1. School of Biological Sciences, University of Hong Kong, Hong Kong
2. Applied Ecosystem and Conservation Research Unit, University of South Africa, Johannesburg, South Africa
3. Elephants Alive, Hoedspruit, South Africa
4. Department of Zoology, University of Cambridge, Cambridge, UK
5. Centre for African Ecology, School of Animal, Plant and Environmental Sciences, University of Witwatersrand, Johannesburg, South Africa