Orca discovery

That’s the conclusion of a three-year study carried out by marine researchers from the University of Aberdeen and the University of Copenhagen.

The work revolved around analysis of skeletal remains held by museums in England, Scotland and Copenhagen, The Scotsman has reported.

The team identified one group of orca, or killer, whales  which are large and consume other, smaller cetaceans, namely dolphins and porpoises; and a smaller group of orcas which feed on fish, mostly mackerel and herring.

The difference in size of adults in the two groups differed by nearly 2m. In addition, tooth wear varied appreciably, reflecting the orcas' different diets.

The study’s leader, Andy Foote of the University of Aberdeen, said: "No-one ever thought there were different types of killer whales in the Atlantic around the UK."