Sperm whale

The sperm whale (Physeter macrocephalus) is the largest of the toothed whales. It is the only living member of genus Physeter, and one of three extant species in the sperm whale family, along with the pygmy sperm whale and dwarf sperm whale of the genus Kogia. Its name derives from a waxy liquid called spermaceti found in its enormous head. The sperm whale is also known as the cachalot.

Mature males average at 16 metres (52 ft) in length but can reach 20.5 metres (67 ft), with the head representing up to one-third of the animal's length. The sperm whale feeds primarily on giant and colossal squid. Plunging to 3 kilometres (9,800 ft) for prey, it is the deepest diving mammal. Its clicking vocalization, a form of echolocation and communication, can be as loud as 230 decibels underwater, making it the loudest sound produced by any animal. It has the largest brain of any animal on Earth, more than five times heavier than a human's.

The sperm whale is cosmopolitan, living across the oceans in small groups called pods. Units of females and their young live separately from sexually mature 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. Living up to 70 years, a mature sperm whale has few natural predators. Calves and weakened adults are taken by pods of orcas.

From the early 18th century through the late 20th the species was a prime target of whalers. The head of the whale contains a liquid wax called "spermaceti", which was used in lubricants, oil lamps, and candles. Ambergris, a waste product from its digestive system, is still used as a fixative in perfumes. Occasionally the sperm whale's great size allowed it to defend itself effectively against whalers. The species is now protected by law, and is currently listed as vulnerable by the IUCN.

Etymology

The name sperm whale is an apocopation of spermaceti whale. Spermaceti, originally mistaken for the whales' "sperm", is the semi-liquid, waxy substance found within the whale's head (see below). 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 or Basque 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. According to Encarta Dictionary, the word cachalot came to English "via French from Spanish or Portuguese cachalote, perhaps from Portuguese cachola, 'big head'". The term is retained in the Russian word for the animal, кашалот (kashalot), as well as in many other languages.

Description

Size

Average sizes

	Length	Weight
Bull	16 metres (52 ft)	41,000 kilograms (40 long tons; 45 short tons)
Cow	11 metres (36 ft)	14,000 kilograms (14 long tons; 15 short tons)
Newborn	4 metres (13 ft)	1,000 kilograms (0.98 long ton; 1.1 short tons)

The sperm whale is the largest toothed whale, with adult males measuring up to 20.5 metres (67 ft) long and weighing up to 57,000 kilograms (56 long tons; 63 short tons). 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 that 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 (26 m). A similar size is reported from a jawbone from the British Museum of Natural History. A 67-foot specimen also is reported from a Soviet whaling fleet near the Kurile Islands in summer of 1965. However, there is disagreement on the claims of adult males approaching or exceeding 80 feet (24 m) in length.

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 long tons; 56 short tons) in weight. Another view holds that exploitation by overwhaling had virtually no effect on the size of the bull sperm whales, and their size may have actually increased in current times on the basis of density dependent effects.

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 as females.

Appearance

The sperm whale's unique body is unlikely to be confused with any other species. The sperm whale's distinctive shape comes from its very large, block-shaped head, which can be one-quarter to one-third of the animal's length. The S-shaped 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. Proportionally, they are larger than that of any other cetacean, and are very flexible. The whale lifts its flukes high out of the water as it begins a feeding 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 and size.

In contrast to the smooth skin of most large whales, its back skin is usually wrinkly and has been likened to a prune by whale-watching enthusiasts. Albinos have also been reported.

Skeleton

The ribs are bound to the spine by flexible cartilage, which allows the ribcage to collapse rather than snap under high pressure.

As with other toothed whales, the skull of the sperm whale is asymmetrical so as to aid echolocation. Sound waves that strike the whale from different directions will not be channelled in the same way. Within the basin of the cranium, the openings of the bony narial tubes (from which the nasal passages spring) are skewed towards the left side of the skull.

