Orca

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Orca Fossil range: Early Pliocene - Recent
Image:Killerwhales jumping.jpg Transient Orcas near Unimak Island, eastern Aleutian Islands, Alaska Image:Orca size.png Size comparison against an average human
Conservation status
LR/c
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Mammalia Order: Cetacea Suborder: Odontoceti Family: Delphinidae Genus: Orcinus Species: O. orca
Binomial name
Orcinus orca Linnaeus, 1758
Image:Cetacea range map Orca.PNG Orca range (in blue)

The Orca or Killer Whale (Orcinus orca) is the largest species of the oceanic dolphin family (Delphinidae). It is found in all the world's oceans, from the frigid Arctic and Antarctic regions to warm, tropical seas.

Orcas are versatile predators with some populations feeding mostly on fish and others on marine mammals, including sea lions, seals, and large whales. There are up to five distinct Orca types, some of which may be separate subspecies or even species. Orcas are highly social; some populations are composed of matrilineal family groups which are the most stable of any animal species.^[1] The sophisticated social behaviour, hunting techniques, and vocal behaviour of Orcas have been described as manifestations of culture.

Although Orcas are not an endangered species, some local populations are considered threatened or endangered due to pollution, depletion of prey species, conflicts with fishing activities and vessels, and habitat loss. Wild Orcas are usually not considered a threat to humans.^[2] There have, however, been isolated reports of captive Orcas attacking their handlers at marine theme parks.^[3]

Contents 1 Taxonomy and evolution 2 Description 3 Lifecycle 4 Distribution 5 Diet 5.1 Fish and other cold-blooded prey 5.2 Marine mammal prey 5.3 Birds 6 Behaviour 7 Vocal behaviour 8 Intelligence 9 Conservation 10 Orcas and humans 10.1 Whaling 10.2 Captivity 10.2.1 Dorsal fin collapse 10.2.2 Attacks on humans 10.2.3 Other incidents 10.3 Cultural references 11 Nomenclature 12 See also 13 Media 14 Notes and references 15 External links

Taxonomy and evolution

The Orca is the sole species in the genus Orcinus. It is one of thirty-five species in the dolphin family. Like the Sperm Whale genus Physeter, Orcinus is a genus with a single, abundant species with no immediate relatives from a cladistic point of view, thus paleontologists believe that the Orca is a prime candidate to have an anagenetic evolutionary history — that is the evolution of ancestral to descendant species without splitting of the lineage. If true, this would make the Orca one of the oldest dolphin species, although it is unlikely to be as old as the family itself, which is believed to date back at least five million years.

However, there are at least three to five types of Orcas that are distinct enough to be considered different races, subspecies, or even species. In the 1970s and 1980s, research off the west coast of Canada and the United States identified the following three types:

• Resident: These are the most commonly sighted of the three populations in the coastal waters of the northeast Pacific. The resident Orcas' diet consists primarily of fish and sometimes squid and they live in complex and cohesive family groups known as pods. Female residents characteristically have a rounded dorsal fin tip that terminates in a sharp corner. They are known to visit certain areas consistently.
• Transient: The diet of these Orcas consists almost exclusively of marine mammals; they do not eat fish. Transients generally travel in small groups, usually of two to six animals. Unlike residents, transients may not always stay together as a family unit. Female transients are characterized by dorsal fins that are more triangular and pointed than those of residents. Transients travel on extremely unpredictable routes; they may be seen once in an area and never be seen after, or return 10 years later.
• Offshore: These Orcas cruise the open oceans and feed primarily on fish, sharks and turtles. They have been seen travelling in groups of up to 60 animals. Currently there is little known about the habits of this population, but they can be distinguished genetically from the residents and transients. Female offshores are characterized by dorsal fin tips that are continuously rounded. Offshores also seem smaller than the two other types. Offshores live only in open seas, hence the name, which makes them difficult to study.

