1. Department of Animal Behaviour; University of Bielefeld; Postfach 100131 33501 Bielefeld Germany
2. Department of Biological Sciences and the Museum; Texas Tech University; Lubbock TX 79409 USA
3. Marine Evolution and Conservation group; Centre for Ecological and Evolutionary Studies; University of Groningen; Nijenborgh 7 NL 9747 AG Groningen The Netherlands
4. Section for Evolutionary Genomics; Centre for Geogenetics; Natural History Museum of Denmark; University of Copenhagen; Øster Voldgade 5-7 DK-1350 Copenhagen K Denmark
5. Sea Mammal Research Unit; Scottish Oceans Institute; University of St Andrews; St Andrews Fife KY16 8LB UK
6. Department of Zoology; University of Cambridge; Downing Street Cambridge CB2 3EJ UK