Habitat utilization, migratory timing, and male escorting strategies of humpback whales in the Hawaiian Islands

Photographs of humpback whales identified in the Hawaiian Islands from 1976 through 1995 and shore-based observations conducted from 1995 through 1998 were used to investigate (a) migratory timing and residency, (b) reproductive rates and habitat preferences of females, (c) regional and temporal trends in density and pod characteristics, and (d) male escorting strategies and female attractiveness. Results suggested that juveniles and females with no calf arrive at and depart from the Hawaiian Islands earlier than females with calf and males, and that the migratory timing of individual females varies with reproductive state. There were no significant differences in within-season resighting rates or resighting intervals among different classes of whale. The interval between first and last identification was less than two weeks in most cases. Calves formed a significantly larger proportion of the population off Maui than off the Big Island, and Maui waters also contained a higher ratio of calves to females. Females with no calf had higher reproductive potential for the following year than females with calf. Individual females appeared to prefer Maui when with calf and the Big Island when without. Whale density and mean pod size were significantly greater off Maui, with significantly fewer singletons and more pods containing four or more adults than were observed off the Big Island. The seasonal peak in abundance occurred earlier at the Big Island than Maui. Females with no calf were significantly less likely to be alone and more likely to be in large pods than females with calf. Individual females attracted more males when without calf than with calf. Head lunges were observed more frequently in non-calf pods than calf pods. The mean number of escorts accompanying females with calf increased as the season progressed. Overall, the results showed that there are regional and temporal variations in the demographic profile of humpback whales wintering in the Hawaiian Islands. Also, the migratory timing, habitat preferences, and attractiveness of individual females vary with reproductive state. Finally, males are more likely to compete for females with no calf than for females with calf, but become less choosy as the season progresses.