Orca populations in other parts of the world have not been as well-studied. However, there appears to be a correlation between a population's diet and its social behaviour. Fish-eating Orcas in Alaska and Norway have also been observed to have resident-like social structures. Mammal-eating Orcas in Argentina and the Crozet Islands have been observed to behave more like transients.^[1]

Transient and resident Orcas live in the same areas, but avoid each other. The name "transient" originated from the belief that these Orcas were outcasts from larger resident pods. Researchers later discovered that transients are not born into resident pods, or vice-versa. The evolutionary split between the two groups is believed to have begun 2 million years ago.^[4] Recent genetic research has found that the types have not interbred for up to 10,000 years.^[5]

Three Orca types have recently been documented in the Antarctic.

• Type A looks like a "typical" Orca, living in open water and feeding mostly on Minke Whales.
• Type B is smaller than Type A. It has a large white eyepatch and a patch of grey colouring on its back, called a dorsal cape. It feeds mostly on seals.
• Type C is the smallest type and lives in larger groups than any other type of Orca. Its eyepatch is distinctively slanted forwards, rather than parallel to the body axis. Like Type B, it has a dorsal cape. Its only prey observed so far is the Antarctic toothfish.

Type B and C Orcas live close to the Antarctic ice pack, and diatoms in these waters may be responsible for the yellowish colouring of both types. Research is ongoing as to whether Type B and C orcas are different species.^[6][7]

Description

Orcas are distinctively marked, with a black back, white chest and sides, and a white patch above and behind the eye. Calves are born with a yellowish or orange tint, which fades to white. Orcas have a heavy and stocky body and a large dorsal fin with a dark grey "saddle patch" at the fin's rear. Males can be up to 9.5 m long (31 ft) and weigh in excess of 6 tonnes; it has been reported that especially large males have reached nearer 8 tonnes. Females are smaller, reaching up to 8.5 m (28 ft) and a weight of about 5 tonnes. The longest Orca ever recorded was a male from Washington state, measuring 9.8 m (32 ft). Calves at birth weigh about 180 kg and are about 2.4 m long (8 ft). The Orca's large size and strength make them one of the fastest marine mammals, often reaching speeds in excess of 56 km/h (35mph).

Unlike most dolphins, the pectoral fin of an Orca is large and rounded — more of a paddle than other dolphin species. Males have significantly larger pectoral fins than females. At about 1.8 m (6 ft), the dorsal fin of the male is more than twice the size of the female's, and is more of a triangle shape — a tall, elongated isosceles triangle, whereas the dorsal fin of the female is shorter and generally more curved.

Adult male Orcas are very distinctive and are unlikely to be confused with any other sea creature. When seen from a distance in temperate waters, adult females and juveniles can be confused with various other species, such as the False Killer Whale or Risso's Dolphin.

Individual Orcas can be identified from a good photograph of the animal's dorsal fin and saddle patch, taken when it surfaces. Variations such as nicks, scratches, and tears on the dorsal fin, and the pattern of white or grey in the saddle patch, are sufficient to distinguish Orcas from each other. For the well-studied Orcas of the northeast Pacific, catalogues have been published with the photograph and name of each Orca. Photo-identification has enabled the local population of Orcas to be counted each year rather than estimated, and has enabled great insight into Orca lifecycles and social structures.

Lifecycle

Females become mature at around 15 years of age. From then they have periods of polyestrous cycling with non-cycling periods of between three and sixteen months. The gestation period varies from fifteen to eighteen months. Mothers calve, with a single offspring, about once every five years. In analysed resident pods, birth occurs at any time of year, with the most popular months being those in winter. Newborn mortality is very high — one survey suggested that nearly half of all calves fail to reach the age of six months. Calves nurse for up to two years, but will start to take solid food at about twelve months. All resident Orca pod members, including males of all ages, participate in the care of young whales.^[4]

Cows breed until the age of 40, meaning that on average they raise five offspring. Typically, females live to the age of fifty, but may survive well into their eighties or nineties in exceptional cases. Males become sexually mature at the age of 15, but do not typically reproduce until age 21. Males live to about 45 on average, and close to 90 in exceptional cases.^[8]

Distribution

Orcas are found in all oceans and most seas, including (unusually for cetaceans) the Mediterranean and Arabian seas. However, they prefer cooler temperate and polar regions. Although sometimes spotted in deep water, coastal areas are generally preferred to pelagic environments.

