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Participants: Dr John Arnould (PI) and Dr Kathryn Wheatley
Aims and background: In sexually dimorphic polygynous species, large size is advantageous in the physical conflicts which establish dominance and access to females. In species where individuals guard a territory and/or females, large size (in the form of stored body reserves) is also beneficial for extending territorial tenure and, thus, increasing mating opportunities. As with most otariid seals (fur seals and sea lions), the Australian fur seal ( Arctocephalus pusillus doriferus ) displays a resource-defence polygynous mating system whereby males defend discrete territories throughout the 6 week breeding period. Males must fast throughout their territorial tenure and, consequently, foraging success in the preceding months will directly impact their ability to meet the energetic demands of territory acquisition, defence and mating. Whereas, numerous recent studies have greatly increased our knowledge of the foraging ecology and factors influencing reproductive success in adult females, information on adult males is limited. What makes a successful territorial male? Do diet, hunting tactics or foraging area influence the ability to acquire a territory, territory quality and tenure duration? In addition, with mean body masses of 229 kg, male Australian fur seals represent the largest predator biomass in the marine ecosystem of south-eastern Australia yet relatively little is known of their influence on the trophic dynamics of the region, how this varies with environmental fluctuations, and how the species, and its prey populations, may respond to a changing climate and oceanographic conditions. This project, therefore, will determine the inter-individual variation in diet, foraging behaviour and habitat use of adult male Australian fur seals, the environmental factors influencing these parameters, and their relationships with indices of reproductive success (territory quality, tenure duration, paternity).
Scientific significance and innovation: As the greatest proportion of the largest marine predator biomass in south-eastern Australia, male Australian fur seals will have a major impact on the region's ecosystem, yet surprisingly little is known about their foraging ecology and the factors influencing it. In addition, while numerous studies have investigated the links between foraging behaviour and reproductive success in female mammals, few have determined these in males, especially in large sexually dimorphic polygynous species. This study will combine a range of techniques, including the latest telemetry technology, behavioural observations, and genetic and stable isotope analyses, to investigate these parameters.
Potential national benefit and strategic alignment with the aims of the CIE: This project falls under the National Research Priority of 'An Environmentally Sustainable Australia' and in particular the priority goals Responding to climate change and variability and Sustainable use of Australia's biodiversity. As apex predators, fur seals play a major role in marine ecosystem function. In the face of ever-increasing human exploitation of marine resources, they are also at increasing risk of interactions with commercial fisheries. Little is known, however, of the role the greatest proportion of the largest marine predator biomass in south-eastern Australia - male Australian fur seals, how this varies between individuals and the reproductive consequences of this variation. Only by understanding differences between individuals will it be possible to predict and quantify the potential impacts of environmental change on this keystone marine apex predator and its prey populations. Consequently, this project is also clearly aligned with the strategic aims of CIE.