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Orca

(Redirected fromKiller whale)
For other uses, seeOrca (disambiguation).
"Killer Whale" redirects here. ForThe Avengersepisode, seeKiller Whale(The Avengers).For 1962 tokusatsu film, seeKiller Whale(film).

Theorca(Orcinus orca), orkiller whale,is atoothed whaleand the largest member of theoceanic dolphinfamily. It is the onlyextantspecies in the genusOrcinusand is recognizable by its black-and-white patterned body. Acosmopolitan species,they are found in diverse marine environments, fromArctictoAntarctic regionsto tropical seas.

Orca
Killer whale[1]
Temporal range:Plioceneto recent[2]
Two killer whales jump above the sea surface, showing their black, white and grey colouration. The closer whale is upright and viewed from the side, while the other whale is arching backward to display its underside.
Transient orcas nearUnimak Island,easternAleutian Islands,Alaska
Diagram showing a 5.4 meter (18 foot) female killer whale compared to a 1.8 meter (5 foot 11 inches) human scuba diver.
5.4 meter (18 foot) female killer whale compared to 1.8 meter (5 foot 11 inches) human scuba diver
CITESAppendix II(CITES)[4]
Scientific classificationEdit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Artiodactyla
Infraorder: Cetacea
Family: Delphinidae
Genus: Orcinus
Species:
O. orca
Binomial name
Orcinus orca
A world map shows killer whales are found throughout every ocean, except parts of the Arctic. They are also absent from the Black and Baltic seas.
Orcinus orcarange
Synonyms
  • Delphinus orcaLinnaeus, 1758
  • Delphinus gladiatorBonnaterre, 1789
  • Orca gladiator(Bonnaterre, 1789)

Orcas areapex predatorswith a diverse diet. Individual populations often specialize in particular types of prey. This includes a variety offish,sharks,rays,andmarine mammalssuch assealsand otherdolphins and whales.They are highlysocial;some populations are composed of highly stablematrilinealfamily groups (pods). Their sophisticated hunting techniques and vocal behaviors, often specific to a particular group and passed along from generation to generation, are considered to be manifestations ofanimal culture.

TheInternational Union for Conservation of Natureassesses the orca'sconservation statusasdata deficientbecause of the likelihood that two or more orca types areseparate species.Some local populations are consideredthreatenedorendangereddue to prey depletion,habitat loss,pollution (byPCBs), capture formarine mammal parks,andconflicts with human fisheries.In late 2005, thesouthern resident orcaswere placed on theU.S. Endangered Species list.

Orcas are not usually a threat to humans, and no fatal attack has ever been documented in their natural habitat. There have been cases ofcaptive orcas killing or injuring their handlersat marine theme parks. Orcas also feature strongly in the mythologies of indigenous cultures, and their reputation in different cultures ranges from being the souls of humans to merciless killers.

Naming

Orcas, despite being dolphins, are commonly called "killer whales" due to a mistranslation of the Spanish "asesino de ballenas" (literally "whale killer" ), reflecting their historical predation on whales.[6][7]Since the 1960s, the use of "orca" instead of "killer whale" has steadily grown in common use.[8]

The genus nameOrcinusmeans "of the kingdom of the dead",[9]or "belonging toOrcus".[10]Ancient Romansoriginally usedorca[11](pl.orcae) for these animals, possibly borrowingAncient Greekὄρυξ(óryx), which referred (among other things) to a whale species, perhaps anarwhal.[12]As part of thefamilyDelphinidae,the species is more closely related to other oceanic dolphins than to other whales.[13]

They are sometimes referred to as "blackfish", a name also used for other whale species. "Grampus" is a former name for the species, but is now seldom used. This meaning of "grampus" should not be confused with the genusGrampus,whose only member isRisso's dolphin.[14]

Taxonomy

Orcinus citoniensisfossil, an extinct species of the same genus, Museo Capellini inBologna
Modern orca skeleton,Naturalis,Leiden
3D model of skeleton

Orcinus orcais the only recognizedextantspecies in the genusOrcinus,and one of many animal species originally described byCarl Linnaeusin his landmark 175810th edition ofSystema Naturae.[15]Konrad Gessnerwrote the first scientific description of an orca in hisPiscium & aquatilium animantium naturaof 1558, part of the largerHistoria animalium,based on examination of a deadstrandedanimal in theBay of Greifswaldthat had attracted a great deal of local interest.[16]

