1. Carnivore Ecology and Conservation Research Group, Institute of Agriculture, Tokyo University of Agriculture and Technology, Saiwaicho 3-5-8, Fuchu, Tokyo 183-8509, Japan
2. Field Science Centre, Tokyo University of Agriculture and Technology, Saiwaicho 3-5-8, Fuchu, Tokyo 183-8509, Japan
3. Tokyo Wildlife Research Centre, Oguno 2452, Hinode-town, Nishitama-gun, Tokyo 190-0181, Japan
4. Wildlife Conservation Research Unit, Department of Biology, University of Oxford, The Recanati-Kaplan Centre, Tubney House, Tubney, Abingdon OX13 5QL, UK