Killer whale

The (great) killer whale (Orcinus orca), also called killer whale, orca or butthead, is a species of cetacean in the dolphin family (Delphinidae). The species is distributed worldwide, but prefers to inhabit coastal waters at higher latitudes.

Killer whales are social animals that have a complex population structure. The smallest unit is the maternal lineage, a very close association of maternally related whales. Both at the level of the maternal lineage and at higher population levels, a transmission of certain hunting tactics and vocalizations to juveniles can be observed, which is sometimes evaluated as culture. The global population of killer whales can be divided into several ecotypes that differ in body structure, vocalizations, and behavior. Whether the ecotypes represent individual species is a matter of scientific debate - but it is particularly striking that members of different ecotypes do not interbreed. DNA analyses from 2010 suggest that several species and subspecies must be distinguished.

On a global scale, the killer whale is a generalist carnivore, preying in particular on fish, marine mammals such as seals, and occasionally other cetaceans. In rare cases, adult baleen whales are also among their prey. Local ecotypes usually specialize in certain prey for which they have particular hunting strategies. Killer whales are apex predators of the oceans because they have no predators. They are known to hunt in groups in a coordinated manner.

The killer whale as a species is not considered endangered, it has been largely spared from whaling. However, individual populations are threatened by environmental pollution. The cultural significance of the killer whale ranges from the traditional veneration by North American Indians to today's controversial keeping in dolphinariums.

Features

The killer whale is the largest species of dolphins - killer whale bulls grow up to 9.8 m long. Cows (the females) remain much smaller with a maximum of 8.5 m. Average lengths are 7 m for females and 8.2 m for males. The largest documented weight was recorded at 6.6 t for a bull 7.65 m long. The bulls have proportionally larger fins. The triangular fin of bulls, up to 1.8 m high, is particularly striking, giving the species the name "killer whale". The fin remains under 1 m in cows. The paddle-shaped flippers grow to about 2 m in length in the bull and 1.5 m in the cow. The fluke grows up to 2.8 m wide, is distinctly notched in the middle and concavely curved at the inner edges. The blow is 1-2 m high and not always visible.

A characteristic feature of the species is its contrasting black and white coloration. The back is black, while the belly and a spot behind each eye are set off in white. A grey saddle is found behind the fin. The underside of the fluke is white except for its margins. In field research, pigmentation and the shape of the saddle as well as the shape of the fin are used to distinguish individuals (photo identification). According to them, Russian scientists have located a completely white adult killer whale near the Commander Islands in the North Pacific.

The skull of the killer whale, especially the upper jaw bones, are very broad and strongly built. A temporal window, unusually well developed for dolphins, provides attachment for strong masticatory muscles. Each half of the jaw bears 10-14 conical teeth 2.5-5 cm in diameter, for a total of 40-56 teeth. To fix and tear strong and mobile prey, the teeth of the upper and lower jaws interlock. The jaws of killer whales often show misalignment or severely worn teeth, which is due to the resistance of large prey. The body of the killer whale is supported by 50 vertebrae.

Size comparison with a diver


Skeleton of a killer whale, Senckenberg Museum (Frankfurt am Main)

Distribution

The killer whale is distributed worldwide, but is comparatively rare in tropical waters. The largest populations are found at higher latitudes, particularly in the North Pacific, North Atlantic and polar seas. The majority of killer whale populations live relatively close to the coast most of the time. In European waters, the killer whale is common, especially off Norway. However, the species also inhabits the waters around Greenland, Iceland, Jan Mayen, the Faroe Islands, Bear Island, Franz Josef Land, Svalbard, Novaya Zemlya, the British Isles and the waters of the northern North Sea. In the southern North Sea, such as off Sweden, Denmark, Germany and the Netherlands, the killer whale is rarer, and the same is true in the Baltic Sea. In the English Channel and off Western Europe, killer whales are very rarely sighted. In the Mediterranean Sea, migrating specimens from the Atlantic are only observed in exceptional cases.

In the past, it has been observed with increasing frequency that, in the wake of global warming and the retreat of ice, killer whales are increasingly venturing into Arctic regions that they have previously avoided because of the ice, which poses a risk of injury to their dorsal fins. As a result, they could challenge the polar bear's role as the Arctic's apex predator. With bears staying in the water longer than before as the ice recedes, killer whales may now be a potential threat to polar bears.

Distribution of the killer whale (blue)