Killer whale
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Orcinus orca

Names

Azores : Quilha - POR : Orca - ITA : Orca - SPAIN : Orca - GB : Killer whale - GER : Schwertwal - NEDER : Orka SWEEDS : Späckhuggare - NOORS : Spekkhogger - DEENS : Spaekhugger - JAP : Syachi

Biology

The killer whale is the largest Delphinidae. Populations are classified in 3 types; resident (sedentary), transient (nomad), and offshore (oceanic). These types are distinguished by their feeding habits, their behaviour, and the shape of the male dorsal fin. Sexual dimorphism in this species is very pronounced. Adult males can reach 9 m long, but exceptionally they can grow to 10 m long, and their maximum weight is up to 10 tons. The females rarely exceed 7 m and weight about 4 tons. The shape and size of the dorsal fin, one of the most distinctive features of this species, can also vary significantly. In the males, it is triangular and it can reach 2 m long while in the females it is falciform and less elevated (maximum to 0.9 m). They have 10 to 13 pairs of robust large conical teeth in each jaw. The coloration of killer whales is particularly contrasted : they have a very striking black on the back and sides and a very vivid white belly. Behind the dorsal fin they have a distinct gray patch in the form of a " saddle ". This saddle is believed to differ in each individual whale helping in their identification at sea. The killer whales are no doubt at the top of the food chain. Their feeding habits are varied, depending on the population type. They can eat squid, fish, sea birds, seals, sea turtles, dolphins and even larger cetaceans. Killer whales hunt larger prey in the same co-ordinated and co-operative way as a pack of wolves. Newborns are on average 2.3 m long, and weigh about 200 kg. Gestation lasts 11 to 16 months, and lactation takes at least 12 months. The reproductive cycle varies from 3 to 8 years. Females can live to 75 years old, an average of 30 years more than the males. The killer whales produce a large variety of sounds, anywhere from clicks of 0.1 to 80 kHz to harsh " scream "-like pulsed calls in the range of 1 to 25 kHz. It is possible to establish the genealogy of the clans because each group has its own dialect.

Observation

The common name, killer whale, is unjustly given to this species since there are no reliable records of unprovoked attacks on humans and there is rarely an aggressive animal among the group. In the Azores, we found some nomad groups composed of both males and females in a total of 6 to 15 animals, moving at swimming speeds of 10 to 12 knots (sometimes at 25 knots) changing directions brusquely and submerging for 5 to 15 minutes. They can dive to 300 m depth and exceptionally to 1000 m depth. On rare occasions, the team at Espaço Talassa has had the opportunity to observe killer whale clans that came to swim in the bow waves for several minutes . Isolated females might be confused with Risso«s because of the dorsal fin. However, females are usually accompanied by males, and their unique pigmentation together with the males' distinctive tall dorsal fin allow an easy group recognition.

Cetaceans in the Azores