Orca, also known as Killer Whale, is the largest member of the dolphin family and is a favorite animal for whale watching groups all around the world. The Killer Whale’s strikingly marked black and white body is unmistakable, being black on the upperparts, sometimes with a light grey ‘saddle patch’ behind the dorsal fin, and white on the underparts, lower jaw and undersides of the tail. White lobes extend up the sides of the body behind the dorsal fin, and there is a white, oval patch behind each eye. In newborn Killer Whales, the white areas of the body have an orange hue.
Both the male and female Killer Whales have a broad, rounded head and snout, an enlarged forehead, large, paddle-shaped pectoral fins and a large dorsal fin. However, males grow larger than females, and on reaching maturity become stockier and develop disproportionately larger fins, with adult males easily recognized by the tall, erect dorsal fin, which is the largest of any cetacean, growing to an impressive 6 feet in height. The female Orca, by contrast, has a more backward-curving dorsal fin , which grows to about 3 feet in height. An Orca’s dorsal fin and saddle patch are unique to each individual.
A number of different forms of Killer Whale have been identified, which specialize in different types of prey, differ in appearance, behavior and habitat use, do not associate with each other and are not known to interbreed. Studies have also revealed genetic differences between the different forms, and the Orca may therefore be split into a number of different subspecies or even distinct species in the near future.
Male Killer whales reach sexual maturity at around 15 years, but do not become physically mature until about 21, while females reach sexual maturity in their early teens. Breeding can occur at any time of year, although in the northern hemisphere births usually peak between Autumn and Spring. The female Orca gestation period is around 15 to 18 months and a single calf is born after that. The calf is usually weaned after a couple of years. Their life span may reach up to 90 years, and a female Orca generally produces a calf once every few years, up to the age of about 40. After that, the female ceases to reproduce, but may instead take on a role as a ‘grandmother’, passing on important experience to younger members of the pod.
The Orca is a very sociable animal. It communicates by using a variety of screams, clicks and whistles, as well as through physical behaviors such as breaching, tail slapping and spyhopping. They use a form of sonar to detect their prey and find their way around dark, murky waters. Click-like sounds are also used for echolocation. An Orca pod can consist of up to 40 or 50 individuals, although larger numbers may gather when several groups temporarily join together.
Killer Whales have a complex group structure. In a pod of ‘resident’ Orcas, the basic social unit is a matriline, consisting of a mature female, her adult offspring, and her daughters’ offspring, with individuals in this group having very strong bonds and staying in the group for life, although they mate outside of it. Groups of related matrilines which are frequently seen together and share a unique call repertoire are known as a pod, while above this are ‘clans’, which include a number of pods with similar vocal ‘dialects’. The social organization of ‘transient’ Orcas is less well known; the basic social unit is still a matriline, but offspring may disperse from the group they were born into, and so groups tend to be smaller and more dynamic than in resident Orcas.