HMW 4 - Family text: Physeteridae (Sperm whale)

Texto de familia: 

Class Mammalia

Order Cetacea

Suborder Odontoceti

Superfamily Physeteroidea

Family PHYSETERIDAE (SPERM WHALE)

 

  • Largest of the odontocetes, with a disproportionately large, box-like head containing the spermaceti organ complex; most sexually dimorphic cetacean in body length and weight.
  • 1100–1900 cm.
  • All oceans.
  • Global; all deep, ice-free ocean waters.
  • 1 genus, 1 species, 1 taxon.
  • 1 species Vulnerable; none Extinct since 1600.

 

Systematics

After the Mysticeti (baleen whales) and Odontoceti (toothed whales) separated about 35 million years ago, species with features comparable to the modern Sperm Whale (Physeter macrocephalus) appeared and evolved as members of the family Physeteridae in the late Oligocene, about 25 million years ago. During the Miocene and Pliocene, a variety of 20 or so genera of physterids roamed the world’s oceans. Physeteridae is customarily divided into two subfamilies: Hoplocetinae (extinct and probably paraphyletic) with functional enamel-capped teeth in both the upper and lower jaws and Physeterinae (probably monophyletic) with rudimentary upper dentition. Deriving its scientific name from the Greek for “blower” and “big head,” the modern Sperm Whale is the only extant species.

Sperm Whales are related to members of the family Kogiidae, which includes two species, the Pygmy Sperm Whale (Kogia breviceps) and the Dwarf Sperm Whale (Kogia sima). Karyotype, cranial morphology, and the presence of a spermaceti organ, among other characters, clearly indicate that the two families comprise a monophyletic group. The kogiids are thought to have separated from the lineage that led to the Sperm Whale as long ago as the Oligocene, more than 23 million years ago, making the Sperm Whale the most phylogenetically distinct of all odontocete species. The Physeteridae and Kogiidae are often grouped together as the superfamily Physeteroidea. Physeteroids are usually considered to be a basal lineage of the odontocetes.

In 1758, Linneaus described four species in the genus Physeter. By the 19th century, these nominal species were deemed to be conspecific. Since then, there has been much debate as to which of the two Linnaean names—macrocephalus or catodon—is the Sperm Whale’s correct species designation. Due to the Principle of the First Reviser, as prescribed by the International Code of Zoological Nomenclature, the name P. macrocephalus takes precedence as the correct scientific name.

 

Morphological Aspects

Morphologically, the Sperm Whale is like no other cetacean. Its unusual form evolved to suit a life spent exploiting the world’s deep ocean waters in search of prey. A key to the species’ remarkable biology can found in the disproportionately large, box-like head, which houses the amazing spermaceti organ complex. The development of the spermaceti organ complex, which seems to be the world’s most powerful natural sonar, has been suggested to explain the evolution of the other extreme characteristics of the species’ biology and its ecological prominence. Possession of the valuable spermaceti oil also led to the targeting of Sperm Whales in two massive waves of commercial whaling.

The Sperm Whale’s head holds the largest brain of any animal on earth (although as a proportion of body weight, the Sperm Whale brain is not exceptional) and a gigantic nose, which is the largest and most highly modified of any in the animal kingdom. Constituting roughly 31% (in females) and 36% (in males) of the animal’s total body length, the protuberant nose contains a complex system of soft structures cradled in a highly modified and asymmetric skull. The spermaceti organ, which whalers called the “case,” dominates the massive nasal complex. The case is a long, ellipsoidal-shaped structure consisting of white, spongy tissue soaked in spermaceti oil, enclosed on the top and sides by a sheath of longitudinal tendons and bounded front and back by air sacs. The “junk,” also saturated with spermaceti oil, is located below the case and above the rostrum of the skull. The junk is comprised of whitish tissue divided into segments by a series of transverse septa of slightly denser connective tissue. Spermaceti oil is a liquid wax, comprised of a unique mixture of wax esters and triglycerides; it is fluid at the body temperature inside a living whale but solidifies into a whitish paraffin-like wax when exposed to air and cooled. The word “spermaceti” means sperm of the whale, a reference by whalers to its similarity in appearance to semen, and hence the species’ common name. Early theories suggested that the spermaceti organ’s purpose was for buoyancy control or as a battering ram used in encounters between males. Current research indicates that the spermaceti organ and related structures function primarily in generating extremely powerful, highly directional sonar for detecting prey. The large head is also important in fights among adult males.

Sperm Whales are larger than any of the other odontoctes and, among cetaceans, are exceeded in size only by the largest baleen whales. They are also the most sexually dimorphic of all cetaceans in body length and weight. Adult females are about 11 m in length and 15,000 kg in weight (maximum of 12·5 m and 24,000 kg) while males are physically mature at about 16 m and 45,000 kg (maximum of 19·2 m and above 70,000 kg). Sperm Whales in the Gulf of Mexico are 1·5–2 m smaller than conspecifics measured in other areas.

