cetaceans that have been taken into captivity for either conservation, research or human entertainment and education purposes currently or in the past, temporarily or permanently.

References

  1. S2CID 86326007
    .
  2. OL 20591860M
    .
  3. ^ M. Raneft, D.; Eaker, H.; W. Davis, R. (2001). "A guide to the pronunciation and meaning of cetacean taxonomic names" (PDF). Aquatic Mammals. 27 (2): 185. Archived (PDF) from the original on 2016-03-27.
  4. S2CID 25036870
    .
  5. ISBN 978-0-85112-235-9
  6. ^ Davies, Ella (2016-04-20). "The longest animal alive may be one you never thought of". BBC Earth. Retrieved 2018-02-14.
  7. ^ "Largest mammal". Guinness World Records.
  8. ^ Perrin, W.F. (2020). "World Cetacea Database". marinespecies.org. Retrieved 2020-12-12.
  9. ^ Notarbartolo di Sciara, G.; Briand, F. (2004). "Investigating the Roles of Cetaceans in Marine Ecosystems - An overview". CIESM Workshop Monographs. 25: 1–15.[1]
  10. ISBN 978-0-646-47224-9. Archived from the original
    (PDF) on 8 September 2015. Retrieved 5 September 2015.
  11. doi:10.1578/am.39.4.2013.356
    .
  12. ^ Lovgren, Stefan (December 14, 2006). "China's Rare River Dolphin Now Extinct, Experts Announce". National Geographic News. Washington, D.C.: National Geographic Society. Archived from the original on December 18, 2006. Retrieved 2015-10-18.
  13. S2CID 16270218
    .
  14. ^ Groves; Colin; Grubb, Peter (2011). "Ungulate taxonomy". JHU Press. [page needed]
  15. ISBN 978-1-4899-0159-0
    .
  16. ISBN 978-1-4398-4257-7
    .
  17. ^
    S2CID 18292677
    .
  18. S2CID 205729032
    .
  19. ^ "How ancient whales lost their legs, got sleek and conquered the oceans". EurekAlert. University of Florida. 2006-05-22. Retrieved 2016-03-20.
  20. PMID 25440939
    .
  21. ISBN 978-3-540-64996-0. [page needed
    ]
  22. ^ "Sperm Whales brain size". NOAA Fisheries – Office of Protected Resources. Retrieved 9 August 2015.
  23. ^ Fields, R. Douglas. "Are whales smarter than we are?". Scientific American. Retrieved 9 August 2015.
  24. PMID 37660322
    .
  25. ^ Moore, Jim. "Allometry". University of California San Diego. Retrieved 9 August 2015.
  26. S2CID 7745280
    .
  27. S2CID 14850316
    .
  28. S2CID 15460266
    .
  29. ^ "Why do whale and dolphin tails go up and down?". Whale & Dolphin Conservation USA. Retrieved 2021-12-23.
  30. ISBN 978-0-521-44418-7
    . Retrieved 5 September 2015.
  31. JSTOR 30155836
    .
  32. ISBN 978-1-108-07960-0
    .
  33. ISBN 978-0-12-804381-3. Archived
    from the original on 29 June 2023. Retrieved 19 October 2020.
  34. ^
    ISBN 9780429063626
    .
  35. JSTOR 27857097. Archived
    (PDF) from the original on 22 November 2021.
  36. ISBN 978-1-4899-0161-3
    .
  37. S2CID 25260840
    .
  38. ^ Mead, James. "Cetacea". Britannica School High. Encyclopædia Britannica, Inc. Retrieved 3 June 2019.
  39. ^ a b Morell, Virginia (July 2011). "Guiana Dolphins Can Use Electric Signals to Locate Prey". Science. American Association for the Advancement of Science (AAAS). Archived from the original on 2013-05-30.
  40. ISBN 978-0-12-551340-1
    .
  41. ^ Ketten, Darlene R. (1992). "The Marine Mammal Ear: Specializations for Aquatic Audition and Echolocation". In Webster, Douglas B.; Fay, Richard R.; Popper, Arthur N. (eds.). The Evolutionary Biology of Hearing. Springer. pp. 717–750. Pages 725–727 used here.
  42. ISBN 978-0-12-373553-9
    .
  43. doi:10.13140/RG.2.1.3764.9765.{{cite journal}}: CS1 maint: multiple names: authors list (link
    )
  44. doi:10.1080/09524622.1997.9753356. Archived from the original
    (PDF) on 2014-08-01. Retrieved 2013-12-21.
