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Spermwhale
The sperm whale, Physeter macrocephalus, is a marine mammal species, order Cetacea, a toothed whale (odontocete) having the largest brain of any animal. The name comes from the milky-white waxy substance, spermaceti, found in the animal's head. The sperm whale is the only living member of genus Physeter. The synonym Physeter catodon refers to the same species. It is one of three extant species in the sperm whale superfamily, along with the pygmy sperm whale and dwarf sperm whale.

A bull can grow to 27.5 metres (90 ft) long. It is the largest living toothed animal. The head can take up to one-third of the animal's length. It has a cosmopolitan distribution across the oceans. The species feeds on squid and fish, diving as deep as 3 kilometres (9,800 ft), which makes it the deepest diving mammal. Its diet includes giant squid and colossal squid. The sperm whale's clicking vocalization is the loudest sound produced by any animal, but its functions are uncertain. These whales live in groups called pods. Pods of females and their young live separately from older males. The females cooperate to protect and nurse their young. Females give birth every three to six years, and care for the calves for more than a decade.

Historically, the sperm whale was also known as the common cachalot; "cachalot" is derived from an archaic French word for "tooth". Over most of the period from the early 18th century until the late 20th century, the sperm whale was hunted to obtain spermaceti and other products, such as sperm oil and ambergris. Spermaceti found many important uses, such as candles, soap, cosmetics and machine oil. Due to its size, the sperm whale could sometimes defend itself effectively against whalers. In the most famous example, a sperm whale attacked and sank the American whaleship Essex in 1820. As a result of whaling, the sperm whale is currently listed as vulnerable by the IUCN. The sperm whale has few natural predators, since few are strong enough to successfully attack a healthy adult; orcas attack pods and kill calves. The sperm whale can live for more than 70 years.

Name Edit

The name sperm whale is an apocopation of spermaceti whale. Spermaceti is the semi-liquid, waxy substance found in the spermaceti organ or case in front of and above the skull bone and also in the junk, the area below the spermaceti organ and just above the upper jaw.[1] The case consists of a soft white, waxy substance saturated with spermaceti oil. The junk is composed of cavities filled with the same wax and spermaceti oil and intervening connective tissue.[1][2][3] The sperm whale is also known as the "cachalot", which is thought to derive from the archaic French for "tooth" or "big teeth", as preserved for example in cachau in the Gascon dialect (a word of either Romance[4] or Basque[5] origin). The etymological dictionary of Corominas says the origin is uncertain, but it suggests that it comes from the vulgar Latin cappula, plural of cappulum, sword hilt.[6] According to Encarta Dictionary, the word cachalot came to English "via French from Spanish or Portuguese cachalote, perhaps from [Portuguese] cachola, 'big head'".

Description Edit

Size Edit

The sperm whale is the largest toothed whale, with adult males measuring up to 27.5 metres (90 ft) long and weighing up to 57,000 kilograms (56 LT; 63 ST). By contrast, the second largest toothed whale, Baird's Beaked Whale measures 12.8 metres (42 ft) and weighs up to 15 short tons (14,000 kg). The Nantucket Whaling Museum has a 5.5 metres (18 ft)-long jawbone. The museum claims this individual was 80 feet (24 m) long; the whale that sank the Essex (one of the incidents behind Moby-Dick) was claimed to be 85 feet (25 m). Extensive whaling may have decreased their size, as males were highly sought, primarily after World War II. Today, males do not usually exceed 18.3 metres (60 ft) in length or 51,000 kilograms (50 LT; 56 ST) in weight. Males might be 100 tons.

It is among the most sexually dimorphic of all cetaceans. At birth both sexes are about the same size, but mature males are typically 30% to 50% longer and three times as massive.

AppearanceEdit

The sperm whale's distinctive shape comes from its very large head, which is typically one-third of the animal's length. The blowhole is located very close to the front of the head and shifted to the whale's left.[2] This gives rise to a distinctive bushy, forward-angled spray.

