Physeter macrocephalus Linnaeus, 1758

English: Sperm whale
German: Pottwal
Spanish: Cachalote
French: Cachalot

Family: Physeteridae

Physeter macrocephalus © Wurtz-Artescienza (see links)

1. Description

The sperm whale is the largest of the toothed whales, and there is a strong sexual dimorphism between males and females: adult females reach approx. 11 m in length and a body mass of 15,000 kg, whereas males are much larger with 16 - 18 m body length and 45,000 - 57,000 kg (Whitehead, 2009, Jefferson et al. 2008). The most striking feature of this species is its massive head, which makes up 25 - 30 % of total length. It contains the spermaceti organ and the underlying "junk", both set above the upper jaw and in front of the parabolic-shaped facial region of the skull. These structures are composed of spongy, oil-filled tissue enclosed in a muscular case and bounded at both ends by air sacs. This spermaceti organ is responsible for the striking echo-locating capabilities of sperm whales (Whitehead, 2009).

The single blowhole is set at the front of the head, offset to the left and S-shaped. There is a thick, low dorsal hump instead of a fin, about 2/3 back from the tip of the head, followed by a series of bumps on the dorsal ridge towards the fluke. The flukes are broad and triangular, resembling a ginkgo-leaf, with an almost straight trailing edge showing individually different nicks, notches and cuts, which are used in photo-identification. The body surface is smooth over the head and wrinkled behind and on the sides. The flippers are short, spatulate and wide. The lower jaw is narrow and underslung and carries 18 - 26 pairs of functional teeth, which are absent from the upper jaw. The predominant colour is black to dark brownish-grey with white areas around the mouth and often on the belly. Some animals have white to yellowish calluses on the dorsal hump, and some adult males have white scratches on the head. Albino sperm whales have been observed and one is well-known from the world literature (Moby Dick, by Herman Melville). The characteristic bushy blow is up to 5 m high and projects to the left of the animal at an angle from the vertical (Jefferson et al. 2008).back to the top of the page

2. Distribution

The sperm whale is one of the animals with the widest distribution on the globe. It ranges from the ice-edge of both hemispheres as far south as the equator but concentrates in so-called "grounds" which coincide with areas of high marine productivity. Such areas can measure a few hundred kilometres across and may contain hundreds or even thousands of sperm whales (Rice 1989; Whitehead, 2009). .

The sperm whale has a world wide distribution, with females inhabiting the lower latitudes
below 40° (except in the north Pacific where they range to 50°N) and males ranging north
and south of this boundary to the ice-edge of the Arctic and Antarctic Oceans
(Whitehead, 2009; Taylor et al. 2008; © IUCN; enlarge map)

Both sexes have very distinct distributions when mature. Most females range usually far from land, except for areas near seamounts or oceanic islands, in waters 1000 m deep or deeper. They prefer water temperatures above 15 °C and low latitudes within 40°N and 40°S (except for the North Pacific where they range to 50°N). Young males accompany these groups of females until they are 4 - 21 years old and then migrate to higher latitudes. There they may range to the ice-edge, preferring productive waters, e.g. in the vicinity of deep sea canyons such as off Andenes, northern Norway, or Kaikoura, New Zealand, but they may also be found in more shallow waters e.g. off Nova Scotia or New York in water only 300 m deep (Whitehead, 2009).

Recent genetic studies have shown significant subdivision between the Gulf of Mexico, the Mediterranean, and the North Atlantic (Drouot, 2003; Engelhaupt, 2004). Mitochondrial DNA results showed significant differentiation among all populations, while microsatellites showed significant differentiation only for comparisons with the Mediterranean Sea, and at a much lower level than seen for mtDNA (Engelhaupt et al. 2009).back to the top of the page

3. Population size

Whitehead (2002) extrapolated from about one quarter of the global habitat that the current population size world-wide is about 360,000 animals (CV = 0.36) or about 29% of the pre-whaling population size. With a maximum rate of increase of around 1% per year (Whitehead 2002), the species is not well adapted to recover from population depletion and the threats exposed below are made responsible for the fact that regional populations of sperm whales are declining or are apparently not recovering from depletion.

There have been several population surveys within the past 10-12 years:.

