1. Division of Environmental and Evolutionary Biology, University of Glasgow, Glasgow G12 8QQ, UK
2. Laboratorio ECOTONO, Universidad Nacional del Comahue, Quintral 1250, 8400 Bariloche, Argentina
3. SUNY College of Environmental Science and Forestry, Syracuse, NY 13210, USA
4. Wildlife Biology Program, College of Forestry and Conservation
5. Montana Cooperative Wildlife Research Unit, University of Montana, 205 Natural Sciences Building, Missoula, MT 59812, USA
6. Sea Mammal Research Unit, Scottish Oceans Institute, University of St Andrews, East Sands, St Andrews, Fife KY16 8LB, UK
7. Centre for Research in Environmental and Ecological Modelling, University of St Andrews, The Observatory, Buchanan Gardens, St Andrews, Fife KY16 9LZ, UK