Latin name

Orcinus orca

Other names

Killer whale

Identification

The Latin orca is thought to derive from the Greek ὄρυξ - a word used by Pliny the Elder to describe a type of predator that could be either an orca or a sperm whale.

The largest carnivorous oceanic dolphin. Unlike most dolphins, orcas' flippers are not pointed and sickle-shaped, but broad and oval. The head is short, flattened at the top, without a beak; the teeth are massive, up to 13 cm long, adapted to tearing up large prey.

In 1972, the upper hearing threshold for killer whales was found to be 31 kHz, which is considerably lower than that of porpoises. The range of highest sensitivity was found to be between 5 and 30 kHz. The 1999 study suggests that the highest hearing sensitivity corresponds to 20 kHz, but both orcas studied were found to respond to 100 kHz sounds. 

Features of fish fins

The dorsal fin is high (up to 1.5 m) and almost straight in males and about half as low and curved in females.

Fish colouring

Distinguished from other oceanic dolphins by their contrasting black and white colouring. 

The colouring of the back and sides of the orca is black, the throat is white and the belly has a white longitudinal stripe. In some forms of Antarctic orca, the back is darker than the sides. On the back, behind the dorsal fin, there is a grey saddle-shaped patch. There is a white patch above each eye.

In Arctic and Antarctic waters, white patches can turn yellowish-green or brown due to a film of diatoms. The shape of the spots is so individual that it is possible to identify individuals. In addition, completely black (melanists) and white (albinos) individuals are found in the North Pacific.

Distribution

Widespread in practically all the world's oceans, occurring both near the coast and in open waters, but mainly confined to the 800 km coastal strip. Its range does not include the Black Sea, the Sea of Azov, the East Siberian Sea and the Laptev Sea. It is less common in the tropics than in cold and temperate waters. 

Habitat

They usually stay at shallow depths, less than 100 metres, but occasionally dive to depths that are unusual for them in normal hunting - more than 750 metres.

Size

Males can grow to 10 metres in length and weigh up to 8 tonnes, while females can grow to 8.7 metres.

Behavior

As highly evolved marine mammals, killer whales have developed complex tactical and even strategic plans for hunting prey in packs. When foraging for fish, pods of killer whales typically form a chain and swim at a speed of around 5 km/h. Using echolocation signals, each animal can determine its position relative to the others, stay in contact with them and participate in the overall activity of the group. When a school of fish is detected, they push it to the shore or gather it into a dense ball at the surface, dive into its centre and kill the fish with tail blows (carousel method). Because of the large number of hunters required for a killer whale hunt, killer whale groups contain an average of 5 to 15 individuals.

Food and feeding habits

It is a wide-ranging predator, and each individual population has a fairly narrow dietary specialisation. For example, some populations in the Norwegian Sea specialise in herring and migrate to the Norwegian coast every autumn after herring, while other populations in the same area mainly hunt pinnipeds. At the same time, food preferences determine the sociobiological characteristics of populations. The level of intraspecific violence among killer whales is close to zero, which distinguishes them from many other mammals.

Reproduction

Sexual maturity occurs at about 12-14 years of age. Average life expectancy is similar to that of humans. In captivity, however, these figures are reduced by a factor of two to three.

Reproduction is poorly understood. Orcas are thought to mate during the summer months and early autumn. The length of gestation is not known, although it is thought to be 16-17 months. The length of the newborn is 2.5-2.7 metres. The minimum time between the birth of two cubs is 2 years, but females give birth even less frequently, about once every 5 years. As with many carnivores, in order to stimulate the young mother to become pregnant again and resume her cycle, the male seeking her may resort to killing the infant she has conceived from a previous mate. However, as observations show, this does not mean that the young mother will remain indifferent to the process of killing her cub. It is highly likely that, driven by maternal instinct, she will ferociously attack her beau. A female will give birth to up to 6 cubs in her lifetime and will stop breeding at around 40 years of age.

Are one of the few mammalian species (including humans) in which females undergo menopause and live for many decades after losing the ability to conceive.

Fishing

Their commercial extraction was banned in 1982 with the imposition of a moratorium. 

Human interaction

In their natural habitat, killer whales show no fear of humans, but there are no documented cases of attacks. There are no known reliable cases of human deaths as a result of killer whale attacks in the wild, indicating that they have no interest in humans as food.