SHORT-TERM ASSOCIATION PATTERNS OF HUMPBACK WHALE (MEGAPTERA-NOVAEANGLIAE) GROUPS ON THEIR FEEDING GROUNDS IN THE SOUTHERN GULF-OF-MAINE

Humpback whale (Megaptera novaeangliae) feeding ground associations sh ow a distinct pattern of group size and composition. Median group size was 2 (mean 1.67), and frequency decreased as group size increased. A dult females and juvenile males were observed in pairs significantly m ore often than singly, whereas adult males and juvenile females were m ore often alone. Adult female-female pairs occurred significantly more frequently than adult male-male pairs, and adult female - juvenile ma le pairs formed more frequently than adult male - juvenile female pair s. The majority of groups remained associated for at least 10 min; how ever, as the size of a group increased, so did its tendency to separat e within that period. Adult male-male pair associations were of signif icantly shorter duration than female-female or male-female pair associ ations. It is hypothesized that adult males may avoid other males on t he feeding ground as an extension of breeding competition. The energet ic burden of reproduction, and hence the need to forage cooperatively to maximize efficiency, may account for the adult female's social natu re. Juveniles of both sexes, less constrained by reproductive costs, e xhibit less structured social behavior.