Structure and stability of humpback whale groups off Newfoundland

Abstract

Humpback whales off Newfoundland in summer formed groupings containing from 1 to over 10 animals. The size of feeding groups was closely related to the horizontal size of the prey school, whereas nonfeeding humpbacks were generally found in pairs. Small groups were considerably more stable than larger ones. Apart from mothers and their 1st-year calves, there were no indications of preferred companionships over more than 1 day, although during a day particular pairings would maintain their identities when within a larger group. The humpbacks often stayed in groups while at depth. Individuals in larger groups produced faeces more frequently. Other displays (side flukes, flipperings, and lunges) were associated with group instability.