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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 its head and originally mistaken for sperm. The sperm whale is the only 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 up to 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 , which makes it the deepest diving mammal. Its diet includes Giant squid and Colossal Squid. It is the largest living predator and possibly the largest ever, not in terms of its taking animal matter (which is true of all cetaceans, including the larger baleen whales) but in that it actively preys on self-functioning animals. 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. The most famous example was the Essexmarker. 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, however orcas attack pods and kill calves. The sperm whale can live for more than 70 years.

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. 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.

The sperm whale is also known as the "cachalot", which is thought to derive from the archaic French for "tooth", for example cachau in the Gascon dialect. 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. According to Encarta Dictionary, the word cachalot came to English "via French from Spanish or Portuguese cachalote, perhaps from [Portuguese] cachola, 'big head'".

Description

Size

Average sizes Length Weight
Bull
Cow
Newborn
The sperm whale is the largest toothed whale, with adult males measuring up to long and weighing up to . By contrast, the second largest toothed whale, Baird's Beaked Whale measures and weighs up to . The Nantucket Whaling Museummarker has a -long jawbone. The museum claims this individual was long; the whale that sank the Essexmarker (one of the incidents behind Moby-Dick) was claimed to be . Extensive whaling may have decreased their size, as males were highly sought, primarily after World War II. Today, males do not usually exceed in length or in weight.

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.

Appearance

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. This gives rise to a distinctive bushy, forward-angled spray.

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. 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.

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. Skin is normally a uniform grey in colour, though it may appear brown in sunlight. Albinos have also been reported.

Jaws and teeth

The sperm whale has 20 to 26 teeth on each side of its lower jaw. The teeth are cone-shaped and weigh up to . 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. 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.

Respiration and diving

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

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. Myoglobin, which stores oxygen in muscle tissue, is much more abundant than in terrestrial animals. 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. The spermaceti organ may also play a role by adjusting buoyancy (see below).

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.

Between dives, the sperm whale surfaces to breathe for about eight minutes before again diving. 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 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.

Brain and senses

The brain is the largest known of any modern or extinct animal, weighing on average about . However, it is not particularly large in proportion to its body size. For example, 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'.

Like other toothed whales (suborder odontoceti), sperm whales use echolocation as one means to find food because their habitat has favorable acoustic characteristics and 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. 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 as the primary echo reception path. A continuous fat-filled canal transmits them to the inner ear.

Spermaceti functions

The spermaceti organs may help adjust the whale's buoyancy. Before diving, cold water enters the organ and the wax solidifies. The increase in specific density generates a down force of about and allows the whale to dive with less effort. During the hunt (max.  oxygen consumption produces heat and melts the spermaceti, increasing its buoyancy, enabling easy surfacing.

Herman Melville's Moby Dick suggests that the "case" containing the spermaceti evolved as a kind of battering ram for use in fights between males. This hypothesis is consistent with the well-documented sinking of the ships Essexmarker and Ann Alexander by attackers estimated to weigh only one-fifth as much as the ships.

Another possibility is that the case aids echolocation (see melon). The organ's variable shape narrows or spreads the sound.

The sperm whale has two nostrils. An external nostril forms the blow hole, and an internal nostril presses against the bag-like spermaceti container. The male's spermaceti organ is much larger than the female's. This may be a case of sexual selection, enabling males to compete for females using sound displays.

Ecology, behaviour and life history

Distribution

The sperm whale is among the most cosmopolitan species. It prefers ice-free waters over deep. Although both sexes range through temperate and tropical oceans and seas, only adult males populate higher latitudes.

It is relatively abundant from the poles to the equator, and is found in all the oceans. It inhabits the Mediterranean Seamarker, but not the Black Seamarker, while its presence in the Red Seamarker is uncertain. The shallow entrances to both the Black Sea and the Red Sea may account for their absence. The Black Sea's lower layers are also anoxic and contain high concentrations of sulphur compounds such as hydrogen sulphide.

Populations are denser close to continental shelves and canyons. Sperm whales are usually found in deep off-shore waters, but may be seen closer to shore in areas where the continental shelf is small and drops quickly to depths of . Coastal areas with significant sperm whale populations include the Azores and the Caribbeanmarker island of Dominicamarker.

Reproduction

Young sperm whale


Sperm whales can live 70 years or more. They are a prime example of a species that has been K-selected, a reproductive strategy associated with stable environmental conditions, a low birth rate, significant parental aid to offspring, slow maturation and high longevity.

