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The Orca (Orcinus orca) is the largest member of the oceanic dolphin family Delphinidae. They are sometimes referred to as blackfish, a group including Pilot whales, Pigmy and False killer whales and Melon headed whales. It is the second-most widely distributed mammal on Earth (after humans) and is found in all the world's oceans, from the frigid arctic regions to warm, tropical seas. It is also a versatile, deadly predator, eating fish, turtles, birds, seals, sharks and even other juvenile and small cetaceans. This puts the Orca at the pinnacle of the marine food chain. Orcas have been known to attack massive baleen whales, in particular Gray and Blue whales.

Actually a dolphin: The name "killer whale" reflects the animal's reputation as a magnificent and fearsome sea mammal that goes as far back as Pliny the Elder's description of the species. Today it is recognized that the Orca is a dolphin rather than a whale and that it is not a danger to humans. Aside from a boy who was charged (but not grabbed) while swimming in a bay in Alaska, there have been no confirmed attacks on humans in the wild. There have, however, been isolated reports of captive Orcas attacking their handlers at marine theme parks.

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Distinctive tuxedo wear: The animals are distinctively marked, with a black back, white chest and sides, and a white patch above and behind the eye. They have a heavy and stocky body and a large dorsal fin with a dark gray "saddle patch" behind it. Males can be up to 9.5 m long (31 ft) and weigh in excess of 6 tons; females are smaller, reaching up to 8.5 m (28 ft) and a weight of about 5 tons. Calves at birth weigh about 180 kg and are about 2.4 m long (8 ft). Unlike most dolphins, the pectoral fin of an Orca is large and rounded — more of a paddle than other dolphin species. Pectoral fins of males are significantly larger than those of 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. Nicks, cuts and scrapes on these fins, as well as distinctive features of each fin, help scientists identify individuals. There are also minor variations in physical characteristics between resident and transient Killer Whales.

Unique looking males: Large male Orcas are very distinctive and are unlikely to be confused with any other sea creature. When seen from a distance in temperate waters, females and juveniles can be confused with various other species, such as the False killer whale or Risso's dolphin.

Second to humans: The Orca is the second-most widely distributed mammal in the world, after the human. They are found in all oceans and most seas including (unusual for cetaceans) the Mediterranean and Arabian Seas. Cooler temperate and polar regions are preferred, however. Although sometimes spotted in deep water, coastal areas are generally preferred to pelagic environments.

Using air pockets: The Orca is particularly highly concentrated in the northeast 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 indeed 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.

Varied water temperatures: 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 northeast Pacific and 1,500 off Norway. Adding very rough estimates for unsurveyed areas, the total population could be around 100,000.

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(Orca range)

Ninety year old females!: Fish-eating Orcas in the North Pacific have a complex system of social grouping. The basic unit is the matriline, which consists 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 sons and daughters of the sons join the matriline of their mates) and so on down the family tree. 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 over many years. Individuals will only split off from their matrilineal group 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. The average matriline size as recorded in northeast Pacific waters is nine animals.

Pods speak the same language: Matrilines form loose aggregations called pods, consisting on average of about 18 animals. Members of a pod all have the same dialect and consist of closely related matriline fragments. Unlike matrilines, pods will split apart for days or weeks at a time in order to carry out foraging before joining back together. The largest recorded pod is 49 animals.

The clan: The next level of grouping is the clan. A clan consists of those 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 recorded 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.

Community orca: 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.

Mammal-eating orcas have a different system: It should be emphasized that these hierarchies are valid for resident groups only. Transient, mammal-eating 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.

Credit: NOAAEnthusiastic socialites: The day-to-day behavior of Orcas is generally divided into four activities: foraging, traveling, resting and socializing. Orcas are generally enthusiastic in their socializing, exhibiting a wide range of breaching, spyhopping, tail-slapping and head-stands. All-male groups often interact with erect penises. Whether this interaction is part of play or a display of dominance is not known.

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

As quiet or loud as the hearing ability of prey: Fish-eating resident groups of killer whales in the Northeast Pacific tend to be much more vocal than transient groups living in the same waters. Scientists surmise that the main reason for this lies in the different hearing abilities of their prey. Resident killer whales feed on fish, particularly Pacific salmon, a prey with poor underwater hearing that cannot detect killer whale calls at any significant distance. Transient killer whales on the other hand feed mainly on marine mammals (primarily seals, sea lions, porpoises and dolphins) 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. For the same reason, mammal-hunting killer whales tend to restrict their echolocation, occasionally using just a single click (called a cryptic click) rather than the long train of clicks observed in other populations.

Resident dialects: 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, only a dialectal group. 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. Calls are learned behavior. Traits that are copied between related individuals through vocal mimicry.

A baby every five: Most life history data about Orcas has been obtained from long-term surveys of the population off the coasts of British Columbia and Washington and by monitoring captive Orcas. Due to the completeness of the study and highly structured nature of the pods in this population, the information is detailed and accurate; however, transient groups and groups in other oceans may have slightly different characteristics. 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.

Winter - popular season for orca birth: In analyzed resident pods, birth occurs at any time of year, with the most popular months being those in winter. New-born 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. 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 30 on average, and to 50 in exceptional cases.

Playful, smart and popular: The Orca's intelligence, trainability, striking appearance, playfulness in captivity, and its sheer size have made it a popular exhibit at aquariums and various aquatic theme parks. The first Orca capture and display took place in Vancouver in 1964. Over the next 15 years around sixty or seventy Orcas were taken from Pacific waters for this purpose. In the late 1970s and the first half of the 1980s, Orcas were generally taken from Icelandic waters (fifty in the five years to 1985). Since that time, Orcas have been successfully bred in captivity and wild specimens are considerably rarer. Orcas in captivity may develop pathologies such as dorsal fin collapse, seen in 60-90% of captive males.

Fin collapse in captivity: Several theories exists as to why the dorsal fin collapse occurs, namely that the cartilage that holds the fin erect is not yet strong enough to support the fin when the Orca is placed in captivity. The hardening of the cartilage occurs 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 cartilage hardens. In captivity, however, the tank the whales reside in lack the sufficient water pressure to produce this effect, and the fin collapses before the cartilage that would support it in nature has solidified. Another theory exists that states that the whale 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.

Killer whales, killing in captivity: There have been incidents with Orcas in captivity attacking humans. In 1991, a group of 3 Orcas (Haida, Nootka, and Tillikum) killed a trainer named Keltie Byrne at Sealand in Victoria, British Columbia by keeping the trainer undewater (where employees were not allowed in the water with Orcas), apparently not knowing she could not survive underwater. In 1999, at the SeaWorld park in Orlando, Florida, one of the same Orcas allegedly killed a tourist who had snuck into the Orca's pool at night. (The dead tourist, who was otherwise physically unharmed, was also thought to be a victim of 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 raging animal after several minutes.

Aggression in captivity: 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 Marineworld 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 hemorrhage, Kandu V died. Opponents of these shows see these incidents as supporting their criticism.

Meant to live free? SeaWorld continued to be under criticism from the Born Free Foundation over its continued captivity of the Orca Corky II, who they want to be returned to her family in the A5 Pod—a large pod of Orcas in British Columbia, Canada.

Much shorter, stressful lives in Sea World: Orcas in captivity have vastly reduced life expectancies, on average only living into their 20s whilst in the wild females may live into their 80s. The captive environment also bears no resemblance to their wild habitat and the social groups that the Orcas are put into are completely foreign to that found in the wild. Critics claim that the captive life of an Orca is stressful due to small tanks, false social groupings and chemically altered water. Organizations such as the WSPA and the Whale and Dolphin Conservation Society campaign against the captivity of Orcas.

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 Kingdom: Animalia

 Phylum: Chordata

 Class: Mammalia

 Order: Cetacea

 Family: Delphinidae

 Genus: Orcinus

 Species: Orca