Killer Whale

The orca (Orcinus orca), or killer whale, is a toothed whale and the largest member of the oceanic dolphin family. The only extant species in the genus Orcinus, it is recognizable by its distinct pigmentation; being mostly black on top, white on the bottom and having recognizable white eye patches. A cosmopolitan species, it inhabits a wide range of marine environments, from Arctic to Antarctic regions to tropical seas, but is more commonly documented in temperate or cooler coastal waters. Scientists have proposed dividing the global population into races, subspecies, or possibly even species.

Orcas are apex predators with a diverse diet. Individual populations often specialize in particular types of prey, including bony fish, sharks, rays, and marine mammals such as seals, dolphins, and whales. They are highly social, with some populations forming stable matrilineal family groups (pods). Their sophisticated hunting techniques and vocal behaviors, often unique to specific groups and passed down from generation to generation, are considered to be manifestations of animal culture. The most studied populations are off the west coast of North America, which include fish-eating "residents", mammal-eating "transients", and offshores.

The International Union for Conservation of Nature (IUCN) lists the orca´s conservation status as data deficient as multiple orca types may represent distinct species. Some local populations are threatened or endangered due to prey depletion, habitat loss, pollution (by PCBs), captures for marine parks, and conflicts with fisheries. In late 2005, the southern resident orcas were added to the U.S. Endangered Species list.

Orcas have been revered by indigenous peoples from regions including the Pacific Northwest, Australia and Peru, while Western cultures have historically feared them. They have been taken by whalers when stocks of larger species have declined. The orca´s image took a positive turn in the 1960s, due to greater public and scientific awareness and their display in captivity. Since then, orcas have been trained to perform in marine parks, a practice that has been criticized as unethical. Orcas rarely pose a threat to humans, and no fatal attack has been recorded in the wild. However, captive orcas have injured or killed their handlers in marine theme parks.

Naming: Orcas are often referred to as "killer whales" because ancient sailors saw them hunt larger whales. Since the 1960s, the term "orca" has increasingly replaced "killer whale" in common usage.

Although some sources suggest that Orcinus means ´of the kingdom of the dead´, relating the name to Orcus and the orcs, the International Code of Zoological Nomenclature (ICZN) mentions that the name orca originates from the Latin word orca, meaning ´a large-bellied pot.´ Orcinus is a derived form created by adding a masculine suffix to it. Ancient Romans originally used orca ( orcae) for these animals, possibly borrowing Ancient Greek (óryx), which was used for various whale species potentially including the narwhal.

They are sometimes referred to as ´blackfish´, a term also used for other cetaceans. Historically, ´grampus´ was another name for the species, though it is now rarely used. This usage should not be confused with the genus Grampus, which includes only Risso´s dolphin (Grampus griseus).

Taxonomy: Orcinus orca is the only extant species recognized in the genus Orcinus and one of many species originally described by Carl Linnaeus in his landmark 1758 10th edition of Systema Naturae. Conrad Gessner wrote the first scientific description of an orca in his Piscium & aquatilium animantium natura of 1558, part of the larger Historia animalium, based on examination of a dead stranded animal in the Bay of Greifswald that had attracted a great deal of local interest.

The orca is one of 35 species in the oceanic dolphin family, which first appeared about 11 million years ago. The orca lineage probably branched off shortly thereafter. Although it has morphological similarities with the false killer whale, the pygmy killer whale, and the pilot whales, a study of cytochrome b gene sequences indicates that its closest extant relatives are the snubfin dolphins of the genus Orcaella. However, a more recent (2018) study places the orca as a sister taxon to the Lissodelphininae, a clade that includes Lagenorhynchus and Cephalorhynchus. In contrast, a 2019 phylogenetic study found the orca to be sister to all other member of the Delphinidae except the Atlantic white-sided dolphin (Leucopleurus acutus), which is sister to that entire clade.

