Early – Present Kingdom: Phylum: Class: Order: Suborder: Infraorder: Cetacea, 1762 Parvorders † ( for families) Cetacea ( ) are a widely and diverse of that today consists of the,, and. Cetaceans are and finned. Most species live in the sea, some in rivers. The name is derived from the ' and 'huge fish'. There are around 89 species, which are divided into two groups or, the or toothed whales, a group of more than 70 species that includes the dolphins and porpoises, and the or whales, of which there are now 15 species.

The extinct ancestors of modern whales are the. While cetaceans were historically thought to have descended from, evidence supports them as a relative of Artiodactyls ().

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Cetaceans belong to the order Cetartiodactyla (formed by combining Cetacea + Artiodactyla) and their closest living relatives are and other hoofed mammals (,, and ), having diverged about 50 million years ago. Cetaceans range in size from the 1 m (3 ft 3 in) and 50 kg (110 lb) to the 29.9 m (98 ft) and 173,000 kg (381,000 lb), which is also the largest animal ever known to have existed. Several species exhibit. They have streamlined bodies and two (external) limbs that are modified into. Though not as flexible or agile as, cetaceans can swim very quickly, with the able to travel at 56 kilometres per hour (35 mph) in short bursts and the able to cruise at 48 kilometres per hour (30 mph). Dolphins are able to make very tight turns while swimming at high speeds. The hindlimbs of cetaceans are internal, and are thought to be.

Baleen whales have on their mouth, unlike the toothed whales. Cetaceans have well-developed senses—their eyesight and hearing are adapted for both air and water, and baleen whales have a in their vibrissae.

They have a layer of fat, or, under the skin to maintain body heat in cold water. Some species are well adapted for diving to great depths. Although cetaceans are widespread, most species prefer the colder waters of the Northern and Southern Hemispheres. They spend their lives in the water, having to mate, give birth, or escape from predators, like, underwater.

This has drastically affected their anatomy to be able to do so. They feed largely on fish and; but a few, like the killer whale, feed on large mammals and birds, such as and seals. Some baleen whales (mainly and right whales) are specialised for feeding on creatures. Male cetaceans typically mate with more than one female (), although the degree of polygyny varies with the species. Cetaceans are not shown to have.

Male cetacean strategies for vary between herding females, defending potential mates from other males, or which attracts mates. Calves are typically born in the fall and winter months, and females bear almost all the responsibility for raising them. Mothers of some species and nurse their young for a relatively short period of time, which is more typical of baleen whales as their main food source (invertebrates) aren't found in their breeding and calving grounds (). Cetaceans produce a number of, notably the clicks and whistles of dolphins and the moaning songs of the.

The meat, blubber and oil of cetaceans have traditionally been used. Cetaceans have been depicted in various cultures worldwide. Dolphins are commonly kept in captivity and are even sometimes trained to perform tricks and tasks, other cetaceans aren't as often kept in captivity (with usually unsuccessful attempts). Cetaceans have been relentlessly by commercial industries for their products, although this is now forbidden by international law. The (Chinese river dolphin) has become 'Possibly Extinct' in the past century, while the and are ranked by the.

Besides hunting, cetaceans also face threats from,, and ongoing climate change. This section does not any. Unsourced material may be challenged and. (March 2016) () The two parvorders, (Mysticeti) and (Odontoceti), are thought to have diverged around thirty-four million years ago. Baleen whales have bristles made of instead of.

The bristles filter and other small from seawater. Feed on bottom-dwelling mollusks. (balaenopterids) use throat pleats to expand their mouths to take in food and sieve out the water. ( and ) 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, killer whales, dolphins and porpoises.

They have conical teeth designed for catching fish. A few, such as the, feed on mammals, such as and other whales. They have well-developed senses – their eyesight and hearing are adapted for both air and water, and they have advanced using their. 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 odontocetes show, in which the males differ from the females, usually for purposes of sexual display or aggression. Toothed whales feed largely on fish and.

Dolphin anatomy Cetacean bodies are generally similar to that 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 (). They have a streamlined shape, and their forelimbs are flippers. Almost all have a on their backs that can take on many forms depending on the species. A few species, such as the, lack them.

