1. Mammal Research Unit, School of Biological Sciences, University of Bristol, Bristol BS8 1UG, UK
2. Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, UK
3. Mammal Research Institute, University of Pretoria, 0002 Pretoria, Republic of South Africa
4. Aberdeen Centre for Energy Regulation and Obesity (ACERO), Department of Zoology, University of Aberdeen, Aberdeen AB24 2TZ, UK
5. Rowett Research Institute, Greenburn Road, Bucksburn, Aberdeen AB21 9SB, UK