  45. PMID 4137586
    .
  46. doi:10.1093/jhered/89.5.451
    .
  47. ^ "Gray Whale Migration". journeynorth.org. Archived from the original on 2019-06-09. Retrieved 3 July 2021.
  48. S2CID 4406032
    .
  49. S2CID 10587736
    .
  50. ^ Scholander, Per Fredrik (1940). "Experimental investigations on the respiratory function in diving mammals and birds". Hvalraadets Skrifter. 22.
  51. PMID 15791584
    .
  52. ^ a b c d e f Janet Mann; Richard C. Connor; Peter L. Tyack; et al. (eds.). Cetacean Societies: Field Study of Dolphins and Whales. University of Chicago.
  53. S2CID 40334723
    .
  54. ^ Siebert, Charles (8 July 2009). "Watching Whales Watching Us". The New York Times Magazine. Retrieved 29 August 2015.
  55. S2CID 55168063
    .
  56. ISBN 978-0-86449-096-4. {{cite book}}: |journal= ignored (help
    )
  57. ^ "Elephant Self-Awareness Mirrors Humans". Live Science. 30 October 2006. Retrieved 29 August 2015.
  58. ^ a b c Derr, Mark (May 2001). "Mirror test". New York Times. Retrieved 3 August 2015.
  59. S2CID 44372881
    .
  60. S2CID 261141293
    .
  61. doi:10.1139/z99-015
    .
  62. ^
    ISBN 978-0-415-25462-5. Archived
    (PDF) from the original on 2006-08-17. Retrieved 23 August 2014.
  63. doi:10.1111/j.1439-0485.2007.00150.x
    .
  64. PMID 22919595
    .
  65. ^
    S2CID 4416444. Archived
    (PDF) from the original on 2013-12-24.
  66. PMID 19194487
    .
  67. PMID 27396988
    .
  68. S2CID 27675176
    .
  69. ^ "First intact fossil of prehistoric whale discovered in Wadi Al-Hitan". International Union for Conservation of Nature. 9 June 2015.
  70. PMID 9159931
    .
  71. PMID 15677331
    .
  72. ^ "Scientists find missing link between the dolphin, whale and its closest relative, the hippo". Science News Daily. 2005-01-25. Retrieved 2011-01-08.
  73. ^ Beck, N.R. (2006). "A higher-level MRP supertree of placental mammals". BMC Evol Biol. 6: 93.
    PMID 17101039
    .
  74. ^ O'Leary, M.A.; Bloch, J.I.; Flynn, J.J.; Gaudin, T.J.; Giallombardo, A.; Giannini, N.P.; et al. (2013). "The placental mammal ancestor and the post-K-Pg radiation of placentals".
    S2CID 206544776
    .
  75. ^ Song, S.; Liu, L.; Edwards, S.V.; Wu, S. (2012). "Resolving conflict in eutherian mammal phylogeny using phylogenomics and the multispecies coalescent model". Proceedings of the National Academy of Sciences. 109 (37): 14942–14947.
    PMID 22930817
    .
  76. ^ dos Reis, M.; Inoue, J.; Hasegawa, M.; Asher, R.J.; Donoghue, P.C.J.; Yang, Z. (2012). "Phylogenomic datasets provide both precision and accuracy in estimating the timescale of placental mammal phylogeny".
    PMID 22628470
    .
  77. ^ Upham, N.S.; Esselstyn, J.A.; Jetz, W. (2019). "Inferring the mammal tree: Species-level sets of phylogenies for questions in ecology, evolution, and conservation".
    PMID 31800571
    .     (see e.g. Fig S10)
  78. ^ Gatesy, John; Geisler, Jonathan H.; Chang, Joseph; Buell, Carl; Berta, Annalisa; Meredith, Robert W.; Springer, Mark S.; McGowen, Michael R. (2012). "A phylogenetic blueprint for a modern whale" (PDF).
    PMID 23103570. Archived
    (PDF) from the original on 2013-02-27. Retrieved 4 September 2015.
  79. ^ "Small cetaceans". iwc.int. International Whaling Commission. Retrieved 2018-04-08.
  80. ^ "Lives of Whales". iwc.int. International Whaling Commission. Retrieved 2018-04-08.
  81. ^
    ISBN 978-0-646-47224-9. Archived from the original
    (PDF) on 8 September 2015. Retrieved 5 September 2015.