Types: 

The three to five types of orcas may be distinct enough to be considered different races, subspecies, or possibly even species (see Species problem). The IUCN reported in 2008, "The taxonomy of this genus is clearly in need of review, and it is likely that O. orca will be split into a number of different species or at least subspecies over the next few years." Although large variation in the ecological distinctiveness of different orca groups complicates simple differentiation into types, research off the west coast of North America has identified fish-eating "residents", mammal-eating "transients", and "offshores". Other populations have not been as well studied, although specialized fish and mammal eating orcas have been distinguished elsewhere. Mammal-eating orcas in different regions were long thought likely to be closely related, but genetic testing has refuted this hypothesis.

A 2024 study supported the elevation of Eastern North Pacific resident and transient orcas as distinct species, O. ater and O. rectipinnus respectively. The Society for Marine Mammalogy declined to recognize the two species, citing uncertainty as to whether the types constituted unique species or subspecies. "Pending a more complete global review and revision", the Society provisionally recognized them as subspecies Orcinus orca ater and O. o. rectipinnus, with O. o. orca as the nominate subspecies.

Four types have been documented in the Antarctic, Types A–D. Two dwarf species, named Orcinus nanus and Orcinus glacialis, were described during the 1980s by Soviet researchers, but most cetacean researchers are skeptical about their status. Complete mitochondrial sequencing indicates the two Antarctic groups (types B and C) should be recognized as distinct species, as should the North Pacific transients, leaving the others as subspecies pending additional data. A 2019 study of Type D orcas also found them to be distinct from other populations and possibly even a unique species.

Characteristics: Orcas are the largest extant members of the dolphin family. Males typically range from long and weigh in excess of . Females are smaller, generally ranging from and weighing about . Orcas may attain larger sizes as males have been recorded at and females at . Large males can reach a weight of over , large females can reach a weight of over . Calves at birth weigh about and are about long. The skeleton of the orca is typical for an oceanic dolphin, but more robust.

With their distinctive pigmentation, adult orcas are rarely confused with any other species. When seen from a distance, juveniles can be confused with false killer whales or Risso´s dolphins. The orca is mostly black but with sharply bordered white areas. The entire lower jaw is white and from here, the colouration stretches across the underside to the genital area; narrowing and expanding some, and extending into lateral flank patches close to the end. The tail fluke (fin) is also white on the underside, while the eyes have white oval-shaped patches behind and above them, and a grey or white "saddle patch" exists behind the dorsal fin and across the back. Males and females also have different patterns of black and white skin in their genital areas. In newborns, the white areas are yellow or orange coloured. Antarctic orcas may have pale grey to nearly white backs. Some Antarctic orcas are brown and yellow due to diatoms in the water. Both albino and melanistic orcas have been documented.

Orca pectoral fins are large and rounded, resembling paddles, with those of males significantly larger than those of females. Dorsal fins also exhibit sexual dimorphism, with those of males about high, more than twice the size of the female´s, with the male´s fin more like an elongated isosceles triangle, whereas the female´s is more curved. In the skull, adult males have longer lower jaws than females, as well as larger occipital crests. The snout is blunt and lacks the beak of other species. The orca´s teeth are very strong, and its jaws exert a powerful grip; the upper teeth fall into the gaps between the lower teeth when the mouth is closed. The firm middle and back teeth hold prey in place, while the front teeth are inclined slightly forward and outward to protect them from powerful jerking movements.

Orcas have good eyesight above and below the water, excellent hearing, and a good sense of touch. They have exceptionally sophisticated echolocation abilities, detecting the location and characteristics of prey and other objects in the water by emitting clicks and listening for echoes, as do other members of the dolphin family. The mean body temperature of the orca is . Like most marine mammals, orcas have a layer of insulating blubber ranging from thick beneath the skin. The pulse is about 60 heartbeats per minute when the orca is at the surface, dropping to 30 beats/min when submerged.

