Orca

The three to five types of orcas may be distinct enough to be considered different races,[20] subspecies, or possibly even species[21] (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."[3] Although large variation in the ecological distinctiveness of different orca groups complicate simple differentiation into types,[22] research off the west coast of North America has identified fish-eating "residents", mammal-eating "transients" and "offshores".[23] Other populations have not been as well studied, although specialized fish and mammal eating orcas have been distinguished elsewhere.[24] Mammal-eating orcas in different regions were long thought likely to be closely related, but genetic testing has refuted this hypothesis.[25]

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.[21] 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.[26] A 2019 study of Type D orcas also found them to be distinct from other populations and possibly even a unique species.[27]

Worldwide population estimates are uncertain, but recent consensus suggests a minimum of 50,000 (2006).[52][3][53] 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.[54] Japan's Fisheries Agency estimated in the 2000s that 2,321 orcas were in the seas around Japan.[55][56]

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, including 65% of large, fatty Chinook.[65] 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.[52] On average, an orca eats 227 kilograms (500 lb) each day.[66] 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 only been documented in the Norwegian orca population, as well as some oceanic dolphin species.[67] Some dolphins recognize fish eating orcas (usually resident) as harmless and remain in the same area.[68]

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.[69][70] With sharks, orcas may herd them to the surface and strike them with their tail flukes,[69] while bottom-dwelling rays are cornered, pinned to the ground and taken to the surface.[71] In other parts of the world, orcas have preyed on broadnose sevengill sharks,[72] small whale sharks[73] and even great white sharks.[72][74] Competition between orcas and white sharks is probable in regions where their diets overlap.[75] The arrival of orcas in an area can cause white sharks to flee and forage elsewhere.[76][77] Orcas appear to target the liver of sharks.[72][74]

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.[78][35] 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.[78] By contrast, orcas appear to be wary of pilot whales, which have been recorded to mob and chase them.[79]

Orca attacking a strap-toothed beaked whale

Orcas also prey on larger species such as sperm whales, grey whales, humpback whales and minke whales.[78][35] In 2019, orcas were recorded to have killed a blue whale on three separate occasions off the south coast of Western Australia, including an estimated 18–22-meter (59–72 ft) individual.[80] 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.[78] 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.[81] 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.[82]

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.[83]

Orca beaching to capture sea lion along Valdes Peninsula

Orcas swimming in close synchronization to create a wave to wash the seal off the floe

Other marine mammal prey includes seal species such as harbour seals, Weddell seals, elephant seals, California sea lions, Steller sea lions, South American sea lions and walruses.[78][35][84] 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.[85] In steeply banked beaches off Península Valdés, Argentina, and the Crozet Islands, orcas feed on sea lions and 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.[86] Orcas can then release the animal near juvenile whales, allowing the younger whales to practice the difficult capture technique on the now-weakened prey.[85][87] In the Antarctic, "wave-hunting" orcas "spy-hop" to locate seals 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.[88]

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.[89] The decline of sea otters followed a decline in seal populations,[lower-alpha 1][91] which in turn may be substitutes for their original prey, now decimated by industrial whaling.[92][93][94] Orcas have been observed preying on terrestrial mammals, such as deer swimming between islands off the northwest coast of North America.[90] 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.[95] One orca was also attacked by its companions after being shot.[24] Although resident orcas have never been observed to eat other marine mammals, they occasionally harass and kill porpoises and seals for no apparent reason.[96]

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.[97] Orcas in many areas may prey on cormorants and gulls.[98] 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.[99]

Orcas are notable for their complex societies. Only elephants and higher primates live in comparably complex social structures.[103] Due to orcas' complex social bonds, many marine experts have concerns about how humane it is to keep them in captivity.[104]

Resident orcas in the eastern North Pacific live in particularly complex and stable social groups. Unlike any other known mammal social structure, resident whales 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 four generations travel together. These matrilineal groups are highly stable. Individuals separate for only a few hours at a time, to mate or forage. With one exception, an orca named Luna, no permanent separation of an individual from a resident matriline has been recorded.[105]

