Portal:Cetaceans
The Cetaceans Portal
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...)
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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...) -
Arktocara is an extinct genus of river dolphin from the Oligocene epoch of Alaska, containing one species, A. yakataga. Having been discovered in 25-million-year-old strata near the 60th parallel north, it is perhaps the oldest-known crown toothed whale and the northmost river dolphin discovered. It was a member of the now-extinct family Allodelphinidae, along with the genera Allodelphis, Goedertius, Ninjadelphis, and Zarhinocetus. It measured approximately 2.26 or 2.28 meters (7.4 or 7.5 ft), comparable to its closest living relative, the South Asian river dolphin, which measures 2.4 meters (7.9 ft). However, the animal probably had an elongated beak and neck, so it may have been longer. The animal is known only from a partially preserved skull. Its ecology may have been similar to the modern-day Dall's porpoise, and it may have competed with contemporaneous delphinoids. Its remains were found in the Poul Creek Formation, which has also yielded several mollusk species. (Full article...) -
The sei whale (/seɪ/ SAY, Norwegian: [sæɪ]; Balaenoptera borealis) is a baleen whale. It is one of ten rorqual species, and the third-largest member after the blue and fin whales. It can grow to 19.5 m (64 ft) in length and weigh as much as 28 t (28 long tons; 31 short tons). Two subspecies are recognized: B. b. borealis and B. b. schlegelii. The whale's ventral surface has sporadic markings ranging from light grey to white, and its body is usually dark steel grey in colour. It is among the fastest of all cetaceans, and can reach speeds of up to 50 km/h (31 mph) over short distances.
It inhabits most oceans and adjoining seas, and prefers deep offshore waters. It avoids polar and tropical waters and semi-enclosed bodies of water. The sei whale migrates annually from cool, subpolar waters in summer to temperate, subtropical waters in winter with a lifespan of 70 years. It is a filter feeder, with its diet consisting primarily of copepods, krill, and other zooplankton. It is typically solitary or can be found in groups numbering half a dozen. During the breeding period, a mating pair will remain together. Sei whale vocalizations usually lasts half a second, and occurs at 240–625 hertz. (Full article...) -
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...) -
Brygmophyseter, known as the biting sperm whale, is an extinct genus of toothed whale in the sperm whale family with one species, B. shigensis. When it was first described in 1994, the species was placed in the genus Scaldicetus based on tooth morphology, but this was later revised in 1995. In 2006, it was classified into the genus Naganocetus, which is considered to be a junior synonym. The only known specimen, a nearly complete skeleton, was dated to be around 16–15 million years old (middle Miocene). Brygmophyseter is thought to have been 6.5–7 meters (21–23 ft) long, and it probably had 11 or 12 teeth in the upper and lower jaws. Brygmophyseter is part of a group of macroraptorial sperm whales (often shortened to "raptorial") which tended to be apex predators using their large teeth to catch struggling prey such as whales. It had a spermaceti organ which was probably used for biosonar like in the modern sperm whale. The whale has made an appearance on The History Channel's TV series Jurassic Fight Club. (Full article...) -
The orca (Orcinus orca), or killer whale, is a toothed whale and the largest member of the oceanic dolphin family. It is the only extant species in the genus Orcinus and is recognizable by its black-and-white patterned body. A cosmopolitan species, they are found in diverse marine environments, from Arctic to Antarctic regions to tropical seas.
Orcas are apex predators with a diverse diet. Individual populations often specialize in particular types of prey. This includes a variety of fish, sharks, rays, and marine mammals such as seals and other dolphins and whales. They are highly social; some populations are composed of highly stable matrilineal family groups (pods). Their sophisticated hunting techniques and vocal behaviors, often specific to a particular group and passed along from generation to generation, are considered to be manifestations of animal culture. (Full article...) -
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...) -
The blue whale (Balaenoptera musculus) is a marine mammal and a baleen whale. Reaching a maximum confirmed length of 29.9 m (98 ft) and weighing up to 199 t (196 long tons; 219 short tons), it is the largest animal known ever to have existed. The blue whale's long and slender body can be of various shades of greyish-blue on its upper surface and somewhat lighter underneath. Four subspecies are recognized: B. m. musculus in the North Atlantic and North Pacific, B. m. intermedia in the Southern Ocean, B. m. brevicauda (the pygmy blue whale) in the Indian Ocean and South Pacific Ocean, and B. m. indica in the Northern Indian Ocean. There is a population in the waters off Chile that may constitute a fifth subspecies.