Both the flipper and the fin are for stabilization and steering in the water. The male genitals and mammary glands of females are sunken into the body. The body is wrapped in a thick layer of fat, known as, 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). Evolved in many toothed whales. Sperm whales,, many members of the family, several species of the family, killer whales,, eastern and show this characteristic.

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. Humpback whale fluke They have a fluke at the end of their tails that is used for propulsion. The fluke is set horizontally on the body, unlike fish, which have vertical tails. Hind legs are not present in cetaceans, nor are any other external body attachments such as a and.

Head [ ] Whales have an elongated head, especially, due to the wide overhanging jaw. Bowhead whale plates can be 4 metres (13 ft) long.

Their nostril(s) make up the, with one in toothed whales and two in baleen whales. 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. The teeth or baleen in the upper jaw sit exclusively on the.

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 as a head buckle. This is filled with air sacs and fat that aid in buoyancy and.

The sperm whale has a particularly pronounced melon; this is called the and contains the eponymous, 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., unlike most other cetaceans, can turn their head 90°. Other cetaceans have fused neck vertebrae and are unable to turn their head at all. The 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 and krill.

Brain [ ] The of many cetaceans is home to elongated that, prior to 2007, were known only in. In humans, these cells are thought to be involved in social conduct, emotions, judgment and theory of mind. Cetacean are found in areas of the brain homologous to where they are found in humans, suggesting they perform a similar function. Was previously considered a major indicator of. 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 cognitive tasks. Analysis indicates that mammalian brain size scales at approximately two-thirds or three-quarter exponent of the body mass. Comparison of a particular animal's brain size with the expected brain size based on such an analysis provides an that can be used as an indication of animal intelligence.

Sperm whales have the largest brain mass of any animal on earth, averaging 8,000 cm 3 (490 in 3) and 7.8 kg (17 lb) in mature males. The 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%. The ( Physeter macrocephalus) is the largest of all toothed predatory animals and possesses the largest brain.

Skeleton [ ]. Sperm whale skeleton The cetacean skeleton is largely made up of, which stabilizes the animal in the water.

For this reason, the usual terrestrial compact bones, which are finely woven, are replaced with lighter and more elastic material. In many places, bone elements are replaced by cartilage and even fat, thereby improving their qualities. The ear and the muzzle contain a bone shape that is exclusive to cetaceans with a high density, resembling. This conducts sound better than other bones, thus aiding. The number of that make up the spine varies by species, ranging from forty to ninety-three. The, found in all mammals, consists of seven vertebrae which, however, are reduced or fused.

This gives stability during swimming at the expense of mobility. The fins are carried by the, ranging from nine to seventeen individual vertebrae.

The is cartilaginous. The last two to three pairs of ribs are not connected and hang freely in the body wall.

The stable lumbar and tail include the other vertebrae. Below the is the. 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. [ ] The is completely absent.

Physiology [ ] Unique characteristics [ ] There are characteristics unique to cetaceans. The first one is the posterior process that is enlarged from the posterior crus, forming the primary bullar articulation to the basicranium. The second defining characteristic is that the sigmoid process is enlarged. The third characteristic is a conical apophysis that is modified from the ectotympanic ring.

Then there is the conical tympani ligament, derived from the tympanic membrane. Lastly, the involucrum formed from the pachyosteosclerosis of the bulla. These unique traits evolved overtime, from the terrestrial Pakicetidae to the crown whales today.

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 and is of particular importance for the life of. 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,, 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.

Organs [ ] The stomach consists of three chambers. The first region is formed by a loose gland and a muscular forestomach (missing in beaked whales), which is then followed by the main stomach and the. Both are equipped with glands to help digestion. A bowel adjoins the stomachs, whose individual sections can only be distinguished. The is large and separate from the.

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. Senses [ ] Cetacean are set on the sides rather than the front of the head. This means only species with pointed 'beaks' (such as dolphins) have good forward and downward. 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 (except dolphins) with excellent hearing.