In the Northwest Pacific a preliminary analysis (Kato and Miyashita, 1998) indicated 102,112 (CV = 0.155) sperm whales, but this was reduced to 29,674 (CV = 0.14) in Kato and Miyashta (2000) using only primary sightings. In the eastern temperate North Pacific a spring 1997 line-transect survey resulted in estimates of 24,000 (CV=0.46) individuals based on visual sightings and 39,200 (CV=0.60) based on acoustic detections and visual group size estimates (Barlow and Taylor 1998). In the EEZ waters off the US west coast from Washington to Califiornia, the most recent of abundance estimate is 2,853 (CV=0.25) animals from ship surveys conducted in 2001 (Barlow and Forney 2007) and 2005 (Forney 2007). In the eastern tropical Pacific, abundance was estimated as 22,700 (95% C.I.=14,800-34,600; Wade and Gerrodette 1993) and in US EEZ around the Hawaii islands, a 2002 shipboard line-transect survey resulted in an abundance estimate of 7,082 (CV=0.30) sperm whales (Barlow 2003), including a correction factor for missed diving animals. No data on current population trends are available from any of these regions (Angliss and Allen, 2008).

In the Northwest Atlantic two 2004 surveys yielded 4,804 (CV =0.38), with an estimate from the northern U.S. Atlantic of 2,607 (CV =0.57) and from the southern U.S. Atlantic of 2,197 (CV =0.47). In the northern Gulf of Mexico oceanic waters, the abundance estimate pooled from 2003 to 2004 is 1,665 (CV=0.20) (Mullin 2007). Similar to Pacific estimates, there are insufficient data to determine population trends (Waring et al. 2009). In the Northeast Atlantic the most recent estimates are dated, with 6,013 (CV = 0.32) (Christensen et al. 1992) and 1,772 (CV= 0.18) in the Faroes-Iceland area (Gunnlaugsson and Sigurjónsson, 1990).

Previous and historical population estimates from the Indian Ocean and the southern Hemisphere are deemed unreliable and therefore not presented here (NMFS, 2009).back to the top of the page

4. Biology and Behaviour

Habitat: Sperm whales show a strong preference for deep waters (Rice 1989), especially in areas with high sea floor relief. Along the U.S. east coast, the overall distribution is centred along the shelf break and over the continental slope 90-1,800 m deep (CETAP 1982; Waring et al. 2005). Very high densities occur in inner slope waters north of Cape Hatteras, North Carolina seaward of the 1,000 m isobath during summer months (Waring et al. 2005). Sperm whales are also known to move onto the continental shelf in waters less than 100 m deep on the southern Scotian Shelf and south of New England, particularly between late spring and autumn (Whitehead et al. 1992a and b).

P. macrocephalus off Andenes, Norway © Boris Culik

In the northern Gulf of Mexico, they occur in greatest density along and seaward of the 1,000 m isobath (Mullin et al. 1991, Mullin and Fulling 2004). They appear to prefer steep rather than shallow depth gradients (Davis et al. 1998). The spatial distribution of sperm whales within the Gulf is strongly correlated with mesoscale physical features such as loop current eddies that locally increase primary production and prey availability (Biggs et al. 2005). However, sperm whales may also be found in rather unproductive marine areas such as the "Charleston grounds" in the Sargasso Sea (Jacquet 1996). These are though to be associated with spawning squid (Jacquet and Whitehead 1996).

Behaviour: On average, sperm whales spend more than 72% of their time in foraging dive cycles. While foraging they make repeated long dives, with a modal depth of 985 m in the Atlantic Ocean, 644 m the Gulf of Mexico and 827 m the Ligurian Sea. Dive durations of about 45 min are interrupted by surface intervals lasting about 9 min (Watwood et al. 2006). However, dives can be much deeper or shallower, and dive durations are also quite flexible (Whitehead, 2009). Dives are initiated by a deep breath, followed by a raising of the head, submersion of the animal, and curving of the tail stock above the water surface until the flukes are raised nearly vertically out of the water. Descent to depth as well as return to the surface can be nearly vertical. During the initial phase of the descent the whales remain quiet, presumably navigating visually, but after reaching a depth of between 100 - 220 m they initiate a series of clicks emitted in intervals of 0,5 - 1 s. Watwood et al. (2006) found that sperm whales descend a mean of 392 m from the start of this regular clicking to the first buzz, i.e. accelerated clicks associated with prey detection, which supports the hypothesis that regular clicks function as a long-range biosonar.
During the late afternoon, females and young gather near the surface to rest, in close aggregation. However, at the onset or end of foraging activities, their behaviour may also show breaches, lobtails, manoeuvres, rolls, and touching of conspecifics, while emitting codas, i.e. stereotyped sequences of clicks, or creaks (Whitehead, 2009).