The orca is one of 35 species in theoceanic dolphin family,which first appeared about 11 million years ago. The orca lineage probably branched off shortly thereafter.[17]Although it has morphological similarities with thefalse killer whale,thepygmy killer whaleand thepilot whales,a study of cytochrome b gene sequences indicates that its closest extant relatives are the snubfin dolphins of the genusOrcaella.[18]However, a more recent (2018) study places the orca as asister taxonto the Lissodelphininae, acladethat includesLagenorhynchusandCephalorhynchus.[19]In contrast, a 2019 phylogenetic study found the orca to be the second mostbasalmember of the Delphinidae, with only theAtlantic white-sided dolphin(Leucopleurus acutus) being more basal.[20]

Types

Further information:Orca types and populations

The three to five types of orcas may be distinct enough to be considered differentraces,[21]subspecies,or possibly evenspecies[22](seeSpecies problem). TheIUCNreported in 2008, "Thetaxonomyof this genus is clearly in need of review, and it is likely thatO. orcawill 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,[23]research off the west coast of North America has identified fish-eating "residents", mammal-eating "transients" and "offshores".[24]Other populations have not been as well studied, although specialized fish and mammal eating orcas have been distinguished elsewhere.[25]Mammal-eating orcas in different regions were long thought likely to be closely related, but genetic testing has refuted this hypothesis.[26][27]

A 2024 study supported the elevation of Eastern North American resident and transient orcas as distinct species,O. aterandO. rectipinnusrespectively.[28]TheSociety for Marine Mammalogydeclined 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 subspeciesOrcinus orca aterandO. o. rectipinnus,withO. o. orcaas thenominate subspecies.[29]

Four types have been documented in theAntarctic,Types A–D. Two dwarf species, namedOrcinus nanusandOrcinus glacialis,were described during the 1980s by Soviet researchers, but most cetacean researchers are skeptical about their status.[22]Completemitochondrial sequencingindicates 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.[30]A 2019 study of Type D orcas also found them to be distinct from other populations and possibly even a unique species.[31]

Characteristics

Different angle views of a typical female orca's appearance

Orcas are the largest extant members of the dolphin family. Males typically range from 6 to 8 m (20 to 26 ft) long and weigh in excess of 6 t (5.9 long tons; 6.6 short tons). Females are smaller, generally ranging from 5 to 7 m (16 to 23 ft) and weighing about 3 to 4 t (3.0 to 3.9 long tons; 3.3 to 4.4 short tons).[32]Orcas may attain larger sizes as males have been recorded at 9.8 m (32 ft) and females at 8.5 m (28 ft).[33]Large males can reach a weight of over 10 t (9.8 long tons; 11 short tons).[34][35]Calves at birth weigh about 180 kg (400 lb) and are about 2.4 m (7 ft 10 in) long.[36][37]The skeleton of the orca is typical for an oceanic dolphin, but more robust.[33]

With their distinctive pigmentation,[33]adult orcas are seldom confused with any other species.[38]When seen from a distance, juveniles can be confused withfalse killer whalesorRisso's dolphins.[39]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.[33][40]Males and females also have different patterns of black and white skin in their genital areas.[41]In newborns, the white areas are yellow or orange coloured.[33][40]Antarctic orcas may have pale grey to nearly white backs.[38]Some Antarctic orcas are brown and yellow due todiatomsin the water.[22]Bothalbinoandmelanisticorcas have been documented.[33]

Sexual dimorphism between male (top) and female (bottom) killer whales. Pectoral fins, dorsal fin, and flukes are larger in adult males

Orcapectoral finsare large and rounded, resembling paddles, with those of males significantly larger than those of females.Dorsal finsalso exhibitsexual dimorphism,with those of males about 1.8 m (5 ft 11 in) high, more than twice the size of the female's, with the male's fin more like an elongatedisosceles triangle,whereas the female's is more curved.[42]In the skull, adult males have longer lower jaws than females, as well as largeroccipital crests.[43]The snout is blunt and lacks the beak of other species.[33]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.[44]

Orcas have good eyesight above and below the water, excellent hearing, and a good sense of touch. They have exceptionally sophisticatedecholocationabilities, detecting the location and characteristics of prey and other objects in the water by emitting clicks and listening for echoes,[45]as do other members of the dolphin family. The mean body temperature of the orca is 36 to 38 °C (97 to 100 °F).[46][47]Like most marine mammals, orcas have a layer of insulatingblubberranging from 7.6 to 10 cm (3.0 to 3.9 in) thick beneath the skin.[46]The pulse is about 60 heartbeats per minute when the orca is at the surface, dropping to 30 beats/min when submerged.[48]

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.[49]

Range and habitat

Further information:Orca types and populations
An orca leaps out of the water when swimming—a behaviour known as porpoising—inHood Canal