At least one species, the or Guiana dolphin, is able to use to sense prey. Teeth/baleen [ ] While among terrestrial archaeocetes the teeth are divided into incisors, canines and molars, the teeth of modern cetaceans are brought into line with each other, which can be seen among the fish-eating odontocetes (transition from heterodont to homodont). The external ear has lost the (visible ear), but still retains a narrow.

To register sounds, instead, the posterior part of the has a thin lateral wall (the pan bone) fronting a concavity that houses a fat pad. The pad passes anteriorly into the greatly enlarged to reach in under the teeth and posteriorly to reach the thin lateral wall of the. The ectotympanic offers a reduced attachment area for the.

The connection between this auditory complex and the rest of the skull is reduced—to a single, small cartilage in. In odontocetes, the complex is surrounded by spongy tissue filled with air spaces, while in mysticetes, it is integrated into the skull as with 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 (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 and the are larger than in odontocetes. In some, the malleus is fused with the ectotympanic. The ear are (dense and compact) and differently shaped from land mammals (other aquatic mammals, such as and earless seals, have also lost their pinnae). T semicircular canals are much smaller relative to body size than in other mammals.

The is separated from the skull and composed of two compact and dense bones (the periotic and tympanic) referred to as the tympanoperiotic complex. This complex is located in a cavity in the middle ear, which, in the Mysticeti, is divided by a bony projection and compressed between the exoccipital and squamosal, but in the odontoceti, is large and completely surrounds the bulla (hence called 'peribullar'), which is, therefore, not connected to the skull except in. In the 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 that form the cavity tend to be more developed in shallow water and riverine species than in 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. Cetaceans use sound to, using groans, moans, whistles, clicks or the 'singing' of the humpback whale. Echolocation [ ] are generally capable of. 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. Mysticeti have exceptionally thin, wide basilar membranes in their without stiffening agents, making their ears adapted for processing low to 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. Chromosomes [ ] The initial includes a set of from 2n = 44. They have four pairs of telocentric chromosomes (whose sit at one of the ), 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. Sperm whales, beaked whales and right whales converge to a reduction in the number of chromosomes to 2n = 42. Ecology [ ] Range and habitat [ ] Cetaceans are found in all oceans. Species live exclusively in fresh water.

While many marine species, such as the, the and the, have a distribution area that includes nearly the entire ocean, some species occur only locally or in broken populations. These include the vacquita, which inhabits a small part of the and, which lives in some coastal waters in New Zealand.

Both species prefer deeper marine areas and species that live frequently or exclusively in coastal and shallow water areas. [ ] Many species inhabit specific latitudes, often in tropical or subtropical waters, such as.

Others are found only in a specific body of water. The and the live only in the. The and the live only in the Arctic Ocean. And the exist only in the Atlantic and the and the 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, and. 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. 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 (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. Diving [ ] 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 can dive for up to 40 minutes, between 60 and 90 minutes and 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).

Social relations [ ] Most whales 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. 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. Whale song [ ] Males in some baleen species communicate via, 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 that sings at a higher frequency than other whales. Some individuals are capable of generating over 600 distinct sounds.

In baleen species such as humpbacks, blues and fins, male-specific song is believed to be used to attract and display fitness to females. Hunting [ ] Pod groups also hunt, often with other species.

Many species of dolphins hunt accompany large tunas on hunting expeditions, following large schools of fish. The killer whale hunts in pods and targets belugas and even larger whales. Humpback whales, among others, form in collaboration to herd krill or plankton into bait balls before lunging at them.

Intelligence [ ]. Bubble net feeding Cetacea are known to teach, learn, cooperate, scheme and grieve. Smaller cetaceans, such as dolphins and porpoises, engage in complex play behavior, including such things as producing stable underwater air-core rings or '. 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 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.

Killer whale 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 and. Humpback whales also display this behaviour. 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 (thinking about thinking) that humans exploit.

