Abstract

(…) Amano and Miyazaki (1996) found a geographic difference in the size of the white flank patch among dalli-type animals and reported that porpoises from the Sea of Japan-Okhotsk population possess smaller flank patches than those from other areas. Their study, however, was based on a rather small number of samples from the Sea of Japan-Okhotsk population and compared only sexually mature porpoises. They did not exclude the possibility that the difference was due to ontogenetic change; e.g., posterior movement of the anterior margin of the flank patch with growth might cause the posterior position of the patch in the Sea of Japan-Okhotsk specimens, which had greater body lengths (Amano and Miyazaki 1996). We therefore reexamined geographic variation in the position of the anterior margin of the flank patch of dalli-type porpoises using a larger number of specimens with a broader body length range. We demonstrate the existence of a new color morph of the species. (…)