Some cetologists think that Killer whale is not one species, but a cryptic species complex, with (at least) four very related and very similar (but not identically marked) species. Different ecotypes seem avoiding to breed with each other and are evolving independently.

Both 'transient' and 'type B' eat marine mammals. Some 'type A' chase cetaceans also. The smaller of all 'Type C' eat fishes. Some species mix in a gradient and things can get very complicated. In the end we could have only one or up to nine species of killer whales here.