Killer whale (Orcinus orca)

Killer whales are found in all of the world’s oceans. As one of the most famous species of the sea, the killer whales are easily recognized by their distinctive colouration and prominent dorsal fin. Most killer whales live around the Antarctic convergence. In the Norwegian and Barents Sea area there are about 3,000 killer whales, and some small fraction of this population spends part of the summer around Svalbard.

Killer whale

Killer whale. Photo: tromsofoto.net

Killer whales are easily recognized by their distinctive colouration and prominent dorsal fin. They are black and white, with black dominating on the back. They have a white eye-patch and white on the belly that sweeps up onto the side of the body between the dorsal fin and the fluke. They also have a grey saddle behind the dorsal fin. Males are significantly larger than females and have a much higher dorsal fin that is triangular in shape. Males are up to nine metres long and weigh up to 5,500 kg whereas females reach a maximum length of 7.7 metres and weight up to 3,800 kg. Calves are about 2.3 m long at birth and weight approximately 200 kg. They are similar to the adults in the pattern of colouration, but the areas that will be white in adulthood are creamy yellow when the calves are young.

Distribution

Killer whales are found in all of the world’s oceans; they range from equatorial waters right up to the northern and southern ice edges. They are most common in areas of high productivity, particularly along coastlines. In Svalbard’s waters killer whales are not often sighted in inshore areas, but they have been reported from fjords on both the west and east coast of Spitsbergen and along the southern fringes of the northern ice pack.

Ecology

The global population of this species is not accurately known. However, summing up estimates for various regions where effort has been expended suggests a world population around 100,000 animals. Most of these live around the Antarctic convergence. In the Norwegian andBarents Seaarea there are about 3,000 killer whales. Some small fraction of this population spends time around Svalbard. 

The killer whale is the largest member of the dolphin family, and like most other dolphins they live in social groups. The stability and nature of their groups varies; there are three recognized types of killer whales societies – offshores, transients and residents. Only one or a few adult males accompany a group of females and their calves. Pods have distinct vocal dialects that appear to reinforce pod discreteness. Individual pods tend to specialize on the type of prey they prefer to target. Co-operative hunting among killer whales has been documented in the capture of many different types of prey, from very small to very large animals. Killer whales have been observed herding fish into a tight ball that is then struck by the tails of other members of the pod. They have been seen encircling penguins or seals that are resting on small ice floes, followed by some members of the pod tipping the floe such that the prey slid down to the waiting jaws of other members of the pod. They have also been seen co-operatively attacking large whales, such as grey whales, repeatedly forcing the baleen whale to submerge prematurely until it is exhausted and then attacked. Resident pods tend to have a defined home range, but many killer whales follow the annual migration patterns of their prey so they travel over considerable distances seasonally. InSvalbardkiller whales have received very little research attention beyond being counted during large whale sighting surveys. The diet of killer whales varies markedly across their range. Their most common food type is fish, ranging in size from small schooling fish such as herring, commonly taken along the European coast, to large salmonids that are commonly taken along the west coast of North America. They also eat cephalopods, cod, flatfish and sometimes also marine turtles. They are probably best known as predators of other warm-blooded animals, including penguins and other birds and other marine mammals. Killer whales are pinnacle marine predators. They are not known to have any natural predators.

Life history and reproduction

killer whales give birth to their calves in the late autumn and then mothers nurse them for between one and two years. The gestation period is 15–18 months. Killer whales reach sexual maturity at an age of 15 years for males and 11–16 years for females. They live to an average age of 50 for females and 30 years for males. Females can live to be 80–90, while maximum longevity for males is about 50–60.

Management status and monitoring

Killer whales have been exploited at low levels in several parts of their range, but have never been a preferred species for consumption. At times in the past they were culled by fishermen where they were seen as being a competitor for salmon. Little is known about the northern pelagic stocks of this species, although there appear to be marked increases in the number of killer whale sightings in the Northwest Atlantic Arctic. Killer whales are protected in Svalbard.

MOSJ indicators (Environmental Monitoring of Svalbard and Jan Mayen):

Awaiting results from MOSJ…