An individual orca can often be identified from its dorsal fin and saddle patch. Variations such as nicks, scratches, and tears on the dorsal fin and the pattern of white or grey in the saddle patch are unique. Published directories contain identifying photographs and names for hundreds of North Pacific animals. Photographic identification has enabled the local population of orcas to be counted each year rather than estimated, and has enabled great insight into life cycles and social structures.

Range and habitat: 

Orcas are found in all oceans and most seas. Due to their enormous range, numbers, and density, relative distribution is difficult to estimate, but they clearly prefer higher latitudes and coastal areas over pelagic environments. Areas which serve as major study sites for the species include the coasts of Iceland, Norway, the Valdés Peninsula of Argentina, the Crozet Islands, New Zealand and parts of the west coast of North America, from California to Alaska. Systematic surveys indicate the highest densities of orcas (>0.40 individuals per 100 km²) in the northeast Atlantic around the Norwegian coast, in the north Pacific along the Aleutian Islands, the Gulf of Alaska and in the Southern Ocean off much of the coast of Antarctica. They are considered "common" (0.20–0.40 individuals per 100 km²) in the eastern Pacific along the coasts of British Columbia, Washington and Oregon, in the North Atlantic Ocean around Iceland and the Faroe Islands.

In the Antarctic, orcas range up to the edge of the pack ice and are believed to venture into the denser pack ice, finding open leads much like beluga whales in the Arctic. However, orcas are merely seasonal visitors to Arctic waters, and do not approach the pack ice in the summer. With the rapid Arctic sea ice decline in the Hudson Strait, their range now extends deep into the northwest Atlantic. Occasionally, orcas swim into freshwater rivers. They have been documented 100 mi up the Columbia River in the United States. They have also been found in the Fraser River in Canada and the Horikawa River in Japan.

Migration patterns are poorly understood. Each summer, the same individuals appear off the coasts of British Columbia and Washington. Despite decades of research, where these animals go for the rest of the year remains unknown. Transient pods have been sighted from southern Alaska to central California.

Population: Worldwide population estimates are uncertain, but recent consensus suggests a minimum of 50,000 (2006). Local estimates include roughly 25,000 in the Antarctic, 8,500 in the tropical Pacific, 2,250–2,700 off the cooler northeast Pacific and 500–1,500 off Norway. Japan´s Fisheries Agency estimated in the 2000s that 2,321 orcas were in the seas around Japan.

Feeding: Orcas are apex predators, meaning that they themselves have no natural predators. They are sometimes called "wolves of the sea", because they hunt in groups like wolf packs. Orcas hunt varied prey including fish, cephalopods, mammals, seabirds, and sea turtles. Different populations or ecotypes may specialize, and some can have a dramatic impact on prey species. However, whales in tropical areas appear to have more generalized diets due to lower food productivity. Orcas spend most of their time at shallow depths, but occasionally dive several hundred metres depending on their prey. On average, an orca eats 227 kg each day.

Fish: Fish-eating orcas prey on around 30 species of fish. Some populations in the Norwegian and Greenland sea specialize in herring and follow that fish´s autumnal migration to the Norwegian coast. Salmon account for 96% of northeast Pacific residents´ diet, particularly Chinook salmon which make up 65% of the salmon eaten by orcas. Chum salmon are also eaten, but smaller sockeye and pink salmon are not a significant food item. Depletion of specific prey species in an area is, therefore, cause for concern for local populations, despite the high diversity of prey. While salmon are usually hunted by an individual whale or a small group, herring are often caught using carousel feeding: the orcas force the herring into a tight ball by releasing bursts of bubbles or flashing their white undersides. They then slap the ball with their tail flukes, stunning or killing up to 15 fish at a time, then eating them one by one. Carousel feeding has been documented only in the Norwegian orca population, as well as some oceanic dolphin species.