Sperm Whale coloration is primarily dark gray, but the skin can appear dark brown when viewed in bright sunlight. White blotches are usually found on the belly and flanks. The upper lips, lower jaw (except for the ventral side), and interior of the mouth are bright white. A single blowhole is situated asymmetrically on the left side at the front end of the rostrum. The bushy blow is distinctly canted forward and to the left of the body. The nasal passages are highly modified; the left nasal passage leads to the lungs while the right nasal passage does not function in ventilation but serves as an air reservoir used for generating sound. The eyes are small, set back far on the head, and aimed laterally so that there is a blind area directly ahead of the animal. The ears are highly modified with structures specialized for hearing high-frequency sounds used for echolocation. Hearing occurs by vibrations transmitted to the middle ear via acoustic fats in the lower jaw.

There are two to ten short, deep grooves on the throat, more obvious in the young and less so in adults. The skin on the head and flippers is smooth and takes on a dimpled appearance beyond the eye. The flippers are flat, paddle-shaped forelimbs that serve as rudders. Sperm Whales have a low dorsal fin with a rounded profile that is followed by a series of crenulations or “knuckles.” There may be a whitish callus on top of the dorsal fin. The callus is a secondary sexual characteristic that is often visible on the dorsal fins of adult females, although not all mature females possess calluses and some immature males do. There is a prominent ventral keel on the caudal peduncle between the anus and the flukes. The flukes are the largest in proportion to body size of any whale. They are similar in shape to an isosceles triangle, with a relatively straight trailing edge.

As physeterids evolved, the rostrum widened and the mandible narrowed, making the upper jaw wider than the lower jaw. This gives the narrow and under slung lower jaw a considerably undersized appearance compared with the upper jaw. Unlike most other mammals, that have sets of deciduous and permanent teeth, all odontocetes have a single, or monophydont, set of teeth. Sperm Whales have 20–26 pairs of large homodont conical teeth in the lower jaw; only rudimentary teeth (if any) appear in the upper jaw. The lower jaw can be opened nearly perpendicular to the body. When the mouth is closed, the tips of the mandibular teeth fit into shallow depressions in the palate.

Sperm Whales are believed to live at least 60 years, with females potentially living into their eighties and perhaps longer. Annual mortality rates of Sperm Whales are thought to vary by age, and adult mortality is likely low, although reliable data are not available. Estimated generation length (the average age of mature females) is estimated at 31·9 years.

 

Habitat

The Sperm Whale has an extremely large geographic distribution and has evolved to thrive in the deeper regions of the oceans. They can be found from the edges of polar pack ice to the equator in both the Northern and Southern hemispheres and in deep semi-enclosed seas. Among marine mammals, only Killer Whales (Orcinus orca) have a greater geographical distribution. Although Sperm Whales are widespread, there are some areas, called “grounds” by early whalers, where they were more abundant. These grounds were usually, but not always, correlated with generally higher primary and secondary productivity. Over smaller scales, however, correlation with productivity is less obvious. This is not particularly surprising given the temporal and spatial lag as primary productivity progresses up the food chain and down the water column. Bathymetric and oceanographic features that may concentrate prey, such as steep continental shelf edges, frontal boundaries, and eddies, seem to be related to the distribution of Sperm Whales.

For most of their adult lives, male and female Sperm Whales have the largest geographical sexual segregation of any animal on the planet. Females and their dependent young can be found almost anywhere in tropical, subtropical, and temperate waters with sea surface temperatures warmer than 15°C and depths greater than 1000 m. This thermal boundary corresponds roughly to waters between the 40° parallel in the Southern Hemisphere and the 50° parallel in the Northern Hemisphere; some females may occur as far north as 60° in the North Pacific. There is a general shift to higher latitudes during the summer. After they leave their natal group, males have an even greater geographical distribution than females and occasionally occur in waters as shallow as 200 m near the edge of the continental shelf. Males may be found around the globe, in all seasons of the year, in ice-free deep waters. The largest males use the highest latitude feeding grounds, which may be near the edge of the pack ice.

 

General Habits

Sperm Whales are intensely social animals. Females are always in the company of other individuals, each whale relying on help from the others to raise young, find food, and defend against predators. The most significant relationships are found in the social unit, typically consisting of about eleven adult females and their young. Females are thought to spend their entire lives in their natal unit, living with close female relatives. Social units may contain two or more matrilines, and individuals sometimes switch between social units. In the Pacific Ocean, units may join together to form temporary groups (typically 20–40 individuals) for periods of hours, days, or months, apparently with other units from the same vocal clan (individuals sharing the same coda types or “dialect”). Clans may contain thousands of females, have distinctive culturally determined vocalizations, and are sympatric. When food is abundant, females and their young may form large concentrations of hundreds to thousands of individuals spanning many kilometers. In the North Atlantic Ocean, social units rarely group with other units, vocal clans are geographically distinct, and there is some indication that strict matrilineality is a more common feature of Sperm Whale social structure than in the Pacific Ocean. The contrasting social patterns between these ocean basins may be due to various features of the environment or the whales themselves, for example, differences in oceanic conditions, predation, whaling history, and local whale culture.

