Intrinsic limitation of the field metabolic rate in a free-ranging Arctic seabird: the role of oxidative stress

The rate of energy expenditure integrates nearly all aspects of the ecology of a species, and knowledge of the factors limiting energy expenditure is of paramount importance for a better understanding of the evolution of life-history traits in free-living species. One factor which may exert a powerful constraint on the rate of energy expenditure, and which currently receives considerable interest, is oxidative stress. It has been suggested that increased energy expenditure leads to an elevated generation of reactive oxygen species which in turn may lead to increased somatic damage and consequently to accelerated aging and death. Hence oxidative stress may be a universal physiological mechanism underlying trade-offs such as the cost of reproduction. In thi s project we propose an experimental approach to test the hypothesis that oxidative stress constraints the field metabolic rate and mediates the cost of reproduction, using the kittiwake as a model species. In two experiments we will manipulate brood size and the energetic costs to raise offspring, respectively, and simultaneously measure energy expenditure, oxidative damage, antioxidant capacity and telomere length. Survival and reproductive output will be recorded during subsequent breeding seasons. By this approach we will be able to determine the relationship of metabolic rate and oxidative stress, and fitness consequences associated with increased metabolism. Utilization of a study population with individuals of known age and known nutritional histor y will allow us to separate age and stress related effects from effects of metabolic rate on oxidative status and telomere length. The proposal comprises a strong collaboration between research institutes in Norway, the US and the UK, providing an excelle nt foundation of research experience, relevant infrastructure and methods. It will contribute significantly to our understanding of the physiological basis of the evolution of life-history trade-offs.