Jaws and teeth

The sperm whales' lower jaw is very narrow and underslung. The sperm whale has 18 to 26 teeth on each side of its lower jaw which fit into sockets in the upper jaw. The teeth are cone-shaped and weigh up to 1 kilogram (2.2 lb) each. The teeth are functional, but 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. Mature males 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. Analyzing the teeth is the preferred method for determining a whale's age; a bit like rings in a tree, the teeth build distinct layers of cementum and dentine as they grow.

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 3 kilometres (1.9 mi) and remain submerged for 90 minutes. More typical dives are around 400 metres (1,300 ft) and 35 minutes in duration. At these great depths, sperm whales had sometimes become entangled in transoceanic telephone cables and drowned until improvements in laying and maintenance techniques were employed.

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 haemoglobin. The oxygenated blood can be directed towards only the brain and other essential organs 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 the same 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 diving again. 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 2 metres (6.6 ft) or more 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.

A sperm whale killed 100 miles south of Durban, South Africa after a 1 hour, 50-minute dive was found with two spiny dogfish, usually found at the sea floor, in its belly.

Brain and senses

The brain is the largest known of any modern or extinct animal, weighing on average about 7.8 kilograms (17 lb), more than five times heavier than a human's, and has a volume of about 8,000 cm³. Although larger brains generally correlate with higher intelligence, it is not the only factor. Elephants and dolphins also have larger brains than humans. 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'.

The sperm whale's cerebrum is the largest in all mammalia, both in absolute and relative terms. The olfactory system is reduced, suggesting that the sperm whale has a poor sense of taste and smell. By contrast, the auditory system is enlarged. The pyramidal tract is poorly developed, reflecting the reduction of its limbs.

Genetics

Sperm whales have 21 pairs of chromosomes ( 2n=42).

Nasal complex and spermaceti functions

	Sperm whales generate clicking sounds both to communicate and sense prey. A coda of rapid clicks A coda of rapid clicks A series of ordinary clicks A series of ordinary clicks A coda exchange
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Atop the whales skull is positioned a large complex of organs filled with a waxy liquid called spermaceti. The spermaceti organ is like a large barrel of spermaceti, and beneath it is the junk, which contains compartments of spermaceti separated by walls of cartilage. The spermaceti organ can contain as much as 1,900 litres of spermaceti. It is proportionately larger in males. The proportion of wax esters in the spermaceti organ increases with the age of the whale: 38–51% in calves, 58–87% in adult females, and 71–94% in adult males.

Early on it was proposed that the nasal complex was used as a battering ram (see below) or for buoyancy regulation (see below); however, researchers' current understanding suggest that the primary function of the spermaceti organ and the associated organs in the nose of the sperm whales are used as part of the world's most powerful natural sonar system.

Due to light absorption by water, most of the ocean is dark beyond a few hundred meters thus limiting visual range. As a result, sperm whales and the other toothed whales (suborder odontoceti) have evolved a system of echolocation as the main way to find food in the darkness of the ocean similar to that used by bats to find food in the darkness of the night sky. When echolocating, the sperm whale emits a directionally focused beam of broadband clicks. Clicks are generated by the forcing of air through a pair of phonic lips (also known as "monkey lips" or "museau de singe") at the front end of the nose, just below the blowhole. The sound then travels backwards along the length of the nose through the spermaceti organ. Most of the sound energy is then reflected off an air sac which sits against the skull and down into the Junk Bodies, where the sound is focused by the junk's lens-like structure. Some of the sound will reflect back into the spermaceti organ and back towards the front of the whale's nose where it will be reflected through the spermaceti organ a third time. This back and forth reflection which happens on the scale of a few milliseconds creates a multi-pulse click structure. This multi-pulse click structure actually allows researchers to measure the whale's spermaceti organ using only the sound of its clicks, and given the size of the spermaceti organ in relation to the size of the whale, biologists can measure the whales by recording their echolocation clicks. The lower jaw is the primary reception path for the echoes. A continuous fat-filled canal transmits received sounds to the inner ear.

