1. Department of Biology–Zoophysiology, Aarhus University 1 , C. F. Møllers Allé 3, building 1131, 8000 Aarhus C, Denmark
2. Department of Ecoscience–Marine Mammal Research, Aarhus University 2 , Frederiksborgvej 399, 4000 Roskilde, Denmark
3. Centre for Research into Ecological and Environmental Modelling, University of St. Andrews 3 , St. Andrews, Scotland, United Kingdom