Portal:Cetaceans

The Cetaceans Portal

A Sperm Whale fluke

Cetacea (/sɪˈteɪʃə/; from Latin cetus 'whale', from Ancient Greek κῆτος (kêtos) 'huge fish, sea monster') is an infraorder of aquatic mammals belonging to the order Artiodactyla that includes whales, dolphins and porpoises. Key characteristics are their fully aquatic lifestyle, streamlined body shape, often large size and exclusively 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.

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 ever known to have existed.

There are approximately 89 living species split into two parvorders: Odontoceti or toothed whales (containing porpoises, dolphins, other predatory whales like the beluga and the sperm whale, and the poorly understood beaked whales) and the filter feeding Mysticeti or baleen whales (which includes species like the blue whale, the humpback whale and the bowhead whale). Despite their highly modified bodies and carnivorous lifestyle, genetic and fossil evidence places cetaceans as nested within even-toed ungulates, most closely related to hippopotamus within the clade Whippomorpha. (Full article...)

Recognized content -

Entries here consist of Good and Featured articles, which meet a core set of high editorial standards.

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  The harbor porpoise (Phocoena phocoena)

  
  Porpoises (/ˈpɔːrpəsɪz/) are small dolphin-like cetaceans classified under the family Phocoenidae. Although similar in appearance to dolphins, they are more closely related to narwhals and belugas than to the true dolphins. There are eight extant species of porpoise, all among the smallest of the toothed whales. Porpoises are distinguished from dolphins by their flattened, spade-shaped teeth distinct from the conical teeth of dolphins, and lack of a pronounced beak, although some dolphins (e.g. Hector's dolphin) also lack a pronounced beak. Porpoises, and other cetaceans, belong to the clade Cetartiodactyla with even-toed ungulates.
  
  Porpoises range in size from the vaquita, at 1.4 metres (4 feet 7 inches) in length and 54 kilograms (119 pounds) in weight, to the Dall's porpoise, at 2.3 m (7 ft 7 in) and 220 kg (490 lb). Several species exhibit sexual dimorphism in that the females are larger than males. They have streamlined bodies and two limbs that are modified into flippers. Porpoises use echolocation as their primary sensory system. Some species are well adapted for diving to great depths. As all cetaceans, they have a layer of fat, or blubber, under the skin to keep them warm in cold water. (Full article...)
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  Cast of a skull at the Museo storia naturale di Pisa in Italy

  
  Zygophyseter varolai is an extinct sperm whale that lived during the Tortonian age of the Late Miocene 11.2 to 7.6 million years ago. It is known from a single specimen from the Pietra Leccese Formation in Italy. It was a member of a stem group of fossil macroraptorial sperm whales (often shortened to "raptorial") also including Brygmophyseter, Acrophyseter, and Livyatan. It probably grew to be around 6.5 to 7 meters (21 to 23 ft) in length and shared some characteristics with other raptorials, such as large teeth with tooth enamel that were functional in both the upper and lower jaws which the modern sperm whale (Physeter macrocephalus) lacks. It also had a beak, the ability to echolocate prey, and could have probably swum faster than the modern-day sperm whale which can reach 4 kilometers per hour (2.5 mph). These were probably used in the capture of large prey, such as large fish, seals, and whales. In fact, its common name, the killer sperm whale, refers to its feeding habits that would have had a resemblance to the modern-day killer whale (Orcinus orca). (Full article...)
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  Whaling in the Faroe Islands, or grindadráp (from the Faroese terms grindhvalur, meaning pilot whale, and dráp, meaning killing), is a type of drive hunting that involves herding various species of whales and dolphins, but primarily pilot whales, into shallow bays to be beached, killed, and butchered. Each year, an average of around 700 long-finned pilot whales and several hundred Atlantic white-sided dolphins are caught over the course of the hunt season during the summer.
  
  The practice dates back to the 9th century, and many Faroe Islanders consider eating whales to be an important part of their history. Since 1948, the hunt has been regulated by the Faroese authorities, required its participants to be trained, involved modern boats and communications, and been supervised by police. (Full article...)
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  Atlantic white-sided dolphin caught in a drive hunt in Hvalba on the Faroe Islands being taken away with a forklift

  
  Dolphin drive hunting, also called dolphin drive fishing, is a method of hunting dolphins and occasionally other small cetaceans by driving them together with boats, usually into a bay or onto a beach. Their escape is prevented by closing off the route to the open sea or ocean with boats and nets. Dolphins are hunted this way in several places around the world including the Solomon Islands, the Faroe Islands, Peru, and Japan, which is the most well-known practitioner of the method. In large numbers dolphins are mostly hunted for their meat; some end up in dolphinariums.
  