The source of the air forced through the phonic lips is the right nasal passage. While the left nasal passage opens to the blow hole, the right nasal passage has evolved to supply air to the phonic lips. It is thought that the nostrils of the land-based ancestor of the sperm whale migrated through evolution to their current functions, the left nostril becoming the blowhole and the right nostril becoming the phonic lips.

The spermaceti organs may also help adjust the whale's buoyancy. It is hypothesized that before the whale dives, cold water enters the organ, and it is likely that the blood vessels constrict, reducing blood flow, and, hence, temperature. The wax therefore solidifies and reduces in volume. The increase in specific density generates a down force of about 392 newtons (88 lb_f) and allows the whale to dive with less effort. During the hunt, oxygen consumption, together with blood vessel dilation, produces heat and melts the spermaceti, increasing its buoyancy and enabling easy surfacing. However, more recent work have found many problems with this theory including the lack of anatomical structures for the actual heat exchange.

Herman Melville's fictional story Moby Dick suggests that the "case" containing the spermaceti serves as a battering ram for use in fights between males. However, there are almost no modern accounts of fights between male sperm whales. Apart from a few famous exceptions of the well-documented sinking of the ships Essex and Ann Alexander by attackers estimated to weigh only one-fifth as much as the ships, this hypothesis is not well supported in current scientific literature.

Vocalizations

Characteristics of sperm whale clicks

Click type	Apparent source level (dB re 1µPa [Rms])	Directionality	Centroid frequency (kHz)	Inter-click interval (s)	Duration of click (ms)	Duration of pulse (ms)	Range audible to sperm whale (km)	Inferred function
Usual	230	High	15	0.5–1.0	15–30	0.1	16	searching echolocation
Creak	205	High	15	0.005–0.1	0.1–5	0.1	6	homing echolocation
Coda	180	Low	5	0.1–0.5	35	0.5	~2	social communication
Slow	190	Low	0.5	5–8	30	5	60	communication by males

Ecology, behaviour, and life history

Distribution

The sperm whale is among the most cosmopolitan species. It prefers ice-free waters over 1,000 metres (3,300 ft) 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 Sea, but not the Black Sea, while its presence in the Red Sea 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 310–920 metres (1,020–3,020 ft). Coastal areas with significant sperm whale populations include the Azores and the Caribbean island of Dominica.

Reproduction

Sperm whales can live 70 years or more. They are a prime example of a species that has been K-selected, i.e., their reproductive strategy is associated with stable environmental conditions and comprises 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). Like other whales, the sperm whale's milk has a higher fat content than that of terrestrial mammals: about 36%, compared to 4% in cow milk. This gives it a consistency similar to cottage cheese, which prevents it from dissolving in the water before the calf can eat it. It has an energy content of roughly 3,840 kcal/kg (16,070 kJ/kg), compared to just 640 kcal/kg (2,700 kJ/kg) in cow milk. 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 behaviour

There is a huge variance in group sizes, but they are most commonly between 6 and 9 individuals large. Within a group, sperm whales show no significant tendency to associate with their genetic relatives.

Females stay in groups of about a dozen individuals and their young. Mature males leave their "natal unit" somewhere between 4 and 21 years of age. Mature males sometimes form loose "bachelor groups" with other males of similar age and size. As males grow older, they typically live solitary lives. Mature males have beached themselves together, suggesting a degree of cooperation which is not yet fully understood. The whales rarely if ever leave their group.

The most common non-human attacker of sperm whales is the orca, but pilot whales and the false killer whale also sometimes harass them. Orcas prey on target groups of females with young, usually making an effort 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, named after the flower, is also used by whales to support an injured unit member. Early whalers exploited this behaviour, attracting a whole unit by injuring one of its members. If the orca pod is extremely large, its members may sometimes be able to kill adult female sperm whales. Individual large mature male sperm whales have no non-human predators, and are believed to be too large, powerful and aggressive to be threatened by orcas. In addition, male sperm whales have been observed to attack and intimidate orca pods. A recent incident was filmed from a long-line trawler; an orca pod was systematically taking fish caught on the trawler's long lines (as the lines were being pulled into the ship) when a male sperm whale appeared to repeatedly charge the orca pod in attempt to drive them away; it was speculated by the film crew that the sperm whale was attempting access the same fish. Ironically the orcas also engaged in a similar tail first and tail slapping defensive position against the bull sperm whale as is used by female sperm whales against attacking orcas.

