| Summary: | This thesis analysed male reproductive success in the Antarctic fur seal <i>Arctocephalus gazella,</i> a highly sexually dimorphic otariid that breeds in dense colonies on remote sub-Antarctic islands. Despite behavioural observations suggesting strong polygyny, a recent genetic analysis of a small colony at Bird Island, South Georgia, failed to assign paternity to over three-quarters of offspring, implicating the presence of alternative male mating strategies. However, since this study spanned only two breeding seasons, little could be learnt about long-term patterns of reproductive behaviour. Over 2000 seals from the same colony were genotyped at nine hypervariable microsatellite loci. Male reproductive success was then analysed by combining a microsatellite paternity analysis spanning seven consecutive seasons with detailed behavioural data. Since inbreeding is known to influence male reproductive success in wild vertebrates, I also explored the relationship between inbreeding coefficient and a variety of fitness traits that relate to success. Territorial males fathered 59% of 660 pups analysed, and male reproductive skew was considerable, with a quarter of all paternities being assigned to just twelve to individuals on a beach where mean annual pup production was 635. Most males were successful for only a single season, but those able to return over many years enjoyed rapidly increasing success with each additional year of tenure. No evidence was found of alternative male reproductive tactics such as aquatic or ‘sneaky’ terrestrial mating. However, paternity was strongly influenced by maternal status, with females observed on the beach without a pup being significantly less likely to conceive to a sampled territorial male than equivalent females with a pup. This suggests that not all female offer equal opportunities for fertilisation.
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