Unmistakable oceanic apex predator, with distinctive two tone black and white colouration and huge dorsal fin, especially the males.

In brief

• Unmistakeable oceanic dolphin with black and white colouration.
• Orca seen in NI waters are nearly always members of the West Coast Community Group.
• There is currently thought to be only two surviving members of this community, Joe Coe and Aquarius.
• Main threat in this area is a build up of contaminants causing reproductive failure.

Species 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).

Life cycle: Average lifespans are around 60 years for males and up to 100 years (or more) for females. There are limited studies available but some work has been done on the NE Pacific resident community. Females reach sexual maturity at 11-16 years and males at around 15 years old. They usually do not breed successfully until they are in their 20s. Gestation lasts 15-18 months, and calving occurs every 3-8 years. A female usually can produce 3-5 calves in her reproductive lifetime and usually stop giving brith at around 40 years of age instead taking on a leadership role. Weaning takes 1-2 years, sometimes as long as 3 years. There have been no calfs produced by the West Coast Community Group in the last 30 years. It is believed that Joe Coe and Aquarius are the only two surviving members left.

Similar species: Difficult to confuse with any other species.

How to see this species: 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. Sightings are rare but they do frequent NI waters occasionally. As of 2016, only Joe Coe and Aquarius have been spotted and it's believed the rest of the West Coast Community Group may have passed away.

Current status: Data deficient. Nationally scarce. West Coast Community Group are experiencing severe decline. Northern Irish waters may see occasional visits from other communities, e.g. East North Atlantic Type 1 may also feed in Irish waters.

Why is this species a priority in Northern Ireland?

• Criterion 1: Internationally listed species.

Threats:

• The main threat to orca is this region is the build-up of contaminants leading to reproductive failure. One of the females from the West Coast Community Group was found dead in 2016 and upon examination was found to have extremely high levels of PCBs, which are known to inhibit reproduction. They are a long-lived species that is slow to reproduce so very vulnerable to decline.

Action: Records of new sites for this species, with details of habitat and population are always valuable. Observations with a photograph can be recorded using iNaturalist, find the MBDP-NI iNaturalist project here.

Alternatively, records can be sent to CEDaR, National Museums Northern Ireland, 153 Bangor Road, Cultra, Holywood, County Down, BT18 0EU. Tel 028 9039 5257, e-mail cedar.records@nationalmuseumsni.org, or via the online portal.

Objectives:

• Monitor current population and ensure any orca sightings in this region are recorded and individuals are identified where possible, to check population level of West Coast community and the extent to which other communities or types are using the region.
• Monitor Joe Coe and Aquarius.
• Investigate if other groups or communities are using Irish waters.

Conservation:

• They are protected under Schedule 5 of the Wildlife (Northern Ireland) Order 1985.
• Protected under Bern Convention (Convention on the Conservation of European Wildlife and Natural Habitats) Appendix II.
• Listed in Appendix II of the Convention on the Conservation of Migratory Species (The Bonn Convention).
• Listed in Part II and III of The Conservation (Natural Habitats, etc.) Regulations (Northern Ireland) 1995.
• Listed in Annex IV (Animal and Plant Species of Community Interest in Need of Strict Protection) of the EC Habitats Directive.
• Listed in Annex A of EU Council Regulation 338/97 and therefore treated by the EU as if they are on CITES, Appendix I
• Covered by the terms of the Agreement on the Conservation of Small Cetaceans of the Baltic, North East Atlantic, Irish and North Seas (ASCOBANS).

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

iNaturalist: Orcinus orca at iNaturalist World Species Observations database.

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