The sperm whales are not known for forging bonds with other species, but it was observed that a bottlenose dolphin with spinal deformity had been joined into the flock of sperm whales.

Feeding

Sperm whales usually dive between 300 to 800 metres (980 to 2,600 ft), and sometimes 1–2 kilometres (3,300–6,600 ft) 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 rays, 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 faecal matter. One study, carried out around the Galápagos, found that squid from the genera Histioteuthis (62%), Ancistrocheirus (16%), and Octopoteuthis (7%) weighing between 12 and 650 grams (0.026 and 1.4 lb) were the most commonly taken. Battles between sperm whales and colossal squid (which have been measured to weigh nearly 500 kilograms (1,100 lb)) have never been observed by humans; however white scars are believed to be caused by the large squid. One study published in 2010 collected evidence that suggests that female sperm whales may collaborate when hunting Humboldt squid. Tagging studies have shown that sperm whales hunt upside down at the bottom of their deep dives. It is suggested that the whales can see the squid silhouetted above them against the dim surface light.

An older study, examining whales captured by the New Zealand whaling fleet in the Cook Strait 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 Alaska 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. 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 100,000,000 short tons (91,000,000 t) — 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 the phonic lips, also known as the monkey lips, through which it blows air. This can create clicks that have a source level up to 176  decibels referenced to a distance of 1 metre (3.3 ft) – making it one of the loudest animals on Earth (compare to the pistol shrimp at 218 decibels), and 10–14 dB louder than a powerful rifle sounds in air at 1 metre (3.3 ft) 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.

It has been stated that sperm whales help to fertilise the surface of the ocean by consuming nutrients at depth and transporting those nutrients to the oceans' surface when they defecate. This fertilises the plants (phytoplankton) on the surface of the ocean and contributes to ocean productivity and the drawdown of atmospheric carbon.

Sleeping

For some time researchers have been aware that pods of sperm whales may sleep for short periods, assuming a vertical position with their heads just below or at the surface. A 2008 study published in Current Biology recorded evidence that whales may sleep with both sides of the brain. It appears that some whales may fall into a deep sleep for about 7 percent of the time, most often between 6 p.m. and midnight.

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 placed either in this family or in the family Kogiidae. In some taxonomic schemes the families Kogiidae and Physeteridae are combined as the superfamily Physeteroidea (see the separate entry on the 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 used, 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, plus all of that ancestor's descendants. These fossils include Ferecetotherium, Idiorophus, Diaphorocetus, Aulophyseter, Orycterocetus, Scaldicetus, Placoziphius, Zygophyseter and Acrophyseter. Ferecetotherium, found in Azerbaijan and dated to the late Oligocene (about 28 to 23 million years ago), 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, 23 to 5 million years ago. Diaphorocetus, from Argentina, 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 States, and Scaldicetus, found in Europe and Japan. Orycterocetus fossils have also been found in the North Atlantic Ocean and the Mediterranean Sea, in addition to the west coast of the United States. Placoziphius, found in Europe, and Acrophyseter, from Peru, are dated to the late Miocene.

Cetacea     Toothed whales Physeteroidea Other Physeteroidea† Kogiidae Pygmy sperm whale Dwarf sperm whale Physeteridae Other Physeteridae† Sperm whale Ganges River dolphin Other river dolphins Oceanic dolphins Porpoises Arctic whales Beaked whales Baleen whales

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 Italy, 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 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 23 million years ago. 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 reaffirmed 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 8 million years ago.

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.