Orcas are found in all oceans and most seas. Due to theirenormous range,numbers, and density, relative distribution is difficult to estimate,[50]but they clearly prefer higher latitudes and coastal areas overpelagicenvironments.[51]Areas which serve as major study sites for the species include the coasts ofIceland,Norway, theValdés Peninsulaof Argentina, theCrozet Islands,New Zealand and parts of the west coast of North America, fromCaliforniatoAlaska.[52]Systematic surveys indicate the highest densities of orcas (>0.40 individuals per 100 km2) in the northeast Atlantic around theNorwegiancoast, in the north Pacific along theAleutian Islands,theGulf of Alaskaand in theSouthern Oceanoff much of the coast ofAntarctica.They are considered "common" (0.20–0.40 individuals per 100 km2) in the eastern Pacific along the coasts ofBritish Columbia,WashingtonandOregon,in the North Atlantic Ocean aroundIcelandand theFaroe Islands.[50]

Variations in Antarctic orcas

In the Antarctic, orcas range up to the edge of thepack iceand are believed to venture into the denser pack ice, finding openleadsmuch likebelugawhales in the Arctic. However, orcas are merely seasonal visitors to Arctic waters, and do not approach the pack ice in the summer. With the rapidArctic sea icedecline in theHudson Strait,their range now extends deep into the northwest Atlantic.[53]Occasionally, orcas swim into freshwater rivers. They have been documented 100 mi (160 km) up theColumbia Riverin the United States.[54][55]They have also been found in theFraser Riverin Canada and theHorikawa Riverin Japan.[54]

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.[56]

Population

Worldwide population estimates are uncertain, but recent consensus suggests a minimum of 50,000 (2006).[57][3][58]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.[59]Japan's Fisheries Agency estimated in the 2000s that 2,321 orcas were in the seas around Japan.[60][61]

Feeding

Tail-slapping inVestfjorden,Norway
Resident orca pursuing a chinook salmon

Orcas areapex 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.[62]Orcas hunt varied prey including fish,cephalopods,mammals,seabirds,andsea turtles.[63]Different populations or ecotypes may specialize, and some can have a dramatic impact on prey species.[64]However, whales in tropical areas appear to have more generalized diets due to lower food productivity.[65][66]Orcas spend most of their time at shallow depths,[67]but occasionally dive several hundred metres depending on their prey.[68][69]

Fish

Fish-eating orcas prey on around 30 species of fish. Some populations in theNorwegianandGreenlandsea specialize inherringand follow that fish's autumnal migration to the Norwegian coast.Salmonaccount for 96% of northeast Pacific residents' diet, including 65% of large, fattyChinook.[70]Chum salmonare also eaten, but smallersockeyeandpink salmonare 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.[57]On average, an orca eats 227 kilograms (500 lb) each day.[71]While salmon are usually hunted by an individual whale or a small group, herring are often caught usingcarousel 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.[72]

In New Zealand,sharksandraysappear to be important prey, includingeagle rays,long-tailandshort-tail stingrays,common threshers,smooth hammerheads,blue sharks,basking sharks,andshortfin makos.[73][74]With sharks, orcas may herd them to the surface and strike them with their tail flukes,[73]while bottom-dwelling rays are cornered, pinned to the ground and taken to the surface.[75]In other parts of the world, orcas have preyed onbroadnose sevengill sharks,[76]smallwhale sharks[77]and evengreat white sharks.[76][78]Competition between orcas and white sharks is probable in regions where their diets overlap.[79]The arrival of orcas in an area can cause white sharks to flee and forage elsewhere.[80][81]Orcas appear to target the liver of sharks.[76][78]In one case a single orca was observed killing and eating a great white shark on its own.[82]

Mammals and birds

Orcas are sophisticated and effective predators ofmarine mammals.They are recorded to prey on other cetacean species, usually smaller dolphins andporpoisessuch ascommon dolphins,bottlenose dolphins,Pacific white-sided dolphins,dusky dolphins,harbour porpoisesandDall's porpoises.[83][40]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 attackbeluga whalesandnarwhalsstuck in pools enclosed by sea ice, the former are also driven into shallower water where juveniles are grabbed.[83]By contrast, orcas appear to be wary ofpilot whales,which have been recorded tomoband chase them.[84]Nevertheless, possible predation onlong-finned pilot whaleshas been recorded inIceland,and one study suggestsshort-finned pilot whalesare among Caribbean Orcas' prey.[85][86]Killer whales have been recorded attacking short-finned pilot whales inPeruas well.[87]