In general, blue whale populations migrate between their summer feeding areas near the poles and their winter breeding grounds near the tropics. There is also evidence of year-round residencies, and partial or age/sex-based migration. Blue whales are filter feeders; their diet consists almost exclusively of krill. They are generally solitary or gather in small groups, and have no well-defined social structure other than mother–calf bonds. Blue whales vocalize, with a fundamental frequency ranging from 8 to 25 Hz; their vocalizations may vary by region, season, behavior, and time of day. Orcas are their only natural predators. (Full article...) -
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...) -
The bottlenose dolphin is a toothed whale in the genus Tursiops. They are common, cosmopolitan members of the family Delphinidae, the family of oceanic dolphins. Molecular studies show the genus contains three species: the common bottlenose dolphin (Tursiops truncatus), the Indo-Pacific bottlenose dolphin (Tursiops aduncus), and Tamanend's bottlenose dolphin (Tursiops erebennus). Others, like the Burrunan dolphin (Tursiops (aduncus) australis), may be alternately considered their own species or be subspecies of T. aduncus. Bottlenose dolphins inhabit warm and temperate seas worldwide, being found everywhere except for the Arctic and Antarctic Circle regions. Their name derives from the Latin tursio (dolphin) and truncatus for the truncated teeth (the type specimen was old and had worn down teeth; this is not a typical characteristic of most members of the species).
Numerous investigations of bottlenose dolphin intelligence have been conducted, examining mimicry, use of artificial language, object categorization, and self-recognition. They can use tools (sponging; using marine sponges to forage for food sources they normally could not access) and transmit cultural knowledge from generation to generation, and their considerable intelligence has driven interaction with humans. Bottlenose dolphins gained popularity from aquarium shows and television programs such as Flipper. They have also been trained by militaries to locate sea mines or detect and mark enemy divers. In some areas, they cooperate with local fishermen by driving fish into their nets and eating the fish that escape. Some encounters with humans are harmful to the dolphins: people hunt them for food, and dolphins are killed inadvertently as a bycatch of tuna fishing and by getting caught in crab traps. (Full article...) -
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...) -
The dwarf sperm whale (Kogia sima) is a sperm whale that inhabits temperate and tropical oceans worldwide, in particular continental shelves and slopes. It was first described by biologist Richard Owen in 1866, based on illustrations by naturalist Sir Walter Elliot. The species was considered to be synonymous with the pygmy sperm whale (Kogia breviceps) from 1878 until 1998. The dwarf sperm whale is a small whale, 2 to 2.7 m (6 ft 7 in to 8 ft 10 in) and 136 to 272 kg (300 to 600 lb), that has a grey coloration, square head, small jaw, and robust body. Its appearance is very similar to the pygmy sperm whale, distinguished mainly by the position of the dorsal fin on the body–nearer the middle in the dwarf sperm whale and nearer the tail in the other.
The dwarf sperm whale is a suction feeder that mainly eats squid, and does this in small pods of typically one to four members. It is preyed upon by the killer whale (Orcinus orca) and large sharks such as the great white shark (Carcharodon carcharius). When startled, the whale can eject a cloud of red-brown fluid. Most of what is known of the whale comes from beached individuals, as sightings in the ocean are rare. Many of these stranded whales died from parasitic infestations or heart failure. (Full article...) -
The false killer whale (Pseudorca crassidens) is a species of oceanic dolphin that is the only extant representative of the genus Pseudorca. It is found in oceans worldwide but mainly in tropical regions. It was first described in 1846 as a species of porpoise based on a skull, which was revised when the first carcasses were observed in 1861. The name "false killer whale" comes from having a skull similar to the orca (Orcinus orca), or killer whale.
The false killer whale reaches a maximum length of 6 m (20 ft), though size can vary around the world. It is highly sociable, known to form pods of up to 50 members, and can also form pods with other dolphin species, such as the common bottlenose dolphin (Tursiops truncatus). It can form close bonds with other species, as well as have sexual interactions with them. But the false killer whale has also been known to eat other dolphins, though it typically eats squid and fish. It is a deep-diver; maximum known depth is 927.5 m (3,043 ft); maximum speed is ~ 29 km/h (18 mph). (Full article...) -
Pilot whales are cetaceans belonging to the genus Globicephala. The two extant species are the long-finned pilot whale (G. melas) and the short-finned pilot whale (G. macrorhynchus). The two are not readily distinguishable at sea, and analysis of the skulls is the best way to distinguish between the species. Between the two species, they range nearly worldwide, with long-finned pilot whales living in colder waters and short-finned pilot whales living in tropical and subtropical waters. Pilot whales are among the largest of the oceanic dolphins, exceeded in size only by the orca. They and other large members of the dolphin family are also known as blackfish.
