COSuccess. Testing the importance of oxidative stress and dietary antioxidants in linking cognitive traits and fitness in free living animals

Cognitive abilities should be beneficial for individuals to optimize decisions when facing environmental changes in the wild and recent studies have shown that inter-individual variation in cognitive performances is related to variation in fitness, in particular reproductive success. Nevertheless, it remains unclear whether the links between cognition and success are causal or driven by a third confounding factor, such as ageing. In humans and laboratory animals, decline in mitochondrial numbers or functioning and increased oxidative stress has been shown to directly contribute to the ageing- or brain pathology-related decline in cognitive performances. Hence, one hypothesis is that a shift in the oxidative balance in particular with age leads to fast accumulation of oxidative damage in metabolically active tissues, such as the brain and muscles, which in turn leads to a decline in cognition and physical performances, and ultimately explains the age-related decline in reproductive performances and survival. This first scenario predicts that links between cognition and fitness are entirely explained by a third variable, the oxidative balance. However, animals can acquire antioxidants from their diet and cognitive capacities are important to search for and better exploit food resources. Therefore, an alternative hypothesis predicts a causal relationship between cognition and fitness that is driven by the ability of birds to adequately exploit their habitat for healthy food for themselves and their offspring. In COSuccess, I will use a long-term database, carefully designed experiments fin the field, state-of-art laboratory and statistical methods to reveal how physiology and cognition interact together in shaping fitness. Findings from this project will lead to important gains of knowledge on (i) whether cognition is under selection (i.e. causally linked to fitness) and (ii) the importance of cognition and access to dietary antioxidants in mitigating ageing.