  Despite the controversial nature of the hunt resulting in international criticism, and the possible health risk that the often polluted meat causes, tens of thousands of dolphins are caught in drive hunts each year. (Full article...)
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  River dolphins are a polyphyletic group of fully aquatic mammals that reside exclusively in freshwater or brackish water. They are an informal grouping of dolphins, which itself is a paraphyletic group within the infraorder Cetacea. Extant river dolphins are placed in two superfamilies, Platanistoidea and Inioidea. They comprise the families Platanistidae (the South Asian dolphins), the recently extinct Lipotidae (Yangtze river dolphin), Iniidae (the Amazonian dolphins) and Pontoporiidae. There are five extant species of river dolphins. River dolphins, alongside other cetaceans, belong to the clade Artiodactyla, with even-toed ungulates, and their closest living relatives the hippopotamuses, from which they diverged about 40 million years ago. Specific types of dolphins can be pink.
  
  River dolphins are relatively small compared to other dolphins, having evolved to survive in warm, shallow water and strong river currents. They range in size from the 5-foot (1.5 m) long South Asian river dolphin to the 8-foot (2.4 m) and 220-pound (100 kg) Amazon river dolphin. Several species exhibit sexual dimorphism, in that the females are larger than the males. They have streamlined bodies and two limbs that are modified into flippers. River dolphins use their conical-shaped teeth and long beaks to capture fast-moving prey in murky water. They have well-developed hearing that is adapted for both air and water; they do not really rely on vision since the water they swim in is usually very muddy. Instead, they tend to rely on echolocation when hunting and navigating. These species are well-adapted to living in warm, shallow waters, and, unlike other cetaceans, have little to no blubber. (Full article...)
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  Granny (born c. 1936-1951 approx, died c. 2016), also known as J2, was a female orca of the J pod of southern resident orcas notable for her long life. Early estimates placed her birth in 1911, putting her at 105 years old at the time of her death. However, this estimate was later theorized to have been based on mistaken information and more recent studies put her at 65–80 years old. If she was 105, she would have been the oldest known orca at the time of her death. Granny lived in the northeast Pacific Ocean and coastal bays of Washington state and British Columbia. She was last seen on October 12, 2016, and was considered deceased by The Center for Whale Research in January 2017. (Full article...)
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  Southern right whale

  
  Whales are a widely distributed and diverse group of fully aquatic placental marine mammals. As an informal and colloquial grouping, they correspond to large members of the infraorder Cetacea, i.e. all cetaceans apart from dolphins and porpoises. Dolphins and porpoises may be considered whales from a formal, cladistic perspective. Whales, dolphins and porpoises belong to the order Cetartiodactyla, which consists of even-toed ungulates. Their closest non-cetacean living relatives are the hippopotamuses, from which they and other cetaceans diverged about 54 million years ago. The two parvorders of whales, baleen whales (Mysticeti) and toothed whales (Odontoceti), are thought to have had their last common ancestor around 34 million years ago. Mysticetes include four extant (living) families: Balaenopteridae (the rorquals), Balaenidae (right whales), Cetotheriidae (the pygmy right whale), and Eschrichtiidae (the grey whale). Odontocetes include the Monodontidae (belugas and narwhals), Physeteridae (the sperm whale), Kogiidae (the dwarf and pygmy sperm whale), and Ziphiidae (the beaked whales), as well as the six families of dolphins and porpoises which are not considered whales in the informal sense.
  
  Whales are fully aquatic, open-ocean animals: they can feed, mate, give birth, suckle and raise their young at sea. Whales range in size from the 2.6 metres (8.5 ft) and 135 kilograms (298 lb) dwarf sperm whale to the 29.9 metres (98 ft) and 190 tonnes (210 short tons) blue whale, which is the largest known animal that has ever lived. The sperm whale is the largest toothed predator on Earth. Several whale species exhibit sexual dimorphism, in that the females are larger than males. (Full article...)
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  The anatomist John Struthers (at left, in top hat) with the Tay Whale at John Woods's yard, Dundee, 1884, photographed by George Washington Wilson

  
  The Tay Whale, known locally as the Monster, was a humpback whale that swam into the Firth of Tay of eastern Scotland in 1883. It was harpooned in a hunt, but escaped, and was found floating dead off Stonehaven a week later. It was towed into Dundee by a showman, John Woods, and exhibited on a train tour of Scotland and England.
  