How they choose mates has not been definitively determined. There is evidence that males have dominance hierarchies and there is also evidence that female choice influences mating. Gestation requires 14 to 16 months, producing a single calf. Lactation proceeds for 19 to 42 months, but calves may suckle up to 13 years (although usually less). Calves can suckle from females other than their mothers. Females generally have birth intervals of three to six years.

Females reach sexual maturity between 7 and 13 years, males follow beginning at 18 years. Upon reaching sexual maturity, males move to higher latitudes, where the water is colder and feeding is more productive. Females remain at lower latitudes.

Males reach their full size at about age 50.

Social behavior

miniature


Females stay in groups of about a dozen individuals and their young. Males leave these "nursery pods" at somewhere between 4 and 21 years of age and join a "bachelor pod" with other males of similar age and size. As males grow older, they tend to disperse into smaller groups, and the oldest males typically live solitary lives. Mature males have beached themselves together, suggesting a degree of cooperation which is not yet fully understood.

The most common non-human attacker of sperm whales is the orca, but pilot whales and the false killer whale also sometimes attack or harass them. Orcas target groups of females with young, usually trying to extract and kill a calf. Female sperm whales repel these attacks by encircling their calves. The adults either face inwards to use their tail flukes against the orcas, or outwards, fighting with their teeth. This Marguerite formation is also employed to support an injured pod member, a behaviour that early whalers exploited, attracting a whole pod by injuring just one of its members. If the orca pod is extremely large, they may sometimes kill adult females. Large bull sperm whales have no non-human predators, and are believed to be too large and strong to be threatened by orcas.

Feeding

A piece of sperm whale skin with giant squid sucker scars


Sperm Whales usually dive between , and sometimes to search for food. Such dives can last more than an hour. They feed on several species, notably the Giant Squid, the Colossal Squid, octopuses, and diverse fish like demersal ray, but the main part of their diet consists of medium-sized squid. Some prey may be taken incidentally while eating other items. Most of what is known about deep sea squid has been learned from specimens in captured sperm whale stomachs, although more recent studies analysed fecal matter. One study, carried out around the Galápagosmarker, found that squid from the genera Histioteuthis (62%), Ancistrocheirus (16%), and Octopoteuthis (7%) weighing between were the most commonly taken. Battles between sperm whales and colossal squid (which have been measured to weigh nearly ) have never been observed by humans; however white scars are believed to be caused by the large squid.

An older study, examining whales captured by the New Zealand whaling fleet in the Cook Straitmarker region, found a 1.69:1 ratio of squid to fish by weight. Sperm whales sometimes steal Sablefish and Toothfish from long lines. Long-line fishing operations in the Gulf of Alaskamarker complain that sperm whales take advantage of their fishing operations to eat desirable species straight off the line, sparing the whales the need to hunt. However, the amount of fish taken is very little compared to what the sperm whale needs per day. New video footage has been captured of a large male sperm whale "bouncing" a long line, to gain the fish. Sperm whales are believed to prey on the Megamouth Shark, a rare and large deep-sea species discovered in the 1970s. In one case, three sperm whales were observed attacking or playing with a megamouth.

The sharp beak of a consumed squid lodged in the whale's intestine may lead to the production of ambergris, analogous to the production of pearls. The irritation of the intestines caused by squid beaks stimulates the secretion of this lubricant-like substance. Sperm whales are prodigious feeders and eat around 3% of their body weight per day. The total annual consumption of prey by sperm whales worldwide is estimated to be about — a figure greater than the total consumption of marine animals by humans each year.

It is not well understood why the sperm whale's head is so large in comparison to the lower jaw. One theory is that the sperm whale's ability to echolocate through its head aids in hunting. However squid, its main prey, may have acoustic properties too similar to seawater to reflect sounds. The sperm whale's head contains a structure called monkey lips, through which it blows air. This can create clicks that have a source level exceeding 230 decibels re 1 micropascal referenced to a distance of – in other words it is by far the loudest sound made by any animal, and 10–14 dB louder than a powerful rifle sounds in air at away. It has been hypothesised that clicks attempt to stun prey. Experimental studies attempting to duplicate this effect have been unable to replicate the supposed injuries, casting doubt on this idea.

Taxonomy and naming

The sperm whale belongs to the order Cetacea, the order containing all whales and dolphins. It is a member of the suborder Odontoceti, the suborder containing all the toothed whales and dolphins. It is the sole extant species of its genus, Physeter, in the family Physeteridae. Two species of the related extant genus Kogia, the pygmy sperm whale Kogia breviceps and the dwarf sperm whale K. simus, are either placed in this family, or in the family Kogiidae. In some taxonomic schemes the families Kogiidae and Physeteridae are combined as the superfamily Physeteroidea (refer separate entry sperm whale family).

