Orca types and populations

Orcas or killer whales have a cosmopolitan distribution and several distinct populations or types have been documented or suggested. Three to five types of orcas may be distinct enough to be considered different races,^[1] subspecies, or possibly even species^[2] (see Species problem). The IUCN reported in 2008, "The taxonomy of this genus is clearly in need of review, and it is likely that O. orca will be split into a number of different species or at least subspecies over the next few years."^[3] Although large variation in the ecological distinctiveness of different orca groups complicate simple differentiation into types.^[4] Mammal-eating orcas in different regions were long thought likely to be closely related, but genetic testing has refuted this hypothesis.^[5]