We study phenotype-environment interactions in vertebrates. We are interested in the phenotypic (structural and functional) responses of the organism to changes in the environment. Research focus is on muscle plasticity and exercise physiology in canids (Inuit dogs in Greenland), cardiovascular flexibility in ectotherm sauropsids (snakes and crocodiles) and feeding biology of ectotherm sauropsids. We use non-invasive Duplex-ultrasonography in combination with minimal invasive biopsy techniques to obtain repeated measures of individuals under variable physiological conditions. Open-flow respirometry and stable isotope labeling techniques are applied to study the energy metabolism of animals under variable external conditions (in the field and in the lab). The goal of this research program is to understand patterns and processes underlying organ size changes on the basis of cellular mechanisms and understanding the energetic costs of plasticity.