Pilot whales feed primarily on squid, but will also hunt large demersal fish such as cod and turbot. They are highly social and may remain with their birth pod throughout their lifetime. Short-finned pilot whales are one of the few non-primate mammal species in which females go through menopause, and postreproductive females continue to contribute to their pod. Pilot whales are notorious for stranding themselves on beaches, but the reason behind this is not fully understood. Marine biologists have shed some light on the matter, suggesting that it is due to the mammals inner ear (their principal navigational sonar) being damaged from noise pollution in the ocean, such as from cargo ships or military exercises. The conservation status of short-finned and long-finned pilot whales has been determined to be least concern. (Full article...) -
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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The Harbour Porpoise (Phocoena phocoena) is one of six species of porpoise. It is one of the smallest ocean mammals in the sea. As its name implies, it stays close to coastal areas or river estuaries and as such is the most familiar porpoise to whale watchers. This porpoise often ventures up rivers and has been seen hundreds of miles from the sea.
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More did you know...
- ...the male narwhal's tusk can be up to 3.5 metres in length which is over the size of an average female without a horn and weigh up to 10 kilograms.
- ...male narwhal(e)s tusk is the canine growing through the lip. Sometimes, the male will have 2 tusks but their number is small. Female narwhal(e) rarely have a tusk and if they do, it must be smaller than the males. Also, there is only 1 recorded case of a dual horned female narwhal(e)
- ...observations of cetaceans date back to at least the classical period in Greece, when fisherpeople made notches on the dorsal fins of dolphins entangled in nets in order to tell them apart years later.
- ...groups of bottlenose dolphins around the Australian Pacific have displayed basic tool use by wrapping pieces of sponge around their beaks to prevent abrasions. This is a display of a cognitive process similar to that of great apes.
- ...Herman Melville's novel Moby-Dick had real-life inspiration, a notorious male sperm whale named Mocha Dick.
- ...the Voyager Golden Record carried into space whale songs, among other sounds.
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General images -
The following are images from various cetacean-related articles on Wikipedia.
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Sei whale illustration -
Archaeomysticetes, like Janjucetus, had teeth. -
Bryde's whale (rorqual) (from Baleen whale) -
North Atlantic right whale illustration -
Japanese scientific whaling on a pair of Antarctic minke whales (from Baleen whale) -
A humpback whale skeleton. Notice how the jaw is split into two. -
The heart of a blue whale with a person standing next to it -
Restoration of Janjucetus hunderi (from Baleen whale) -
South Atlantic right whale illustration -
Atlantic white-sided dolphin caught in a drive hunt in Hvalba on the Faroe Islands being taken away with a forklift (from Toothed whale) -
Orange whale lice on a right whale -
Eden's whale illustration -
Anatomy of the bottlenose dolphin (from Toothed whale) -
Orca hunting a Weddell seal (from Toothed whale) -
The remains of a North Atlantic right whale after it collided with a ship propeller -
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World population graph of blue whales -
Accessory baleen plates taper off into small hairs (from Baleen whale) -
Bowhead whale illustration -
Fin whale illustration -
Gray whale illustration -
Pakicetus attocki skeleton (from Evolution of cetaceans) -
Humpback whale illustration -
Acrophyseter skull (from Evolution of cetaceans) -
Spectrogram of dolphin vocalizations. Whistles, whines, and clicks are visible as upside down V's, horizontal striations, and vertical lines, respectively. (from Toothed whale) -
Their eyes are relatively small for their size. -
Pygmy right whale illustration -
Fossil of Squalodon (from Toothed whale) -
Possible relationships between cetaceans and other ungulate groups. (from Evolution of cetaceans) -
Humpback whales lunge-feeding in the course of bubble net fishing -
Common minke whale illustration -
Biosonar by cetaceans (from Toothed whale) -
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) -
A phylogenetic tree showing the relationships among cetacean families. (from Evolution of cetaceans) -
A protest against Japan's scientific whaling -
Female right whale with calf -
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) -
An orca by the name of Ulises performing at SeaWorld, 2009 (from Toothed whale) -
Antarctic minke whale illustration -
Baleen whales vary considerably in size and shape, depending on their feeding behavior. (from Baleen whale) -
The nose of the whale is filled with a waxy substance that was widely used in candles, oil lamps, and lubricants (from Toothed whale) -
Archaeocetes (like this Basilosaurus) had a heterodont dentition (from Evolution of cetaceans) -
Blue whale illustration -
Megalodon hunted Miocene baleen whales (from Baleen whale) -
Features of a sperm whale skeleton (from Toothed whale) -
Diagram illustrating sound generation, propagation and reception in a toothed whale. Outgoing sounds are red and incoming ones are green (from Toothed whale) -
Species of the infraorder Cetacea (from Evolution of cetaceans)
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Did you know (auto-generated)
- ... that the South Asian river dolphin is nearly blind and relies on echolocation for navigation?
- ... that one can swim with humpback whales in the Niue Nukutuluea Multiple-Use Marine Park?
- ... that one of the first researchers to propose dolphin-assisted therapy for humans later renounced it?
- ... that Celia Kaye won the Golden Globe Award for Most Promising Newcomer in 1965 for her starring role in Island of the Blue Dolphins?
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