Social groups of Sperm Whales are likened to “bond groups” in elephants. Like elephants, Sperm Whales engage in allomaternal (shared) care, where females collectively care for offspring in their social group. The diving ability of newborn Sperm Whale is relatively poor, and neonates show a strong “following response” that wanes rapidly with age. Shared care provides greater protection for young Sperm Whales while allowing mothers the freedom to forage. It also indicates a very high level of cooperation among adult females that may, or may not, be related. Shared care can include babysitting, when foraging females sequentially accompany young at the surface, and communal suckling. Field observations, along with data from whaling operations and mass strandings, show that lactating females may considerably outnumber suckling offspring in social groups. Communal suckling, as well as a long lactation and extended weaning (particularly in older females), enhances the chance of survival of offspring.

Much less is known about male sociality of Sperm Whales. While mature males do not appear to engage in the long-term relationships and social units that are characteristic of females and immature Sperm Whales, there is likely much more to be discovered about male association patterns. Pubertal males typically leave their natal unit sometime between four and 21 years of age. Loosely coordinated “bachelor groups” tend to be comprised of 20–40 subadult males of a similar size and age. As male Sperm Whales mature, they tend to travel with fewer and fewer individuals; the largest males are frequently solitary.

The strength of the social bonds among Sperm Whales is evident when individuals are threatened. Other than humans, Killer Whales appear to be the Sperm Whale’s primary predator. During the few occasions when attacks on groups of female Sperm Whales have been witnessed, individuals did not attempt to flee, dive to deeper water, or strike back. Instead, individuals remained clustered tightly at the water’s surface and confronted the Killer Whales as a group. In one attack, female Sperm Whales were observed risking personal injury to assist another unit member and return it to the formation. In another aborted attack, long-distance, most likely acoustic, communication of alarm was observed and responded to by several other whales. When Sperm Whales are in larger groups (30–50 individuals), observers describe individuals positioned in a tight flotilla with their heads facing their attackers. In the rosette or “marguerite” formation, whales gather in a tightly grouped circle with their heads together and their tails pointing outward. If present, young offspring and injured whales are positioned near the center for the greatest protection. This formation tends to be observed when a smaller number of individuals are threatened (about 10–15 animals).

Whalers, particularly in the era of sailing vessels exploited the strength of the social bonds among Sperm Whales by purposefully harpooning a young whale or a female, and then waiting for other individuals to arrive and “stand by” the injured individual. This strategy provided the whalers lethal access to the other members of the group.

Sperm Whales are one of the species of social cetaceans to strand (purposefully come ashore) in groups. A mass stranding may comprise a group of females with young, a group of subadult males, and sometimes multiple adult males. Social bonds are apparently so strong among members of these groups that when a single individual comes ashore others in the group are likely to follow. Observations of mass strandings involving male Sperm Whales suggest that social cohesion and facilitation are important factors in the lives of subadult and adult males, despite their apparently looser social organization.

Sperm Whales spend about 75% of their day foraging. During the remainder of the day, a group may be still and tightly clustered at the surface or just beneath it, apparently resting, or they may spend time socializing. While socializing, individuals are active with a great deal of vocal, tactile, and aerial behavior. Socializing tends to occur before and after foraging bouts. In contrast, adult male Sperm Whales are generally solitary. They also may be still at the surface for long periods of time. When adult males join groups of females and young, they may socialize with other whales.

 

Communication

Sperm Whales have been credited with creating the loudest sounds ever made in nature and with having the planet’s most powerful natural sonar system. Their vocalizations consist almost entirely of clicks, which are used for communication, orientation, and finding food by echolocation. The spermaceti organ complex—the junk, nasal passages, air sacs, and a pair of valvular lips called the “museau de singe” (monkey’s muzzle)—produces the clicks. Together, these structures form, focus, and broadcast Sperm Whale clicks into the ocean. While other odontocetes use echolocation clicks, Sperm Whale clicks are more powerful and contain significantly more low-frequency energy. Their click energy is directional and ranges between 5 kHz and 25 kHz, with source levels up to 236 dB re 1 μPa-m (loudness expressed in “in water” decibels), by far the highest sound pressure level produced by any animal.

Researchers have identified four distinct types of Sperm Whale clicks. “Usual” clicks are the most common click pattern. They consist of evenly spaced clicks strung together in a long train and are used as echolocation to help individuals locate prey. A group of foraging females produces a cacophony of clicks. “Creaks” are closely spaced clicks that resemble the sound of a hinge opening. Creak click rates usually accelerate when emitted at depth and are thought to provide fast biosonar updates on the location of prey. In contrast, surface creaks are shorter, have constant intervals, and may help Sperm Whales locate objects.