Orca attacking astrap-toothed beaked whale

Orcas also prey on larger species such assperm whales,grey whales,humpback whalesandminke whales.[83][40]On three separate occasions in 2019 orcas were recorded to have killedblue whalesoff the south coast of Western Australia, including an estimated 18–22-meter (59–72 ft) individual.[88]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.[83]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.[89]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.[90]

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 ofexploding harpoonsindicating 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.[91]

Orca beaching to capture sea lion alongValdes Peninsula
Orcas swimming in close synchronization to create a wave to wash thecrabeater sealoff the floe

Other marine mammal prey includessealspecies such asharbour seals,elephant seals,California sea lions,Steller sea lions,South American sea lionsandwalruses.[83][40]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.[92]In steeply banked beaches offPenínsula Valdés,Argentina, and theCrozet Islands,orcas feed on South American sea lions andsouthern elephant sealsin shallow water, evenbeachingtemporarily 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.[93]Orcas can then release the animal near juvenile whales, allowing the younger whales to practice the difficult capture technique on the now-weakened prey.[92][94]In the Antarctic, type B orcas huntWeddell sealsand other prey by "wave-hunting". They"spy-hop"to locate them on 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.[95][96]

In theAleutian Islands,a decline insea otterpopulations in the 1990s was controversially attributed by some scientists to orca predation, although with no direct evidence.[97]The decline of sea otters followed a decline in seal populations,[a][99]which in turn may be substitutes for their original prey, now decimated by industrial whaling.[100][101][102]Orcas have been observed preying onterrestrial mammals,such asmooseswimming between islands off the northwest coast of North America.[98][103]Orcacannibalismhas also been reported based on analysis of stomach contents, but this is likely to be the result of scavenging remains dumped by whalers.[104]One orca was also attacked by its companions after being shot.[25]Although resident orcas have never been observed to eat other marine mammals, they occasionally harass and kill porpoises and seals for no apparent reason.[105]Some dolphins recognize resident orcas as harmless and remain in the same area.[106]

Orcas do consumeseabirdsbut are more likely to kill and leave them uneaten.Penguinspecies recorded as prey in Antarctic and sub-Antarctic waters includegentoo penguins,chinstrap penguins,king penguinsandrockhopper penguins.[107]Orcas in many areas may prey oncormorantsandgulls.[108]A captive orca atMarineland of Canadadiscovered it could regurgitate fish onto the surface, attracting sea gulls, and then eat the birds. Four others then learned to copy the behaviour.[109]

Behaviour

Orcas, like this one near Alaska, commonlybreach,often lifting their entire bodies out of the water.

Day-to-day orca behaviour generally consists offoraging,travelling, resting and socializing. Orcas frequently engage insurface behavioursuch as breaching (jumping completely out of the water) and tail-slapping. These activities may have a variety of purposes, such as courtship, communication, dislodgingparasites,orplay.Spyhoppingis a behaviour in which a whale holds its head above water to view its surroundings.[110]Resident orcas swim alongsideporpoisesand otherdolphins.[111]

Orcas will engage insurplus killing,that is, killing that is not designed to be for food. As an example, a BBC film crew witnessed orca inBritish Columbiaplaying with a maleSteller sea lionto exhaustion, but not eating it.[112]

Social structure

Orcas are notable for their complex societies. Onlyelephantsandhigher primateslive in comparably complexsocial structures.[113]Due to orcas' complex social bonds, many marine experts have concerns about how humane it is to keepthem in captivity.[114]

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 onmatrilinesconsisting 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 namedLuna,no permanent separation of an individual from a resident matriline has been recorded.[115]

A pair of orcas in thePacific 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.[115]DNAtesting indicates resident males nearly always mate with females from other pods.[116]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.[115]The highest association layer is the community, which consists of pods that regularly associate with each other but share no maternal relations or dialects.[117]

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.[118]As in resident clans, transient community members share an acoustic repertoire, although regional differences in vocalizations have been noted.[119]

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 theCrozet Islandsbehave more like transients.[120]

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".[121][122]

Vocalizations

Multimedia relating to the orca
Orca calls
Orca calls at a distance
Vocalizations of an orca
Problems playing these files? Seemedia help.
See also:Whale sound

Like allcetaceans,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.[58]

Northeast Pacific resident groups tend to be much more vocal than transient groups in the same waters.[123]Residents feed primarily onChinookandchumsalmon, which are insensitive to orca calls (inferred from the audiogram of Atlantic salmon). In contrast, themarine mammalprey of transients hear whale calls well and thus transients are typically silent.[123]Vocal behaviour in these whales is mainly limited to surfacing activities and milling (slow swimming with no apparent direction) after a kill.[124]