The sperm whale is one of the species originally described by Linnaeus in 1758 in his 18th century work, Systema Naturae. He recognised four species in the genus Physeter. Experts soon realised that just one such species exists, although there has been debate about whether this should be named P. catodon or P. macrocephalus, two of the names used by Linnaeus. Both names are still, although most recent authors now accept macrocephalus as the valid name, limiting catodon's status to a lesser synonym.

Evolutionary History

Fossil record

Although the fossil record is poor, several extinct genera have been assigned to the clade Physeteroidea, which includes the last common ancestor of the modern sperm whale, pygmy sperm whale and dwarf sperm whale, plusall of that ancestor's descendants. These fossils include Ferecetotherium, Idiorophus, Diaphorocetus, Aulophyseter, Orycterocetus, Scaldicetus, Placoziphius, Zygophyseter and Acrophyseter. Ferecetotherium, found in Azerbaijanmarker and dated to the late Oligocene (about ), is the most primitive fossil that has been found which possesses sperm whale-specific features such as an asymmetric rostrum ("beak" or "snout"). Most sperm whale fossils date from the Miocene period, . Diaphorocetus, from Argentinamarker, has been dated to the early Miocene. Fossil sperm whales from the Middle Miocene include Aulophyseter, Idiorophus and Orycterocetus, all of which were found on the west coast of the United Statesmarker, and Scaldicetus, found in Europe and Japanmarker. Orycterocetus fossils have also been found in the North Atlantic Oceanmarker and the Mediterranean Seamarker, in addition to the west coast of the United States. Placoziphius, found in Europe, and Acrophyseter, from Perumarker, are dated to the late Miocene.


Evolutionary family tree of sperm whales,

including simplified summary of extinct groups ()Fossil sperm whales differ from modern sperm whales in tooth count and the shape of the face and jaws. For example Scaldicetus had a tapered rostrum. Genera from the Oligocene and early and middle Miocene, with the possible exception of Aulophyseter, had teeth in their upper jaws. Acrophyseter, from the late Miocene, also had teeth in both the upper and lower jaws as well as a short rostrum and an upward curving mandible (lower jaw). These anatomical differences suggest that fossil species may not have necessarily been deep-sea squid eaters like the modern sperm whale, but that some genera mainly ate fish. Zygophyseter, dated from the middle to late Miocene and found in southern Italymarker, had teeth in both jaws and appears to have been adapted to feed on large prey, rather like the modern Orca (Killer Whale).

Phylogeny

The traditional view has been that the Mysticeti (baleen whales) and Odontoceti (toothed whales) arose from more primitive whales early in the Oligocene period, and that the super-family Physeteroidea, which contains the sperm whale, dwarf sperm whale and pygmy sperm whale, diverged from other toothed whales soon after that, over . In 1993–1996 molecular phylogenetics analyses by Milinkovitch and colleagues, based on comparing the genes of various modern whales, suggested that the sperm whales are more closely related to the baleen whales than they are to other toothed whales, which would have meant that Odontoceti were not monophyletic, in other words did not consist of a single ancestral toothed whale species and all its descendants. However more recent studies, based on various combinations of comparative anatomy and molecular phylogenetics, criticised Milinkovitch's analysis on technical grounds and re-affirmed that the Odontoceti are monophyletic.

These analyses also confirm that there was a rapid evolutionary radiation (diversification) of the Physeteroidea in the Miocene period. The Kogiidae (dwarf and pygmy sperm whales) diverged from the Physeteridae (true sperm whales) at least .

Relationship with humans

Historical hunting

Spermaceti, obtained primarily from the spermaceti organ, and sperm oil, obtained primarily from the blubber in the body, were much sought after by 18th, 19th and 20th century whalers. These substances found a variety of commercial applications, such as candles, soap, cosmetics, machine oil, other specialized lubricants, lamp oil, pencils, crayons, leather waterproofing, rust-proofing materials and many pharmaceutical compounds.
Ambergris, a solid, waxy, flammable substance produced in the digestive system of sperm whales, was also sought as a fixative in perfumery.


Sperm whaling
Prior to the early 18th century, hunting was mostly by indigenous Indonesians. Legend has it that sometime in the early 18th century, around 1712, Captain Christopher Hussey, while cruising for Right Whales near shore, was blown offshore by a northerly wind, where he encountered a Sperm whale pod and killed one. Although the story may not be true, sperm whales were indeed soon exploited by American whalers. Judge Paul Dudley, in his Essay upon the Natural History of Whales (1725), states that one Atkins, ten or twelve years in the trade, was among the first to catch sperm whales sometime around 1720 off the New England]] coast.

