Orca types and populations
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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]