Description: Large oceanic dolphin with distinctive two tone black and white colouration, sometimes with patches of grey. Males are larger than females growing 5.6-9 m in length, while females are 4.5-7.7 m. Maximum size recorded is 9.8 m long and a weight of 9000-10000 kg. There is usually a white saddle patch behind the dorsal fin although this is highly variable. Fluke is broad with a distinct notch in the centre, and a black upper side and white underside. Males have an exceptionally large (up to 1.8 m) dorsal fin, while that of female or juvenile orca is smaller (up to 90 cm). Several distinct communities exist and several ecotypes exist who exhibit specific behaviours and feeding preferences. The West Coast Community Group for example appear to be marine mammal hunters, having been seen to take harbour porpoise and seals, while other ecotypes recorded in the region feed on fish (e.g. mackerel).

Habitat: Open water species that may sometimes be in seen closer to shore.

Distribution: The orca seen in Northern Irish waters are nearly always part of the West Coast Community Group (East North Atlantic Type 2) who have a range that includes Pembrokeshire, west coast of Ireland and western Scotland to Outer Hebrides. They are most well known from the west coast of Scotland hence their name. Joe Coe and Aquarius (2 easily recognisable West Coast males) have been sighted around NI coast and were even in Strangford Lough in May 2020.

Similar Species: Difficult to confuse with any other species.

Key Identification Features:

• Distinctive black and white colouration.
• White saddle patch behind dorsal fin (variable).
• Large dorsal fin.

Distribution Map from NBN: Orcinus orca at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Orcinus orca at iNaturalist World Species Observations database.

GBIF data for Orcinus orca

WoRMS: Orcinus orca at World Register of Marine Species. Accepted name: Orcinus orca (Linnaeus, 1758). AphiaID: 137102.

Classification: Biota; Animalia; Chordata; Vertebrata; Gnathostomata; Tetrapoda; Mammalia; Theria; Cetartiodactyla; Cetancodonta; Cetacea; Odontoceti; Delphinidae; Orcinus