There were only a few recorded catches during the first few decades (1709-1730s) of offshore sperm whaling. Instead sloops concentrated on Nantucket Shoals where they would have taken Right Whales or went to the Davis Straitmarker region to catch Bowhead Whales. By the early 1740s, with the advent of spermaceti candles (before 1743), American vessels began to focus on sperm whales. The diary of Benjamin Bangs (1721-1769) shows that, along with the bumpkin sloop he sailed, he found three other sloops flensing sperm whales off the coast of North Carolina in late May 1743. On returning to Nantucket in the summer 1744 on a subsequent voyage he noted that "45 spermacetes are brought in here this day," another indication that American sperm whaling was in full swing.

American sperm whaling soon spread from the east coast of the American colonies to the Gulf Stream, the Grand Banksmarker, West Africa (1763), the Azores (1765) and the South Atlantic (1770s). From 1770 to 1775 Massachusetts, New York, Connecticut, and Rhode Island ports produced 45,000 barrels of sperm oil annually, compared to 8,500 of whale oil. In the same decade the British began sperm whaling, employing American ships and personnel. By the following decade the French had entered the trade, also employing American expertise. Sperm whaling increased until the mid-1800s. Spermaceti oil was important in public lighting (for example, in lighthouses, where it was used in the United States until 1862, when it was replaced by lard oil, in turn replaced by petroleum) and for lubricating the machines (such as those used in cotton mills) of the Industrial Revolution. Sperm whaling declined in the second half of the 19th century, as petroleum came in to broader use. In that sense, it may be said to have protected whale populations from even greater exploitation.

Sperm whaling in the 18th century began with small sloops carrying only one or two whaleboats. The fleet's scope and size increased over time, and larger ships entered the fishery. In the late 18th and early 19th century sperm whaling ships sailed to the Pacific, the Indian Ocean, Japan, the coast of Arabia, Australia and New Zealand. Hunting could be dangerous to the crew. For example, on November 20, 1820, a sperm whale claimed to be about long attacked the Nantucketmarker whaleship Essexmarker. Only 8 out of 21 sailors survived to be rescued by other ships.

Whaling activity declined from the 1880s until 1946, but picked up again after World War II. Modern whaling was more efficient than open-boat whaling, employing steam-powered ships and exploding harpoons. Initially, modern whaling activity focused on large baleen whales, but as these populations were taken, sperm whaling increased. Cosmetics, soap and machine oil were the major buyers. After populations declined significantly, the International Whaling Commission gave the species full protection in 1985. Hunting by Japanmarker in the northern Pacific Oceanmarker continued until 1988.

It is estimated that the historic worldwide population numbered 1,100,000 before commercial sperm whaling began in the early 18th century. By 1880 it had declined an estimated 29 per cent. From that date until 1946 the population appears to have recovered somewhat as whaling pressure lessened, but after the Second World War, the population declined even further, to only 33 per cent of the pre-whaling era. It has been estimated that in the 19th century between 184,000 and 236,000 sperm whales were killed by the various whaling nations, while in the modern era, at least 770,000 were taken, the majority between 1946 and 1980.

Remaining sperm whale populations are large enough that the species' conservation status is rated as vulnerable rather than endangered. However, the recovery from the whaling years is a slow process, particularly in the South Pacificmarker, where the toll on breeding-age males was severe.

Current conservation status

The number of sperm whales throughout the world is unknown, but is thought to be in the hundreds of thousands. The conservation outlook is brighter than for many other whales. Historically, Japan has taken ten sperm whales a year, and until 2006 tens of these whales were hunted off Indonesia. They are protected practically worldwide, and commercial whaling has ceased. Fishermen do not target the creatures that sperm whales eat. However, long-line fishing operations in the Gulf of Alaskamarker have complained about sperm whales stealing fish from their lines.

Entanglement in fishing nets and collisions with ships represent the greatest threats to the sperm whale population currently. Other current threats include ingestion of marine debris, ocean noise, and chemical pollution. The IUCN regards the sperm whale as being "vulnerable". The U.S. lists them as endangered.