All members of a resident pod use similar calls, known collectively as adialect.Dialects are composed of specific numbers and types of discrete, repetitive calls. They are complex and stable over time.[125]Call patterns and structure are distinctive within matrilines.[126]Newborns produce calls similar to their mothers, but have a more limited repertoire.[119]Individuals likely learn their dialect through contact with pod members.[127]Family-specific calls have been observed more frequently in the days following a calf's birth, which may help the calf learn them.[128]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.[129]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.[126]

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.[129]

Norwegian and Icelandicherring-eating orcas appear to have different vocalizations for activities like hunting.[130]A population that live inMcMurdo Sound,Antarcticahave 28 complex burst-pulse and whistle calls.[131]

Intelligence

Main article:Cetacean intelligence

Orcas have the second-heaviest brains among marine mammals[132](aftersperm whales,which have the largest brain of any animal).[133]Orcas have moregray matterand more cortical neurons than any mammal, including humans.[134]They can betrainedin captivity and are often described as intelligent,[135][136]although defining and measuring "intelligence" is difficult in a species whose environment and behavioural strategies are very different from those of humans.[136]Orcas imitate others, and seem to deliberately teach skills to their kin. Off theCrozet Islands,mothers push their calves onto the beach, waiting to pull the youngster back if needed.[92][94]In March 2023, a female orca was spotted with a newbornpilot whaleinSnæfellsnes.[137]

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 numerousanecdotesdemonstrating the whales' curiosity, playfulness, and ability to solve problems. Alaskan orcas have not only learned how to steal fish fromlonglines,but have also overcome a variety of techniques designed to stop them, such as the use of unbaited lines as decoys.[138]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.[138]

In other anecdotes, researchers describe incidents in which wild orcas playfully tease humans by repeatedly moving objects the humans are trying to reach,[139]or suddenly start to toss around a chunk of ice after a human throws a snowball.[140]

The orca's use of dialects and the passing of other learned behaviours from generation to generation have been described as a form ofanimal culture.[141]

The complex and stable vocal and behavioural cultures ofsympatricgroups of killer whales (Orcinus orca) appear to have no parallel outside humans and represent an independent evolution of cultural faculties.[142]

Life cycle

Adult female orca with calf nearSouth Georgia

Female orcas begin to mature at around the age of 10 and reach peak fertility around 20,[143]experiencing periods ofpolyestrouscycling separated by non-cycling periods of three to 16 months. Females can often breed until age 40, followed by a rapid decrease in fertility.[143]Orcas are among the fewanimals that undergo menopauseand live for decades after they have finished breeding.[144][145]The lifespans of wild females average 50 to 80 years.[146]Some are claimed to have lived substantially longer:Granny (J2)was estimated by some researchers to have been as old as 105 years at the time of her death, though a biopsy sample indicated her age as 65 to 80 years.[147][148][149]It is thought that orcas held in captivity tend to have shorter lives than those in the wild, although this is subject to scientific debate.[146][150][151]

Males mate with females from other pods, which preventsinbreeding.Gestationvaries from 15 to 18 months.[152]Mothers usually calve a single offspring about once every five years. In resident pods, births occur at any time of year, although winter is the most common. Mortality is extremely high during the first seven months of life, when 37–50% of all calves die.[153]Weaningbegins at about 12 months of age, and is complete by two years. According to observations in several regions, all male and female pod members participate in the care of the young.[113]

Males sexually mature at the age of 15, but do not typically reproduce until age 21. Wild males live around 29 years on average, with a maximum of about 60 years.[147]One male, known asOld Tom,was reportedly spotted every winter between the 1840s and 1930 offNew South Wales,Australia, which would have made him up to 90 years old. Examination of his teeth indicated he died around age 35,[154]but this method of age determination is now believed to be inaccurate for older animals.[155]One male known to researchers in thePacific Northwest(identified as J1) was estimated to have been 59 years old when he died in 2010.[156]Orcas are unique among cetaceans, as their caudal sections elongate with age, making their heads relatively shorter.[43]

Infanticide,once thought to occur only in captive orcas, was observed in wild populations by researchers off British Columbia on December 2, 2016. In this incident, an adult male killed the calf of a female within the same pod, with the adult male's mother also joining in the assault. It is theorized that the male killed the young calf in order to mate with its mother (something thatoccurs in other carnivore species), while the male's mother supported the breeding opportunity for her son. The attack ended when the calf's mother struck and injured the attacking male. Such behaviour matches that of many smaller dolphin species, such as thebottlenose dolphin.[157]

Conservation

The "type C" orca has two-toned grey colouring, including a dark "dorsal cape", in body areas where most orcas have solid black colouring. Research is ongoing into whether one or more orca types are distinct species in need of protection.

