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 wildand recent studies have shown that inter-individual variation in cognitive performances is related to variation in fitness, inparticular reproductive success. Nevertheless, it remains unclear whether the links between cognition and success arecausal or driven by a third confounding factor, such as ageing. In humans and laboratory animals, decline in mitochondrialnumbers or functioning and increased oxidative stress has been shown to directly contribute to the ageing- or brainpathology-related decline in cognitive performances. Hence, one hypothesis is that a shift in the oxidative balance inparticular with age leads to fast accumulation of oxidative damage in metabolically active tissues, such as the brain andmuscles, which in turn leads to a decline in cognition and physical performances, and ultimately explains the age-relateddecline in reproductive performances and survival. This first scenario predicts that links between cognition and fitness areentirely explained by a third variable, the oxidative balance. However, animals can acquire antioxidants from their diet andcognitive capacities are important to search for and better exploit food resources. Therefore, an alternative hypothesispredicts a causal relationship between cognition and fitness that is driven by the ability of birds to adequately exploit theirhabitat for healthy food for themselves and their offspring. In COSuccess, I will use a long-term database, carefully designedexperiments fin the field, state-of-art laboratory and statistical methods to reveal how physiology and cognition interacttogether in shaping fitness. Findings from this project will lead to important gains of knowledge on (i) whether cognition isunder selection (i.e. causally linked to fitness) and (ii) the importance of cognition and access to dietary antioxidants inmitigating ageing.