Pseudorca crassidens

For reasons unknown, the false killer whale is among the most common cetaceans involved in mass strandings. The sheer size of these episodes is hard to absorb - 835 animals were beached in the largest documented case. They are found in tropical and temperate waters worldwide, swimming with as many as ten other species of cetaceans. They feed primarily on fish and squid and have been seen sharing food in the wild, an unusual occurrence in mammals. In captivity, they have hybridized with bottlenose dolphins and given birth to viable offspring. The false killer whale is the second largest of the dolphins, measuring 3.3 - 6 m in length and weighing up to 1,360 kg; in the family Delphinidae, only killer whales are larger.

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Despite its name, the false killer whale is not a close relative of the killer whale (Orcinus orca), and, in fact, any resemblance between the two species is relatively superficial (2) (4) (5). The false killer whale's body is long and slender, with a tall, backwardly curving dorsal fin and uniquely shaped flippers that possess a large bulge at the midpoint reminiscent of an elbow (6) (7). The head tapers into a long, rounded snout, which overhangs the lower jaw and is marked with a crease running above the mouthline (7). The jaws are armed with 8 to 11 pairs of formidable-looking, large, conical teeth, from which the species derives its Latin name crassidens, meaning “thick-tooth” (7). The colouration is almost uniformly black, with the exception of faint grey marks on the heads of some individuals and a whitish chest patch located between the flippers (4) (7).

Pseudorca crassidens is found throughout the Atlantic, Pacific, and Indian Oceans. It is nearly cosmopolitan, occurring at latitudes as far north as 50 degrees north and as far south as 52 degrees south.

This species has been observed as far south as New Zealand, Peru, Argentina, South Africa, and the north Indian Ocean. They also range from Australia, the Indo-Malayan Archipelago, Philippines, and north to the Yellow Sea. They have been observed in the Sea of Japan, coastal British Columbia, coastal Maryland (USA), the Bay of Biscay, and have been discovered in the Red and Mediterranean Seas. Many pods live near the Gulf of Mexico and surrounding the Hawaiian Islands.

Biogeographic Regions: indian ocean (Native ); atlantic ocean (Native ); pacific ocean (Native ); mediterranean sea (Native )

Other Geographic Terms: cosmopolitan

circumtropical to warm temperate

Maryland to South America

occurs (regularly, as a native taxon) in multiple nations

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: (>2,500,000 square km (greater than 1,000,000 square miles)) Widely distributed, though apparently nowhere abundant, in tropical, subtropical, and warm temperate waters throughout the world. In North America, usually not north of Maryland and southern California, but occasionally strays into northern temperate waters.

The false killer whale is incredibly widespread, with populations found in all the world's major oceans, from northern locations such as the waters around Japan and British Columbia, south to New Zealand and Argentina (1) (5). Although normally found in tropical to warm temperate waters, individuals have been seen in cool waters as far afield as Norway and Alaska (5).

False killer whales are black or dark gray with a white blaze on their ventral side. Some have a paler gray coloring on their head and sides. Their heads are rounded and often described as blunt and conical with a melon-shaped forehead. Their bodies are elongated. The dorsal fin is sickle-shaped and protrudes from the middle of their back, the pectoral flippers are pointed. They have a slight overbite--the upper jaw extends beyond the lower jaw. This gives them a slight beaked look to their rostrum. No subspecies have been described.

Adult males range from 3.7 to 6.1 m in length, while adult females range from 3.5 to 5 m. Adults may weigh 917 to 1842 kg. Newborns range from 1.5 to 1.9 m in length and weigh about 80 kg. The dorsal fin can grow to be 18 to 40 cm high. This species has a more slender build compared to other dolphins and they have tapering heads and flippers. Their flippers average about one-tenth of the head and body length and have a distinct hump on the leading margin of the fin. There is a definite median notch on their flukes and they are very thin with pointed tips. False killer whales also have 8 to 11 teeth on each side of their jaw.

The skulls of females range in length from 55 to 59 cm, while males are 58 to 65 cm. They have 47 to 52 vertebrae: 7 cervical, 10 thoracic, 11 lumbar, and 20 to 23 caudal vertebrae. They have 10 pairs of ribs. Their manus consists of 6 carpals, 5 metacarpals, and 14 phalanges.

This species is often mistaken for bottlenose dolphins (Tursiops truncatus), short-finned pilot whales (Globicephala macrorhynchus), or long-finned pilot whales (Globicephala melas) as they inhabit the same regions. To distinguish these species, bottlenose dolphins have beaks, and pilot whales are larger with obvious dorsal fin differences.

Range mass: 916.26 to 1841.59 kg.