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 Strait 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 Banks, 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-19th century. 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 century 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, since sperm whales (especially bulls) will readily fight to defend themselves against attack, unlike most baleen whales. When dealing with a threat, sperm whales will use their huge head effectively as a battering ram. Arguably the most famous sperm whale counterattack occurred on November 20, 1820, when a whale claimed to be about 25.9 metres (85 ft) long rammed and sank the Nantucket whaleship Essex. Only 8 out of 21 sailors survived to be rescued by other ships. This instance is popularly believed to have inspired Herman Melville's famous book " Moby-Dick".

The sperm whale's ivory-like teeth were often sought by 18th and 19th-century whalers, who used them to produce inked carvings known as scrimshaw. Thirty teeth of the sperm whale can be used for ivory. Each of these teeth (up to 8 inches long and 3 inches across), are hollow for the first half of their length. Like walrus ivory, sperm whale ivory has two distinct layers. However, sperm whale ivory contains a much thicker inner layer. Though a widely practiced art in the 19th century, scrimshaw using genuine sperm whale ivory declined substantially after the retirement of the whaling fleets in the 1880s. Currently the Endangered Species Act and CITES, the Convention on International Trade in Endangered Species of Wild Fauna and Flora, prevents the sales of or trade in sperm whale ivory harvested after 1973 or in scrimshaw crafted from it.

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. This was especially true during World War II when spermaceti, the fine waxy oil produced by sperm whales, was in high demand for lubricating the American war machine. In both the 1941-2 and 1942-3 seasons, the Norwegian expedition took over 3,000 sperm whales off the coast of Peru alone. After the war whaling continued unabated to obtain oil for cosmetics and high-performance machinery, such as automobile transmissions.

The hunting led to the near extinction of large whales including sperm whales until bans on whale oil use were instituted in 1972. The International Whaling Commission gave the species full protection in 1985 but hunting by Japan in the northern Pacific Ocean 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 by 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.

Sperm whales increase the levels of primary production and carbon export by depositing iron rich faeces into surface waters of the Southern Ocean. The iron rich faeces cause phytoplankton to grow and take up more carbon from the atmosphere. When the phytoplankton dies, it sinks to the deep ocean and takes the atmospheric carbon with it. By reducing the abundance of sperm whales in the Southern Ocean, whaling has resulted in an extra 2 million tonnes of carbon remaining in the atmosphere each year.

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 Pacific, 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 Alaska 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 species is listed as endangered on the United States Endangered Species Act.

The species is listed on Appendix I and Appendix II of the Convention on the Conservation of Migratory Species of Wild Animals (CMS). It is listed on Appendix I as this species has been categorized as being in danger of extinction throughout all or a significant proportion of their range and CMS Parties strive towards strictly protecting these animals, conserving or restoring the places where they live, mitigating obstacles to migration and controlling other factors that might endanger them. It is listed on Appendix II as it has an unfavourable conservation status or would benefit significantly from international co-operation organised by tailored agreements. It is also covered by the Agreement on the Conservation of Cetaceans in the Black Sea, Mediterranean Sea and Contiguous Atlantic Area ( ACCOBAMS) and Memorandum of Understanding for the Conservation of Cetaceans and Their Habitats in the Pacific Islands Region ( Pacific Cetaceans MOU).

Cultural importance

Rope-mounted teeth are important cultural objects throughout the Pacific. In New Zealand, the Māori know them as "rei puta"; such whale tooth pendants were rare objects because sperm whales were not actively hunted in traditional Māori society. Whale ivory and bone were taken from beached whales. In Fiji 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 Tonga, 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.

Herman Melville's novel Moby-Dick is based on a true story about a sperm whale that attacked and sank the whaleship Essex. 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.

The sperm whale was designated as the Connecticut state animal by the CT General Assembly in 1975. It was selected because of its specific contribution to the state's history and because of its present-day plight as an endangered species.

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 Kaikoura on New Zealand's South Island, Andenes and Tromsø in Arctic Norway; as well as the Azores, where the continental shelf is so narrow that whales can be observed from the shore, and Dominica where a long-term scientific research program, The Dominica Sperm Whale Project, has been in operation since 2005.