TY  - THES
AU  - Saraux C.
PY  - 2011//
TI  - Response of penguins to environmental changes across the Southern Ocean.
N2  - Global warming is now hardly a disputable matter. The rapid changes in climate are unequivocal and foreseen to continue drastically within the next centuries, profoundly affecting the biological component of our planet. As the 6th mass extinction crisis is looming,it is becoming urgently necessary to increase our understanding of ecosystems and their responses to climate change. This is especially true for the poorly known yet important marine ecosystems. Covering most of the Earth’s surface, oceans are indeed key actors in climate regulation, and the responses of their ecosystems to climate change have been insufficiently studied. In particular, due to its geographical location at high latitudes which makes it strongly prone to the effects of climate, and due to its connectivity with all the other major oceans of the Earth, understanding how climate change might affect the remote Southern Ocean is a scientific priority. In this thesis, we investigated the effects of climate on Southern Ocean ecosystems through the monitoring of their emblematic top predators: the penguins. As top-predators, penguins are considered good indicators of their environment as they integrate the effects of climate which occur at every level of the food chain. The present work relied on data collected over several years on three penguin species (little penguins, king penguins and Adélie penguins) using automatic monitoring systems based on Radio-Frequency- IDentification, that we suggest to be a relatively harm-free method for monitoring individual penguins over the long-term. We found juvenile survival in king penguins to be higher than previously thought and close to adult survival rate. Surprisingly, it increased in years of high sea surface temperature (SST), indicating contrasted effects of climate on king penguins depending on the life-history trait considered. SST has also been shown to possibly bias the sex ratio of king penguin fledglings, which may affect in return the population dynamics. The study of different species enabled us to highlight the importance of the time-scale at which the effect of climate is investigated and the necessity of adapting it to the species biology. For instance, in little penguins chick mortality was concentrated on some weeks, underlining the dependence of reproductive success on punctual conditions, probably due to the low reserves accumulated by the chicks. Finally, we also show the importance of taking into account individual heterogeneity and quality, leading to consistent differences in parental effort in little penguins and in the ability to face different sea-ice conditions in Adélie penguins. Such inter-individual differences along with the flexibility exhibited in some behaviour (such as foraging in little penguins) may help penguins to adapt to new environmental pressures through phenotypic plasticity, though the rapidity and strength of climate change under these latitudes leave little hope for these long-lived animals.
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ID  - SarauxC.2011
ER  -