Resightings of humpback whales in Hawaiian waters over spans of 10–32 years: Site fidelity, sex ratios, calving rates, female demographics, and the dynamics of social and behavioral roles of individuals



From a database of approximately 5,000 Hawaiian humpback whales identified photographically between 1976 and 2010, we extracted 71 males and 39 females having resighting spans of 10 or more years, from first to most recent sighting. Findings included: (1) the male-biased sex ratio was like that found in breeding grounds worldwide; (2) the mean span for males of 20.7 yr (maximum = 32 yr) did not differ significantly from the mean of 19.8 yr (maximum = 29 yr) for females, but males were seen in significantly more years during their spans than were females; (3) the mean number of females seen with and without calf across 11 three-year intervals from 1977 to 2009 did not differ significantly; (4) the calving rate for the 39 females was 0.48 and seven females produced two to eight calves over spans of 22–26 yr; (5) females attracted significantly more escorts in years without calf than in years with calf; (6) individuals showed great diversity in the social units they occupied over their sighting spans, but with the most frequently observed unit for both sexes being the trio of mother, calf, and escort. Males were also observed frequently in competitive groups centered about a female without calf.