  82. ^ "Hagar & seyðamark". heimabeiti.fo. Archived from the original on 2014-09-24. Retrieved 2018-04-07.
  83. ^ "Total Catches". iwc.int. Retrieved 2018-04-07.
  84. S2CID 52827761
    .
  85. PMID 17148151
    .
  86. doi:10.1578/am.39.4.2013.356
    .
  87. S2CID 31676969
    .
  88. ^ Aristotle. "Chapter 2". The History of Animals, Book VIII. Translated by Thompson, D'Arcy Wentworth. Archived from the original on April 16, 2022. Retrieved April 16, 2022.
  89. ^ Conrad Gesner. Historiae animalium. Archived from the original on 6 September 2008. Retrieved 4 September 2015.
  90. S2CID 186210473
    .
  91. ^ 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: 6.
  92. ^ "PCAS Quarterly - Rock Art on the Channel Islands of California" (PDF).
  93. ^ "BBC News - Rock Art Hints at Whaling Origins". 20 April 2004.
  94. ^ Psalms 104:26
  95. ^ Psalms 74:14
  96. ^ Isaiah 27:1.
  97. ^ Job 40:25
  98. ^ Job 41:26
  99. ^ Cunliffe, B.; Gosden, C.; Joyce, R. "The circumpolar zone". The Oxford Handbook of Archaeology.
  100. doi:10.1006/jasc.1996.0167
    .
  101. ^ unknown. "Movie Retriever: Whales". movieretriever.com. Archived from the original on 2015-10-15.
  102. ^ "The Whales, New York Tribune, August 9, 1861". New York Tribune. 9 August 1861. Retrieved 5 December 2011.
  103. ^ a b c d e "Beluga Whales in Captivity: Hunted, Poisoned, Unprotected" (PDF). Special Report on Captivity 2006. Canadian Marine Environment Protection Society. 2006. Archived from the original (PDF) on 26 December 2014. Retrieved 26 December 2014.
  104. ^ "Beluga (Delphinapterus leucas) Facts – Distribution – In the Zoo". World Association of Zoos and Aquariums. Archived from the original on 10 February 2012. Retrieved 5 December 2011.
  105. ISBN 978-0-7137-0887-5
    .
  106. ^ NMFS (2005). "Conservation Plan for Southern Resident Killer Whales (Orcinus orca)" (PDF). Seattle, U.S.: National Marine Fisheries Service (NMFS) Northwest Regional Office. pp. 43–44. Archived from the original (PDF) on June 26, 2008. Retrieved January 2, 2009.
  107. ^ 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. Archived (PDF) from the original on 2011-10-26. Retrieved December 21, 2014.
  108. ^ "Whale Attack Renews Captive Animal Debate". CBS News. March 1, 2010. Retrieved 6 September 2015.
  109. ISBN 978-0-415-27589-7
    .
  110. ^ "Orcas in Captivity – A look at killer whales in aquariums and parks". 23 November 2009. Archived from the original on 2 June 2007. Retrieved 6 September 2015.
  111. ^ "Chapter I: Space requirements". Electronic Code of Federal Regulation. 1. Retrieved 6 September 2015.
  112. ^ Whiting, Candace Calloway. In the Wake of Blackfish – Is it Time to Retire the Last Killer Whale Whose Capture Was Shown in the Film?", HuffPost, October 29, 2013. Retrieved October 29, 2013.
  113. ^ Buss, Dale (2016-03-24). "Shamu Goes Out With the Tide: SeaWorld CEO On Its Abrupt Change – And What Comes Next". Forbes. Retrieved 2016-03-26.
  114. ^ Klinowska, Margaret; Cooke, Justin (1991). Dolphins, Porpoises, and Whales of the World: the IUCN Red Data Book (PDF). Archived (PDF) from the original on 2015-05-09. Retrieved 6 September 2015.
  115. ^ J. L. Sumich; T. Goff; W. L. Perryman (2001). "Growth of two gray whale calves" (PDF). Aquatic Mammals: 231–233. Archived (PDF) from the original on 2015-10-15. Retrieved 6 September 2015.

External links

Look up Cetacea in Wiktionary, the free dictionary.
Wikispecies has information related to Cetacea.
Wikimedia Commons has media related to Cetacea.
Retrieved from "https://en.wikipedia.org/w/index.php?title=Cetacea&oldid=1218299855"