A pair of orcas in the Pacific Northwest

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.[105] DNA testing indicates resident males nearly always mate with females from other pods.[106] 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.[105] The highest association layer is the community, which consists of pods that regularly associate with each other but share no maternal relations or dialects.[107]

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.[108] As in resident clans, transient community members share an acoustic repertoire, although regional differences in vocalizations have been noted.[109]

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.[110]

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".[111][112]

Like all cetaceans, orcas depend heavily on underwater sound for orientation, feeding, and communication. They produce three categories of sounds: clicks, whistles, and pulsed calls. Clicks are believed to be used primarily for navigation and discriminating prey and other objects in the surrounding environment, but are also commonly heard during social interactions.[53]

Northeast Pacific resident groups tend to be much more vocal than transient groups in the same waters.[113] Residents feed primarily on Chinook and chum salmon, which are insensitive to orca calls (inferred from the audiogram of Atlantic salmon). In contrast, the marine mammal prey of transients hear whale calls well and thus transients are typically silent.[113] Vocal behaviour in these whales is mainly limited to surfacing activities and milling (slow swimming with no apparent direction) after a kill.[114]

All members of a resident pod use similar calls, known collectively as a dialect. Dialects are composed of specific numbers and types of discrete, repetitive calls. They are complex and stable over time.[115] Call patterns and structure are distinctive within matrilines.[116] Newborns produce calls similar to their mothers, but have a more limited repertoire.[109] Individuals likely learn their dialect through contact with pod members.[117] Family-specific calls have been observed more frequently in the days following a calf's birth, which may help the calf learn them.[118] Dialects are probably an important means of maintaining group identity and cohesiveness. Similarity in dialects likely reflects the degree of relatedness between pods, with variation growing over time.[119] When pods meet, dominant call types decrease and subset call types increase. The use of both call types is called biphonation. The increased subset call types may be the distinguishing factor between pods and inter-pod relations.[116]

Dialects also distinguish types. Resident dialects contain seven to 17 (mean = 11) distinctive call types. All members of the North American west coast transient community express the same basic dialect, although minor regional variation in call types is evident. Preliminary research indicates offshore orcas have group-specific dialects unlike those of residents and transients.[119]

Norwegian and Icelandic herring-eating orcas appear to have different vocalizations for activities like hunting.[120] A population that live in McMurdo Sound, Antarctica have 28 complex burst-pulse and whistle calls.[121]

Orcas have the second-heaviest brains among marine mammals[122] (after sperm whales, which have the largest brain of any animal).[123] Orcas have more gray matter and more cortical neurons than any mammal, including humans.[124] They can be trained in captivity and are often described as intelligent,[125][126] although defining and measuring "intelligence" is difficult in a species whose environment and behavioural strategies are very different from those of humans.[126] Orcas imitate others, and seem to deliberately teach skills to their kin. Off the Crozet Islands, mothers push their calves onto the beach, waiting to pull the youngster back if needed.[85][87] In March 2023, a female orca was spotted with a newborn pilot whale in Snæfellsnes.[127]

An orca plays with a ball of ice, soon after a researcher threw a snowball at the whale.

People who have interacted closely with orcas offer numerous anecdotes demonstrating the whales' curiosity, playfulness, and ability to solve problems. Alaskan orcas have not only learned how to steal fish from longlines, but have also overcome a variety of techniques designed to stop them, such as the use of unbaited lines as decoys.[128] Once, fishermen placed their boats several miles apart, taking turns retrieving small amounts of their catch, in the hope that the whales would not have enough time to move between boats to steal the catch as it was being retrieved. The tactic worked initially, but the orcas figured it out quickly and split into groups.[128]

In other anecdotes, researchers describe incidents in which wild orcas playfully tease humans by repeatedly moving objects the humans are trying to reach,[129] or suddenly start to toss around a chunk of ice after a human throws a snowball.[130]

The orca's use of dialects and the passing of other learned behaviours from generation to generation have been described as a form of animal culture.[131]

