The misidentification of species and populations is a hindrance to effective cetacean management. We devised a method of species identification using 10 fin and body measurements obtainable from at‐sea photographs, and demonstrated its ability to distinguish four species of Hawaiian “blackfish”: pygmy killer, melon‐headed, short‐finned pilot, and false killer whales. Measurements from photos of 382 known individuals were converted into 14 ratios and reduced using nonmetric multidimensional scaling and principal component analysis. The first three components of the PCA explained 81% of variance among species. Ratios indicated by PCA and NMDS were tested using analysis of variance, and results identified three fin ratios that had distinct means across all four species: height/base, depth (from anterior insertion) at trailing edge apex/depth at topmost point, and width (from leading edge) at posterior point/base. Dual analysis of adults and all age classes showed near‐identical sources of variance, 90% similarity in interspecies ratio relationships, and overlapping ratio means and ranges. Results suggest similar ontogenetic growth across these four species, and confirm the efficacy of this discrimination technique for all age classes. This study established a reliable means of distinguishing these cetacean species, which will improve the efficacy of management in areas with sympatric distributions.
Adults of many free-ranging delphinid species cannot be reliably sexed at sea. Sexually mature, known-sex adult short-finned pilot, pygmy killer, melon-headed, and false killer whales were profiled from at-sea photos to assess proportional fin and body dimorphism. Males of all four species had larger dorsal fins proportional to anterior body length. False killer whales showed no further dimorphism, while melon-headed whales showed subtle dimorphism in dorsal fin overhang. Pygmy killer whales showed subtle dimorphism in lateral positioning of the top-most point and overhang. Lastly, short-finned pilot whales showed strong dimorphism in the leading edge, lateral positioning of the top-most point, and height of the overhang. Generalized linear models showed strong predictive accuracy for pilot and false killer whales, and moderate accuracy for pygmy killer and melon-headed whales. Results indicate that adult shortfinned pilot and false killer whales can be accurately sexed in the field or via morphometrics. Adult pygmy killer and melon-headed whales have subtle sexual dimorphism that can be detected using morphometrics. The presence of dimorphism gives insight into potential reproductive strategies and social structure. Further analysis is needed to explore morphometric differences between inshore and
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.