Institution: | Department of Wildlife, Fish and Conservation Biology, University of California, Davis, CA 95616, USA and Tanzania Wildlife Research Institute, PO Box 661, Arusha, Tanzania;and Institute of Environmental Science, Leiden University, c/o Nieuwe Teertuinen 12C, 1013 LV Amsterdam, the Netherlands and Socotra Conservation and Development Programme, PO Box 16494 Sana'a, Yemen |