Killer Whales are apex predators that as a species take a range of different prey types from schooling fish to baleen whales (Jefferson et al. 1991, Ford and Ellis 2006, Pitman and Durban 2010). Although as a species they are generalist predators, at population and community levels they can show highly specialised hunting techniques and behaviours which may limit the prey species taken at individual levels (Saulitis et al. 2000). These specialised hunting techniques include beaching to catch pinnipeds off Patagonia (Lopez and Lopez 1985) and causing waves that knock seals from ice flows in the Antarctic (Visser et al. 2008); Within European waters, Killer Whales off Norway coordinate to drive Herring schools from deep water to the ocean surface to allow for easier capture, and stun with tail slaps (Domenici et al. 2000, Nøttestad et al. 2002). Differences in foraging technique can even be observed at community levels within small populations, this is exemplified by pods off Gibraltar that either depredate from long line fisheries and those that do not (Esteban et al. 2016a).

Within European waters there is growing evidence that Killer Whales that feed on fish also take marine mammals such as seals, with dietary specialisation being a gradient rather than distinct ecotypes as is seen in the North Pacific with transient, resident, and offshore ecotypes (Jourdain et al. 2020, Remili et al. 2021). Off Greenland, Killer Whales feed multiple prey species but are thought to feed predominantly on marine mammals (Heide-Jorgensen, 1988, Pedro et al. 2017).

Killer whales occupy both coastal and offshore waters throughout the North Atlantic and within European waters (Bloch and Lockyer 1988, Similä et al. 1996, Samarra et al. 2017, Vogel et al. 2021).

Killer Whales have a cosmopolitan distribution and are found in all the World’s oceans from polar to equatorial latitudes. Within European waters, they occur throughout the Barents Sea, off East Greenland, around Iceland and the Faroe Islands, and offshore in deep waters of the North Atlantic. They occur all along the Norwegian coast and are seasonal visitors to Svalbard (Storrie et al. 2018). They also occur off the British Isles, specifically Orkney and Shetland and the northwestern North Sea. There is also a small subpopulation that occupies waters off the west coast of Scotland and around Ireland (Beck et al. 2014). Further South there are Killer Whales off Gibraltar and the Canary Islands. The species is considered vagrant in the Mediterranean Sea (Mrusczok et al. 2022).

Killer Whale is listed in Appendix II of the Convention on International Trade in Endangered Species (CITES) and Appendices I and II of the Convention on Migratory Species (CMS). Subpopulations outside of Europe, including the eastern North Atlantic and the eastern North Pacific subpopulations are included in Appendix II of CMS.