The most unusual patterns of clicks of Sperm Whales are called “codas.” Ranging from three to 20 clicks, codas are heard primarily when groups of female Sperm Whales are socializing. They are heard either singly or in overlapping sequences when multiple whales vocalize simultaneously. Structurally, codas are different than usual clicks, and they generally have less directionality and power. Based on the number of clicks and the pattern of interclick intervals, codas have been classified into various types. During vocal bouts, the types of codas are not used randomly. Some codas may be common while others are rare, some may tend to initiate a vocal bout, and some follow other coda types. There is also regional and geographical variation in coda types. Individual Sperm Whales sharing the same coda types or “dialect” are considered a vocal clan. Clans may have sympatric or allopatric distributions. Dialects have been found to be temporally stable within social units for at least six years, and they are thought to be culturally inherited from other members of the social unit. Mothers and offspring may have distinct repertoires within social units, and there may also be individually distinctive characteristics of codas. Overlapping and matching codas are thought to function to reinforce social bonds among individuals. Large males rarely emit codas.

Slow clicks, or “clangs,” are tremendously loud. These ringing clicks are repeated every 5–8 seconds and are heard from large males, particularly on the breeding grounds. The lower directionality and frequency of these clicks may contribute to their tremendous reverberations, which Sperm Whales may be able to hear up to 60 km away (compared to 16 km for usual clicks and 6 km for creaks). The function of slow clicks is unknown, but they may serve as some type of inter- or intrasexual signal.

 

Food and Feeding

Sperm Whales are dominant predators of the mesopelagic ocean. They are great generalists, preying on many of the larger meso- and bathypelagic species of the deep ocean. Sperm Whales are known to consume more than 25 different species of cephalopods, from small chiroteuthids (less than 100 g) to large giant squid, Architeuthisspp. (up to 400 kg). Squid consumed by Sperm Whales differ geographically, in nutritive value, and in ease of capture. Some of the most common taxa eaten include species from the families Histioteuthidae, Ommastrephidae, Octopoteuthidae, Onychoteuthidae, and Architeuthidae. Sperm Whales are also known to eat more than 60 species of medium to large sized bottom-dwelling fish and the occasional assortment of crustaceans, jellies, and other marine life, either intentionally or incidentally while consuming other prey. Females tend to eat smaller prey than males, but they also feed on Humboldt squid (Dosidicus gigas), robust clubhook squid (Onykia robusta), and giant squid. Male Sperm Whales feed on larger individuals in the same taxa than females and also consume species found at higher latitudes, such as the colossal squid (Mesonychoteuthis hamiltoni), a deep-water, circumpolar, Antarctic species. They are also more likely to prey on fish, sharks, and rays than females.

Abundance of Sperm Whales and their wide geographical distribution make them formidable mesopelagic competitors, and they comprise the dominant biomass among the guild of mammalian teuthivores (squid-eaters) in most oceans. It is estimated that Sperm Whales take about 75 million metric tons of food per year from the ocean (roughly the same amount as all human marine fisheries combined). Female Sperm Whales eat approximately 750 squid per day, consuming on average about 37 squid per foraging dive. Because they consume larger prey, male Sperm Whales are estimated to eat 350 squid per day. Sperm Whale foraging typically consists of dives to depths of 300 m to 1200 m lasting about 30–45 minutes and occasionally to depths of 1000–2000 m lasting more than one hour. These dives often have a U-shaped profile, and both the descent and ascent can be nearly vertical in orientation. During the initial descent, Sperm Whales travel 30–100 m per minute, slowing down as they reach maximum dive depth. After stalking their prey at maximum depths, bursts of speed accompanied by creak vocalizations are reportedly associated with prey capture. Between dives, Sperm Whales rest at the surface at 7–10-minute intervals. Groups of females forage together, diving asynchronously and spanning 1 km or more, while mature males are more likely to dive to the bottom and appear to forage independently.

Because Sperm Whales feed at great depths, there is little direct knowledge of how they capture prey. Evidence suggests that Sperm Whales generate a series of regularly spaced clicks that act as short-range sonar (echolocation) used to locate prey and fast-paced creaks to hone in at close range. The blue-shifted eye pigments present in Sperm Whales and other deep-diving animals may indicate that the whales use visual cues to locate certain prey types. Other theories suggest that the large white mouth of the Sperm Whale may attract prey. Because the Sperm Whale’s maxillary teeth are vestigial and the mandibular teeth do not emerge until puberty, researchers have concluded that these teeth are likely not necessary for feeding. Rather, Sperm Whales are thought to draw prey into their mouths by suction feeding, created by rapid retraction of the hyoid apparatus.

Sperm Whales occasionally produce a rare substance known as ambergris, which is a lumpy masses of waxy, unsaturated, high molecular-weight alcohols and fecal matter that solidifies around indigestible beaks of cephalopods that have passed into a whale’s large intestine. Pieces of ambergris found in Sperm Whales range in size from 15 g to 455 kg. Ambergris floats and is sometimes found on beaches; during the days of whaling, it was one of the most valuable products of the industry. Ambergris was found in about 1% of Sperm Whales killed by whalers.