Cetaceans appear to possess self-awareness. The most widely used test for self-awareness in animals is the, 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. Critics claim that the results of these tests are susceptible to the effect. This test is much less definitive than when used for. Primates can touch the mark or the mirror, while cetaceans 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. Cetaceans show less definitive behavior of self-awareness, because they have no pointing ability. In 1995, Marten and Psarakos used video 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 replicated, dolphins later 'passed' the mirror test. Life history [ ] Reproduction and brooding [ ] Most cetaceans sexually mature at seven to 10 years. An exception to this is the, which is sexually mature at two years, but lives only to about 20. The sperm whale reaches sexual maturity within about 20 years and a lifespan between 50 and 100 years. For most species, reproduction is seasonal. Coincides with male.

This cycle is usually coupled with seasonal movements that can be observed in many species. Most toothed whales have no fixed bonds. In many species, females choose several partners during a season. Baleen whales are largely 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. During gestation, the embryo is fed by a special nutritive tissue, the.

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.

Suckling [ ] Like other placental mammals, cetaceans give birth to well-developed calves and nurse them with milk from their. 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. 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 ( Balaena mysticetus), can reach over 200 years. Based on the annual rings of the bony, the age of the oldest known specimen is a male determined to be 211 years at the time of death.

Main article: 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 biodiversity hotspots, such as and. Deterioration of whale carcasses happens through three stages. Initially, organisms such as and scavenge the soft tissues at a rapid rate over a period of months and as long as two years. This is followed by the colonization of bones and surrounding sediments (which contain organic matter) by enrichment opportunists, such as and, throughout a period of years. Finally, sulfophilic bacteria reduce the bones releasing enabling the growth of 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. Disease [ ] affects almost all mammals. It is distributed worldwide, while fishing and pollution have caused porpoise population density pockets, which risks further infection and disease spreading., most prevalent in dolphins, has been shown to cause, increasing the chance of failed birth and,, neurobrucellosis,, bone and skin, 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. Evolution [ ]. Comparison of the skeleton of and in swimming position and show that cetaceans are phylogenetically closely related with the (Artiodactyla).

Whales direct lineage began in the early, more than 50 million years ago, with early artiodactyls. Fossil discoveries at the beginning of the 21st century confirmed this. Most molecular biological evidence suggests that are the closest living relatives.

Common anatomical features include similarities in the of the posterior, and the bony ring on the temporal bone (bulla) and the involucre, a skull feature that was previously associated only with cetaceans. The fossil record, however, does not support this relationship, because the hippo lineage dates back only about 15 million years. The most striking common feature is the, a bone in the upper ankle. Early cetaceans,, show double castors, which only occur in even-toed ungulates.

Corresponding findings are from deposits in northern India and Pakistan. The Tethys Sea was a shallow sea between the Asian continent and northward-bound Indian plate. Cetaceans display with fish and Mysticetes evolved baleen around 25 million years ago and lost their teeth. Development [ ] Ancestors [ ] The direct ancestors of today's cetaceans are probably found within the whose most famous member, Dorudon atrox, lived at the same time as Basilosaurus. Both groups had already developed the typical anatomical features of today's whales, such as hearing.

Life in the water for a formerly terrestrial creature required significant adjustments such as the fixed bulla, which replaces the mammalian, 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. Transition from land to sea [ ].

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

One of the oldest members of ancient cetaceans () is from the Middle Eocene. 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 dentition. The transition from land to sea dates to about 49 million years ago, with the ('running whale'), discovered in. It was up to 3 m (9.8 ft) long. The limbs of this archaeocete were adapted to swimming, but terrestrial locomotion was still possible. It probably crawled like a seal or crocodile.

The snout was elongated with overhead nostrils and eyes. The tail was strong and supported movement through water. Ambulocetus probably lived in mangroves in and fed in the as a predator of fish and other vertebrates. Dating from about 45 million years ago are species such as,, and, all of which were adapted to life in water. The hind limbs of these species were regressed and their body shapes resemble modern whales.

Family member Rodhocetus is considered the first to be fully aquatic. Apa The Easy Way 2nd Edition Pdf. The body was streamlined and delicate with extended hand and foot bones. The merged pelvic 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. 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-m-long, sometimes referred to as Zeuglodon. The transition from land to water was completed in about 10 million years. The ('Whale Valley') in Egypt contains numerous skeletons of Basilosaurus, as well as other marine vertebrates. Taxonomy [ ]. Main article: (Mysticeti) owe their name to their baleen. (Odontoceti), which include the and, have conical teeth or spade-shaped teeth and can perceive their environment through biosonar.