The Orca is particularly highly concentrated in the north-east Pacific Basin, where Canada curves into Alaska, off the coast of Iceland and off the coast of northern Norway. They are regularly sighted in Antarctic waters right up to the ice-pack and are believed to venture under the pack and survive breathing in air pockets like the beluga does. In the Arctic, however, the species is rarely seen in winter, as it does not approach the ice pack. It does visit these waters during summer.

Information for off-shore regions and tropical waters is more scarce but widespread, if not frequent, sightings indicate that the Orca can survive in most water temperatures. Sightings are rare in Indonesian and Philippine waters. No estimate for the total worldwide population exists. Local estimates include 70-80,000 in the Antarctic, 8,000 in the tropical Pacific (although tropical waters are not the Orca's preferred environment, the sheer size of this area — 19 million square kilometres — means there are thousands of Orcas), up to 2,000 off Japan, 1,500 off the cooler north-east Pacific and 1,500 off Norway. Adding very rough estimates for unsurveyed areas, the total population could be around 100,000.

With the rapid decline of Arctic sea ice in the Hudson Strait, the range of Orcas has now extended into the far northern waters of Canada. Through the 1990s, Orcas were sighted in western Hudson Bay at a rate of six per decade; sightings rose to more than 30 between 2001-2006.^[9]

Diet

The Orca is an apex predator. They are sometimes called the wolves of the sea because they hunt in packs like wolves. On average, an Orca eats 500 lbs. (227 kg) of food each day.^[10] The array of species on which Orcas prey is diverse.

Specific populations show a high degree of specialization on particular prey species. For example, some populations in the Norwegian and Greenland sea specialise in herring and follow that fish's migratory path to the Norwegian coast each autumn. Other populations in the area prey on seals. In field observations of the resident whales of the northeast Pacific, salmon accounted for 96% of animals' diet, with 65% of the salmon being the large, fatty Chinook.^[1] They have been observed to swim through schools of the smaller salmon species without attacking any of them. Depletion of specific prey species in an area is therefore cause for concern for the local Orca population, despite the high overall diversity of potential Orca prey.

Although resident Orcas have never been observed to eat other marine mammals, they are known to occasionally harass and kill porpoises and seals for no apparent reason.^[1] They may do this to prevent them from competing for scarce resources.^{[citation needed]}

Fish and other cold-blooded prey

Fish-eating Orcas prey on 30 species of fish, particularly salmon (including Chinook and Coho), herring, and tuna. Basking sharks, oceanic whitetip sharks, and occasionally even great white sharks are taken for their nutrient-rich livers. In New Zealand killer whales have been observed hunting stingrays as well. Cephalopods, such as octopuses and a wide range of squids, are also targets.

While salmon are usually hunted by a single Orca or a small group of individuals, 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. The Orcas then slap the ball with their tail flukes, either stunning or killing up to 10-15 herring with a successful slap. The herring are then eaten one at a time. Carousel feeding has only been documented in the Norwegian Orca population and with some oceanic dolphin species.

Marine mammal prey

The Orca is the only cetacean species to regularly prey on other cetaceans.^{[citation needed]} Twenty-two species have been recorded as preyed on, either through an examination of stomach contents, examining scarring on the prey's body, or from observing the Orcas' feeding activity. Groups of Orcas attack even larger cetaceans such as Minke Whales, Gray Whales, and very occasionally Sperm Whales or Blue Whales. Orcas generally choose to attack whales which are young or weak. However, a group of five or more Orcas may attack healthy adult whales.

When hunting a young whale, a group chases it and its mother until they are worn out. Eventually the Orcas manage to separate the pair and surround the young whale, preventing it from returning to the surface to breathe. Whales are typically drowned in this manner. Pods of female Sperm Whales can sometimes protect themselves against a group of Orcas by forming a protective circle around their calves with their flukes facing outwards. This formation allows them to use their powerful flukes to repel the Orcas. Hunting large whales, however takes a lot of time, usually several hours.

Other marine mammals prey species include most species of seal and sea lion, and less frequently Walruses and Sea Otters. Orcas often using complex hunting strategies to find and subdue their prey. Sea lions are killed by head-butting or by being slapped and stunned by a tail fluke. They occasionally throw seals through the air in order to stun and kill them. Often, to avoid injury, they 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.

