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Abstract
Variation in the behavior of individuals within a seasonally returning population of humpback whales on Stellwagen Bank, Massachusetts, was studied using data collected between 1979 and 1985. The data presented were derived from observations aboard 30m commercial whalewatching vessels and dedicated cruises aboard a 12m research vessel. Possible relationships between behavioral measures and sex, age-class and reproductive status were examined.
Individual whales were photographically identified by natural markings on the ventral surface of the flukes as well as dorsal fin shape and prominant scarification. One hundred and twenty-seven individual humpback whales of known gender, that had been observed for more than one year, were chosen for the study.
Results of statistical analyses indicate that although there are few strong behavioral correlations between individuals, individual whales may be arranged in a rough continuum ranging from social to less social individuals.
The most significant differences in behavior between classes of whales were found between juveniles and adults. Juvenile whales generally approach boats, lobtail, breach, spyhop, flipper and rest more than adults, who are more social, feed more frequently and tend to be a greater distance from the centroid of whale distribution. There are significant relationships between age and sociality, mean group size and resting behaviors. Rates of resting were greater in younger whales while sociality generally increased with age.
Significant differences were found between gender and rates of feeding, sociality and arrival time with males generally feeding more frequently and arriving later than females. Females were generally more social. Pregnant and lactating females differed significantly in rates of arrival time, departure time, mean group size and sociality.
Statistical analyses indicate significant differences between individuals for near-boat, breaching and feeding events, time of residence, mean group size and sociality. Individual females tend to vary their behavior more than males, except for boat approaches and arrival time.
The behavioral events examined are reviewed and their possible function(s) discussed in the context of the new data presented.