In New Zealand, sharks and rays appear to be important prey, including eagle rays, long-tail and short-tail stingrays, common threshers, smooth hammerheads, blue sharks, basking sharks, and shortfin makos. Orcas pursuing sharks may herd them to the surface and strike them with their tail flukes, while bottom-dwelling rays are cornered, pinned to the ground and taken to the surface. In other parts of the world, orcas have preyed on broadnose sevengill sharks, whale sharks, and even great white sharks, whose livers orcas have been observed to target by flipping the sharks onto their backs, inducing a paralysis called tonic immobility. Competition between orcas and white sharks is probable in regions where their diets overlap. The arrival of orcas in an area can cause white sharks to flee and forage elsewhere.

Mammals and birds: Orcas are sophisticated and effective predators of marine mammals. They are recorded to prey on other cetacean species, usually smaller dolphins and porpoises such as common dolphins, bottlenose dolphins, Pacific white-sided dolphins, dusky dolphins, harbour porpoises and Dall´s porpoises. While hunting these species, orcas usually have to chase them to exhaustion. For highly social species, orca pods try to separate an individual from its group. Larger groups have a better chance of preventing their prey from escaping, which is killed by being thrown around, rammed and jumped on. Arctic orcas may attack beluga whales and narwhals stuck in pools enclosed by sea ice, the former are also driven into shallower water where juveniles are grabbed. By contrast, orcas appear to be wary of pilot whales, which have been recorded to mob and chase them. Nevertheless, possible predation on long-finned pilot whales has been recorded in Iceland, and one study suggests short-finned pilot whales are among Caribbean orcas´ prey. Orcas have been recorded attacking short-finned pilot whales in Peru as well.

Orcas also prey on larger species such as sperm whales, grey whales, humpback whales and minke whales. On three occasions in 2019, orcas were recorded to have killed blue whales off the south coast of Western Australia, among them was an individual measuring . Large whales require much effort and coordination to kill and orcas often target calves. A hunt begins with a chase followed by a violent attack on the exhausted prey. Large whales often show signs of orca attack via tooth rake marks. Pods of female sperm whales sometimes protect themselves by forming a protective circle around their calves with their flukes facing outwards, using them to repel the attackers. There is also evidence that humpback whales will defend against or mob orcas who are attacking either humpback calves or juveniles as well as members of other species.

Prior to the advent of industrial whaling, great whales may have been the major food source for orcas. The introduction of modern whaling techniques may have aided orcas by the sound of exploding harpoons indicating the availability of prey to scavenge, and compressed air inflation of whale carcasses causing them to float, thus exposing them to scavenging. However, the devastation of great whale populations by unfettered whaling has possibly reduced their availability for orcas, and caused them to expand their consumption of smaller marine mammals, thus contributing to the decline of these as well.

Other marine mammal prey includes seal species such as harbour seals, elephant seals, California sea lions, Steller sea lions, South American sea lions and walruses. Often, to avoid injury, orcas disable their prey before killing and eating it. This may involve throwing it in the air, slapping it with their tails, ramming it, or breaching and landing on it. In steeply banked beaches off Península Valdés, Argentina, and the Crozet Islands, orcas feed on South American sea lions and southern elephant seals in shallow water, even beaching temporarily to grab prey before wriggling back to the sea. Beaching, usually fatal to cetaceans, is not an instinctive behaviour, and can require years of practice for the young. Orcas can then release the animal near juvenile whales, allowing the younger whales to practice the difficult capture technique on the now-weakened prey. In the Antarctic, type B orcas hunt Weddell seals and other prey by "wave-hunting". They "spy-hop" to locate them resting on ice floes, and then swim in groups to create waves that wash over the floe. This washes the prey into the water, where other orcas lie in wait.