The complex and stable vocal and behavioural cultures of sympatric groups of killer whales (Orcinus orca) appear to have no parallel outside humans and represent an independent evolution of cultural faculties.[132]

Haida sculpture by Bill Reid

The indigenous peoples of the Pacific Northwest Coast feature orcas throughout their art, history, spirituality and religion. The Haida regarded orcas as the most powerful animals in the ocean, and their mythology tells of orcas living in houses and towns under the sea. According to these myths, they took on human form when submerged, and humans who drowned went to live with them.[164] For the Kwakwaka'wakw, the orca was regarded as the ruler of the undersea world, with sea lions for slaves and dolphins for warriors.[164] In Nuu-chah-nulth and Kwakwaka'wakw mythology, orcas may embody the souls of deceased chiefs.[164] The Tlingit of southeastern Alaska regarded the orca as custodian of the sea and a benefactor of humans.[165]

The Maritime Archaic people of Newfoundland also had great respect for orcas, as evidenced by stone carvings found in a 4,000-year-old burial at the Port au Choix Archaeological Site.[166][167]

In the tales and beliefs of the Siberian Yupik people, orcas are said to appear as wolves in winter, and wolves as orcas in summer.[168][169][170][171] Orcas are believed to assist their hunters in driving walrus.[172] Reverence is expressed in several forms: the boat represents the animal, and a wooden carving hung from the hunter's belt.[170] Small sacrifices such as tobacco or meat are strewn into the sea for them.[172][171]

The Ainu people of Hokkaido, the Kuril Islands, and southern Sakhalin often referred to orcas in their folklore and myth as Repun Kamuy (God of Sea/Offshore) to bring fortunes (whales) to the coasts, and there had been traditional funerals for stranded or deceased orcas akin to funerals for other animals such as brown bears.[173]

Male orca depicted in St Mary's in Greifswald, Germany, 1545[15]

In Western cultures, orcas were historically feared as dangerous, savage predators.[174] The first written description of an orca was given by Pliny the Elder circa AD 70, who wrote, "Orcas (the appearance of which no image can express, other than an enormous mass of savage flesh with teeth) are the enemy of [other kinds of whale]... they charge and pierce them like warships ramming." (see citation in section "Naming", above).[175]

Of the very few confirmed attacks on humans by wild orcas, none have been fatal.[176] In one instance, orcas tried to tip ice floes on which a dog team and photographer of the Terra Nova Expedition were standing.[177] The sled dogs' barking is speculated to have sounded enough like seal calls to trigger the orca's hunting curiosity. In the 1970s, a surfer in California was bitten, and in 2005, a boy in Alaska who was splashing in a region frequented by harbour seals was bumped by an orca that apparently misidentified him as prey.[178] Unlike wild orcas, captive orcas have made nearly two dozen attacks on humans since the 1970s, some of which have been fatal.[179][180]

Competition with fishermen also led to orcas being regarded as pests. In the waters of the Pacific Northwest and Iceland, the shooting of orcas was accepted and even encouraged by governments.[174] As an indication of the intensity of shooting that occurred until fairly recently, about 25% of the orcas captured in Puget Sound for aquariums through 1970 bore bullet scars.[181] The U.S. Navy claimed to have deliberately killed hundreds of orcas in Icelandic waters in 1956 with machine guns, rockets, and depth charges.[182][183]

Western attitudes towards orcas have changed dramatically in recent decades. In the mid-1960s and early 1970s, orcas came to much greater public and scientific awareness, starting with the live-capture and display of an orca known as Moby Doll, a southern resident orca harpooned off Saturna Island in 1964.[174] He was the first ever orca to be studied at close quarters alive, not postmortem. Moby Doll's impact in scientific research at the time, including the first scientific studies of an orca's sound production, led to two articles about him in the journal Zoologica.[184][185] So little was known at the time, it was nearly two months before the whale's keepers discovered what food (fish) it was willing to eat. To the surprise of those who saw him, Moby Doll was a docile, non-aggressive whale who made no attempts to attack humans.[186]

In 2002, the orphan Springer was successfully returned to her family.

