Killer Whale

Killer Whale (Orca): Orcinus orca

IUCN status: data deficient

Status and distribution summary:

The taxonomic situation with Killer Whales is far from clear with several distinct forms some with overlapping ranges but differing ecologies, which may turn out to be distinct species. Some of these forms are under considerable threat.

Occupies all oceans of the globe, including the high latitudes, and appears to be more common in cooler waters. Nowhere abundant, but concentrations occur in areas of good hunting, for example in the fiord lands of western Canada and Alaska. In the Atlantic is more frequent in higher latitudes, and is for instance a regular visitor to the Shetland Islands.

Exploitation:

Has suffered persecution, and was heavily hunted by the Russians in the late 20thC as large whale stocks crashed.

Other threats:

Disruption to the food chain through over-fishing is known to have caused marked local population declines. Some populations have high enough concentrations of PCBs and other chemical pollutants to cause adverse effects. By-catch particularly in long line fisheries. Collecting for showing in aquaria, although at very low levels.

Where is it seen:

Potentially can occur anywhere throughout the area. Is seen annually off Cornwall, and in the Western Approaches. Has also been recorded in deep water in the southern Bay.

Frequency of sightings:

Rare, probably seen less than annually from ferries. In summer 2008 two different groups were seen in Biscay, one on the northern continental shelf slope and the other in the Cap Breton canyon.

Recognition:

Unique and highly familiar species.

Up to 10 metres in length, males grow to 20% bigger than females; heavily built.

The black and white patterning is unique, and the white patch above the eye is readily seen even when sub-surface. A broad grey 'saddle' is visible behind the dorsal fin when surfacing in good light conditions.

A very tall dorsal fin is centrally placed. In males this is massive (up to 20% of body length), and erect, triangular and is diagnostic even at long distance. The female dorsal fin is smaller, and more falcate, though proportionally still larger than most other species.

Blow is bushy and visible.

Behaviour:

Lives in pods of 3 - 20, though males may occur as singles or in twos.

When at rest the pod moves slowly, often breathing synchronously, or is motionless, logging on the surface.

When fast swimming or hunting, travels very quickly, frequently leaping clear of the water, creating large splashes on re-entry.

Sometimes acrobatic, which includes breaching, belly flops, somersaults, and fin slaps.

Some populations adopt inshore habits and feed mainly on migratory fish, eg Herring in the NE Atlantic.  Another more offshore so-called transient form is thought to specialise in mammalian prey, including seals, dolphins and larger cetaceans (adult Blue Whales have been seen with scars from Killer Whale attacks!). However much is still to be discerned about the different populations and their behaviours and ecological adaptations.

Confusion species:

  • Adult males are distinctive even at distance with their huge triangular dorsal fins.
  • Females seen poorly could be confused with Risso's Dolphin, which has a similar fin shape, or possibly False Killer Whale, whose dorsal fin however is proportionately much shorter and more curved.