 

Breeding

Sperm Whales mate in a prolonged breeding season that lasts from late winter through early summer. Sperm Whales in the Northern Hemisphere typically breed from January to August, with activity intensifying between March and June. In the Southern Hemisphere, breeding extends from July to March, peaking between September and December. The mating season of whales residing in tropical waters near the equator is unknown. There are a number of descriptions of what is presumably copulation—short belly-to-belly pairings either vertically or horizontally that typically last less than 30 seconds—but intromission was not observed in any of these cases, so Sperm Whale mating largely remains a mystery. There is some evidence of synchrony of estrus within groups of females.

Mature male Sperm Whales breed on an unknown schedule. Large males roam among groups of females, spending only a few minutes or hours with each group before moving on, presumably searching for receptive females. Males appear to travel independently on the breeding grounds and generally avoid one another, although more than one male is sometimes observed within the same group of females. Fights between males are rarely observed, but large males are often heavily scared from the teeth of other males and have broken teeth and jaws attributed to intraspecific fighting.

Like many large mammals, Sperm Whales grow slowly, mature late, and have low birth rates and high survival rates as adults. Females reach sexual maturity at 7–13 years (8·3–9·2 m in length) and typically give birth every 4–6 years to a single offspring. Gestation lasts for 14–16 months. Newborn calves typically weigh 1000 kg and measure 4 m in length. Solid food is taken for the first time before the age of one year and weaning begins at about two years, although suckling can continue for many years. Lactose has been recorded in the stomachs of females up to 7·5 years and males up to 13 years. Female growth ceases at physical maturity when individuals are 25–45 years old and 10·4–11 m in length. The reproductive rate of females declines significantly with age; very few give birth after age 40. The duration of lactation may increase with female age, and although data for a post-reproductive period (or menopause) are inconclusive, it is possible that older females live for many years past the birth of their last offspring.

Male Sperm Whales reach sexual maturity at 18–21 years of age (11–12 m in length), coincident with a spurt of accelerated growth, the formation of bachelor schools, and their movement into higher latitudes. While a male as small as 10 m long can produce spermatozoa, there is a marked rise in the density of spermatozoa with body size, particularly in males more than 14 m long. Male Sperm Whales continue to grow until reaching physical maturity at 35–60 years and 16–18 m long. Males do not appear to engage in breeding until at least their late twenties, although the fertility of the larger males is considerably greater than smaller males.

 

Movements, Home range and Social organization

When observed on the ocean’s surface, Sperm Whales move at rates of 4–7 km/h. While relatively unremarkable at the surface, Sperm Whales are among the deepest divers on the planet. They spend nearly 75% of their lives engaging in long, deep foraging dives. While most foraging dives are 300–1200 m in depth, dives of large males may exceed one hour, with maximum-recorded dive duration of 138 minutes and extreme dive depths estimated to be 2000–3000 m. Although Sperm Whales can swim shortly after birth, young whales take shorter and shallower dives than adults, descending only a few hundred meters before surfacing. Adult females in groups stagger their foraging dives, leaving adults scattered at the surface to accompany and protect young in the social group.

Mature male Sperm Whales are frequently found at high latitudes. They make periodic migrations on an unknown schedule from these cooler, more productive foraging waters to warmer breeding grounds to mate. While little is known about these movements, some mature males may cover thousands of kilometers, traversing from one hemisphere to another, and it is not unreasonable to expect some interbasin movements around the southern tips of the continents. The extent to which males return to their natal grounds to mate is unknown. Movements of female Sperm Whales do not appear to follow any migration routes. Their movements appear best described as nomadic responses to changes in food abundance. Based on research in the eastern Pacific Ocean, the home ranges of females are thought to span about 1500 km in any direction. Although females are known to make occasional long-distance movements within an ocean basin, there is unlikely to be much movement between basins.

Compared with male Sperm Whales, the more limited distribution of females suggests that genetic differentiation would evolve. Recent studies tend to find low levels of genetic differentiation among ocean basins and little evidence of subdivision within ocean basins, with the exception of the California Current, possibly Hawaii, and some distinct basins such as the Gulf of Mexico and the Mediterranean. Sperm Whales in the Gulf of Mexico and the Mediterranean also have different dominant acoustic codas, consistent with the genetic evidence that these areas support resident populations. In the Pacific Ocean, vocal clans are sympatric but genetically differentiated, suggesting that culture is likely to be important in structuring populations of Sperm Whales over large spatial scales.

 

Relationship with Humans

Few species, terrestrial or marine, have had a more far-reaching and transformative effect on human society, economies, and exploration than Sperm Whales. The human relationship with Sperm Whales can be traced back thousands of years: Aristotle’s Historia Animalium, written over 2300 years ago, described Sperm Whales from observations in the Aegean Sea and the North Atlantic and references to Sperm Whales can be found in the medieval Icelandic text, Speculum Regale, written around 1250 ad. The first measurements and scientific illustrations of Sperm Whales date from the late 16th century from an individual that stranded on the coast of The Netherlands. Teeth of the Sperm Whale figure prominently in Polynesian culture, both past and present. Necklaces with whale-tooth pendants are important spiritual and cultural objects throughout Polynesia, including Fiji, Hawaii, and New Zealand. The Polynesians did not hunt Sperm Whales; teeth were obtained from stranded individuals and thus were rare. The only known aboriginal fishery for Sperm Whales is on the island of Lembata in Indonesia where records report that a whaling tradition may date back to at least the 1640s.

