STABLE SOCIAL ASSOCIATIONS AMONG HUMPBACK WHALES (MEGAPTERA-NOVAEANGLIAE) IN THE SOUTHERN GULF OF MAINE

Groups of humpack whales (Megaptera novaeangliae) were observed from 1 980 to 1987 on their feeding grounds in the southern Gulf of Maine. Al though most groups were together for only brief periods, two types of stable association were found: 'continuous' (individual whales associa ted for at least 7 consecutive days; n = 30) or 'recurring' (individua ls associated at least five times in a 6-week period; n = 21). Thirty- seven stable pairs and 3 stable trios involving 56 individual whales w ere recorded; 11 stable pairs re-associated during more than 1 year. C ontinuous associations lasted up to 79 days (mean 29.65). Thirty of th e 40 associations (75.0%) contained only adults. Females were present in 22 adult associations (73.3%), whereas males were present in only 8 (26.6%). Females sighted with a calf the following year, and therefor e pregnant, were members of 6 of the 11 (54.5%) associations that refo rmed. It is hypothesized that stable associations allow adult females to maximize their net energy gain through cooperative feeding, and may be comprised of closely related animals or individuals with compatibl e feeding styles.