Flexible foraging strategies of gentoo penguins help buffer the impacts of inter-annual changes in prey availability

Gentoo penguins Pygoscelis papua show considerable plasticity in their diet, diving and foraging behaviors among colonies; we expected that they might exhibit similar variability over time, at a single site, since flexible foraging habits would provide a buffer against changes in prey availability. We examined inter-annual changes in the foraging strategies and diet of gentoo penguins in the South Shetland Islands, Antarctica, over five years. Antarctic krill Euphausia superba was the primary diet item, and fish the secondary, though the importance of these items varied among years. Diving behavior also varied over time; different dive depth-distributions were observed in each year. Nonetheless, chick-rearing success remained relatively constant, indicating that gentoo penguins were able to cope with differences in prey availability by altering their foraging strategy among years. We suggest that this flexibility may contribute to why gentoo penguin populations have remained stable in the region, while their congeners with less flexible foraging strategies have declined.