We particularly target the mechanisms of natural selection and sexual selection that underlie evolutionary changes in body size. Like all animals in the Galapagos archipelago, marine iguanas are totally tame and therefore can be observed very easily. Marine iguanas occur in enormous densities - we have 8000 individuals per km coastline in my colony. Marine iguanas are totally undisturbed by human activities on most islands and 4.
Marine iguanas are the only reptiles known to mate in 'leks'.
Leks are aggregations of males in a mating arena where they vigorously display on territories that do not contain important resources besides the males themselves. The benefits of mating with certain types of males are currently investigated by determining the survival of offspring in relation to male phenotype. The best method to directly determine the energetic costs of individual behavioral decisions makes use of the fact that energy expenditure is closely related to heart rate. Thus, by measuring heart rate of animals in the field and concurrently observing the behavior of individual animals, we can assign energy units to specific behaviors. Costs of salt excretion .