Karen J. Heywood¹, Yixi Zheng², Lars Boehme³, Michael A Fedak⁴, Benjamin Webber¹, David P Stevens², Louise C Biddle⁵ and Anna Wahlin⁵, (1)University of East Anglia, Norwich, NR4, United Kingdom, (2)University of East Anglia, Norwich, United Kingdom, (3)Scottish Oceans Institute, Sea Mammal Research Unit, St. Andrews, United Kingdom, (4)University of St Andrews, St Andrews, United Kingdom, (5)University of Gothenburg, Gothenburg, Sweden