Killer whale

  (Orcinus orca)
Killer whale

Description: Killer Whales are robust animals. The head has a characteristic bulbous melon. The flippers are highly mobile and rounded, looking like large paddles. The most striking feature is the large dorsal fin. It is tall (1.8 m or more) and triangular in males and may even be curved slightly forward. In juveniles, the dorsal fin is smaller and falcate (sickle shaped).

The coloration is basically black dorsally and white ventrally. There is a grey "saddle" just behind the dorsal fin, a white patch behind the eye and a white or greyish intrusion on the side above the genital region. There is a lot of variation on the colour and shape of the saddle and this can potentially be used for identification of individuals. The whale's belly, lower jaw and the underside of the tail flukes are white. The rest of the body is black.

Size: Killer Whales are the largest member of the dolphin family. Maximum body lengths are 9 m in males and 7 m in females. Males reach 9 tons, whereas females weigh a maximum of 4 tons. Certain studies show that life longevity is longer in females than in males; females can live 90 years while males only 50-60 years.

Behaviour: Generally they live forming groups of few individuals, although from time to time they gather in hundreds. Usually, the relations established among the different members of the group are long lasting, and from time to time even for life. They are quite fast animals, they are able to reach 55 Km/h. It is not unusual for them to approach the boats or leap out of the water, sometimes striking the surface with the pectoral flippers, or with the tail. At times with these leaps, overall the young, they do some acrobatics.

Distribution: : Killer Whales are true cosmopolitans and can be found in virtually all oceans and major seas, with some preference for cold waters. They occur in groups of 1 to 70-100 animals and they are seen along the coast and also pelagically. Some groups migarte to follow their prey from the coast to offshore.

Feeding: It is a great marine predator. Killer Whales are best known for their habits of preying on warm-blooded animals; they have been observed attacking marine mammals of all groups. However, they often eat various species of fish and cephalopods and occasionally seabirds and marine turtles. Pods often co-operate during a hunt. Relationship with the prey is complex: pods tend to specialise and may frequently ignore potential prey. It has been calculated Killer Whales eat 5% of their body weight daily.

Reproduction: Not much is known about reproductive biology of this species. Female Killer Whales become sexually mature at 4.6-4.9 m in length (age 8-10 years) and males at 5.8 m (age 15-17 years). Physical maturity is attained at 20-25 years. After a gestation period of 15 months, a single calf is born, which is 2.5 m length and weight 180 Kg. The lactation period lasts 12 months and calving interval is around 2 years.