In the Aleutian Islands, a decline in sea otter populations in the 1990s was controversially attributed by some scientists to orca predation, although with no direct evidence. The decline of sea otters followed a decline in seal populations, which in turn may be substitutes for their original prey, now decimated by industrial whaling. Orcas have been observed preying on terrestrial mammals, such as moose swimming between islands off the northwest coast of North America. Orca cannibalism has also been reported based on analysis of stomach contents, but this is likely to be the result of scavenging remains dumped by whalers. One orca was also attacked by its companions after being shot. However, in a 2026 study, evidence was found that transient (Bigg´s) orcas cannibalize resident orca individuals, and it was also considered more appropriate to interpret the interactions between ecotypes as interspecies predation rather than cannibalism of fellows with the same ecological role. Although resident orcas have never been observed to eat other marine mammals, they occasionally harass and kill porpoises and seals for no apparent reason. Some dolphins recognize resident orcas as harmless and remain in the same area.

Orcas do consume seabirds but are more likely to kill and leave them uneaten. Penguin species recorded as prey in Antarctic and sub-Antarctic waters include gentoo penguins, chinstrap penguins, king penguins and rockhopper penguins. Orcas in many areas may prey on cormorants and gulls. A captive orca at Marineland of Canada discovered it could regurgitate fish onto the surface, attracting sea gulls, and then eat the birds. Four others then learned to copy the behaviour.

Behaviour: Day-to-day orca behaviour generally consists of foraging, travelling, resting and socializing. Orcas frequently engage in surface behaviour such as breaching (jumping completely out of the water) and tail-slapping. These activities may have a variety of purposes, such as courtship, communication, dislodging parasites, or play. Spyhopping is a behaviour in which a whale holds its head above water to view its surroundings. They can also reach speeds of up to . Resident orcas swim alongside porpoises and other dolphins.

Orcas will engage in surplus killing, that is, killing that is not designed to be for food. As an example, a BBC film crew witnessed orcas in British Columbia playing with a male Steller sea lion to exhaustion, but not eating it.

Some orcas have been observed swimming with dead salmon on their heads, resembling hats.

Social structure: Orcas have complex societies. Only elephants and higher primates live in comparably complex social structures. Due to orcas´ complex social bonds, many marine experts have concerns about how humane it is to keep them in captivity.

Resident orcas in the eastern North Pacific live in particularly complex and stable social groups. Unlike any other known mammal social structure, resident whales of both sexes live with their mothers for their entire lives. These family groups are based on matrilines consisting of the eldest female (matriarch) and her sons and daughters, and the descendants of her daughters, etc. The average size of a matriline is 5.5 animals. Because females can reach age 90, as many as six generations may travel together. These matrilineal groups are highly stable. Individuals separate for only a few hours at a time, to mate or forage. The permanent separation of an individual from a resident matriline has only been recorded once, in the case of an orca named Luna.

Closely related matrilines form loose aggregations called pods, usually consisting of one to four matrilines. Unlike matrilines, pods may separate for weeks or months at a time. DNA testing indicates resident males nearly always mate with females from other pods. Clans, the next level of resident social structure, are composed of pods with similar dialects, and common but older maternal heritage. Clan ranges overlap, mingling pods from different clans. The highest association layer is the community, which consists of pods that regularly associate with each other but share no maternal relations or dialects.

Transient pods are smaller than resident pods, typically consisting of an adult female and one or two of her offspring. Males typically maintain stronger relationships with their mothers than other females. These bonds can extend well into adulthood. Unlike residents, extended or permanent separation of transient offspring from natal matrilines is common, with juveniles and adults of both sexes participating. Some males become "rovers" and do not form long-term associations, occasionally joining groups that contain reproductive females. As in resident clans, transient community members share an acoustic repertoire, although regional differences in vocalizations have been noted.

As with residents and transients, the lifestyle of these whales appears to reflect their diet; fish-eating orcas off Norway have resident-like social structures, while mammal-eating orcas in Argentina and the Crozet Islands behave more like transients.

Orcas of the same sex and age group may engage in physical contact and synchronous surfacing. These behaviours do not occur randomly among individuals in a pod, providing evidence of "friendships".

Vocalizations: