Dolphins and Whales Window

Website Privacy Statement
Your Ad Here


Orca: The orca (Orcinus orca), commonly known as the killer whale, and sometimes called the grampus, is the largest member of the oceanic dolphin family. It is the second-most widely distributed mammal on Earth (after humans) and is found in all the world's oceans. It is also a versatile 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. 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 neither a whale (except in the broadest sense, i.e., the sense that all cetaceans are whales) nor a danger to humans; no attack on a human by an orca in the wild has ever been recorded, though there have been isolated reports of captive orcas attacking their handlers at marine theme parks.

Since the 1960s, "orca" (plural "orcas") has steadily grown in popularity as the common name used to identify the species in English and is now more popular than the traditional name, "killer whale", among those in the field (though the latter is still widely used by the general public).

There are several reasons for the change. First, having the word whale in the name of a species that is really a dolphin causes confusion. Second, the species is called orca in most other European languages and, as there has been a steady increase in the amount of international research into the species, there has been a convergence in naming. Further, the killer in "killer whale" is often wrongly assumed to imply that the creature will kill humans. This historical reputation is downplayed by rebranding the species with a different name.

It is commonly accepted that "killer whale" is an 18th-century mistranslation of the name given by Spanish sailors for the species — which would properly be translated as whale-killer. That the original name was itself a mistranslation has also strengthened the case for "orca".

However there are many who prefer the original name on account of the fact that it is a good description of a species that does indeed kill many animals, including other cetaceans. These 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."

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 palaeontologists 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 known to date back at least five million years.

Physical characteristics:
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. 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). At about 1.8 m (6 ft), the dorsal fin of the male is taller than the female's, and more upright.

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.

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 whales. 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. In analysed 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. Mothers breed until the age of 40, meaning that on average they raise five children. Typically females live to the age of fifty, but may survive well into their eighties or nineties in exceptional cases. Males become sexually active at the age of 15, and live to about 30 on average, and to 50 in exceptional cases.

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 (unusually 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.

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.

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. 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 whales), 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.

Social interaction: Orcas have a complex system of social grouping. The basic unit is the matriline, which consists of a single female orca (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 of orcas living in the same line. 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.

Matrilines tend to congregate with a small number of other matrilines to form a pod, consisting on average of about 18 animals. Members of a pod all have the same dialect (see the song section below) 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 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.

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.

In the northeast Pacific there have been three communities identified:

The southern community (1 clan, 3 pods, 83 orcas as of 2000)
The northern community (3 clans, 16 pods, 214 orcas as of 2000)
The south Alaskan community (2 clans, 11 pods, 211 orcas as of 2000)
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, males are much more likely to split off to live a solitary life. However, transient groups still have a loose connection defined by their dialect.

The day-to-day behaviour 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.