The infraorder comprises the families (right and bowhead whales), (rorquals), (the ), (oceanic dolphins), (Arctic whales), (porpoises), (), (lesser sperm whales), (Old World ), (New World river dolphins), (the La plata dolphin) and (beaked whales). An caught in a in on the 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. In the, reasons for whaling included their, usable as fuel and the jawbone, which was used in house construction. At the end of the Middle Ages, early whaling fleets aimed at, such as.

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, which was used as a replacement for wood, or in products requiring strength and flexibility such as and skirts. In addition, the found in the was used as a machine lubricant and the as a material for pharmaceutical and perfume industries. In the second half of the 19th century, the explosive 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 populations were completely eradicated and the population fell to some 300-600. The population is estimated to be around 14,000. The first efforts to protect whales came in 1931. Some particularly endangered species, such as the (which then numbered about 100 animals), were placed under international protection and the first protected areas were established. In 1946, the (IWC) was established, to monitor and secure whale stocks. Whaling for commercial purposes was prohibited worldwide by this organization from 1985 to 2005.

The stocks of species such as humpback and blue whales have recovered, though they are still threatened. The United States Congress passed the sustain the marine mammal population. It prohibits the taking of marine mammals. Japanese whaling ships are allowed to hunt whales of different species for ostensibly scientific purposes. Is still permitted, but under limited circumstances as defined by IWC. 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 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, the, and (the most well-known practitioner). Dolphins are mostly hunted for their, though some end up in. Despite the controversy thousands of dolphins are caught in drive hunts each year. 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.

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. Strandings [ ].

Main article: 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 and sperm whales.

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. The causes are not clear.

Possible reasons for mass beachings are: • 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 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.

Influences the major wind systems and ocean currents, which also lead to cetacean strandings. Researchers studying strandings on the Tasmanian coast from 1920–2002 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. Once stranded, large whales are crushed by their own body weight, if they cannot quickly return to the water. In addition, body temperature regulation is compromised.

[ ] Environmental hazards [ ]. 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 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.

Damage to the 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 is, in addition to intensive exploitation, damaged by the radiation. Food supplies are also reduced long-term by due to increased absorption of increased atmospheric carbon dioxide. The CO 2 reacts with water to form, which reduces the construction of the skeletons of food supplies for zooplankton that baleen whales depend on. The military and resource extraction industries operate strong and blasting operations. Marine seismic surveys use loud, low-frequency sound that show what is lying underneath the Earth's surface. Vessel traffic also increases noise in the oceans. Such noise can disrupt cetacean behavior such as their use of for orientation and communication.

Severe instances can panic them, driving them to the surface. This leads to bubbles in blood gases and can cause. 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 [ ]. A whale as depicted by Conrad Gesner, 1587, in Historiae animalium In 's time, the 4th 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.

His detailed descriptions were assimilated by the Romans, but mixed with a more accurate knowledge of the dolphins, as mentioned by in his. In the art of this and subsequent periods, dolphins are portrayed with a high-arched head (typical of porpoises) and a long snout. The was one of the most accessible species for early; 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. 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. 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 (1758), Swedish biologist and taxonomist asserted that cetaceans were mammals and not fish.

His groundbreaking binomial system formed the basis of modern whale classification. Culture [ ] Cetaceans play a role in human culture. Prehistoric [ ], such as those in Roddoy and Reppa (Norway), depict them. [ ] Whale bones were used for many purposes.

In the settlement of Skara Brae on sauce pans were made from whale vertebrae. Antiquity [ ]. Constellation Cetus Dolphins belong to the domain of and led him to his wife. Dolphins are associated with other gods, such as, Dionysus and. The Greeks paid tribute to both whales and dolphins with their own constellation. The constellation of the (Ketos, lat. Cetus) is located south of the Dolphin (Delphi, lat.

Delphinus) north of the. Ancient art often included dolphin representations, including the Cretan. Later they appeared on reliefs, gems, lamps, coins, mosaics and gravestones. A particularly popular representation is that of Arion or the riding on a dolphin. In early, the dolphin is a popular motif, at times used as a symbol of. Middle Ages to the 19th century [ ].

