GEOGRAPHIC-VARIATION IN VENTRAL FLUKE PIGMENTATION OF HUMPBACK WHALE MEGAPTERA-NOVAEANGLIAE POPULATIONS WORLDWIDE

Abstract

Ventral fluke patterns of humpback whales Megaptera novaeangliae were assessed to determine if pigmentation shows geographical variation across different breeding areas. Fluke photographs (n = 3854) were collected from 7 major breeding grounds worldwide and were ranked into categories 1 (white) through 5 (black) based on the proportion of white and black pigment on the ventral surface. Average coloration varied primarily between oceanic populations, with the Southern Ocean stocks (Area IV, western Australia, and Area V, eastern Australia) characterized by significantly more light-colored flukes, while the North Pacific subpopulations consisted of individuals with significantly more dark-colored flukes. Results of statistical analyses revealed that all populations differed significantly from one another in the distribution of pigmentation classes, with the exceptions of Hawaii vs Japan, Mexico vs Japan, Mexico vs Hawaii, eastern Australia vs western Australia, and West Indies vs Colombia. Results of pigmentation analyses reveal historic and current interactions among oceanic subpopulations of humpback whales and reflect population sub-division in this species.