  The Regius Professor of Anatomy at Aberdeen University, John Struthers dissected the whale, much of the time in public with a military band playing in the background, organised by Woods. The decomposing whale made Woods a great deal of money, and Struthers famous. (Full article...)
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  "Whale Whores" is the eleventh episode of the thirteenth season of the American animated television series South Park. The 192nd overall episode of the series, it aired on Comedy Central in the United States on October 28, 2009. In the episode, Stan joins an anti-whaling crew in order to save dolphins and whales from Japanese whalers.
  
  The episode was written and directed by series co-creator Trey Parker, and was rated TV-MA LV in the United States. "Whale Whores" addressed the topic of Japanese whaling, condemning both the whalers themselves and the activists who fight against them. The episode is particularly critical of the reality television series Whale Wars and its star Paul Watson, an environmental activist who is prominently featured in "Whale Whores". (Full article...)
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  Cryptolepas rhachianecti

  
  Whale barnacles are species of acorn barnacle that belong to the family Coronulidae. They typically attach to baleen whales, and sometimes settle on toothed whales. The whale barnacles diverged from the turtle barnacles about three million years ago.
  
  Whale barnacles passively filter food, using tentacle-like cirri, as the host swims through the water. The arrangement is generally considered commensal as it is done at no cost or benefit to the host. However, some whales may make use of the barnacles as protective armor or for inflicting more damage while fighting, which would make the relationship mutualistic where both parties benefit; alternatively, some species may just increase the drag that the host experiences while swimming, making the barnacles parasites. (Full article...)
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  The holotype and only specimen

  
  Orcinus meyeri is a fossil species of Orcinus (killer whales) found in the Early Miocene deposits of southern Germany, known from two jaw fragments and 18 isolated teeth. It was originally described as Delphinus acutidens in 1859, but reclassified in 1873. Its validity is disputed, and it may be a synonymous with the ancient sperm whale Physeterula dubusi. It was found in the Alpine town of Stockach in the Molasse basin, which was a coastal area with strong tidal currents. (Full article...)
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  Skull of Janjucetus hunderi at the Melbourne Museum

  
  Janjucetus is an extinct genus of cetacean, and a basal baleen whale (Mysticeti), from the Late Oligocene around 25 million years ago (mya) off south-east Australia, containing one species J. hunderi. Unlike modern mysticetes, it possessed large teeth for gripping and shredding prey, and lacked baleen, and so was likely to have been a predator that captured large single prey animals rather than filter feeding. However, its teeth may have interlocked, much like those of the modern-day filter-feeding crabeater seal (Lobodon carcinophaga), which would have allowed some filter-feeding behaviour. Its hunting behaviour was probably similar to the modern-day leopard seal (Hydrurga leptonyx), probably eating large fish. Like baleen whales, Janjucetus could not echolocate; however, it did have unusually large eyes, and so probably had an acute sense of vision. The only specimen was found on the Jan Juc beach, where the remains of the extinct whales Mammalodon, Prosqualodon and Waipatia have also been discovered. (Full article...)
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  Boudewijn Seapark dolphinarium in Bruges, Belgium

  
  A dolphinarium is an aquarium for dolphins. The dolphins are usually kept in a pool, though occasionally they may be kept in pens in the open sea, either for research or public performances. Some dolphinariums (sometimes called dolphinaria in plural) consist of one pool where dolphins perform for the public, others are part of larger parks, such as marine mammal parks, zoos or theme parks, with other animals and attractions as well.
  