See also: and 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. 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.

Stranded sperm whale engraving, 1598 Whalers in the 17–19th 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 from Great Britain, who published the book Northern Whale Fishery, describing the hunt for northern baleen whales. This was followed by, a British surgeon, in his 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.

Whales were described in narrative literature and paintings, most famously in the novels by and. In the 1882 children's book by, the wooden figures and Geppettos' creators were swallowed by a whale. Baleen was used to make vessel components such as the bottom of a bucket in the Scottish National Museum. The crafted ornamented plates from baleen, sometimes interpreted as boards. In the Canadian Arctic (east coast) in Punuk and culture (1000–1600 C.E.), I 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. Modern culture [ ].

Sea World show featuring and In the 20th century perceptions of cetaceans changed. They transformed from monsters into objects 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 was a bottle-nose dolphin. The TV series (1993–1996), the movies, and the book series by are examples. The study of also produced a popular album,.

Captivity [ ] Whales and dolphins have been kept in captivity for use in education, research and entertainment since the 19th century. Main article: were the first whales to be kept in captivity. Other species were too rare, too shy or too big. The first was shown at in in 1861. For most of the 20th century, Canada was the predominant source.

They were taken from the estuary until the late 1960s, after which they were predominantly taken from the estuary until capture was banned in 1992. Russia then became the largest provider. Belugas are caught in the delta and their eastern coast and are transported domestically to aquaria or in, and, or exported to countries such as Canada. They have not been domesticated. As of 2006, 30 belugas lived in Canada and 28 in the United States. 42 deaths in captivity had been reported. A single specimen can reportedly fetch up to US$100,000 (UK£64,160).

The beluga's popularity is due to its unique color and its. 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. Killer whales [ ].

Shamu the killer whale, 2009 The killer whale's, 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. Organizations such as and the campaign against the practice of keeping them in captivity.

Jensen Universal Remote Jr 400 Manual there. In captivity, they often develop pathologies, such as the 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. 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. Killer whales 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 being held in aquaria as of 2012.

Each country has its own tank requirements; in the US, the minimum enclosure size is set by the, 9 CFR E § 3.104, under the Specifications for the Humane Handling, Care, Treatment and Transportation of Marine Mammals. Dawn Brancheau doing a show four years before Aggression among captive killer whales is common. They attack each other and their trainers as well. In 2013, SeaWorld's treatment of killer whales in captivity was the basis of the movie, which documents the history of, a killer whale at SeaWorld Orlando, who had been involved in the deaths of three people. The film was a sensation, leading the company to announce in 2016 that it would phase out its killer whale program after various unsuccessful attempts to restore its reputation and stock price.

With trainers Dolphins and porpoises are kept in captivity. Are the most common, as they are relatively easy to train, have a long lifespan in captivity and have a friendly appearance. Bottlenose dolphins live in captivity across the world, though exact numbers are hard to determine.

Other species kept in captivity are, and,, as well as, but all in much lower numbers. There are also fewer than ten,,,, or in captivity. Two unusual and rare dolphins, known as, are kept at in, which is a cross between a bottlenose dolphin and a. Also, two /bottlenose hybrids reside in captivity at and. In repeated attempts in the 1960s and 1970s, kept in captivity died within months.

A breeding pair of were retained in a netted area. They were eventually released in South Africa. In 1971, SeaWorld captured a California gray whale calf in Mexico. The calf, later named Gigi, was separated from her mother using a form of lasso attached to her flukes. Gigi was displayed at for a year.

She was then released with a radio beacon affixed to her back; however, contact was lost after three weeks. Gigi was the first captive baleen whale. JJ, another calf, was kept.

JJ was an orphaned calf that beached itself in April 1997 and was transported two miles to SeaWorld. The 680 kilograms (1,500 lb) calf was a popular attraction and behaved normally, despite separation from his mother. A year later, the then 8,164.7 kilograms (18,000 lb) whale though smaller than average, was too big to keep in captivity, and was released on April 1, 1998. A captive housed at is the only trained in captivity.