In 2008, theIUCN(International Union for Conservation of Nature) changed its assessment of the orca'sconservation statusfromconservation dependenttodata deficient,recognizing that one or more orca types may actually be separate,endangered species.[3]Depletion of prey species,pollution,large-scaleoil spills,andhabitat disturbancecaused by noise and conflicts with boats are the most significant worldwide threats.[3]In January 2020, the first orca in England and Wales since 2001 was found dead with a large fragment of plastic in its stomach.[158]

Like other animals at the highesttrophic levels,the orca is particularly at risk of poisoning frombioaccumulationof toxins, includingPolychlorinated biphenyls(PCBs).[159]Europeanharbour sealshave problems in reproductive and immune functions associated with high levels of PCBs and related contaminants, and a survey off theWashingtoncoast found PCB levels in orcas were higher than levels that had caused health problems in harbour seals.[159]Blubber samples in theNorwegian Arcticshow higher levels of PCBs, pesticides andbrominated flame-retardantsthan inpolar bears.A 2018 study published inSciencefound that global orca populations are poised to dramatically decline due such toxic pollution.[160][161]

In thePacific Northwest,wild salmon stocks, a main resident food source, have declined dramatically in recent years.[3]In thePuget Soundregion, only 75 whales remain with few births over the last few years.[162]On the west coast of Alaska and theAleutian Islands,seal and sea lion populations have also substantially declined.[163]

In 2005, the United States government listed thesouthern residentcommunity as an endangered population under theEndangered Species Act.[58]This community comprises three pods which live mostly in theGeorgiaandHaro StraitsandPuget SoundinBritish Columbiaand Washington. They do not breed outside of their community, which was once estimated at around 200 animals and later shrank to around 90.[164]In October 2008, the annual survey revealed seven were missing and presumed dead, reducing the count to 83.[165]This is potentially the largest decline in the population in the past 10 years. These deaths can be attributed to declines inChinook salmon.[165]

ScientistKen Balcombhas extensively studied orcas since 1976; he is the research biologist responsible for discoveringU.S. Navy sonar may harm orcas.He studied orcas from the Center for Whale Research, located inFriday Harbor,Washington.[166]He was also able to study orcas from "his home porch perched above Puget Sound, where the animals hunt and play in summer months".[166]In May 2003, Balcomb (along with otherwhale watchersnear the Puget Sound coastline) noticed uncharacteristic behaviour displayed by the orcas. The whales seemed "agitated and were moving haphazardly, attempting to lift their heads free of the water" to escape the sound of the sonars.[166]"Balcomb confirmed at the time that strange underwater pinging noises detected with underwater microphones were sonar. The sound originated from a U.S. Navy frigate 12 miles (19 kilometres) distant, Balcomb said."[166]The impact of sonar waves on orcas is potentially life-threatening. Three years prior to Balcomb's discovery, research in the Bahamas showed 14 beaked whales washed up on the shore. These whales were beached on the day U.S. Navy destroyers were activated into sonar exercise.[166]Of the 14 whales beached, six of them died. These six dead whales were studied, andCAT scansof two of the whale heads showed hemorrhaging around the brain and the ears, which is consistent withdecompression sickness.[166]

Another conservation concern was made public in September 2008 when the Canadian government decided it was not necessary to enforce further protections (including theSpecies at Risk Actin place to protect endangered animals along with their habitats) for orcas aside from the laws already in place. In response to this decision, six environmental groups sued the federal government, claiming orcas were facing many threats on theBritish Columbia Coastand the federal government did nothing to protect them from these threats.[167]A legal and scientific nonprofit organization,Ecojustice,led the lawsuit and represented theDavid Suzuki Foundation,Environmental Defence,Greenpeace Canada,International Fund for Animal Welfare,theRaincoast Conservation Foundation,and theWilderness Committee.[167]Many scientists involved in this lawsuit, including Bill Wareham, a marine scientist with the David Suzuki Foundation, noted increased boat traffic, water toxic wastes, and low salmon population as major threats, putting approximately 87 orcas on the British Columbia Coast in danger.[167]

Underwater noisefrom shipping, drilling, and other human activities is a significant concern in some key orca habitats, includingJohnstone StraitandHaro Strait.[168]In the mid-1990s, loud underwater noises fromsalmon farmswere used to deter seals. Orcas also avoided the surrounding waters.[169]High-intensity sonar used by theNavydisturbs orcas along with other marine mammals.[170]Orcas are popular withwhale watchers,which may stress the whales and alter their behaviour, particularly if boats approach too closely or block their lines of travel.[171]

