1. Centre for Behaviour and Evolution, IoN, Newcastle University, Henry Wellcome Building, Framlington Place, Newcastle NE2 4HH, UK
2. Institute of Biodiversity, Animal Health and Comparative Medicine, College of Medical, Veterinary & Life Sciences, The University of Glasgow, Glasgow G12 8QQ, UK
3. Department of Biological Sciences, North Dakota State University, Fargo, ND 58108, USA
4. Environment Department, University of York, York YO10 5NG, UK