| Summary: | Gentoo Penguins (Pygoscelis papua) are known to be generalist foragers, while Adélie (P. adeliae) and Chinstrap (P. Antarctica) tend to specialize on krill within the Western Antarctic Peninsula and South Shetland Islands, particularly during the breeding season. However, little is known on temporal consistency in diet and foraging habitat of these species, particularly at the individual level. We used stable isotope analysis (SIA) of blood and feathers to evaluate seasonal and individual foraging consistency within Adélie, Chinstrap and Gentoo Penguins breeding in the South Shetland Islands, as well as among three Gentoo Penguins populations in the Western Antarctic Peninsula and South Shetland Islands. Our results suggest that Pygoscelis penguins can differ in foraging ecology not only at the population level among species, sites and seasons, but also in the level of individual variation within populations, and in the degree of seasonal consistency within individuals.
Previous dietary analyses suggest Gentoo penguins have a generalist foraging niche, which may help buffer them from recent climate-driven declines in key prey species, such as Antarctic krill (Euphausia superba). Ecological theory indicates that generalist populations fall under two different categories: Type A generalist populations exhibit large variation within individuals, and little variation between individuals, where Type B generalist populations are comprised of individual specialists, with large variation between individuals. We conducted SIA using tail feathers from Gentoo penguins at four geographically isolated breeding sites across the Scotia arc to assess individual variation in winter diets and determine the type of generalist strategies that Gentoo penguins utilize. Our results indicate the presence of individual specialization (type B generalism) within all four geographically distinct breeding colonies, with lower degrees of individual specialization in southern populations and higher degrees of individual specialization in northern populations. In addition, our results also suggest that individual specialization may be driven by prey abundance and diversity, as foraging habitat in the southern populations are marked by high abundance of Antarctic krill and low prey diversity, while the northern populations forage on a wider diversity of prey.
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