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Female southern elephant seals are expected to adopt behaviours that reduce the costs of male harassment. We studied the strategies and tactics of harassment reduction in two populations, at Punta Delgada (Valdés Peninsula, Argentina) and at Sea Lion Island (Falkland Islands) during five breeding seasons in all. Females synchronized their breeding activities to reduce harassment risk, and rarely bred alone to reduce the likelihood of encounters with subadult males. Females showed a clear preference for larger harems, that guaranteed a reduced harassment risk: movements between arrival on land and parturition were mostly from smaller to larger harems, and the likelihood of abandonment was lower for large harems. Females protested against approaching males in the vast majority of interactions, regardless of the social context and the status of the interacting male, but protest varied with female breeding status and male phenotype. Frequency of protest of individual females decreased linearly from the beginning of oestrus to departure to sea. Interactions with mature males were less protested. The frequency of protest linearly decreased with increase in age class, and mating attempts by males of higher status and dominance rank were less often protested. Most of this variation with male phenotype, however, was due to the higher probability of older and more dominant males to interact with oestrus females that had an intrinsicly lower tendency to protest. Protest variation in relation to male phenotype was more parsimoniously explained as a consequence of differential access of males to oestrus females rather than of female selectivity. Protests had a role in disruption of mating attempts, although the phenotype of interactors was more important: adult, large and dominant males disrupted interactions regardless of incitation by female protest.

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