The objective is to understand various aspects of the structure and functioning of feral cat populations and predator-prey interactions in the ecosystem of Grande Terre (the main island of the Kerguelen archipelago), combining empirical and theoretical approaches. More specifically we aim to understand: (1) the biotic (prey availability) and abiotic (climatic conditions) determinants of cat population dynamics and in particular the influence of density-dependent and density-independent factors on the synchronization of the fluctuations in cat numbers; (2) the role of prey and predator behaviour in driving cat-rabbit interactions. The rabbit is the most consumed prey by cats, especially in winter when most seabirds have left their colonies and remain at sea. We will focus on both cat (prey selection, activity, home-range patterns) and rabbit (vigilance, feeding site selection) behaviour. Expected results should help managers in the prioritization and optimization of management efforts towards invasive species on Grande Terre.