Schooling: Female sperm whales are organized in groups in which adults travel with their sub-adult offspring. Males eventually leave these groups, at age 4 to 21, after which they live in "bachelor schools". The cohesion among males within a bachelor school declines as the animals age (Best 1979) and they generally move to higher latitudes. During their prime breeding period and old age, male sperm whales are essentially solitary (Christal and Whitehead 1997).
Entire schools of sperm whales occasionally strand, but the causes of this phenomenon are uncertain (Rice 1989). Changes in wind patterns which result in colder and presumably nutrient-rich waters being driven closer to the surface (Evans et al. 2005), lunar cycles (possibly as a result of the effects that light levels have on the vertical migration of their prey species (Wright 2005)), and solar driven geomagnetic variations (Vanselow and Ricklefs 2005), which over the last 400 years may account for 20% of all observed stranding events around the North Sea (Vanselow et al. 2009), all play a role.

Reproduction: Females become sexually mature at 7-13 years of age. The peak breeding season is generally in the spring: in the northern hemisphere between March/April and June, and in the southern hemisphere between October and December (Best et al. 1984). Gestation lasts between14 - 16 months and females lactate for at least two years. The inter-birth interval is 4-6 years for prime-aged females. Female sperm whales rarely become pregnant after the age of 40 (Best et al. 1984; Whitehead 2003).
Puberty in males usually begins between the ages of 10 and 20, and most individuals do not become fully mature until their late twenties (Best, 1979). Longevity can reach at least 50 years (Whitehead, 2009).

Food: Sperm whales forage in mesopelagic and benthic habitats, primarily targeting cephalopods (Kawakami 1980) but occasionally also fish (Clarke et al. 1993). Histioteuthids, mesopelagic gelatinous squid ranging in mass between 0.1 and 1 kg, are at the top of the list of preferred food items. However, females also feed on larger prey such as giant squid (Archaeteuthys sp.) and jumbo squid (Dosidicus sp.), and males prey on species such as the Antarctic colossal squid (Mesonychoteuthis hamiltoni) (Whitehead, 2009).

The yearly turnover of biomass by sperm whales is estimated to be comparable to the total catches of human fisheries, and the impact of sperm whales on deep ocean food webs and nutrient cycling in the ocean is probably significant (Clarke 1976; Kanwisher & Ridgway 1983; Whitehead 2003).

Stomachs of male sperm whales from the Northeast Atlantic stranded in 1997 on the Netherlands coast, in 1998 at Bettyhill (Scotland) and in 1996 at Tory Island (Ireland) consisted almost entirely of cephalopod beaks, with some containing also fish remains. Gonatus sp. (probably Gonatus fabricii, Oegopsida: Gonatidae) was the main prey. The fish remains were saithe (Pollachius virens, Gadiformes: Gadidae), and remains of monkfish (Lophius sp., Lophiiformes: Lophiidae). A specimen stranded in Ireland had consumed a wider range of prey, mainly Histioteuthis bonnellii (Oegopsida: Histiotetuhidae), but also Architeuthis sp. (Oegopsida: Architeuthidae), Chiroteuthis sp. (Oegopsida: Chiroteuthidae), Teuthowenia megalops (Oegopsida: Cranchiidae) and the octopod Haliphron atlanticus (Incirrata: Alloposidae) (Santos et al. 2002).

