REGIONAL AND SEXUAL DIFFERENCES IN FLUKE PIGMENTATION OF HUMPBACK WHALES (MEGAPTERA-NOVAEANGLIAE) FROM THE NORTH-ATLANTIC OCEAN

The relative amount of pigmentation on the flukes of 3812 humpback wha les from five feeding and three breeding regions in the western North Atlantic Ocean was ranked subjectively into categories 1 (white) throu gh 5 (black). The distribution of rankings was examined to determine w hether differences existed between regions or sexes. Fluke pigmentatio n differed significantly among whales photographed in the five norther n feeding regions (Iceland, southwestern Greenland, Newfoundland (incl uding the Labrador coast), the Gulf of St. Lawrence, and the Gulf of M aine). Whales photographed in the Gulf of Maine were characterized by a significantly higher proportion of dark-colored nukes than whales in all feeding regions except Iceland. Whales photographed near Greenlan d were characterized by significantly more light-colored flukes than o ther feeding regions. Fluke pigmentation also varied significantly amo ng whales photographed in the three southern breeding regions (Virgin Bank, Puerto Rico, and the Dominican Republic). The flukes of whales p hotographed near Virgin Bank differed from those of whales near the Do minican Republic and included a higher proportion of light flukes. Flu ke pigmentation of males and females differed significantly in the Gul f of Maine and in the Dominican Republic. Both areas showed higher pro portions of dark-fluked females and light-fluked males. Sex bias diffe rences in other regions were not examined because sample sizes were sm all. Fluke pigmentation of whales photographed only on the summer rang e did not differ significantly from the pigmentation of those photogra phed only on the winter range, supporting the belief that all northern feeding aggregations mix on the southern breeding grounds. Regional d ifferences in fluke pigmentation suggest that the western North Atlant ic humpback whale population includes a number of relatively isolated subunits, as suggested previously by photoidentification and DNA studi es.