Some highly specialized hunting techniques have been observed. Off Argentina and the Crozet Islands, Orcas feed on South American sea lion and elephant seal pups in shallow water; even beaching themselves temporarily. Beaching, usually fatal to whales, is not an instinctive behaviour. Adult Orcas have been observed to teach the younger whales the skills of hunting in shallow water. Off Argentina, adults pull seals off the shoreline for younger whales to recapture. Off the Crozet Islands, mothers have been seen pushing their calves onto the beach, waiting to pull the youngster back if needed.^[4]

Another technique for capturing seals is known as wave-hunting: Orcas spy-hop to locate seals resting on ice floes, and then create waves by swimming together in groups to wash over the floe. This causes the seal to be thrown into the water where another Orca waits to kill it. This behaviour has only been recorded a few times and it is not known how often it occurs. The most recent recorded instance in April 2006 ended with the group of Orcas actually returning the seal to the ice floe after they had shown the younger animals how to properly perform the technique.

There has also been one recorded case of probable Orca cannibalism. A study in the South Pacific in 1975 recorded two male Orcas whose stomachs contained the remains of other Orcas. Of the 30 Orcas captured and examined in this survey, 11 had empty stomachs — an unusually high percentage which indicates the Orcas were forced to cannibalism through a lack of food.^{[citation needed]}

Birds

Several species of bird are also preyed upon, including penguins, cormorants and sea gulls. A captive Orca in Friendship Cove discovered that it could regurgitate fish onto the surface, attracting sea gulls, and then eat them. Other Orcas then learned the behaviour by example.^[11] Orcas at Sea World California have also been observed hunting birds.^[12]

Behaviour

The day-to-day behaviour of Orcas is generally divided into four activities: foraging, travelling, resting and socializing. Orcas are generally enthusiastic in their socializing, engaging in behaviours such as breaching, spyhopping, and tail-slapping.

Resident Orcas can also be seen swimming with porpoises, other dolphins, seals, and sea lions, which are common prey for transient Orcas. Resident Orcas are continually on the move, sometimes travelling as much as 160 km (100 miles) in a day, but may be seen in a general area for a month or more. Range for resident Orca pods may be as much as 1300 km (800 miles) or as little as 320 km (200 miles).

Social structure of resident Orca communities

Fish-eating Orcas in the North Pacific have a complex but extremely stable system of social grouping. Unlike any other mammal species whose social structure is known, resident Orcas of both genders live with their mothers for their entire lives. Therefore, Orca societies are based around matrilines consisting of a single female (the matriarch) and her descendants. The sons and daughters of the matriarch form part of the line, as do the sons and daughters of those daughters. The average size of a matriline is nine animals.

Because females can live for up to ninety years, it is not uncommon for four or even five generations to travel together. These matrilineal groups are highly stable. Individuals split off from their matrilineal group only for up to a few hours at a time, in order to mate or forage. No permanent casting-out of an individual from a matriline has ever been recorded.

Closely-related matrilines form loose aggregations called pods, consisting on average of about 18 animals. All members of a pod use a similar set of calls, known as a dialect. Unlike matrilines, pods may split apart for days or weeks at a time in order to forage. Orcas within a pod do not interbreed; mating occurs only between members of different pods.

Resident pods have up to 50 or more members. Occasionally, several pods join to form "superpods," sometimes with more than 150 animals.

The next level of grouping is the clan. A clan consists of pods which have a similar dialect. Again the relationship between pods appears to be genealogical, consisting of fragments of families with a common heritage on the maternal side. Different clans can occupy the same geographical area; pods from different clans are often observed travelling together. When resident pods come together to travel as a clan, they greet each other by forming two parallel lines akin to a face-off before mingling with each other.

The final layer of association, perhaps more arbitrary and devised by humans rather than the other very natural divisions, is called the community and is loosely defined as the set of clans that are regularly seen mixing with each other. Communities do not follow discernible familial or vocal patterns.^[13]

Transient groups are generally smaller because, although they too are based on matrilines, some male and female offspring eventually disperse from the maternal group. However, transient groups still have a loose connection defined by their dialect.