Cephalopod beaks from the stomachs of 10 males stranded in Denmark between 1991 and 2000 revealed Gonatus fabricii as the dominant prey species (>98%), the majority (73.5%) individuals with an estimated mantle length between 192 and 257 mm. Other species found were: Todarodes sagittatus, Histioteuthis sp., Cyclioteuthis sp., Haliphron atlanticus, and Bathypolypus sp. (Simon et al. 2003). back to the top of the page

5. Migration

Movements and migratory behaviour of sperm whales has been studied using photo-identification, tags, and satellite tags as well as by following individual groups at sea. When feeding conditions are adequate, sperm whales usually stay in small areas, 10 - 20 km across. During travelling episodes the animals cover about 4 km/hr or about 90 km/day. Female home ranges are approx. 2,000 km across, but males roam more widely (Whitehead, 2009).

Whitehead (2003) found that females and juveniles identified off the Galápagos Islands frequently moved to the waters off the mainland of Ecuador, more than 1,000 km away, to Panama and Perú, about 1,500 - 2,000 km away and rarely to Chile or California, travelling more than 3,000 km. Long-range movements are also reported by tagged females in the South Pacific, where females tagged for periods of over one month travelled on average 650 km (Best, 1979).

Available data suggests periodic migrations of mature males between low latitude breeding and high latitude feeding grounds (Best, 1979). Tagged males in the Southern Ocean showed average displacements of 1,600 km (Best, 1979) or about twice the value recorded for females. In the North Pacific, tagged whales were identified as having traveled1,300 km (Kasuya and Miyashita, 1988). There are more extreme values, such as a male marked off Nova Scotia and killed off Spain, 4,300 km away (Mitchell, 1975), or a male marked south of Mexico and killed off British Columbia, 4,850 km to the North (Kasuya and Miyashita, 1988) and finally a male marked off the north African coast and killed off South Africa, 7,400 km to the South (Ivashin and Rovnin, 1967). In their feeding grounds, males off Kaikoura, New Zealand, or Bleik Canyon, Andenes, Norway, show long term site fidelity, returning over years to the same sites (Whitehead, 2003).

These findings are confirmed by more recent investigations. Genetic comparison of putative sperm whale populations located in the Gulf of Mexico, western North Atlantic, Mediterranean Sea and North Sea indicate a strong fidelity of females to coastal basins on either side of the North Atlantic and suggest the movement of males among these populations for breeding (Engelhaupt et al. 2009). This confirms previous genetic studies based on maternally inherited markers showing inter-oceanic movement to be more prevalent among males than females (Lyrholm et al. 1999) and is consistent with observation of females having smaller geographic ranges.back to the top of the page

6. Threats

Direct catch: Local whaling dates back to the 1500s and intense commercial whaling to around 1712. Highly mechanised "modern" whaling was particularly intense around 1950, and at its peak killed around 25,000 whales per year, significantly depleting the global population. After the cessation of commercial whaling in 1989, the annual catch decreased to some tens of whales taken each year from small boats in Indonesia (Reeves 2002), although none have been taken in recent years (H. Whitehead, pers. comm. to Taylor et al. 2008), and 10 taken annually by Japan under a special IWC scientific permit (Clapham et al. 2003).

Incidental catch: Incidental capture in fishing gear, such as gillnets and bottom-set longline gear, continues to take a toll on sperm whale populations, although the degree of threat is considered low. They have been found as bycatch in pelagic drift gillnets targeting swordfish and tuna in U.S. east-coast waters (Waring et al. 1997), and in artisanal gillnets targeting sharks and large pelagic fishes off the Pacific coasts of northwestern South America, Central America, and Mexico (Palacios and Gerrodette 1996). The pelagic drift gillnet fishery closed in 1997 and the use of drift gillnets was prohibited in 1999, but sperm whales are still threatened by fishing gear. An estimated average of >0.2 sperm whales are killed or seriously injured annually in the driftnet fishery for thresher sharks and swordfish and unknown fisheries off Oregon and California (Carretta et al. 2009). No estimates of mortality are available for the Mexican driftnet fisheries (NMFS, 2009).

