Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 8822
Title: Quantifying variation in killer whale (Orcinus orca) morphology using elliptical Fourier analysis
Author: Candice K. Emmons, Jeffrey J. Hard, M. E. Dahlheim, J. Waite
Publication Year: 2018
Journal: Marine Mammal Science

In the northeastern Pacific Ocean, there are three ¿ecotypes¿ of killer whales that differ in diet, ecology, behavior, acoustics, genetics, and morphology. Previous attempts to describe the morphological differences among populations of killer whales (Orcinus orca) have been limited to descriptive accounts or categorical studies.  We used elliptical Fourier analysis (EFA) to quantify shape differences of dorsal fins and pigmentation patterns among the ecotypes from photo-identification data of more than 500 individuals.  Variation in shapes of the dorsal fin, saddle patch, and eye patch were successfully quantified using EFA, and there were highly significant (P <0.01) differences among the ecotypes in all three morphological traits.  The ability of EFA to discriminate ecotypes based on dorsal fin and eye patch shapes was substantial, while it did not perform as well for saddle patches.  Visualization of the shape variation along principal component axes mirrored previous descriptions of the differences among ecotypes. Although the degree of inheritance of morphology in killer whales has not been determined, these results are consistent with previous inference of reduced gene flow between the ecotypes, and introduces elliptical Fourier analysis to the study of cetacean morphometrics.

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Theme: Recovery and rebuilding of marine and coastal species
Foci: Characterize the population biology of species, and develop and improve methods for predicting the status of populations.