BEHAVIORAL-DIFFERENCES AMONG ADULT MALE HARBOR SEALS DURING THE BREEDING-SEASON MAY PROVIDE EVIDENCE OF REPRODUCTIVE STRATEGIES

We studied the behaviour of 43 male harbour seals (Phoca vitulina) dur ing the 1991 breeding season on Sable Island, Canada. Males were class ified as subadults (n = 21) or adults (n = 22) based on their initial body mass. Throughout the 40-d study, twice-daily beach surveys were c arried out to locate marked males. Two spatial (average distance moved between haul outs, and the proportion of possible sightings in which a male was hauled out) and three social (fighting and composition and number of different groups in which the male was observed) variables w ere used to describe the behaviour of males during the premating perio d, when there were no, or few, receptive females, and the mating perio d, when receptive females were increasingly numerous. Of 39 males with complete behavioural data, principal components and cluster analyses identified a subset of 7 adults that differed from the other males. Th ese seven adults exhibited evidence of intermale fighting (i.e., wound ing on the neck and hind flippers), showed greater fidelity to a singl e haul-out site, associated with fewer groups, and were more often sig hted alone or in all-male groups. We suggest that these adults may rep resent the most successful males.