In 2006, there were three observed serious injuries in the Gulf of Alaska sablefish longline fishery, which extrapolates to 10 estimated serious injuries for that fishery for that year (R.P. Angliss, in NMFS, 2009). Entanglements in longline fishing gear have also been observed in South Georgia (Purves et al. 2004) and Chile (Ashford et al. 1996). Sperm whales have been found following deep-water trawlers during hauling operations targeting Greenland halibut, and one case of entanglement in the trawl was reported (Karpouzli and Leaper 2004). Between 1998-2006, no sperm whales were known to be killed due to fishery interactions in the U.S. Atlantic Gulf of Mexico (Waring et al. 2009), indicating that current fishing practices pose a low threat to the recovery of sperm whale populations.
However, unreported by-catch and levels of mortality and injury due to entanglement in lost or discarded gear are still a matter of concern, especially in the Mediterranean (Taylor et al. 2008). Even in the absence of whaling, the Mediterranean population appears to have declined over the past 20 years, with bycatch in driftnets targeted at swordfish a likely principal cause (Reeves and Notarbartolo di Sciara 2006).

Killing: Although the magnitude of these interactions is infrequently documented, there are reports of sperm whales having been killed to keep them away from fishing gear (Gonzalez 2001).

Pollution: Increases in the rate of sperm whale strandings in western Europe since the early 1980s have raised concern that anthropogenic effects, including pollution, may be a contributing factor (Goold et al. 2002). However, the results of a tissue analyses of stranded whales for a wide range of contaminants showed no clear link between contamination and stranding (Jacques and Lambertsen 1997). Nevertheless, levels of mercury, cadmium, and certain organochlorines in these whales' tissues were high enough to cause concern about toxicity and other possibly indirect health effects (Bouquegneau et al. 1997; Law et al. 1997). Fossi et al. (2003) stated that high concentrations in the Mediterranean could have an effect on reproductive rates of this species. The levels of organochlorine compounds found in females were consistently higher than those in males, which is contrary to the typical findings in other marine mammals. Given that male and female sperm whales are geographically separated during much of the year, it is possible that males feed in less polluted waters or perhaps on less contaminated prey than females (NMFS, 2009).

Noise pollution: Sperm whales may be adversely affected by anthropogenic noise causing permanent or temporary damage to their hearing, masking biologically relevant sounds, or enticing negative changes in behaviour. However, it is difficult to ascertain the level of threat from anthropogenic sound sources with currently available information (NMFS, 2009). During seismic experiments in the northern Gulf of Mexico a whale carrying an acoustic tag moved away from an operating seismic vessel once the seismic pulses were received at roughly 137 dB re 1 µPa (Johnson et al. 2003). As opposed to this, Davis et al. (2000) noted that sighting frequency in the northern Gulf of Mexico did not differ significantly among different acoustic levels. Off Nova Scotia an active seismic program did not elicit any obvious changes in sperm whale distribution or behaviour (McCall 1999). Offshore northern Norway, animals continued to call when exposed to pulses from a distant seismic vessel of up to 146 dB re 1 µPa peak-to-peak (Madsen et al. 2002). And seismic work off Angola (Weir 2008) resulted in no difference in encounter rates of sperm whales or obvious behavioural changes due to air gun activity.

However, in United Kingdom waters sperm whales exhibited some changes in behaviour in the presence of operating seismic vessels (Stone 2003). And in the Gulf of Mexico Jochens et al. (2008) found decreases in foraging activity.

There have been no sperm whale strandings attributed to naval sonar. However, there is some evidence of disruptions of clicking and behaviour from sonars, pingers, and the Acoustic Thermometry of Ocean Climate studies (summarised in NMFS, 2009).

Ship strikes: The most recent statistics, in the world-wide large whale ship strike database (Jensen and Silber 2004), indicate that from 1975 to 2002 out of a total record of 292 strikes of all large whales, sperm whales were struck 17 times, 13 of which resulted in death of the whale. Vessel types include Navy vessels, container/cargo ships, whale-watching vessels, cruise ships, ferries, Coast Guard vessels, and tankers. The estimates of serious injury or mortality should be considered minimum values because many ship strikes go either undetected or unreported for various reasons (NMFS, 2009). The most severe injuries are caused by larger vessels (80 m or longer) and vessels travelling at a speed of 14 knots or faster (Laist et al. 2001).