  While cetaceans have been held in captivity since the 1860s, the first commercial dolphinarium was opened only in 1938. Their popularity increased rapidly until the 1960s. Since the 1970s, increasing concern for animal welfare led to stricter regulation, which in several countries ultimately resulted in the closure of some dolphinariums. Despite this trend, dolphinariums are still widespread in Europe, Japan and North America. The most common species of dolphin kept in dolphinariums is the bottlenose dolphin, as it is relatively easy to train and has a long lifespan in captivity. While trade in dolphins is internationally regulated, other aspects of keeping dolphins in captivity, such as the minimum size and characteristics of pools, vary among countries. Though animal welfare is perceived to have improved significantly over the last few decades, many animal rights groups still consider keeping dolphins captive to be a form of animal abuse. (Full article...)
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  The narwhal (Monodon monoceros) is a species of toothed whale native to the Arctic. It is the only member of the genus Monodon and one of two living representatives of the family Monodontidae. The narwhal has a similar build to the closely related beluga whale, with which it overlaps in range and can interbreed. It is a stocky cetacean with a relatively blunt snout, a large melon, and a shallow ridge in place of a dorsal fin. Males of this species have a large 1.5–3.0 m (4 ft 11 in – 9 ft 10 in) long tusk, which is a left protruded canine thought to serve as a weapon or as a tool for feeding, attracting mates or sensing water salinity. Specially adapted slow-twitch muscles, along with the jointed neck vertebrae and shallow dorsal ridge allow for easy movement through the Arctic environment, where the narwhal spends extended periods at great depths.
  
  The narwhal inhabits the Arctic waters of Canada, Greenland and Russia. Every year, it migrates to ice-free summering grounds, usually in shallow waters, and often returns to the same sites in subsequent years. Its diet mainly consists of polar and Arctic cod, Greenland halibut, cuttlefish, shrimp, and armhook squid. Plunging at depths of up to 2,370 m (7,780 ft), the narwhal is among the deepest-diving cetaceans. It travels in groups of three to eight, with aggregations of up to 1,000 occurring in the summer months. It mates in the offshore pack ice from March to May, and the young are born in July or August of the following year. When communicating, a variety of clicks, whistles and knocks are used. (Full article...)
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  Species of the infraorder Cetacea

  
  The evolution of cetaceans is thought to have begun in the Indian subcontinent from even-toed ungulates (Artiodactyla) 50 million years ago (mya) and to have proceeded over a period of at least 15 million years. Cetaceans are fully aquatic mammals belonging to the order Artiodactyla and branched off from other artiodactyls around 50 mya. Cetaceans are thought to have evolved during the Eocene (56-34 mya), the second epoch of the present-extending Cenozoic Era. Molecular and morphological analyses suggest Cetacea share a relatively recent closest common ancestor with hippopotami and that they are sister groups. Being mammals, they surface to breathe air; they have five finger bones (even-toed) in their fins; they nurse their young; and, despite their fully aquatic life style, they retain many skeletal features from their terrestrial ancestors. Research conducted in the late 1970s in Pakistan revealed several stages in the transition of cetaceans from land to sea.
  
  The two modern parvorders of cetaceans – Mysticeti (baleen whales) and Odontoceti (toothed whales) – are thought to have separated from each other around 28–33 mya in a second cetacean radiation, the first occurring with the archaeocetes. The adaptation of animal echolocation in toothed whales distinguishes them from fully aquatic archaeocetes and early baleen whales. The presence of baleen in baleen whales occurred gradually, with earlier varieties having very little baleen, and their size is linked to baleen dependence (and subsequent increase in filter feeding). (Full article...)

Selected picture

Blue Whale skeleton

Photo credit: Bronwen Lea, 14 May 2004

A Blue whale skeleton, outside the Long Marine Laboratory at the University of California, Santa Cruz.

Blue Whales are the largest animal ever to have existed. Hunting of Blue Whales has led to a severe decline in numbers across the globe.

More did you know...

• ...when right whales and humpback whales breach (leap out of the water), seagulls can often be seen darting in to pick up pieces of skin that become dislodged from the breaching whales. Presumably this is an easy source of food for seagulls.
• ...whales and dolphins don’t sleep in the way humans do. Although we don’t know how they sleep, some scientists believe they sleep with half the brain asleep and half the brain awake, keeping them aware of danger.
• ...all whales and dolphins have the remains of the pelvis, but it is reduced to two small bones at the rear of the animal.
• ...the ‘strapped-toothed whale’ is so called because in mature males there are only two teeth in the bottom jaw and these completely ‘strap’ the upper jaw, preventing it from opening more than a few centimetres. How these animals eat is unknown, but it may be that they stun their prey with high intensity sound.
• ...some cetaceans can dive to depths of more than a kilometre and stay there for more than an hour.

Things you can do..

Here are some Cetaceans WikiProject tasks you can do. Patrol: Look through the Category:Cetaceans for recent changes Assessment: Unassessed cetacea articles and unknown-importance cetacea articles. Copyedit/Formatting: Bottlenose dolphin, Beached whale, Cetacea Expand: Hector's beaked whale, Ginkgo-toothed beaked whale, Shepherd's beaked whale, Archaeoceti, Cumberland Sound beluga, Blubber, Baiji, Humpback dolphin, Amazon river dolphin Verify: Spinner dolphin, Whale, Dolphin, Cetacea Stubs: Bolivian river dolphin (new species), Cephalorhynchus Images: Pictures of the baiji are wanted.