Sperm Whales were the targets of two massive waves of commercial whaling: “open boat” (early 1700s until 1925) and “modern” whaling (1856, ending in 1986). The first commercial operations directed at Sperm Whales began off the North American coast in New England in the early 18th century when Yankee (colloquial for New Englanders at the time) whalers in open boats pursued slow swimming species such as right whales (Eubalaena) and Humpback Whales (Megaptera novaeangliae). Yankee whalers perfected on-board furnaces, known as “tryworks,” which allowed Sperm Whales to be processed entirely at sea and refining of oil from the spermaceti organ from which the most desirable candles—the brightest and cleanest-burning candles ever made—were manufactured. Driven by an explosion of urban growth in the mid-18th century, demand for lighting soared, and refined oil from Sperm Whales’ spermaceti organ provided a favored source of illumination for much of the Western World, Africa, and the Caribbean. Whaling became one of the new American nation’s first and most lucrative industries, and the New England cities of New Bedford and Nantucket were among the nation’s wealthiest. Over the next 150 years, the open-boat hunt for Sperm Whales provided lubrication for the Industrial Revolution.

American whalers dominated the whaling industry in the early years, but other countries, including England and France, also set sail after Sperm Whales, and the hunt expanded from the Atlantic to the Pacific and Indian oceans. Sailing vessels ranged from smaller brigs and schooners to the larger square-rigged and longer-ranging “barks” (three or more masts sailing vessel) and ships. Trips lasted months or years (1000 days away from the homeport was roughly the average for the larger barks and ships in the mid-19th century). When a Sperm Whale was sighted, the crew lowered open boats propelled by oars or sail, caught the whales with hand-thrown harpoons, killed them with lances, and then rowed the whales back to the sailing vessel where they were processed. The work was grueling, filthy, crowded, and dangerous. A typical whaling ship, 30–50 m in length, could carry five whaleboats and 36 crew. Most of the profits (60–70%) went to the owners while a strict hierarchy allotted wages of seamen. The captain might earn an eighth of the net proceeds, and ordinary sailors might earn less than US$ 100 for 1000 days at sea for a typical crewmember. Whaling was one of the few industries of the era in which it was possible (although not frequent) for a man to work his way up from seaman to captain.

Socially, the impacts of whaling on human society were profound and extended far beyond the communities of the Atlantic seaports from which most of the ships originated. Pursuit of Sperm Whales initiated a wave of global exploration, and the introduction of alcohol, muskets, commercial trade, and new diseases in the wake of whalers transformed native populations around the world. As whaling spread to the Pacific Ocean, San Francisco (California, USA) but more so Honolulu and Lahaina (Hawaii) became major ports annually hosting hundreds of boats and all manner of associated trade and the consequences for native communities.

Open-boat whaling peaked in the 1840s, with the world whaling fleet estimated at about 1000 vessels. While most of the fleet was US registered, crews hailed from around the world. At the peak, American whalers killed an estimated 5000 Sperm Whales per year. In the 72 years between 1804 and 1876, the total number of whales taken by the American fishery was estimated at 225,521, and the global catch was estimated at 271,000 throughout the 19th century. A female might yield 15–30 barrels of oil while adult males might average 70–90 barrels, with very large males yielding 100 barrels, or more. Large males might yield 10–30 barrels of pure spermaceti oil.

In addition to spermaceti oil, ambergris was even more valuable. Known for over a thousand years, rare pieces of ambergris were picked up on beaches or found floating at sea—their origin a mystery. Ambergris was highly valued in Muslim culture and also known in China and India as incense, an aphrodisiac, spice for food, seasoning in wine, an ingredient in candles and cosmetics, and a medication for a variety of ailments. A Flemish botanist in 1574 was the first to observe squid beaks in ambergris, and early American whalers discovered that Sperm Whales produced ambergris. Ambrein and its degraded products, particularly naphthofuran, are the substances that give ambergris its peculiar properties and odor. During the 18th and 19th centuries, ambergris became prized mainly as a fixative and intensifier for the volatile fragrances in perfumes and was also used in candles and hair products.