Vocal behaviour

See also: Whale song

As with other dolphins, Orcas are highly vocal. They produce a variety of clicks and whistles that are used for communication and echolocation. The vocalization types vary with activity. While resting they are much quieter, merely emitting an occasional call that is distinct from those heard when engaging in more active behaviour.

Fish-eating resident groups of Orcas in the northeast Pacific tend to be much more vocal than transient groups living in the same waters. Resident Orcas feed on fish, particularly salmon, a prey with poor underwater hearing that cannot detect Orca calls at any significant distance. Transient Orcas on the other hand feed mainly on marine mammals and occasionally on seabirds. Because all marine mammals have excellent underwater hearing, transients probably remain silent for much of the time to avoid detection by their acoustically-sensitive prey. They sometimes use a single click (called a cryptic click) rather than the long train of clicks observed in other populations. On the other hand, residents will make sounds to identify themselves when they are approaching other sea mammals.

Resident pods have group-specific dialects. Each pod has its own vocal repertoire or set of particular stereotyped underwater calls (call types). Every member of the pod seems to know all the call types of the pod, so it is not possible to identify a single animal using voice alone. A particular call type might be used by only one group or shared among several.

The number of call types shared by two groups appears to be a function of their genealogical relatedness rather than their geographical distance. Two groups that share a common set of ancestors but have grown apart in distance are likely to have a similar set of call types, indicating that calls are a learned behaviour.

Orca mothers have been observed training their young in the pod's dialect. The mother uses a simplified version of the pod's dialect when training a calf; a sort of baby-talk. This suggests that Orca vocalization has a learned basis in addition to an instinctual one.

Intelligence

Main article: Cetacean intelligence

Orcas are well known for their mental capabilities. Studies have indicated that an Orca has an outstanding memory, perhaps even photographic. In tests conducted with Orcas in captivity, they recalled testing patterns up to 25 years after they were initially conducted.^{[citation needed]}

The Orca's use of dialects and the passing of other learned behaviours from generation to generation, has been described as a form of culture. The paper Culture in Whales and Dolphins,^[14] goes as far as to say, "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."

Conservation

Environmental degradation, depletion of prey species, conflicts with fishing activities, and habitat degradation are currently the most significant threats to Orcas worldwide.^[2][1]

Like other animals at the highest trophic levels of the food chain, the Orca is particularly susceptible to poisoning via accumulation of Polychlorinated biphenyls (PCBs) in the body. A survey of animals off the Washington coast found that PCB levels in Orcas were higher than those in harbour seals in Europe that have been sickened by the chemical. Samples from the blubber of Orcas in the Norwegian Arctic show higher levels of PCBs, pesticides and brominated flame-retardants than in Polar Bears.

Stocks of most species of salmon, a main food source for resident Orcas in the northeast Pacific, have declined dramatically in recent years. On the west coast of Alaska and the Aleutian Islands, populations of seals and sea lions have also undergone a major decline.^[1] If food is scarce, Orcas must draw from their blubber for energy, which further magnifies the effects of pollutants. In 2005, the United States government listed the Southern Resident community of Orcas as an endangered population under the Endangered Species Act. The Southern Resident community comprises three pods which spend most of the year in the Georgia and Haro Straits and Puget Sound in British Columbia and Washington state. These Orcas do not breed outside of their community, which was previously estimated at around 200 animals and had shrunk to around 90.^[15]

Noise from shipping, drilling, and other human activities can interfere with the acoustic communication and echolocation of Orcas. In the mid-1990s, loud underwater noises from salmon farms were used to deter seals. Orcas subsequently avoided the surrounding waters.^[16] In addition high intensity navy sonar has become a new source of distress for orcas.^[17] Orcas are popular with whale watchers, which may change Orca behaviour and stress Orcas, particularly if boats approach Orcas too closely or block their line of travel.^[18]

The Exxon Valdez oil spill had an adverse effect on Orcas in Prince William Sound and the Kenai Fjords region of Alaska. One resident pod was caught in the spill; though the pod successfully swam to clear water, eleven members (about half) of the pod disappeared in the following year. The spill had a long-term effect by reducing the amount of available prey, such as salmon, and has thus been responsible for a local population decline. In December 2004, scientists at the North Gulf Oceanic Society said that the AT1 transient population of Orcas (currently considered part of a larger population of 346 transients), now only numbering 7 individuals, has failed to reproduce at all since the spill. This population is expected to become extinct.^[19]

Orcas and humans

Although only scientifically identified as a species in 1758, the Orca has been known to humans since prehistoric times.

