|The Orca or Killer Whale (Orcinus orca), less commonly, Blackfish or Seawolf, 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 and opportunistic predators. Some populations feed mostly on fish, and other populations hunt marine mammals, including sea lions, seals, and even 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. The sophisticated social behavior, hunting techniques, and vocal behavior 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, habitat loss, and whaling. Wild Orcas are usually not considered a threat to humans. There have, however, been isolated reports of captive Orcas attacking their handlers at marine theme parks.
Taxonomy and evolution
However, there are at least three to five types of Orcas that are distinct enough to be considered different races, subspecies, or possibly even species. In the 1970s and 1980s, research off the west coast of Canada and the United States identified the following three types:
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 behavior. 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.
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 two million years ago. Recent genetic research has found that the types have not interbred for up to 10,000 years.
Three Orca types have recently been documented in the Antarctic.
Type B and C Orcas live close to the Antarctic ice pack, and diatoms in these waters may be responsible for the yellowish coloring of both types. Research is ongoing as to whether Type B and C Orcas are different species.
The naming system in The Pacific Northwest
* Residents: each resident pod has a letter and the number of the most distinctively marked individual; then, each other member has a number. Because most pods are made of several subpods, these have the name of the matriarch of the subpod.
* Transients: early in the 1970s, researchers used the same naming system as for residents, but as said before, the social structure of transients is so fluid the naming system proved inefficient and confusing. They then renamed each individual with the letter "T" (transient) and a number. the pods simply became groups with the name of one of the members, most of the time the matriarch. Because of the fact that, unlike residents, offspring often leave their mother, they gave for each known offspring a letter following the name of the mother. For example, the offspring of the mother T7 will be named T7A, her second oneT7B, etc. If the offspring herself gives birth, the calf will have a number following the name, like T7A who would have a calf named T7A1.
The naming system has been very successful and several other places in the world have used too.
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.
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 meant "whale that brings death," or "demon from hell." The name of this species is similarly intimidating in many other languages, including Finnish, Dutch, German, Haida, Japanese and Chinese.
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, whose only member is Risso's Dolphin.
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.
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 up to 90 in exceptional cases. The life spans of captive Orcas are significantly shorter, usually less than 25 years.
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 kilometers - 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 un-surveyed 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.
The migration patterns of Orcas are poorly understood. Each summer, the same resident Orcas appear off the coasts of British Columbia and Washington State. After decades of research, it is still unknown where these animals go for the rest of the year.
Orcas prey on a diverse array of species. However, specific populations show a high degree of specialization on particular prey species. For example, some populations in the Norwegian and Greenland sea specialize 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. 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.
Fish and other cold-blooded prey
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.
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. Orca cannibalism has also been reported.
Other marine mammals prey species include most species of seal and sea lion. Walruses and Sea otters are taken less frequently and Polar bears are rarely taken. Orcas often use 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 Península Valdés, Argentina and the Crozet Islands, Orcas feed on South American sea lions and Southern elephant seals in shallow water; even beaching themselves temporarily. Beaching, usually fatal to whales, is not an instinctive behavior. Adult Orcas have been observed to teach the younger whales the skills of hunting in shallow water. Off Península Valdés, 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.
Another technique for capturing seals is known as wave-hunting: Orcas spy-hop to locate Weddell seals, Ross seals, Crabeater seals and Leopard 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 behavior 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.
Orcas have also been observed preying on terrestrial mammals, such as deer and moose, swimming between islands off the northwest coast of North America.
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 traveling 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
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. Resident pods often include subpod which comprises one daughter or cousin that sometimes travels only with her offspring and sometimes join the rest of the pod.
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 traveling 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.
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.
Fish-eating resident groups of Orcas in the northeast Pacific tend to be much more vocal than transient groups in the same waters. Resident Orcas feed primarily on salmon, whose hearing is too poor to detect Orca calls at any significant distance. Residents make sounds to identify themselves when they are approaching another marine mammal. Transient Orcas, on the other hand, feed mainly on marine mammals. Because all marine mammals have excellent underwater hearing, the usual silence of transients is probably necessary 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.
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 behavior.
Orca mothers have been observed training their young in the pod's dialect. The mother uses a simplified version of the pod's dialect, a sort of baby-talk, when training a calf. This suggests that Orca vocalization has a learned basis in addition to an instinctual one.
The Orca's use of dialects and the passing of other learned behaviors from generation to generation has been described as a form of culture. The paper Culture in Whales and Dolphins, goes as far as to say, "The complex and stable vocal and behavioral cultures of sympatric groups of killer whales (Orcinus orca) appear to have no parallel outside humans and represent an independent evolution of cultural faculties."
Like other animals at the highest tropic 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 harbor 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. 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.
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. In addition high intensity navy sonar has become a new source of distress for Orcas. Orcas are popular with whale watchers, which may change Orca behavior and stress Orcas, particularly if boats approach Orcas too closely or block their line of travel.
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.
Orcas and humans
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 harbor 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."
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 over fishing 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, which included amongst its members a distinctive 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. Old Tom's role was commonly to alert the human whalers to the presence of a baleen whale in the bay by breaching or tail slapping at Kiah river mouth where the Davidson family had their tiny cottages. This role endeared him to the whalers and led to the idea that he was "leader of the pack", although such a role was more likely taken by a female as is more typical in Orca cultures. 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.
The practice of keeping Orcas in captivity is controversial, and organizations 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; however there are examples of Orcas living longer, including many who are over 30 years old and 2 Orcas (Corky II and Lolita/Tokitae of the Miami Sea Aquarium) are around 40 years of age. 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 foreign to those found in the wild. 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
One theory is that in deep ocean waters, 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. According to another theory, 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.
Other possible explanations include alterations in water balance caused by the stresses of captivity or dietary changes, lowered blood pressure due to reduced activity patterns, or overheating of the collagen brought on by greater exposure of the fin to the ambient air.
In the wild, dorsal fin collapse is rare, and the deformity is believed to have a different set of causes than in captivity. In wild Orcas, it usually results from a serious injury to the fin. After the 1989 Exxon Valdez oil spill, the dorsal fins of two male resident Orcas who had been exposed to the oil collapsed, and the animals subsequently died. In 2002, the dorsal fin of a stranded Orca showed signs of collapse after three days, but regained its natural upright appearance as soon as the whale resumed strong normal swimming upon release.
Amongst the well-studied wild Orcas off the coast of British Columbia, the rate of dorsal fin collapse is around 1%. According to one study, 23% of wild Orca males off the coast of New Zealand have collapsed dorsal fins.
Attacks on humans
Much more common than wild Orcas attacking people are captive Orcas attacking people, either their handlers or intruders. ABC News has reported that Orcas have attacked nearly two dozen people since the 1970s.
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. 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. A semi-documentary was named after him.
Orcinus orca Linnaeus, 1758
Orca range (in blue)
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