Intra- and inter-individual variation in the foraging ecology of a generalist subantarctic seabird, the gentoo penguin

Individual specialisations have been suggested to improve foraging efficiency by optimising individual capacity (physiological and behavioural) and reducing intra-specific competition in exploiting prey resources. In this study, we investigated the inter-and intra-individual variation in behaviour in an opportunistic forager, the gentoo penguin Pygoscelis papua, at Kerguelen Island, southern Indian Ocean. We used complementary bio-logging and stable isotope analyses, coupled with morphometric measurements, to: (1) determine the inter-individual variation in morphology and foraging behaviour; (2) quantify intra-individual variation in foraging behaviour; (3) investigate the links between consistency in foraging, distances travelled and body condition; and (4) determine if dietary specialisations exist and are maintained outside the breeding season. We show that this species exhibits a large inter-individual variation in foraging behaviour, with some individuals conducting very short trips close to the colony while others travelled considerably farther. Heavier individuals tended to forage in more distant locations, dive deeper and perform more benthic dives. Individual specialisation in behaviour was low to moderate at the population level, yet some individuals were very consistent. The rate of travel was not influenced by consistency, and there was a lack of correlation between body condition and foraging consistency. High inter-individual variation in feeding ecology and dietary specialisations outside of a single breeding season were observed, consistent with gentoo penguins being Type 'B' generalists (i.e. generalist populations composed of individuals each consuming a different range of foods).