Cultural importance

Rope-mounted teeth are important cultural objects throughout the Pacific. In New Zealandmarker Māori know them as "rei puta" and were rare because sperm whales were not actively hunted in traditional Māori society. Whale ivory and bone were taken from beached whales. In Fijimarker the teeth are known as tabua and they were traditionally given as gifts for atonement or esteem (called sevusevu), and were important in negotiations between rival chiefs. Friedrich Ratzel in The History of Mankind reported in 1896 that, in Fiji, whales' or cachalots' teeth were the most-demanded article of ornament or value. They occurred often in necklaces. Today the tabua remains an important item in Fijian life. The teeth were originally rare in Fiji and Tongamarker, which exported teeth, but with the Europeans' arrival, teeth flooded the market and this "currency" collapsed. The oversupply led in turn to the development of the European art of scrimshaw.

The title character of Herman Melville's novel Moby-Dick is a sperm whale. Melville associated the sperm whale with the Bible's Leviathan. The fearsome reputation perpetuated by Melville was based on bull whales' ability to fiercely defend themselves from attacks by early whalers, occasionally resulting in the destruction of the whaling ships.

Jules Verne's Twenty Thousand Leagues Under the Sea, mentions cachalots (perhaps incorrectly) as preying on fellow whales.

In the Disney film Pinnochio, Monstro the whale is a mean sperm whale very much like Moby Dick except that monstro is black rather than white.

Female in Dominican Pod, 2005


Watching sperm whales

Sperm whales are not the easiest of whales to watch, due to their long dive times and ability to travel long distances underwater. However, due to the distinctive look and large size of the whale, watching is increasingly popular. Sperm whale watchers often use hydrophones to listen to the clicks of the whales and locate them before they surface. Popular locations for sperm whale watching include the picturesque Kaikouramarker on New Zealandmarker's South Islandmarker, where the continental shelf is so narrow that whales can be observed from the shore, Andenesmarker and Tromsømarker in Arctic Norwaymarker and at the Azores where it can be seen throughout the year. Dominicamarker is believed to be the only Caribbean island with a year-round residential pod of females and calves.

See also

Bibliography



Footnotes

  • Until 1974 the species was generally known as P. catodon, however in that year Husson & Holthuis proposed that the correct name should be P. macrocephalus, the second name in the genus Physeter published by Linnaeus concurrently with P. catodon, on the grounds that the names were synonyms published simultaneously and therefore the ICZN principle of "First Reviser" should apply, in this instance leading to the choice of P. macrocephalus over P. catodon, a view re-stated in Holthuis, 1987. This has been adopted by most subsequent authors, although Schevill (1986 and 1987) argued that macrocephalus was published with an inaccurate description and that therefore only the species catodon was valid, rendering the principle of "First Reviser" inapplicable. At the present time, the name P. catodon is used in the Catalogue of Life, however this is expected to be changed to follow the most recent version of ITIS which has recently altered its usage from P. catodon to P. macrocephalus following L. B. Holthuis, and recent (2008) discussions with relevant experts (refer cited ITIS page for additional information).


References

  1. .
  2. The Southwestern Company: "The Volume Library 1", page 65, 1987, ISBN 0-87197-208-5
  3. spermwhale.org - Cranford
  4. Pitman, RL; Ballance, LT; Mesnick, SI; Chivers, SJ (2001) "Killer whale predation on sperm whales: Observations and implications" Marine Mammal Science 17(3): 494-507 Abstract
  5. Piper, Ross (2007), Extraordinary Animals: An Encyclopedia of Curious and Unusual Animals, Greenwood Press.
  6. http://www.helium.com/items/564297-animal-facts-megamouth-shark
  7. http://www.flmnh.ufl.edu/fish/Sharks/Megamouth/Mega13.htm
  8. Over 680,000 officially reported at . In addition, studies have found that official reports understated USSR catches by at least 89,000 . Furthermore, other countries, such as Japan have been found to have understated catches
  9. Ratzel, Friedrich. The History of Mankind. (London: MacMillan, 1896). URL: www.inquirewithin.biz/history/american_pacific/oceania/melanesian-ornament.htm accessed 21 October 2009.
  10. Husson, A.M. & Holthuis, L.B. (1974). Physeter macrocephalus Linnaeus, 1758, the valid name for the sperm whale. Zoologische Mededelingen 48: 205-217.
  11. Holthuis, L. B. (1987). The scientific name of the sperm whale. Marine Mammal Science 3(1): 87-89.
  12. Schevill, W.E. (1986). The International Code of Zoological Nomenclature and a paradigm: the name Physeter catodon Linnaeus 1758. Marine Mammal Science 2(2): 153-157.
  13. Schevill, W.E. (1987). Reply to L. B. Holthuis "The scientific name of the sperm whale", Marine Mammal Science 3(1): 89-90.


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