Between 1964 and 1976, 50 orcas from the Pacific Northwest were captured for display in aquaria, and public interest in the animals grew. In the 1970s, research pioneered by Michael Bigg led to the discovery of the species' complex social structure, its use of vocal communication, and its extraordinarily stable mother–offspring bonds. Through photo-identification techniques, individuals were named and tracked over decades.[187]

Bigg's techniques also revealed the Pacific Northwest population was in the low hundreds rather than the thousands that had been previously assumed.[174] The southern resident community alone had lost 48 of its members to captivity; by 1976, only 80 remained.[188] In the Pacific Northwest, the species that had unthinkingly been targeted became a cultural icon within a few decades.[154]

The public's growing appreciation also led to growing opposition to whale–keeping in aquarium. Only one whale has been taken in North American waters since 1976. In recent years, the extent of the public's interest in orcas has manifested itself in several high-profile efforts surrounding individuals. Following the success of the 1993 film Free Willy, the movie's captive star Keiko was returned to the coast of his native Iceland in 2002. The director of the International Marine Mammal Project for the Earth Island Institute, David Phillips, led the efforts to return Keiko to the Iceland waters.[189] Keiko however did not adapt to the harsh climate of the Arctic Ocean, and died a year into his release after contracting pneumonia, at the age of 27.[190] In 2002, the orphan Springer was discovered in Puget Sound, Washington. She became the first whale to be successfully reintegrated into a wild pod after human intervention, crystallizing decades of research into the vocal behaviour and social structure of the region's orcas.[191] The saving of Springer raised hopes that another young orca named Luna, which had become separated from his pod, could be returned to it. However, his case was marked by controversy about whether and how to intervene, and in 2006, Luna was killed by a boat propeller.[192]

The orca named Old Tom swims alongside a whaleboat, flanking a whale calf. The boat is being towed by a harpooned whale (not visible here), near Eden, Australia.

The earlier of known records of commercial hunting of orcas date to the 18th century in Japan. During the 19th and early 20th centuries, the global whaling industry caught immense numbers of baleen and sperm whales, but largely ignored orcas because of their limited amounts of recoverable oil, their smaller populations, and the difficulty of taking them.[106] Once the stocks of larger species were depleted, orcas were targeted by commercial whalers in the mid-20th century. Between 1954 and 1997, Japan took 1,178 orcas (although the Ministry of the Environment claims that there had been domestic catches of about 1,600 whales between late 1940s to 1960s[193]) and Norway took 987.[194] Extensive hunting of orcas, including an Antarctic catch of 916 in 1979–80 alone, prompted the International Whaling Commission to recommend a ban on commercial hunting of the species pending further research.[194] Today, no country carries out a substantial hunt, although Indonesia and Greenland permit small subsistence hunts (see Aboriginal whaling). Other than commercial hunts, orcas were hunted along Japanese coasts out of public concern for potential conflicts with fisheries. Such cases include a semi-resident male-female pair in Akashi Strait and Harimanada being killed in the Seto Inland Sea in 1957,[195][196] the killing of five whales from a pod of 11 members that swam into Tokyo Bay in 1970,[197] and a catch record in southern Taiwan in the 1990s.[198][199]

Orcas have helped humans hunting other whales.[200] One well-known example was the orcas of Eden, Australia, including the male known as Old Tom. Whalers more often considered them a nuisance, however, as orcas would gather to scavenge meat from the whalers' catch.[200] Some populations, such as in Alaska's Prince William Sound, may have been reduced significantly by whalers shooting them in retaliation.[20]