Photo of vertical tail at the ocean's surface

The flukes of a sperm whale as it dives into the Gulf of Mexico (courtesy NMFS)

The sperm whale's flukes are triangular and very thick. The whale lifts its flukes high out of the water as it begins a dive.[2] It has a series of ridges on the back's caudal third instead of a dorsal fin. The largest ridge was called the 'hump' by whalers, and can be mistaken for a dorsal fin because of its shape.[7]

In contrast to the smooth skin of most large whales, its back skin is usually knobbly and has been likened to a prune by whale-watching enthusiasts.[8] Skin is normally a uniform grey in color, though it may appear brown in sunlight. Albinos have also been reported.[9][10][11]

Jaws and teethEdit

The sperm whale has 20 to 26 teeth on each side of its lower jaw.[2] The teeth are cone-shaped and weigh up to Template:Convert/kg.[12] The purpose of the teeth is unknown. Teeth do not appear to be necessary for capturing or eating squid, and well-fed animals have been found without teeth. One hypothesis is that the teeth are used in aggression between males.[13] Bulls often show scars which seem to be caused by the teeth. Rudimentary teeth are also present in the upper jaw, but these rarely emerge into the mouth.[14]

Respiration and divingEdit

Sperm whales, along with bottlenose whales and elephant seals, are the deepest-diving mammals.[2] Sperm whales are believed to be able to reach Template:Convert/km and remain submerged for 90 minutes.[2][15] More typical dives are around Template:Convert/LoffAoffDbSoff and 35 minutes in duration.[2] At these great depths, sperm whales sometimes become entangled in transoceanic telephone cables and drown.[16]

The sperm whale has adapted to cope with drastic pressure changes when diving. The flexible ribcage allows lung collapse, reducing nitrogen intake, and metabolism can decrease to conserve oxygen.[17][18] Myoglobin, which stores oxygen in muscle tissue, is much more abundant than in terrestrial animals.[19] The blood has a high red blood cell density, which contain oxygen-carrying hemoglobin. The oxygenated blood can be directed towards the brain and other essential organs only when oxygen levels deplete.[20][21][22] The spermaceti organ may also play a role by adjusting buoyancy (see below).[23]

While sperm whales are well adapted to diving, repeated dives to great depths have long term effects. Bones show pitting that signals decompression sickness in humans. Older skeletons showed the most extensive pitting, whereas calves showed no damage. This damage may indicate that sperm whales are susceptible to decompression sickness, and sudden surfacing could be lethal to them.[24]

Between dives, the sperm whale surfaces to breathe for about eight minutes before diving again.[2] Odontoceti (toothed whales) breathe air at the surface through a single, S-shaped blowhole. Sperm whales spout (breathe) 3–5 times per minute at rest, increasing to 6–7 times per minute after a dive. The blow is a noisy, single stream that rises up to Template:Convert/LoffAoffDbSoff above the surface and points forward and left at a 45° angle. On average, females and juveniles blow every 12.5 seconds before dives, while large males blow every 17.5 seconds before dives.[25]


Brain and sensesEdit

Template:Annotated image The brain is the largest known of any modern or extinct animal, weighing on average about Template:Convert/kg,[26][27] though the sperm whale has a lower encephalization quotient than many other whale and dolphin species, lower than that of non-human anthropoid apes and much lower than humans'.[27][28]

Like other toothed whales (suborder odontoceti), sperm whales use echolocation as one means to find food because their habitat has favorable acoustic characteristics and light absorption by water and suspended material limits visual range. The whale emits a focused wide angle beam of high-frequency clicks. Passing air generates sounds from the bony nares through the phonic lips (also known as "monkey lips"), a structure within the head.[29] The skull, melon, and various air sacs in the whale's head all play important roles in forming and focusing the beam of sound. The lower jaw is the primary echo reception path. A continuous fat-filled canal transmits received sounds to the inner ear.[30]


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