TheExxon Valdezoil spilladversely affected orcas inPrince William Soundand Alaska'sKenai Fjordsregion. Eleven members (about half) of one resident pod disappeared in the following year. The spill damaged salmon and other prey populations, which in turn damaged local orcas. By 2009, scientists estimated the AT1 transient population (considered part of a larger population of 346 transients), numbered only seven individuals and had not reproduced since the spill. This population is expected to die out.[172][173]

Orcas are included in Appendix II of theConvention on International Trade in Endangered Species(CITES), meaning international trade (including in parts/derivatives) is regulated.[4]

Relationship with humans

Indigenous cultures

See also:Animal worship
Haidasculpture byBill Reid

Theindigenous peoples of the Pacific Northwest Coastfeature orcas throughouttheir art,history, spirituality and religion. TheHaidaregarded 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.[174]For theKwakwaka'wakw,the orca was regarded as the ruler of the undersea world, withsea lionsfor slaves and dolphins for warriors.[174]InNuu-chah-nulthandKwakwaka'wakw mythology,orcas may embody the souls of deceased chiefs.[174]TheTlingitof southeastern Alaska regarded the orca as custodian of the sea and a benefactor of humans.[175] TheLummiconsider orca to be people, referring to them as "qwe'lhol'mechen" which means "our relations under the waves".[176]

TheMaritime Archaicpeople ofNewfoundlandalso had great respect for orcas, as evidenced by stone carvings found in a 4,000-year-old burial at thePort au Choix Archaeological Site.[177][178]

In the tales and beliefs of theSiberian Yupikpeople, orcas are said to appear aswolvesin winter, and wolves as orcas in summer.[179][180][181][182]Orcas are believed to assist their hunters in driving walrus.[183]Reverence is expressed in several forms: the boat represents the animal, and a wooden carving hung from the hunter's belt.[181]Smallsacrificessuch as tobacco or meat are strewn into the sea for them.[183][182]

TheAinu peopleofHokkaido,theKuril Islands,and southernSakhalinoften referred to orcas in their folklore and myth asRepun 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 asbrown bears.[184]

Attacks by wild orcas on humans and animals

Further information:Orca attack
Male orca depicted in St Mary's inGreifswald,Germany, 1545[16]

InWestern cultures,orcas were historically feared as dangerous, savage predators.[185]The first written description of an orca was given byPliny the EldercircaAD 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).[186]

Of the very few confirmed attacks on humans by wild orcas, none have been fatal.[187]In one instance, orcas tried to tip ice floes on which a dog team andphotographerof theTerra Nova Expeditionwere standing.[188]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, but the Orca then retreated,[189]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.[190]

Orca attacks on sailboats and small vessels

Main article:Iberian orca attacks

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.[191]According to the Atlantic Orca Working Group (GTOA) as many as 500 vessels have been damaged between 2020 and 2023.[192]In one video, an orca can be seen biting on one of the two rudders ripped from a catamaran nearGibraltar.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."[193]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.[194]This has led to recommendations that sailors now carry bags of sand.[195]Dropping sand into the water near the rudder is thought to confuse the sonar signal.[196]Experts were divided as to whether the behavior was some sort of revenge or protection response to a previous traumatic incident, or playful or frustrated attempts to get a boat's propeller to emit a stream of high-speed water.[197]

Attacks on humans by captive orcas

Unlike wild orcas, captive orcas have made nearly two dozenattacks on humanssince the 1970s, some of which have been fatal.[198][199]

Human attacks on orcas

Competition with fishermen also led to orcas being regarded as pests. In the waters of thePacific NorthwestandIceland,the shooting of orcas was accepted and even encouraged by governments.[185]As an indication of the intensity of shooting that occurred until fairly recently, about 25% of the orcas captured inPuget Soundfor aquariums through 1970 bore bullet scars.[200]The U.S. Navy claimed to have deliberately killed hundreds of orcas in Icelandic waters in 1956 with machine guns, rockets, anddepth charges.[201][202]

Modern Western attitudes

See also:Orcas in popular culture
Ingrid Visser's research team filming orcas in New Zealand

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 asMoby Doll,asouthern resident orcaharpooned offSaturna Islandin 1964.[185]He was the first ever orca to be studied at close quarters alive, not postmortem.Moby Doll's impact in scientific researchat the time, including the first scientific studies of an orca's sound production, led to two articles about him in the journalZoologica.[203][204]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.[205]

In 2002, the orphanSpringerwas successfully returned to her family.