The first written description of an Orca is given in Pliny the Elder's Natural History (written circa 70 AD). The aura of invincibility around the all-consuming Orca was well-established by this time. Having observed the public slaughter of an Orca stranded at a harbour near Rome, Pliny writes, "Orcas (the appearance of which no image can express, other than an enormous mass of savage flesh with teeth) are the enemy of [other whales]... they charge and pierce them like warships ramming."^[20]

Whaling

Orcas were targeted in commercial whaling for the middle part of the twentieth century once stocks of larger species had been depleted. Commercial hunting of Orcas came to an abrupt halt in 1981 with the introduction of a moratorium on all whaling. (Although from a taxonomic point of view an Orca is a dolphin rather than a whale, it is sufficiently large to come under the purview of the International Whaling Commission.)

The greatest hunter of Orcas was Norway, which took an average of 56 animals per year from 1938 to 1981. Japan took an average of 43 animals from 1946 to 1981. (War year figures are not available but are likely to be fewer). The Soviet Union took a few animals each year in the Antarctic, with the extraordinary exception of the 1980 season when it took 916.

Today, no country carries out a substantial hunt. A small level of subsistence whaling is carried out by Indonesia and Greenland. As well as being hunted for their meat, Orcas have also been killed because of competition with fishermen. In the 1950s the United States Air Force, at the request of the Government of Iceland, used bombers and riflemen to slaughter Orcas in Icelandic waters because they competed with humans for fish. The operation was considered a great success at the time by fishermen and the Icelandic government. However, many were unconvinced that orcas were responsible for the drop in fish stocks, blaming overfishing by humans instead. This debate has led to repeated studies of North Atlantic fish stocks, with neither side in the whaling debate giving ground since that time.

Orcas have been known to co-operate with humans in the hunting of other whales. One well-known example occurred near the port of Eden in South-Eastern Australia in the 1920s. A pod of Orcas, led by a dominant male called Old Tom, would assist whalers in hunting baleen whales. The Orcas would find the target whales, shepherd them into Twofold Bay and then alert the whalers to their presence and often help to kill the whales. After the harpooning, some of the Orcas would even grab the ropes in their teeth and aid the whalers in hauling. The skeleton of Old Tom is on display at the Eden Killer Whale Museum, and significant wear marks still exist on his teeth from repeatedly grabbing fast moving ropes. In return for their help, the whalers allowed the Orcas to eat the tongue and lips of the whale before hauling it ashore. The Orcas would then also feed on the many fish and birds that would show up to pick at the smaller scraps and runoff from the fishing. Fear of Orcas has dissipated in recent years due to better education about the species, including the appearance of Orcas in aquariums.

Captivity

See also: List of marine parks with Orcas

The Orca's intelligence, trainability, striking appearance, playfulness in captivity and sheer size have made it a popular exhibit at aquariums and aquatic theme parks. The first Orca capture and display occurred in Vancouver in 1964. Over the next 15 years around 60 or 70 Orcas were taken from Pacific waters for this purpose. The Southern Resident community of the northeast Pacific lost 48 of its members to captivity; by 1976 only 80 Orcas were left in the community, which remains endangered.^[4] In the late 1970s and the first half of the 1980s, Orcas were generally taken from Icelandic waters (50 in the five years to 1985). Since then, Orcas have been successfully bred in captivity and wild specimens are considerably rarer.

The practice of keeping Orcas in captivity is controversial, and organisations such as the World Society for the Protection of Animals and the Whale and Dolphin Conservation Society campaign against the captivity of Orcas.

Orcas in captivity may develop physical pathologies such as dorsal fin collapse, seen in 60-90% of captive males. Captive Orcas have vastly reduced life expectancies, on average only living into their 20s. In the wild, Orcas usually live into their 40s. The captive environment usually bears little resemblance to their wild habitat, and the social groups that the Orcas are put into are completely foreign to those found in the wild.^[21] Critics claim that captive life is stressful due to small tanks, false social groupings and chemically-altered water. Captive Orcas have occasionally acted aggressively towards themselves, other Orcas, or humans, which critics say is a result of stress.