Sperm whales spend long periods (typically up to 10 minutes; Jacquet et al. 1998) "rafting" at the surface between deep dives. Reports of ships colliding with sperm whales are frequent in the Canary Islands, where ship traffic is heavy and the local density of sperm whales relatively high (André et al. 1997). In the North Atlantic, a merchant ship reported a strike in Block Canyon in May 2000 (Waring et al. 2007), and from 2001-2003, one stranded sperm whale was reported struck by a naval vessel and another by a merchant vessel near Rhode Island (Waring et al. 2005). More recently in the Pacific, two sperm whales were struck by a ship in 2005, but it is not known if these ship strikes resulted in death or injury (NMFS, 2009). In general, however, it does not appear that ship strikes are a significant threat to sperm whale populations (Whitehead 2003).

Whale watching: In Kaikoura, New Zealand resident whales respond to whale-watching activities with small changes in ventilation and vocalization patterns. These changes may not be of biological importance (Richter et al. 2006). However, transient whales, which receive less whale-watching effort, respond differently, and usually more strongly to whale-watching boats. They spend less time at the surface and adjust their breathing intervals and acoustic behaviour (Gordon et al. 1992).

Marine debris: Instances of stomach obstruction caused by marine debris have been documented in sperm whales, but severity of threat is considered low due to the small number of known cases. In 1989, a necropsy on a stranded sperm whale indicated that its death was caused by a stomach obstruction following accidental ingestion of plastic bags and sheets in the Lavezzi Islands of the Tyrrhenian Sea (Viale et al. 1992). In Iceland a necropsied animal had a lethal obstruction of the gut with plastic marine debris (Lambertsen 1990). The stomach contents of two sperm whales that stranded separately in California (California Marine Mammal Stranding Database 2008, in NMFS, 2009) included extensive amounts of netting from discarded fishing nets; however, the cause of death was not determined. back to the top of the page

7. Remarks

Range states (Taylor et al. 2008) :
Albania; Algeria; Angola; Antarctica; Antigua and Barbuda; Argentina; Australia; Bahamas; Bangladesh; Barbados; Belgium; Belize; Benin; Brazil; Brunei Darussalam; Cameroon; Canada; Cape Verde; Chile; China; Colombia; Comoros; Costa Rica; Croatia; Cyprus; Denmark; Djibouti; Dominica; Dominican Republic; Ecuador; Egypt; El Salvador; Equatorial Guinea; Falkland Islands (Malvinas); Faroe Islands; Fiji; France; Gabon; Gambia; Ghana; Gibraltar; Greece; Greenland; Grenada; Guatemala; Guinea; Guinea-Bissau; Guyana; Haiti; Honduras; Iceland; India; Indonesia; Iran, Islamic Republic of; Ireland; Israel; Italy; Jamaica; Japan; Kenya; Kiribati; Korea, Democratic People's Republic of; Korea, Republic of; Lebanon; Liberia; Libyan Arab Jamahiriya; Madagascar; Malaysia; Maldives; Malta; Marshall Islands; Mauritania; Mauritius; Mexico; Micronesia, Federated States of; Monaco; Morocco; Mozambique; Namibia; Nauru; Netherlands; Netherlands Antilles; New Zealand; Nicaragua; Nigeria; Niue; Norway; Oman; Pakistan; Palau; Panama; Papua New Guinea; Peru; Philippines; Portugal; Russian Federation; Saint Helena; Saint Kitts and Nevis; Saint Lucia; Saint Vincent and the Grenadines; Samoa; Sao Tomé and Principe; Senegal; Seychelles; Sierra Leone; Singapore; Slovenia; Solomon Islands; Somalia; South Africa; Spain; Sri Lanka; Suriname; Syrian Arab Republic; Taiwan, Province of China; Tanzania, United Republic of; Thailand; Timor-Leste; Togo; Tonga; Trinidad and Tobago; Tunisia; Turkey; Tuvalu; United Kingdom; USA; Uruguay; Vanuatu; Venezuela; Viet Nam; Yemen.

Sperm whales are classified as Vulnerable by the IUCN. Whitehead (2002) provided a model-based estimate of global trend giving a 6% probability for Endangered, a 54% probability of meeting the Vulnerable category, and a 40% probability of falling into the Near Threatened category.

P. macrocephalus
is on Appendix I of CITES and Appendices I and II of CMS.back to the top of the page

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© Boris Culik (2010) Odontocetes. The toothed whales: "Physeter macrocephalus". UNEP/CMS Secretariat, Bonn, Germany.
© Illustrations by Maurizio Würtz, Artescienza.
© Maps by IUCN.

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