Range length: 3.5 to 6.1 m.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry

Sexual Dimorphism: male larger; sexes shaped differently

Length: 550 cm

False killer whales are common in tropical or temperate seas. They visit coastal waters but prefer to remain in deeper waters. They are known to dive as deep as 2000 meters.

Range depth: 0 to 2000 m.

Average depth: 500 m.

Habitat Regions: temperate ; tropical ; saltwater or marine

Aquatic Biomes: pelagic ; coastal

oceanic

Depth range based on 134 specimens in 1 taxon.
Water temperature and chemistry ranges based on 116 samples.

Environmental ranges
  Depth range (m): 0 - 0
  Temperature range (°C): 1.915 - 29.248
  Nitrate (umol/L): 0.048 - 23.409
  Salinity (PPS): 32.029 - 37.045
  Oxygen (ml/l): 4.476 - 7.572
  Phosphate (umol/l): 0.070 - 1.578
  Silicate (umol/l): 0.777 - 18.227

Graphical representation

Temperature range (°C): 1.915 - 29.248

Nitrate (umol/L): 0.048 - 23.409

Salinity (PPS): 32.029 - 37.045

Oxygen (ml/l): 4.476 - 7.572

Phosphate (umol/l): 0.070 - 1.578

Silicate (umol/l): 0.777 - 18.227
 
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.

Habitat Type: Marine

Comments: Primarily pelagic; usually not near land except around oceanic islands and coast with deep water nearby (Leatherwood and Reeves 1983).

Although the false killer whale is most commonly found in open ocean waters, it also frequents the coastal areas around oceanic islands such as Hawaii, and may enter semi-enclosed seas such as the Mediterranean (5) (7).

Non-Migrant: No. All populations of this species make significant seasonal migrations.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

May make seasonal migrations into northern Pacific waters during spring-summer warming (Leatherwood and Reeves 1983).

False killer whales are carnivores, eating primarily fish and squid. They mainly eat squid (Loligo) but also opportunistically take fish and occasional marine mammals, such as seals (Phocidae) or sea lions (Otariidae). Some of the fish they eat include salmon (Oncorhynchus), squid (Loligo, Berryteuthis magister, or Gonatopsis borealis), sciaenid and carangid fishes, bonito (Sarda lineolata), mahi mahi (Coryphaena hippurus), yellowfin tuna (Thunnus albacares), yellowtail (Pseudosciana manchurica), and perch (Lates calcarifer). On one occasion researchers found the remains of a humpback whale Megaptera noveangliae in the stomach of a false killer whale.

This species moves quickly in order to catch fish. They have been observed catching a fish in their mouth while completely breaching the waters' surface. They have also been seen shaking their prey until the head and entrails are shaken off. They then peel the fish using their teeth and discard all the skin before eating the remains. Some mothers will hold a fish in the mouth and allow their calf to feed on the fish. This food manipulation is rare in cetaceans.

Animal Foods: mammals; fish; mollusks; other marine invertebrates

Primary Diet: carnivore (Piscivore , Molluscivore )

Comments: Diet mainly squid and large fishes (Stacey et al. 1994), including some obtained from fishing lines. May attack dolphins released from purse seines in eastern tropical Pacific (Leatherwood and Reeves 1983).

False killer whales are predators of fish and squid (Uroteuthis duvauceli), and they also eat smaller delphinids and pinnipeds (e.g., seals [Phocidae], and sea lions [Otariidae]).

One protozoan that is found in false killer whales are the parasites Bolbosoma capitatum. They are also carriers of two types of whale lice: Lsocyamus delphini and Cyamus antarcticensis.

Commensal/Parasitic Species:

• Lsocyamus delphini
• Cyamus antarcticensis
• Bolbosoma capitatum

Due to their harmful effects on fisheries, humans kill false killer whales. In some regions in the eastern tropical Pacific, they are hunted for meat.

Known Predators:

• humans (Homo sapiens)

Unknown

Comments: Nowhere abundant.

Gregarious, often in herds of >100 individuals; mean group size off Japan was 55; group size from 14 mass strandings (not uncommon) averaged 180 (50-835). Herds usually include both sexes and all age classes (or minus males in the late maturing stage) and appear to be socially cohesive. Often associates with other cetaceans (Leatherwood and Reeves 1983).

Pseudorca crassidens use echolocation primarily in the frequency range of 20 yo 60 kHz. They also use higher frequencies of 100 to 130 kHz.  False killer whales, like other toothed whales also use other sounds, such as whistles, squeals, or less distinct pulsating sounds. It has been noted that whenever researchers get close to a group of false killer whales, they have been able to detect the whales' piercing whistles from about 200 meters away. James Porter notes, "The noises were astonishingly diverse, much more varied than the sounds of human speech, both in pitch and intensity. Each whale seemed to be making different sounds. The cacophony gave the impression that whatever they were 'saying', they were not all 'saying' the same thing at the same time (Watson 1981)."