Dorsal fin collapse

Several theories exists as to why the dorsal fin of male Orcas collapses. One theory is that the collagen, or compressed lipid cells, which holds the tall dorsal fin erect is not strong enough when the Orca is placed in captivity. The collagen normally hardens in late adolescence, in which the Orca spends much time in deep ocean waters, and it is theorized that the pressure the water exerts on the fin allows it to remain supported while the collagen hardens. In captivity, however, shallow tanks lack sufficient water pressure to produce this effect, and the fin collapses before the collagen solidifies.^[22] Another theory states that the Orca is almost always in a state of turning in a tank, since it is not large enough to allow swimming in one direction for any normal duration. The constant turning exerts pressure on the dorsal fin, which in turn causes it to collapse.^[23] Yet, another theory states the Orca's genetics, body structure, and weight are all key factors. Recently, scientists and biologists documented 23% of wild Orca males off the coast of New Zealand with collapsed dorsal fins.^[24] Therefore, scientists are even more baffled concerning the causes of an Orcas' collapsed dorsal fin.

Attacks on humans

There are few confirmed attacks on humans by wild Orca. Two such recorded instances include a boy charged while swimming in Alaska, and Orcas trying to tip ice floes on which the photographer of the Terra Nova Expedition was standing.^[25]

Much more common than wild Orcas attacking people are captive Orcas attacking people, either their handlers or intruders. There have been several such instances. ABC News has reported that Orcas have attacked nearly two dozen people since the 1970s.^[26]

• On April 20, 1971; SeaWorld secretary Annette Eckis was riding on Shamu at the park in San Diego, California. Ms. Eckis slid off and Shamu grabbed her leg in its mouth. After a few minutes, Shamu was coaxed into letting Ms. Eckis go, and she was taken away from the tank on a stretcher, and required 100 stitches on her leg. Shamu may have done this out of curiosity, as Ms. Eckis was the first person to wear a bathing suit while riding the orca.^[27]

• On February 20, 1991, a group of 3 Orcas (Haida, Nootka, and Tilikum) killed a trainer named Keltie Byrne at Sealand in Victoria, British Columbia (where employees were not allowed in the water with Orcas). After this, and due to Tilikum being bullied by the two females in the tank, Tilikum was relocated to SeaWorld of Orlando, Florida, where he remains. He is currently the largest Orca in captivity.

• On July 26, 1999, at the SeaWorld park in Orlando, Florida, a man with a history of mental illness hid at Sea World after hours and climbed into the Orca tank with Tilikum, the park's huge bull. The next morning, the nude man was found dead, draped across Tilikum's back. Although some claimed that Tilikum killed the man, an autopsy revealed that the cause of death was hypothermia.

• In late July 2004, during a show at the SeaWorld park in San Antonio, Texas, an Orca pushed its trainer of ten years underwater and barred the way to the rim of the pool; the trainer could only be rescued from the animal after several minutes.

• On November 29, 2006, Kasatka at SeaWorld twice grabbed its trainer by the foot (breaking it in the process) and pulled him underwater. Trainers from the SeaWorld parks met to try and figure out why that happened.^[28]

Other incidents

One of the more infamous incidents involving Orca aggression took place in August 1989, when a dominant female Orca, Kandu V, struck a newcomer Orca, Corky II, with her mouth during a live show. Corky II had been imported from Marineland California just months prior to the incident. According to reports, a loud smack was heard across the stadium. Although trainers tried to keep the show rolling, the blow severed an artery near Kandu V's jaw, and she began spouting blood. The crowd was quickly ushered out, and after a 45-minute haemorrhage, Kandu V died. Opponents of these shows, such as PETA, see these incidents as supporting their criticism.^[29]

SeaWorld continued to be under criticism from the Born Free Foundation over its continued captivity of the Orca Corky II, whom they want returned to her family, the A5 Pod, a large pod of Orcas in British Columbia, Canada.^[30]

The captive Orca Namu developed a bacterial infection which damaged his nervous system, causing him to become non-responsive to people. During his illness he charged full speed into the wire mesh of his pen, thrashed violently for a few minutes and then died.^[31] A semi-documentary was named after him.^[32]

Cultural references

Indigenous peoples in the Pacific Northwest of North America such as the Kwakwaka'wakw, Coast Salish, Nuu-chah-nulth, Tlingit, Haida, and Tsimshian have featured the Orca prominently in their culture through history, art, spirituality and religion.

