Da. Helweg et Lm. Herman, DIURNAL PATTERNS OF BEHAVIOR AND GROUP MEMBERSHIP OF HUMPBACK WHALES (MEGAPTERA-NOVAEANGLIAE) WINTERING IN HAWAIIAN WATERS, Ethology, 98(3-4), 1994, pp. 298-311
We examined the behaviour of humpback whales (Megaptera novaeangliae)
in Hawaiian waters in relation to time of day using visual observation
s from shore platforms and acoustic observations using hydrophones. As
humpbacks are not observed to feed in Hawaiian waters, we assumed tha
t the data were free from the influence of diel cycles of prey availab
ility. The majority of mothers with calves were likely to be escorted
by one or more male consorts only after 0700 h. The percentage of pods
with three or more adults increased across the day and the rates of m
ale-male agonistic behaviour typical of multiple-adult pods also incre
ased. Noon observations were characterized by high rates of behaviour
such as breaching that may serve as visual and/or acoustic signals. No
diel variation in the number of singers was observed, suggesting that
the number of singers was independent of the late afternoon peak in m
ale-male competition within surface-active groups. The results suggest
that the whales were rearing in the dawn hours, behaviour related to
mating begins shortly after sunrise, and that male-male competition pe
aked in the afternoon.