The dramas and dangers of the open-boat hunt for Sperm Whales were depicted in literature, paintings, and crafts of the time. Published in 1851, Herman Melville’s Moby Dick was based on recorded events of the southern Sperm Whale fishery and the author’s own experience as a harpooner. Scrimshaw—carving and engraving on the hard byproducts of the whale fishery including mainly Sperm Whale teeth, but also bone—arose as an occupational handicraft among British and American whalers. The earliest known engraved pictorial scrimshaw is on “pan bone” (lower jaw bone) from around the 1760s and the earliest known scrimshaw on Sperm Whale teeth dates from about 1817–1824 in the Pacific Ocean when whalers had idle time between captures of whales. Pictorial scrimshaw involved smoothing the teeth with a knife or file, polishing with sharkskin or sandpaper, optionally stippling a pattern with a sail maker’s needle, and then engraving pictures or sculptural carvings on the teeth with a knife or stylus (burin). The usual pigment was lampblack (carbon ash mixed with oil) or store-bought China ink (“India ink”). Depictions included whaling scenes, portraiture, landscapes, naval battles, and family scenes. In addition to decorative pieces, practical objects were also made out of Sperm Whale “ivory” for use on board ship and as gifts for the family back home, such as kitchen gadgets, sewing implements, and swifts (yarn winders).

The open-boat hunt for Sperm Whales declined rapidly into the late 19th and early 20th centuries, both in the number of voyages and landings, and hunting contracted back into the Atlantic Ocean. The decline was attributed to several factors: declining encounter rates on whaling grounds in the Pacific Ocean, capital and labor shifting to more lucrative pursuits onshore, and increasing competition from other sources of illumination and ultimately petroleum discovered in Pennsylvania in 1859. The petroleum revolution quickly replaced many applications of Sperm Whale oil. The American Civil War (1861–1865) further reduced not only the labor force but also destroyed a considerable portion of the whaling fleet. Additional ships were lost to ice in Alaska in 1871. Several small subsistence fisheries for Sperm Whales developed out of the harpoon fishery, some of which survived until the late 20th century, for example in the Azores, Madeira, Saint Vincent in the Lesser Antilles, and Lembata in Indonesia (which may have been a continuation of an earlier aboriginal fishery).

As the traditional, sail-powered, hand-held harpoon fishery waned, a new type of whaling was beginning in Norway. Modern-era whaling began in the 1860s and differed from open-boat whaling technically and economically and in the species targeted, the countries involved, and the sheer number of whales killed. Innovations included steam-powered (later diesel-powered) whaling ships and catcher boats, an exploding harpoon fired from a cannon mounted on the bow of the catcher boat, sonar to follow the whale, and a line attached to the harpoon from which captured whales were towed to a factory ship or shore-station. Those innovations enabled pursuit of speedier baleen whales; Sperm Whales were targeted but not as intensely until the 1950s when many populations of baleen whales were severely depleted and attention shifted back to Sperm Whales.

After World War II, the demand for industrial oil was high, and spermaceti oil was valuable as a lubricant of fine machinery and in military applications (fine lubricant in submarines). In addition to spermaceti and blubber from Sperm Whales, modern whalers processed their organs, skin, and even soft tissues for a diversity of uses including cosmetics, medicines, soap, leather, gelatin, and lithographic ink; bones and viscera were ground for animal feed. Initially developed by the Norwegians, the industry was dominated in later years by Japanese and Soviet pelagic whalers and major shore stations operating in Japan, South Africa, USSR (Kuril Islands), Peru, Chile, and Australia. The factory ships were large: a Soviet whaling ship could be 200 m in length with a crew of 600, accompanied by a fleet of ten catcher boats, scouting vessels, and supply ships. The total catch for one such factory ship could reach 100 Sperm Whales per day—a catch greater than the total number of whales taken during a typical three-year or four-year voyage in the era of whaling by sail.

The fishery peaked in the 1960s with an estimated 25,000 whales killed per year; a total of over 600,000 Sperm Whales were estimated to be killed during the modern era of factory ship whaling. Massive illegal whaling and falsification of catches were rampant by Soviet whalers (and to a much less severe degree by Japanese shore-based whaling stations), and thus numbers reported misrepresent the sex and underestimate the true number of Sperm Whales actually killed. Modern whalers preferentially targeted adult males but also took females, and whaling was particularly intense in the North Pacific, off Peru in the South Pacific, and in the Southern Ocean. Eventually, whaling nations became signatories of the International Convention for the Regulation of Whaling in 1946, establishing the International Whaling Commission (IWC) that oversaw the large catches despite on-going discussion of declining populations. Area closures, length restrictions, and catch quotas were eventually imposed, but commercial catches continued through the late 1970s and 1980s until the adoption of the IWC moratorium on commercial whaling. The ban on commercial whaling went into effect for the 1986 coastal season and the 1985/1986 pelagic whaling season, prohibiting the harvest of sperm whales worldwide.

 

Status and Conservation

Sperm Whales are classified globally as Vulnerable on The IUCN Red List, and the Mediterranean subpopulation is classified as Endangered and is considered to be in decline most likely due to entanglement in high-seas swordfish (Xiphiidae) and tuna (Scombridae) driftnets. The species is listed on Appendix I of the Convention on International Trade in Endangered Species of Wild Flora and Fauna (CITES) and on Appendices I and II of the Convention on Migratory Species (CMS). The IWC manages Sperm Whale populations under the International Convention for the Regulation of Whaling. Currently, catch limits are set at zero for all whales, and there are whale sanctuaries in the Indian and Southern oceans. While it is often assumed that the worldwide population of Sperm Whales has increased since the moratorium, there are insufficient data on critical population parameters to accurately determine population trends. Despite these uncertainties, it is clear that Sperm Whale populations can increase only very slowly; maximal rates of population increase are estimated to be about 1% per year.