Creatures by the name of orca or "orc" have appeared throughout the history of Western literature. In Ludovico Ariosto's epic poem Orlando Furioso, the Orca (sometimes translated "orc") was a sea-monster from whom the damsel Angelica was rescued by Orlando. This Orca-like sea monster first appears in English in Michael Drayton's Polyolbion, an epic poem about Brutus the Trojan, the mythical founder of Great Britain. It later appears in John Milton's epic poem Paradise Lost.

As late as the 1970s, Orca were depicted negatively in fiction as ravenous predators whose behaviour caused heroes to interfere to help a prey animal escape. The poorly-received film Orca features the story of a male Orca going on a vengeful rampage after his pregnant mate is killed by humans. In Jaws (1975), the name of the boat used to hunt the shark is called the Orca, given the Orca's status as a known enemy of the shark. Payback arrives in the sequel Jaws 2, where the shark's first victim (chronologically) is an Orca.

In recent years, increased research and the animal's popularity in public venues has brought about a dramatic rehabilitation of the Orca's image, much as the North American Wolf's image has been changed. It is now widely seen as a respected predator that poses little actual threat to humans.

The film Free Willy (1993) focused on the quest for freedom for a captive Orca. The Orca starring in the movie, Keiko, was originally captured in Icelandic waters. After rehabilitation at the Oregon Coast Aquarium in Newport, Oregon, he was later returned to the waters of the Nordic countries, his native habitat, but continued to be dependent on humans until he died of pneumonia in December 2003. The film Happy Feet featured an attack on penguins, in which they demonstrated various documented behaviours, such as spyhopping, flinging their prey into the air (inspired by the images in the nature documentary The Blue Planet) and beaching themselves to attack.

Nomenclature

The name "Orca" (plural "Orcas") was originally given to these animals by the ancient Romans, possibly borrowed from the Greek word ὄρυξ which (among other things) referred to a species of whale. The term "orc" (or its variant "ork") has been used to describe a large fish, whale or sea-monster. It is now considered an obsolete equivalent for "Orca."

The name "killer whale" is widely used in common English. However, since the 1960s, "Orca" has steadily grown in popularity as the common name to identify the species, and both names are now used. The species is called Orca in most other European languages, and, as there has been a steady increase in the amount of international research on the species, there has been a convergence in naming.

It is commonly thought that 18th-century Spanish sailors dubbed these creatures asesina-ballenas, or "whale killer" as Orcas do attack large whales. However, this title was improperly translated into English as "killer whale". The term became so prevalent that Spanish speakers commonly used its retranslation of ballena asesina.

Supporters of the original name point out that the naming heritage is not limited to Spanish sailors. Indeed the genus name "Orcinus" means "from Hell" (see Orcus), and although the name "Orca" (in use since antiquity) is probably not etymologically related, the assonance might have given some people the idea that it means "whale that brings death," or "demon from hell."

The name of this species is similarly intimidating in many other languages. In Finnish and in Dutch it is called miekkavalas and zwaardwalvis respectively, which means "sword whale". To the Haida people native to the islands of Haida Gwaii off the coast of British Columbia, the animal was known as skana or "killing demon". The Japanese call them shachi (鯱), whose kanji character combines the radicals for fish (魚) and tiger (虎). In Chinese it's called "虎鲸" (tiger whale) or "逆戟鲸" (reversed halbert whale).

They are sometimes referred to as blackfish, a group including pilot whales, pygmy and false killer whales, and melon-headed whales.

A former name for the species is grampus. This is now seldom used and should not be confused with the Grampus genus (containing Risso's Dolphin).

See also

• Famous Orcas

Media

Notes and references

General references

Wikipedia information about Orca This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Orca". It may not have been reviewed by professional editors (see full disclaimer). Help contribute to Americola and edit this article.