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Long-term foraging success in an Antarctic top-predator, the Adélie Penguin: effect of individual quality, colony size and access to prey

Final Activity Report Summary - ADELIEPENGUINSUCCESS (Long-term foraging success in an Antarctic top-predator, the Adelie Penguin: effect of individual quality, colony size and access to prey)

Polar regions are highly sensitive to climate change, raising real concerns for the future of polar ecosystems. Some of the most important signals of global climate warming have come from Antarctica, whose surrounding waters support one of Earth's most productive marine ecosystems. As integrators of food web changes, Antarctic marine top predators are reliable indicators of changes in marine food webs. Hence, demographic parameters, such as reproductive success or survival, of top predators integrate environmental variability over large spatial and temporal scales, being also affected by individual and colonial variability.

As part of an international project on the Adélie penguin, Dr Lescroël studied:
1. how individual quality was linked to differences in foraging strategies;
2. how colony size affected the relationship between individual quality and foraging strategies; and
3. how high and low quality individuals coped with years of high environmental stress related to changing climate.

To achieve the abovementioned targets Dr Lescroël had access to a unique demographic and foraging dataset, collected by Dr Ainley's research group in three Adélie penguin colonies of the Ross Sea in Antarctica, for more than 10 years. Using state-of-the-art technology in the form of computerised weighbridges and passive transponders to assess body condition and foraging effort, time-depth-recorders, satellite transmitters and archival tags to identify individual foraging tactics, she:
1. confirmed that individuals were not equally successful in raising offspring and surviving; and
2. showed that better, i.e. more successful, breeders foraged more efficiently than poorer breeders under harsh environmental conditions and when offspring needs were higher.

Colony size did not affect the relationship between individual quality and foraging strategies, nevertheless foraging efficiency decreased with increasing colony size. In contrast to the usually accepted paradigm, this suggested that it was probably more difficult to achieve good reproductive performance or to maintain good body conditions in large colonies rather than in small ones. Over the long-term, harsh environmental conditions might select breeding individuals on the basis of their foraging ability. Adélie penguins showed important phenotypic plasticity, suggesting that some portion of the population was capable of coping with large scale variability in their physical and biological environment. This variability was likely to be associated with climate change and, ultimately, to the species' evolution.