Whale watching continues to increase in popularity, but may have some problematic impacts on orcas. Exposure to exhaust gases from large amounts of vessel traffic is causing concern for the overall health of the 75 remaining southern resident orcas (SRKWs) left as of early 2019.[201] This population is followed by approximately 20 vessels for 12 hours a day during the months May–September.[202] Researchers discovered that these vessels are in the line of sight for these whales for 98–99.5% of daylight hours.[202] With so many vessels, the air quality around these whales deteriorates and impacts their health. Air pollutants that bind with exhaust fumes are responsible for the activation of the cytochrome P450 1A gene family.[202] Researchers have successfully identified this gene in skin biopsies of live whales and also the lungs of deceased whales. A direct correlation between activation of this gene and the air pollutants can not be made because there are other known factors that will induce the same gene. Vessels can have either wet or dry exhaust systems, with wet exhaust systems leaving more pollutants in the water due to various gas solubility. A modelling study determined that the lowest-observed-adverse-effect-level (LOAEL) of exhaust pollutants was about 12% of the human dose.[202]

As a response to this, in 2017 boats off the British Columbia coast now have a minimum approach distance of 200 metres compared to the previous 100 metres. This new rule complements Washington State's minimum approach zone of 180 metres that has been in effect since 2011. If a whale approaches a vessel it must be placed in neutral until the whale passes. The World Health Organization has set air quality standards in an effort to control the emissions produced by these vessels.[203]

Lolita, at the Miami Seaquarium, was one of the oldest orcas in captivity.

The orca's intelligence, trainability, striking appearance, playfulness in captivity and sheer size have made it a popular exhibit at aquaria and aquatic theme parks. From 1976 to 1997, 55 whales were taken from the wild in Iceland, 19 from Japan, and three from Argentina. These figures exclude animals that died during capture. Live captures fell dramatically in the 1990s, and by 1999, about 40% of the 48 animals on display in the world were captive-born.[204]

Organizations such as World Animal Protection and the Whale and Dolphin Conservation campaign against the practice of keeping them in captivity. In captivity, they often develop pathologies, such as the dorsal fin collapse seen in 60–90% of captive males. Captives have vastly reduced life expectancies, on average only living into their 20s.[lower-alpha 2] That said, a 2015 study coauthored by staff at SeaWorld and the Minnesota Zoo suggested no significant difference in survivorship between free-ranging and captive orcas.[140] However, in the wild, females who survive infancy live 46 years on average, and up to 70–80 years in rare cases. Wild males who survive infancy live 31 years on average, and up to 50–60 years.[205] Captivity usually bears little resemblance to wild habitat, and captive whales' social groups are foreign to those found in the wild. Critics claim captive life is stressful due to these factors and the requirement to perform circus tricks that are not part of wild orca behaviour, see above.[206] Wild orcas may travel up to 160 kilometres (100 mi) in a day, and critics say the animals are too big and intelligent to be suitable for captivity.[125] Captives occasionally act aggressively towards themselves, their tankmates, or humans, which critics say is a result of stress.[179] Between 1991 and 2010, the bull orca known as Tilikum was involved in the death of three people, and was featured in the critically acclaimed 2013 film Blackfish.[207] Tilikum lived at SeaWorld from 1992 until his death in 2017.[208][209]

In March 2016, SeaWorld announced that they would be ending their orca breeding program and their theatrical shows.[210] However, as of 2020, theatrical shows featuring orcas are still ongoing.[211]

Beginning around 2020 one or more pods of orcas began to attack sailing vessels off the Southern tip of Europe and a few were sunk. At least 15 interactions between orcas and boats off the Iberian coast were reported in 2020.[212] According to the Atlantic Orca Working Group (GTOA) as many as 500 vessels have been damaged between 2020 and 2023.[213] In one video, an orca can be seen biting on one of the two rudders ripped from a catamaran near Gibraltar. The captain of the vessel reported this was the second attack on a vessel under his command and the orcas focused on the rudders. "Looks like they knew exactly what they are doing. They didn't touch anything else."[214] After an orca repeatedly rammed a vessel off the coast of Norway in 2023, there is a concern the behavior is spreading to other areas.[215] This has led to recommendations that sailors now carry bags of sand.[216] Dropping sand into the water near the rudder is thought to confuse the sonar signal.[217]

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