Between 1964 and 1976, 50 orcas from the Pacific Northwest were captured for display inaquaria,and public interest in the animals grew. In the 1970s, research pioneered byMichael Biggled to the discovery of the species' complex social structure, its use of vocal communication, and its extraordinarily stable mother–offspring bonds. Throughphoto-identificationtechniques, individuals were named and tracked over decades.[206]

Bigg's techniques also revealed the Pacific Northwest population was in the low hundreds rather than the thousands that had been previously assumed.[185]The southern resident community alone had lost 48 of its members to captivity; by 1976, only 80 remained.[207]In the Pacific Northwest, the species that had unthinkingly been targeted became a cultural icon within a few decades.[164]

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 filmFree Willy,the movie's captive starKeikowas returned to the coast of his nativeIcelandin 2002. The director of the International Marine Mammal Project for theEarth Island Institute,David Phillips, led the efforts to return Keiko to the Iceland waters.[208]Keiko however did not adapt to the harsh climate of theArctic Ocean,and died a year into his release after contractingpneumonia,at the age of 27.[209]In 2002, the orphanSpringerwas discovered inPuget 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.[210]The saving of Springer raised hopes that another young orca namedLuna,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.[211]

Whaling

Main article:Whaling
The orca namedOld Tomswims alongside awhaleboat,flanking a whale calf. The boat is being towed by a harpooned whale (not visible here), near Eden, Australia.

The earliest known records of commercial hunting of orcas date to the 18th century in Japan. During the 19th and early 20th centuries, the globalwhalingindustry caught immense numbers ofbaleenand sperm whales, but largely ignored orcas because of their limited amounts ofrecoverable oil,their smaller populations, and the difficulty of taking them.[116]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 theMinistry of the Environmentclaims that there had been domestic catches of about 1,600 whales between late 1940s to 1960s[212]) and Norway took 987.[213]Extensive hunting of orcas, including anAntarcticcatch of 916 in 1979–80 alone, prompted theInternational Whaling Commissionto recommend a ban on commercial hunting of the species pending further research.[213]Today, no country carries out a substantial hunt, althoughIndonesiaandGreenlandpermit small subsistence hunts (seeAboriginal 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 inAkashi StraitandHarimanadabeing killed in theSeto Inland Seain 1957,[214][215]the killing of five whales from a pod of 11 members that swam intoTokyo Bayin 1970,[216]and a catch record in southern Taiwan in the 1990s.[217][218]

Cooperation with humans

Orcas have helped humans hunting other whales.[219]One well-known example was theorcas of Eden, Australia,including the male known asOld Tom.Whalers more often considered them a nuisance, however, as orcas would gather to scavenge meat from the whalers' catch.[219]Some populations, such as in Alaska'sPrince William Sound,may have been reduced significantly by whalers shooting them in retaliation.[21]

Whale watching

Whale watchingcontinues 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.[220]This population is followed by approximately 20 vessels for 12 hours a day during the months May–September.[221]Researchers discovered that these vessels are in the line of sight for these whales for 98–99.5% of daylight hours.[221]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.[221]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.[221]

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.[222]

Captivity

Main article:Captive orcas
Lolita,at theMiami Seaquarium,was one of the oldest orcas in captivity.

The orca'sintelligence,trainability, striking appearance, playfulness in captivity and sheer size have made it a popular exhibit at aquaria andaquatic 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.[223]

Organizations such asWorld Animal Protectionand theWhale and Dolphin Conservationcampaign against the practice of keeping them in captivity. In captivity, they often develop pathologies, such as thedorsal fincollapse seen in 60–90% of captive males. Captives have vastly reduced life expectancies, on average only living into their 20s.[b]That said, a 2015 study coauthored by staff atSeaWorldand theMinnesota Zoosuggested no significant difference in survivorship between free-ranging and captive orcas.[150]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.[224]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 performcircus tricksthat are not part of wild orca behaviour, seeabove.[225]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.[135]Captives occasionally act aggressively towards themselves, their tankmates, or humans, which critics say is a result ofstress.[198]Between 1991 and 2010, the bull orca known asTilikumwas involved in the death of three people, and was featured in the critically acclaimed 2013 filmBlackfish.[226]Tilikum lived at SeaWorld from 1992 until his death in 2017.[227][228]

In March 2016, SeaWorld announced that they would be ending their orca breeding program and their theatrical shows.[229]However, as of 2020, theatrical shows featuring orcas are still ongoing.[230]

See also

Footnotes

  1. ^According to Baird,[98]killer whales prefer harbour seals to sea lions and porpoises in some areas.
  2. ^Although there are examples of killer whales living longer, including several over 30 years old, and two captive orcas (Corky II and Lolita) are in their mid-40s.

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Works cited

Further reading

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