Short-term variation in the winter diet of Gentoo penguins Pygoscelis papua at South Georgia during July 1989

During winter 1989 at South Georgia, gentoo penguins showed a very rapid change in diet over a 10-day period. On 11-12 July, food samples were of low masses (150g) and had a high proportion of fish prey (75%) and of heavily digested material (33%). On 21-22 July, samples had higher masses (485g), consisted predominantly of crustacean prey (99%) and had little, heavily digested material (2%). Antarctic krill Euphausia superba was the most abundant crustacean species, forming 80% and 99% by number of individuals in the two sample periods. Data on winter diet are also compared over three years (1987-89). There was close similarity, between years, in the mass and composition of the two "alternative' diets: low-mass, fish-dominated and high-mass, krill-dominated diets, but there was no consistent pattern in the seasonal occurrence of these changes in diet between years. The change in diet may reflect short-term, local decreases in availability of krill in the inshore waters.

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