英文原文：
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， subspecies， or possibly even species (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“ although large variation in the ecological distinctiveness of different orca groups plicate simple differentiation into types mammal-eating orcas in different regions were long thought likely to be closely related， but geic testing has refuted this hypothesis
northern waters
north pacific
research off the west coast of c