Despite considerable effort, the Sperm Whale’s global distribution and offshore habitat make it difficult to accurately estimate abundance. Extrapolation from estimates of Sperm Whale density that covered 24% of their global habitat suggests a current global population of about 360,000 individuals. An effort to model the pre-whaling population size estimated about 1,110,000 whales and suggested that the population was about 71% of its original level in 1880 when open-boat whaling drew to a close and about 32% of its original population size in 1999, a decade after the end of whaling. These estimates, however, are hampered by uncertainties in Sperm Whale biology and the history of exploitation. The loss of historical whaling records during the age of sail and extensive illegal and pirate whaling, along with falsification of data by Soviet whalers, make it especially difficult to evaluate the spatial, temporal, and population-level impacts of industrial whaling on past and current populations.

Sperm Whales are still targeted in a few areas. There is a subsistence catch by local people in the village of Lamalera on the island of Lembata in the Suva Sea, Indonesia, and Japan controversially issues special permits to take up to ten Sperm Whales annually for scientific research. While the primary threat to Sperm Whales was addressed by the IWC whaling moratorium, current threats to Sperm Whale populations and recovery include vessel collisions; anthropogenic noise from shipping, naval sonar, explosives, and oil and gas exploration; contaminants and chemical pollutants that can bioaccumulate in tissues; entanglement in marine debris; loss of prey base due to overfishing or climate-induced ecosystem change; disturbance from whale watching; entanglement in fishing gear; lingering effects of whaling, which removed large males and individuals from female social groups, on Sperm Whale sociality; and the potential of illegal or renewed whaling efforts at unsustainable levels.

Sperm Whales are the focus of whale-watching operations in several locations around the world, including New Zealand (Kaikoura), Japan, Norway, Portugal (the Azores), Spain (Canary Islands), Sri Lanka, and the West Indies (Dominica). Sperm Whale interactions with fisheries are on the increase. Male Sperm Whales foraging at high latitudes have been observed engaging in depredation (taking of fish) off long lines in demersal (near the seabed) fisheries for sablefish or black cod (Anoplopoma fimbria) and Pacific halibut (Hippoglossus stenolepis) in the North Pacific; Greenland halibut (Reinhardtius hippoglossoides), Atlantic halibut (Hippoglossus hippoglossus), Atlantic cod (Gadus morhua), and Greenland cod (Gadus ogac) in the North Atlantic; and toothfish (Dissostichus spp.) in the Southern Ocean. Long-line fisheries provide an easy foraging method for Sperm Whales because they can remove fish as the line is hauled, reducing their time at greater depths. Nevertheless, whales engaged in such depredation risk injury, entanglement, and mortality. For fishermen, these whales can reduce catch rates, increase fishing effort, and damage gear.

Sperm Whales survived two massive waves of commercial whaling, but their naturally low reproductive rate and complex social structure means that population recovery will be slow. Today, researchers around the world pursue knowledge and understanding of this extraordinary species. Building on a wealth of data collected by dedicated biologists during the whaling era, we know quite a bit about the life history, distribution, and foraging habits of Sperm Whales. In the early 1980s H. Whitehead and colleagues pioneered field methods for studying the natural history and social behavior of Sperm Whales at sea, and today researchers apply a variety of standard methods and new technologies to tackle the logistic challenges involved in observing this deep-diving and oceanic species.

Recent advances in satellite telemetry, for example, enable researchers to follow Sperm Whale movements across ocean basins and to track fine-scale movements in response to human activities such as military sonar. Tissue samples obtained from sloughed skin or directed biopsy and analyzed with an array of molecular markers yields data on global Sperm Whale population structure and the presence of contaminants and chemical pollution. Advances in passive acoustics permit the detection of patterns in the communication of individuals, groups, and clans, disclosing layer upon layer of social complexity. Hydrophone arrays reveal the spatial arrangement of vocalizing individuals underwater and tags attached to the animals can record dive time, depth, and orientation, providing insights into how sperm whales forage in the darkness at depth. Digital photography, from boats and, more recently, from aerial vehicles, enables the estimation of body size and the identification of individuals along with their fine-scale behavior and social interactions. Important advances have been made regarding many of the current questions surrounding the Sperm Whale, but many knowledge gaps remain. Future studies are likely to unravel more mysteries of the lives of Sperm Whales: social, cultural, and cognitive complexity, foraging ecology and habitat use, and global structure. In the meantime, Sperm Whales are vulnerable to a new array of threats humans are introducing into the ocean, and success in the recovery and conservation of Sperm Whale populations will be conditioned by the understanding and mitigation of these human impacts.