Communication Channels: tactile ; acoustic

Perception Channels: visual ; acoustic ; ultrasound ; echolocation

Researchers estimate that males live an average of 57.5 years and females live an average of 62.5 years in the wild. No known age-dependent mortality rate has been discovered. Because few false killer whales are kept in captivity, captive lifespans are unknown.

Average lifespan
Status: wild: 60 years.

Average lifespan
Status: wild: 22.0 years.

Maximum longevity: 62.5 years (captivity) Observations: One captive specimen was still alive at 33.6 years of age (Richard Weigl 2005). Females are estimated to live over 62 years.

Although false killer whales breed year-round, their breeding peaks in late winter to early spring. Studies suggest they are polygynandrous.

Mating System: polygynandrous (promiscuous)

False killer whales will only have one calf per pregnancy and she carries that calf for 11 to 15.5 months. The calf stays with the mother for 18 to 24 months. Between 18 and 24 months old, the calf is gradually weaned. Sexual maturity occurs in females between 8 and 11 years of age and in males at 8 to 10 years.

In this species and a few others in the family Didelphinidae, if the female doesn't conceive after the first ovulation, she will keep ovulating until she does conceive. After giving birth, the female will not breed again for an average of 6.9 years.

Breeding interval: Females give birth every 6.9 years, on average.

Breeding season: Breeding occurs year-round, but peaks December to January and again in March.

Range number of offspring: 1 (high) .

Average number of offspring: 1.

Range gestation period: 11 to 15.5 months.

Range weaning age: 18 to 24 months.

Range age at sexual or reproductive maturity (female): 8 to 11 years.

Range age at sexual or reproductive maturity (male): 8 to 10 years.

Key Reproductive Features: iteroparous ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); induced ovulation ; viviparous

Average number of offspring: 1.

After false killer whales calves are born, they are cared for and nursed by their mother for up to 24 months. Young are capable of swimming on their own shortly after birth. Young are likely to remain in the same social group with their mother beyond weaning.

Parental Investment: precocial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female); post-independence association with parents; extended period of juvenile learning

Protracted breeding season, reportedly with no fixed breeding or calving season, though a peak in calving in March was found off Japan. Gestation lasts about 15-16 months. Lactation lasts apparently about 18 months. Sexually mature at about 3.2-3.8 m (Leatherwood and Reeves 1983), probably at a minimum age of 8 years (IUCN 1991, Stacey et al. 1994). Off Japan, the average interval between births has been estimated at about 7 years, with females over 45 years old post-reproductive (see Stacey et al. 1994). May live several decades.

Although false killer whales are hunted by humans and there are annual mass strandings, populations are considered stable. There are only a few countries that hunt them for food or remove them as threats to the fisheries industry.

US Federal List: no special status

CITES: appendix ii

State of Michigan List: no special status

IUCN Red List of Threatened Species: data deficient

Accidental?

United States

Rounded National Status Rank: NU - Unrankable

Rounded Global Status Rank: G4 - Apparently Secure

Reasons: Widespread in oceans, not significantly threatened.

Classified as Data Deficient (DD) on the IUCN Red List (1) and listed on Appendix II of CITES (3).

Global Short Term Trend: Relatively stable (=10% change)

Degree of Threat: D : Unthreatened throughout its range, communities may be threatened in minor portions of the range or degree of variation falls within natural variation

Comments: No known major threats, though some mortality occurs as a result of direct and indirect taking associated with various fisheries (IUCN 1991). Culls have occurred in Japan in efforts to reduce perceived damage to fisheries (IUCN 1991).

Before a conservation plan for the false killer whale can be developed, it is imperative that more information about its population status and migratory movements be gathered. Until this happens, the impact of the threats faced by this species will remain unclear (1). Even with evidence to support the decline of this species, it may prove difficult to safeguard the false killer whale from military exercises and the use of sonar, as the development of protective legislation has become a contentious issue (8).

These whales will eat fish off of fishing lines and out of nets of commercial fishing operations.

In the eastern tropical Pacific, Pseudorca crassidens is taken for food and also to limit their consumption of tuna Osteoglossiformes and inhibit their competition with commercial fisheries.

Positive Impacts: food

Comments: Has been successfully maintained in several marine aquaria. Sometimes taken for human food and oil in mass shore drives in Japan and in small cetacean fisheries in Taiwan and the Caribbean (Leatherwood and Reeves 1983, Stacy et al. 1994). Sometimes regarded as pest by fishermen who perceive these whales as a competitor for fishes. Sometimes takes fishes hooked on fishing lines; sometimes causes significant impact on tuna long-line fishery in the tropical Pacific (IUCN 1991).