Thesis defence Amandine HERRADA

     The increase in human activities is causing severe environmental pollution that threatens the health of human populations, animals and ecosystems. Studies on humans and laboratory models focus mainly on the effects of exposure to contaminants under controlled conditions. However, in an ecological context, exposure to multiple contaminants and the chronic nature of this exposure are factors that can affect toxicity, even at low doses of contaminants. The impact of these contaminants on the health and survival of wildlife remains however poorly understood.

     Through the longitudinal monitoring of two populations living in contrasting ecological contexts, this thesis aims to gain a better understanding of the impact of prolonged exposure to low doses of toxic metals on the physiology and survival of a long-lived mammal, the European roe deer (Capreolus capreolus).

     The thesis is divided into three complementary chapters. The first aims to establish metal exposure profiles in roe deer, and to define, for the first time, reference values for these elements in a wild ungulate. The results reveal a high degree of inter-population variability, but overall a low level of exposure in the populations studied, compared with other populations of wild ungulates. Based on these data, the second chapter looks at the physiological consequences of this exposure on the redox status of individuals (i.e. the balance between the production of reactive oxygen species and the organism's antioxidant capacities). The results show that an increase in toxic metal concentrations is associated with an increase in oxidative damage and a disruption of antioxidant defences. These effects are partially modulated by meteorological conditions, but are little influenced by concentrations of essential metals such as iron or magnesium. Finally, the third chapter examines the demographic impact of exposure to toxic metals by modelling annual survival using capture-mark-recapture data. It reveals a negative effect of this exposure on survival probabilities, more marked in the youngest and oldest individuals in one of the two populations.

     By combining physiological markers and long-term survival data, this thesis highlights a potential link between physiological disturbances and demographic consequences in a long-lived mammal. It thus contributes to a better understanding of the effects of exposure to low doses of contaminants in natural populations, and highlights the risks that such exposure could pose to wildlife health, and potentially to human health. These results argue in favour of considering the effects of low-dose contaminants in conservation strategies, based in particular on ecophysiological approaches.