General images -

The following are images from various cetacean-related articles on Wikipedia.

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  Restoration of Janjucetus hunderi (from Baleen whale)
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  North Atlantic right whale illustration
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  Japanese scientific whaling on a pair of Antarctic minke whales (from Baleen whale)
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  Archaeocetes (like this Basilosaurus) had a heterodont dentition (from Evolution of cetaceans)
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  South Atlantic right whale illustration
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  A humpback whale skeleton. Notice how the jaw is split into two.
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  Pakicetus attocki skeleton (from Evolution of cetaceans)
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  Possible relationships between cetaceans and other ungulate groups. (from Evolution of cetaceans)
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  Fossil of Squalodon (from Toothed whale)
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  Features of a sperm whale skeleton (from Toothed whale)
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  Sei whale illustration
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  World population graph of blue whales
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  A phylogenetic tree showing the relationships among cetacean families. (from Evolution of cetaceans)
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  The remains of a North Atlantic right whale after it collided with a ship propeller
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  Eden's whale illustration
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  Common minke whale illustration
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  Megalodon hunted Miocene baleen whales (from Baleen whale)
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  Bryde's whale (rorqual) (from Baleen whale)
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  Diagram illustrating sound generation, propagation and reception in a toothed whale. Outgoing sounds are red and incoming ones are green (from Toothed whale)
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  Antarctic minke whale illustration
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  Species of the infraorder Cetacea (from Evolution of cetaceans)
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  Biosonar by cetaceans (from Toothed whale)
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  An orca by the name of Ulises performing at SeaWorld, 2009 (from Toothed whale)
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  A whale as depicted by Conrad Gessner, 1587, in his Historiae animalium (from Toothed whale)
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  Gray whale illustration
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  Pygmy right whale illustration
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  Acrophyseter skull (from Evolution of cetaceans)
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  Baleen whales vary considerably in size and shape, depending on their feeding behavior. (from Baleen whale)
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  Female right whale with calf
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  Atlantic white-sided dolphin caught in a drive hunt in Hvalba on the Faroe Islands being taken away with a forklift (from Toothed whale)
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  The nose of the whale is filled with a waxy substance that was widely used in candles, oil lamps, and lubricants (from Toothed whale)
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  Archaeomysticetes, like Janjucetus, had teeth.
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  Blue whale illustration
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  Dolphins (aquatic mammals) and ichthyosaurs (extinct marine reptiles) share a number of unique adaptations for fully aquatic lifestyle and are frequently used as extreme examples of convergent evolution (from Evolution of cetaceans)
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  Fin whale illustration
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  Humpback whales lunge-feeding in the course of bubble net fishing
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  Bowhead whale illustration
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  A protest against Japan's scientific whaling
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  The skeleton of a bowhead whale with the hind limb and pelvic bone structure circled in red. This bone structure stays internal during the entire life of the species. (from Evolution of cetaceans)
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  Orca hunting a Weddell seal (from Toothed whale)
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  Their eyes are relatively small for their size.
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  Humpback whale illustration
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  Orange whale lice on a right whale
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  Anatomy of the bottlenose dolphin (from Toothed whale)
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  The heart of a blue whale with a person standing next to it
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  Accessory baleen plates taper off into small hairs (from Baleen whale)
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  Pacific white-sided dolphins porpoising (from Toothed whale)
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  Spectrogram of dolphin vocalizations. Whistles, whines, and clicks are visible as upside down V's, horizontal striations, and vertical lines, respectively. (from Toothed whale)

Did you know (auto-generated)

• ... that one of the first researchers to propose dolphin-assisted therapy for humans later renounced it?
• ... that the South Asian river dolphin is nearly blind and relies on echolocation for navigation?
• ... that Celia Kaye won the Golden Globe Award for Most Promising Newcomer in 1965 for her starring role in Island of the Blue Dolphins?
• ... that one can swim with humpback whales in the Niue Nukutuluea Multiple-Use Marine Park?

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• List of cetaceans
• List of extinct cetaceans
• List of whale species
• List of dolphin species
• List of porpoise species
• List of whale vocalizations

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